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"AIR WATER HARVESTER" PATENTS






Here are several more patents for Air Wells.
See also :


Aakash Amrit
Air Wells
Air Wells ( Solar Adsorption )
Air Well Patents (#1)
Air Wells Patents (#2)
AUGUSTIN : Watercone
BLEECHER : NeverWet
CHATTRE : Fog-Collector
Dew Pond Construction
ELLSWORTH : AirWell
ESTEVES : Fog Collector
Fog Fences
HENG / LUO : Fog Collector
HOFF : WaterBoxx
JAGTOYEN : Auto Exhaust Water Recovery System
KLAPHAKE : Air Wells
KOHAVI : Air Well
OLMO / GIL : Fog Collector
PARENT : Air Well
QINETIQ : Dew Collector
RETEZAR : Fontus Air Well

RICHARDS : AquaMagic Water Generator
SHER : Air Well

THEILOW : Air Well
VITTORI : WarkaWater Airwell
WHISSON : Air Well






WATER HARVESTER AND PURIFICATION SYSTEM
WO2015057502

An optimized system creates potable water from water vapor in the atmosphere, or purifies salt water or contaminated water. The system employs a condenser having multiple metal condensation surfaces. These condensation surfaces are cooled by coolant passing through conduits attached to the condensation surfaces. The coolant is cooled by a cooling unit. Power is supplied to the cooling unit by solar photovoltaic panels, or wind turbines, or the electric grid. The system can be mobile or fixed and can produce potable water at remote locations. The system may employ an evaporator which evaporates non-potable water into an air stream. The evaporator includes a solar or gas heater which increases the temperature of the air. Metals may be extracted from the salt water.; If sewage is used, solid organic waste may be processed into combustible gas which is burned by an engine running a generator to power that system.

BACKGROUND

1. Field of Invention

[0002] The present invention relates generally to apparatus designed to harvest moisture and purify non-potable water, and more particularly, to harvest moisture and purify non-potable water to produce potable water.

2. Description of Related Art

[0003] Increasing population requires more clean water. Urban population growth will increase demand for household water, and the need for clean, potable water will increase. Conventional water supplies will run short because of increased demand and local overuse of natural water supplies.

[0004] Large amounts of potable water are currently being used by industries which release chemicals into the water that make the water unfit for drinking. One industry use which uses large amounts of water is hydraulic tracking. Much of the tracking solutions are not purified, further reducing the clean water supply.

[0005] Some non-operational industries, such as the coal mining industry have ceased operations in certain areas. Since some of them went bankrupt, they have left abandoned mines which now release large amounts of mine drainage into waterways.

[0006] Similarly, sometimes wastewater, water contaminated with microorganisms, pharmaceuticals and fertilizers make large amounts of water unfit for drinking.

[0007] Another source of non-potable water is salt water, such as seawater or brackish water.

Salt water can be desalinated to create fresh water by conventional methods; however these are not practical in certain regions. The best known methods for desalinization are a) vacuum evaporation by boiling, b) distillation or c) reverse osmosis.

[0008] Unfortunately, boiling and distillation requires significant energy to operate efficiently and the resultant cost of treated water puts this technology out of reach for the majority in need. Desalination plants exist in rich nations such as the United States and Saudi Arabia but are not feasible everywhere due to the costs. The lack of capital in developing nations makes large desalination plants with high-volume production impractical.

[0009] Another method of desalinating salt water is by using reverse osmosis. Desalinating by reverse osmosis requires placing water under high pressure and forcing the water through porous membranes. The pores are sized to allow water molecules through but do not pass charged ions, such as salt ions. Reverse osmosis requires equipment to raise the water pressure to high levels, again requiring significant energy. Reverse osmosis also only results in a small volume of clean water being produced. Therefore, while it is not very economical or efficient to use reverse osmosis for desalination, it is the most widely used method for desalination, despite its high costs.

[0010] Even if one were to use one of these methods, they typically are done in stationary plants and the clean water would have to be transported to where it is needed. Producing potable water near its place of use removes the requirement for transporting the water to where it is needed. Therefore, pipelines, canals or tanker trucks are not required.

[0011] Production of high-quality water at or near its place of use is superior to transporting drinking water, which requires substantial consumption of energy for delivery and if bottled, container waste disposal.

[0012] Another source of water is moisture in the air. Current technology exists that utilizes fans, pumps, and refrigeration units to extract water vapor from the air; however, it is dependent on electricity or fossil fuels to power the devices. These technologies are not suitable for much of the world's population where artificial power sources are not readily available.

[0013] There currently is a global need for cost-effective, simple, efficient, stationary and mobile systems for producing potable water where it is needed.

One embodiment of the present invention takes the form of an apparatus capable of harvesting atmospheric water. The apparatus includes a harvester comprised of a thin sheet of material connected to a cooling source. As the surface of the thin sheet is cooled, evaporated water condenses and precipitates on to the thin sheet. The precipitated water is then collected.

[0015] Another embodiment of the present invention may take the form of a desalinization apparatus. In this embodiment, seawater or other brine may be loaded into a basin and evaporated. The process of evaporation separates fresh water from the minerals. The evaporated water may then be brought in proximity to the thin sheet, thereby condensing and collecting the fresh water.

[0016] Still another embodiment of the present invention may take the form of a wastewater treatment apparatus. In this embodiment, municipal or industrial wastewaters may be loaded into one or more process vessels. The wastewater may then be evaporated, with fresh water condensing on the thin sheet.

[0017] An embodiment of the current invention may be described as a system for producing potable water having a fan for creating an air stream of ambient air and a condenser within the air stream having a number of conduits adapted to carry a liquid coolant. The liquid coolant reduces the temperature of the condenser and surrounding air below the dew point of the ambient air, causing moisture in the ambient air to condense on the condenser.

[0018] A cooling device that runs on electric power is coupled to the conduits and is adapted to lower the temperature of the liquid coolant below a dew point of the ambient air.

[0019] A solar photovoltaic array creates electric power to power the system.

[0020] A plurality of sensors is adapted to measure physical parameters of the system and provide their measurements to a control unit coupled to the sensors. The control unit is also coupled to the fan, the cooling device and the photovoltaic array and can read information from the sensors and adjust elements of the system accordingly to optimize operation of the system.

[0021] The current invention may also be embodied as a system for producing potable water from non-potable water having an evaporator with a chamber for receiving, containing and heating a stream of air, a second chamber for receiving non-potable water having an air passageway in contact with the non-potable water and an airflow exit, at least one passageway fluidically connecting the first chamber to the second chamber allowing the heated stream of air to pass from the first chamber through the second chamber and out of the airflow exit, thereby increasing the amount of water vapor in the air stream leaving the airflow exit. The system also includes a condenser fluidically coupled to the airflow exit of the evaporator adapted to receive the moist airstream, a number of condensation surfaces cooled by a coolant to a temperature below the dew point, causing the moist airstream to condense the water vapor in the air stream into potable liquid water. At least one cooling unit is adapted to cool the coolant to a temperature below the dew point of the moist air. A plurality of sensors measure physical parameters of the system. A control unit is coupled to the sensors, the fan, the cooling device and the photovoltaic array. The control unit reads information from the sensors and adjusts elements of the system accordingly to optimize operation of the system. The system is powered by a solar photovoltaic array adapted to create electric power. There also may be a windmill driving an electric generator acting to power the system. Battery storage may be employed to store electricity for later use. In alternative embodiments, the system also employs at least one pressure sensor adapted to measure pressure within the conduit; and the control unit is coupled to the pressure sensors and fan for interactively measuring the pressure within the vessel to adjust the fan operation to optimize condensation.

[0022] The system may also employ a number of temperature sensors adapted to measure temperature at various locations within the conduit, and a heating device in the evaporator. The control unit is coupled to at least one of the temperature sensors and the heating device for interactively measuring the temperature within the vessel to adjust the heater operation to optimize evaporation.

[0023] The current invention may also be embodied as a system for creating potable water from non-potable water employing an evaporator section employing a plurality of evaporators, with each evaporator having an input for receiving input air and an output for exhausting air. Each evaporator is adapted to evaporate non-potable water into an input air stream received at its input and to create a moist air stream at its output. The evaporators are connected in series such that the output of one is coupled to the input of the next. The system also employs at least one humidity sensor near the input of each evaporator capable of determining the relative humidity, a bypass conduit which bypasses at least one evaporator, at least one bypass valve adapted to divert the moist air stream to the bypass conduit when activated, a control unit coupled to the humidity sensors and at least one bypass valve, adapted to sense when the humidity of the moist air stream exceeds a predetermined level and to activate at least one bypass valve causing the moist air stream to bypass at least one evaporator, and a condenser for receiving the moist air stream and condensing potable water from the moist air stream.

[0024] The current invention may also be embodied as a system for creating potable water from non-potable water having an evaporator for receiving the non-potable water and evaporating it into a moist air stream flowing in a direction, a condenser section employing a plurality of condensers, each positioned behind a previous one within the direction of the moist stream such that the air stream must flow past a first condenser to reach a next condenser, wherein the condensers receive a liquid coolant to reduce their temperature below the dew point of the moist air; at least one humidity sensor between the condensers, for measuring the relative humidity, a bypass conduit which bypasses at least one condenser; at least one bypass valve adapted to divert the moist air stream to the bypass conduit when activated, a control unit coupled to the humidity sensors coupled to the sensors and the at least one bypass valve, adapted to sense when the humidity of the moist air stream drops below a predetermined level and to activate at least one bypass valve causing the moist air stream to bypass at least one condenser.

[0025] These and other advantages and features of the present invention will become apparent to those of ordinary skill in the art upon reading this disclosure in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The advantages of the instant disclosure will become more apparent when read with the exemplary embodiment described specification and shown in the drawings, wherein:

[0027] Figure 1 is an overall block diagram of one embodiment of a water harvesting system for extracting water from the air according to the present invention.

[0028] Figure 2 is a diagram of one embodiment of a condenser section according to the present invention.

[0029] Figure 3 is a diagram of another embodiment of a condenser section of the present invention.

[0030] Figure 4 is an overall block diagram of one embodiment of a salt water purification system according to the present invention.

[0031] Figure 5 is a side elevational diagram of one embodiment of an evaporator section according to the present invention.

[0032] Figure 6 is an overall block diagram of one embodiment of a wastewater purification system according to the present invention.

[0033] Figure 7 is an overall block diagram of one embodiment of a river water purification system according to the present invention.

[0034] Figure 8 shows an alternative embodiment of the system which may be implemented into the systems of Figures 4, 6 and 7.

[0035] Figure 9 shows an alternative embodiment of a portion of the system relating to the evaporator which may be merged into the systems of Figures 4, 6, 7 and 8.

[0036] Figure 10 shows an alternative embodiment of a portion of the system relating to the evaporator which may be merged into the systems of Figures 4, 6, 7 and 8.

[0037] Figure 11 shows a schematic plan view of an embodiment of the system according to the present invention employing the multiple condensers.

[0038] Figure 12 shows a schematic elevational view of an embodiment of Figure 11.

[0039] Figure 13 shows a schematic plan view of an embodiment of the system according to the present invention employing the multiple condensers of Figure 10.

[0040] Figures 14, 15 and 16 together illustrate a flowchart illustrating the functioning of an embodiment of the current invention.



DETAILED DESCRIPTION

[0041] The present invention will now be described in detail by describing various illustrative, non- limiting embodiments thereof with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. Rather, the embodiments are provided so that this disclosure will be thorough and will fully convey the concept of the invention to those skilled in the art. The claims should be consulted to ascertain the true scope of the invention.

[0042] The conventional methods of distillation and reverse osmosis are not feasible in the third world countries where the water is needed the most. The device and process proposed in this application use neither of these methods. It is an evaporative method that uses the natural process of evaporation of a liquid into air.

[0043] The proposed process is the opposite of conventional evaporation devices wherein the water is heated to move the water molecules from the liquid phase to the vapor phase. In this device, the air is heated so that the water-carrying capacity of the air increases over the water- carrying capacity available at lower temperatures. This alone does not produce high rate evaporation, as the air at the water/air interface becomes rapidly saturated with water vapor and the rate of evaporation decreases significantly and rapidly. To effect high rate evaporation of the water volume, the saturated air at the water/air boundary must be removed and replaced with moisture-deficient air. A fan or blower may be used to effect this movement from the evaporator unit.

Constrained Optimization

[0044] The system of the current application is optimized to produce high rate production of potable water for the least cost that is compatible with existing resources. Since the water is intended to be potable, there must be less than a predetermined acceptable level of contaminants. The evaporator and the condenser are each optimized for the least cost to produce the required amount of potable water.

Evaporator Optimization

[0045] To optimize the evaporator, one would like to increase the surface area interaction between the water and the air. On way to do this is by creating a microclimate near the water. A microclimate is a local atmospheric zone where the climate differs from the surrounding area. Thereby by at least partially enclosing a volume near the water's surface, humidity near the water surface creates a microclimate. The airflow then carries humid air from this microclimate away. One would also try to increase the air flow rate to increase the amount of potable water produced. Therefore, bubbling the air through the non-potable water would increase surface area interaction; however, at higher flow rates this causes droplets to become entrained in the air stream, contaminating it, making the water non-potable.

[0046] Therefore, it was found that running a laminar air stream over the non-potable water would cause the water to evaporate into the air stream at high volumetric flow rates. If the air stream has laminar flow, few droplets become entrained in the air steam, even at higher air velocities. This allows more throughput of the water vapor.

[0047] It was also determined that a large surface area having laminar air stream rather than a turbulent air stream passing over the surface of the non-potable water achieved very good results. It was also determined that only the air adjacent the water surface received water vapor. Therefore, the height of the air flow chamber was minimized to maximize air relative humidity, and keep the flow laminar.

Condenser Optimization

[0048] It was determined that using metal sheeting with common metal piping material that was either cast or fabricated was the most cost-effective way to make condensers while achieving acceptable heat transfer efficiency. Again, creating a local microclimate around the condenser surface creates cooled air which interacts with the moist humid air, causing precipitation even before the moist air touches the condenser surfaces. The efficiency of this design was measured for various temperatures. The square footage required to condense the water vapor provided by the evaporator was then determined.

[0049] To convert the water from the vapor phase back to the liquid phase a condenser must be used to create microclimate where the temperature surrounding the condenser unit is lowered to a point below the dew point of the air wherein upon contact with the microclimate, the water will condense through precipitation. The now moisture-deficient air is directed back to the evaporator unit. The salts or contaminants present in the original water source remain behind in the concentrate left in the evaporator and the precipitated water is potable and ready for human consumption.

Embodiments

[0050] The embodiments of this application may be classified into three categories, such as those that:

1) directly remove moisture from the atmosphere, referred to as a 'water harvesting system',

2) desalinate salt water, referred to as a 'desalination system', and

3) purify contaminated water, or non-potable water in the environment, such as from a river stream, settling pond, lake, or other body of water, referred to as a 'water purification system'.

1) Water Harvesting System [0051] The water harvesting device designed for atmospheric operation condenses water directed to the unit from the atmosphere where it precipitates as it contacts the micro-climate modifications surrounding the condensation panels.

[0052] While there will be some condensation of the moisture as it comes in contact with the panels, the majority of the condensation will occur in the zone of cooled air surrounding the panel surface where the dew point of the air mass is reduced in relation to the dew point of the air carrying the moisture effecting rapid condensation of the water molecules.

[0053] Embodiments of the invention are discussed below with reference to Figures 1-7. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments.

[0054] Figure 1 is a block diagram of a water harvester apparatus 100 for extracting moisture from the atmosphere. The apparatus 100 is comprised, in part, of a condenser 200 connected to a coolant device 105, which may be a water chiller or any device which cools a circulating fluid capable of transferring heat referred to as a coolant. The coolant device 105 receives and cools the coolant passing through condenser 200. In preferred embodiments of the present invention, a fan 101 is included to direct ambient moisture laden air 3 through the condenser 200. It also may include a cooling tower 107 that couples with the coolant device 105 to absorb the heat extracted by the coolant device 105 and dissipate the heat through the cooling tower 107.

[0055] Preferred embodiments also include a power source that may take the form of a storage battery 113 fed by a solar photovoltaic array 109 and/or wind turbine system 111. The power source is used to operate the coolant device 105, and is able to do so where power is unavailable.

[0056] In an alternative embodiment, the condenser 200 may be enclosed in a containment vessel 115 having an air flow valve at an air exit, where the dry air 7 exits the system. By using the fan 101 to force air into the containment vessel 115, a slightly higher air pressure is created. Since air releases moisture as pressure decreases, this further increases the amount of potable water 5 created. The air flow valve 225 is adjustable so that the amount of flow and the pressure may be adjusted to optimize the potable water 5 created. Optionally, a control unit may monitor the pressure inside of the containment vessel 115, and operate the air flow valve 225 to interactively optimize the water harvester system 100. [0057] Figure 2 shows a preferred embodiment of the condenser 200 of Figure 1. The condenser 200 may be mounted to a base using mounting supports 230. It may also include a plurality of panels 210 arranged above each other. The panels 210 in one embodiment are covered with thin metal sheets each referred to as a collection surface 211. The panels 210 are preferably manufactured of thin-gage stainless steel and have varying dimensions dependent on the water volume and condensation rate desired. In certain embodiments, the sheet dimensions are approximately 8 feet wide x 6 feet high with an overall height of 12 feet.

[0058] A coolant at a low temperature enters the inlet 221 of the distribution piping 220. The coolant flows through the distribution piping 220 and through the panels 210 to the distribution piping 220 on the opposite side of the panels 210 and out of the outlet 223. The purpose is to cool the collection surfaces 211 below the dew point to cause condensation of moisture in the air impacting the collection surfaces 211 and the cooled air volume (microclimate) surrounding the collection surfaces. The moisture that condenses is pure, potable water and falls into an optional collection basin 250 which collects it.

[0059] In a preferred embodiment, the panels 210 include an integrated series of stainless steel tubes, referred to as intermediate tubes, passing through them.

[0060] Figure 3 is another preferred embodiment of the condenser shown as condenser structure 300, which may be used in place of condenser 200. It may be mounted to a base with mounting supports 330. This embodiment has several panels 310 behind each other with respect to the direction of air flow. Low temperature coolant enters the distribution piping 320 at inlet 321.

[0061] This embodiment also includes an integrated series of stainless steel tubes referred to as intermediate pipes 315 that abut the water harvest collection surfaces 311. Coolant enters distribution pipes 320 at inlet pipe 321 then passes through a lower common pipe 313 and a cross pipe which feeds the other panels 310. The coolant then flows through the lower common pipe 313 then upward through the intermediate pipes 315 to collect in the upper common pipes 317. This cools the water harvest collection surfaces 31 land attendant microclimate below the dew point of the ambient air in the air flowing past the condenser structure 300. Distribution pipes 320 have a discontinuity 325 which prevents the coolant from bypassing panel 310.

[0062] Cooling the water harvest collection surfaces 31 land microclimate causes the humid air in the air stream passing the surface of the thin sheet to cool as well, thereby condensing the moisture therein. As the moisture carrying capacity of the air volume is exceeded, water condenses both on the water harvest collection surfaces 31 land within the microclimate volume and drops into an optional collection basin 350 resulting in potable water.

[0063] It is preferred that the conduits carrying coolant and the panels are not exactly horizontal, but slightly inclined. This allows condensation to run to a common lowest point and drip into a collection basin.

2) Desalination System

[0064] The current system may also be embodied as one that efficiently desalinates salt water, including brackish water, saline hydraulic fracturing water used in "fracking", and seawater.

[0065] The design of the system to treat salt water is twofold: 1) the first portion of the method is to create a precisely designed environment, causing a large amount of water vapor to be evaporated into a volume of air, and, 2) creating an environment and condensation chamber conducive to rapid condensation of the evaporated moisture from the atmosphere.

[0066] Figure 4 shows an embodiment of a desalination system. Salt water, such as seawater, is received at a salt water intake 402. The salt water received is passed through a heat exchanger 403 coupled to a coolant device 405. The cold seawater extracts heat from a hot side of a coolant device 405. The coolant device 405 may be a refrigeration unit or a heat pump. These typically pump heat out of one area and release it to another area. In this case, the coolant device 405 is pumping heat out of the coolant running through the condenser 200. The heat is then passed through the heat exchanger 403 to preheat the salt water entering the evaporator 500. While the additional heat allows for faster evaporation of the salt water, it is optional and not necessary for the operation of the system. Typically, the evaporator 500 is heated by the sun; however, an infrared heater 425, or other type of heater may be used at night, or when the sky is overcast. Moisture depleted dry air 11 also enters the evaporator 500. The moisture depleted dry air 1 1 receives water vapor as it evaporates to result in moist air 9.

[0067] The evaporator 500 also releases the salt water concentrate 13 which is what remains after much of the water is removed. This salt water concentrate may have dissolved minerals, and heavy metals. These may be gold, silver and other valuable substances. A resource recovery device 419 receives the salt water concentrate and processes it to increase the concentration of the brine and allow concentration of dissolved metals to low grade ore levels for the recovery of metals. This process is used to extract and recover metals 423 and other substances. What remains is salt solution 421 which is returned to the water source, or is processed for industrial or commercial uses.

[0068] The moist air 9 is then brought into proximity of the condenser 200 or 300 as indicated in Figure 1 above and performs the same functions to result in potable water 5 being produced.

[0069] The coolant device 405 functions in much of the same manner as coolant device 105 of Figure 1.

[0070] The coolant device 405 is optionally powered by solar photovoltaic array 409, wind turbine 411 and battery storage 413, similar to elements of the same names in Figure 1.

[0071] Figure 5 is a side elevational diagram of one embodiment of an evaporator 500 of

Figures 4, 6, and 7 according to the present invention. Please note that going forward, salt water, sewage water, polluted water, water contaminated with chemicals, and other non-potable water may be collectively be referred to as "non-potable water".

[0072] The evaporator 500 is designed to evaporate the largest amount of into the air without suspending non-potable water 23 droplets in the air stream 25. Since this system is optimized to create large amounts of potable water, it must use a high air flow rate that does not kick up water droplets.

[0073] Moisture depleted dry air 11 enters a heating chamber 501 from a return air distribution plenum 539. The heating chamber 501 may be a greenhouse-like structure or other structure designed to collect the energy from the sun. An air baffle 503 arranged vertically creates an air flow channel 525 which is separated from the air heating chamber 501 by the air baffle 503.

[0074] A straightening plenum 509 is positioned at the end of the air flow channel 525 to redirect the downward air stream to a horizontal air stream 25.

[0075] A separation deck 506 is a horizontal separator which creates a top of an evaporation chamber 507. The water surface 21 in the evaporation chamber 507 creates the floor. The evaporation chamber 507 is designed to allow an air stream with a significant amount of volumetric flow to pass between the separation deck 506 and the water surface 21 of non-potable water 23 with little or no turbulence. It is intended to have laminar airflow. The air flow along the surface of the non-potable water 23 in the evaporation chamber 507 allows a substantial amount of water molecules to be released from the surface and jump into the vapor phase. As indicated above, the width, length and shape are designed to have substantial laminar air stream. The laminar air flow reduces the amount of non-potable water 23 being swept up by the air stream as suspended water droplets, reducing the potential for contamination for the purified water. The closed evaporation chamber 507 creates a micro climate of high humidity which is highest at the air water boundary. This boundary layer air absorbs moisture to have a high relative humidity. Once the relative humidity is high, the air absorbs little additional moisture. Therefore, this boundary layer must be constantly replaced.

[0076] There are water inlets 511 underneath the water in the evaporation chamber 507. The non-potable water 23 enters here to replace the water that has evaporated.

[0077] A fan 401 draws the moist air 9 out of the evaporator 500, thereby causing a slight reduction of the air pressure. If the air flow valve 523 is partially closed, the air pressure is further reduced. Reduced air pressure facilitates evaporation of water into the flowing air.

[0078] In an alternative embodiment of the described system, the evaporation chamber 507 includes elongated vanes 541 along the air stream direction which facilitate laminar air stream. The vanes 541 run parallel to the length of the evaporation chamber 507 which minimize turbulence and increase laminar flow of the air stream 25 along the length of the vanes 541. These vanes may run for any length of the evaporator chamber 507.

[0079] In order to minimize the amount of liquid droplets from becoming swept up into the air stream 25 and becoming entrained in the airstream and contaminating the air stream 25, a barrier is to be used. This barrier may be a screen 543 as shown in Figure 5. Water droplets get caught in the screen and accumulate. When enough accumulate, they drop back into the non-potable water 23 in the bottom of the evaporation chamber 507. This screen 543 may run only the length of a portion which exhibits substantial turbulence or increased air flow velocity, or it may extend the entire length of the evaporation chamber 507.

[0080] There may be sensors 827 throughout the evaporator 500 which measure any physical parameter, such as temperature, relative humidity, air velocity, air turbulence, etc. These can be monitored by a control unit (825 of Figure 8) which then makes decisions based upon the input received, makes decisions and actuated elements of the system to optimize the operation of the system.

[0081] In an alternative embodiment of the described system, the evaporation chamber 507 includes a narrowed portion followed by an enlarged portion, thereby causing an area of reduced air pressure, allowing for greater evaporation into the airstream.

3) Water Purification System

[0082] Another embodiment of the system described in this application purifies contaminated water. This contaminated water may be hydraulic fracturing brines which include other chemical contaminants besides the dissolved salts, abandoned mine water discharges, industrial wastewater, municipal wastewater, waters containing pharmaceuticals, fertilizers, or other chemicals, and water containing microorganisms, such as giardia and Cryptosporidium spores.

[0083] Referring now to Figure 6, an alternative embodiment of the present invention comprises a waste water system 600 capable of producing fresh water from wastewater such as having sewage with human waste. The elements function similarly to their counterparts in the desalination system 400 of Figure 4. Wastewater is received at the wastewater intake 602 and is preheated by heat exchanger 603. A fan 601 draws moist air 9 from the evaporator 500 and passes it over a condenser 200 causing potable water 5 to be collected. Condenser 200 is cooled by a coolant cooled by a coolant device 605. The evaporator 500 receives wastewater with organic solid matter, such as human feces. There will also be dissolved organic material. The dissolved and solid organic material of the wastewater may be referred to as biochemical oxygen demand (BOD) material. In this embodiment, special material handling equipment should be used to extract solid materials and concentrated BOD material, referred to as concentrated wastewater 15 from the wastewater before it is evaporated. The concentrated wastewater 15 is provided to an anaerobic reactor 615. This will be used to create methane and other combustible gases. The water vapor in the collected gases is removed by a gas dryer 617 using conventional equipment and methods. The dried gas is now available to be used as fuel for a gas-fired engine 619. The gas-fired engine 619 drives a generator 621 to create electric power that is provided to battery storage 613.

[0084] In an alternative embodiment, the power is provided directly to the coolant device 605 and to any other piece of equipment requiring electric power, such as pumps and fans.

[0085] The gas from the gas dryer 617 is also provided to a gas-fired heater 625. This heats the air in the evaporator 500 that is used to absorb the water vapor.

[0086] Figure 7 discloses a water purification system 700 for non-potable water other than salt water. This may include natural bodies of water such as lakes, streams and ponds. Non-potable water 23 is received at the water intake 702 and is preheated by heat exchanger 703. A fan 701 draws moist air 9 from the evaporator 500 and passes it over a condenser 200 causing potable water 5 to be collected. Condenser 200 is cooled by a coolant cooled by a coolant device 605. This functions the same as the salt water system 400 of Figure 4, except that it does not include the elements for resource recovery 419 and an element to hold the recovered metals 423 since this water typically has little valuable metals to recover. It also does not include an element to collect the salt solution 421. These elements are replaced by a sludge handling element 723. This takes the sludge from the evaporator 500 and disposes it.

[0087] Figure 8 shows an alternative embodiment of the system which may be implemented into the systems of Figures 4, 6 and 7. Block 827 represents elements of these previous figures that are not shown in Figure 8.

[0088] Wastewater is received at the water intake 802 and is preheated by heat exchanger 803. A fan 801 draws moist air 9 from the evaporator 500 and passes it over a condenser 200 causing potable water 5 to be collected. Condenser 200 is cooled by a coolant cooled by a coolant device 805.

[0089] In this embodiment, a plurality of sensors 827 are located within the air stream to measure at least one of air temperature, air humidity, air flow rate, turbulence and other physical parameters. These sensors 827 may be located in or after the evaporator, in or after the condenser 200 or on either side of the air flow valves 225 and 523. These connect to the control unit 825. Control unit 825 reads all necessary input from the sensors and makes determinations on how the system is running and what adjustments must be made to achieve the desired results.

[0090] Control unit 825 is connected to fan 801 and can read its current status. This may include the current it is receiving, its speed, the load, its past operation parameters values over time which can be paired with other information pertaining to the same time. The control unit can start, stop, adjust the speed and otherwise operate the fan.

[0091] Control unit 825 is connected to a coolant device 805. It can read any pertinent information from the coolant device 805 and also record this information along with its time of acquisition. The control unit can start, stop, adjust the speed, output and otherwise operate the coolant device 805. Control unit 825 is connected to all elements of the system and monitors them as well as actuates them to optimize the system.

[0092] In an alternative embodiment based upon Figure 8, there may be more than one fan, located at the inlet and/or outlet of the evaporator 500, or the vessel 240 or anywhere within the evaporator 500, the vessel 240 or other conduits of the system. Each fan may be interactively and independently controlled by the control unit 825 to adjust the air flow rate entering the evaporator 500/vessel 240, exiting the evaporator 500/vessel 240 and any airflow within the evaporator 500/vessel 240. The varying air flow velocities can adjust local air pressures and be used to optimize the operation of the evaporator 500/vessel 240.

[0093] Also, the air flow valves 523 of the evaporator 500 and 225 of the vessel 240 may be interactively and independently controlled by the control unit 825 in combination with the fans to adjust the air flow and pressures in various parts of the system to optimize its operation. In an additional embodiment, there may also be an air flow valve on an outlet of the evaporator(s) 500 and on an inlet of the vessel(s) 240. These may also be independently and interactively controlled by the control unit 825 along with other air flow control devices and fans to optimize the system.

[0094] Figure 9 shows an alternative embodiment of a portion of the system relating to the evaporator which may be merged into the systems of Figures 4, 6, 7 and 8. This evaporator section 900 can be used to replace the evaporator 500 of the previously described embodiments.

[0095] Depending upon the air flow rate, and the efficiency and size of the condensers, it may be more efficient to employ several evaporators 500. These evaporators 500 are connected here with connection conduits 933 which allow air flow to pass from an air flow outlet 525 of one evaporator 500 to a bypass valve 929. The bypass valve 929 may direct the air flow into an inlet of another evaporator 500 or to a bypass conduit, bypassing the remaining evaporators 500. There are sensors 827 which measure physical parameters such as temperature, relative humidity or other physical parameters. In this embodiment, they are at least measuring relative humidity. The output of the sensors 827 is provided to the control unit 825. The control unit 825 can then make determinations regarding the evaporators 500. For example, if the humidity sensed by sensor 827 after the first evaporator is 70% relative humidity, it is determined that the humidity should be increased. Therefore the control unit 825 will leave bypass valve 929 open allowing the air stream to pass to the second evaporator 500. A sensor 827 after the second evaporator 500, determines that the relative humidity is at 95% and determines that passing it through another evaporator will use more energy but will not produce significant additional amount of potable water. Therefore, control unit 825 decides to operate the bypass valve 929 between the second and third evaporators 500 causing the air stream to be redirected through a connection conduit 933. The air stream then bypasses the last evaporator 500 since no further evaporation is required for this air stream.

[0096] Figure 10 shows an alternative embodiment of a portion of the system relating to the condenser which may be merged into the systems of Figures 4, 6, 7, 8 and 9.

[0097] Depending upon the air flow rate, and the efficiency and size of the evaporator 500, it may be more efficient to employ several condensers 201, 202, 203. These condensers 201, 202, 203 have sensors 827 associated with them that provide information to the control unit 825. The control unit 825 can then make determinations regarding the condensers 201, 202, 203. For example, if the humidity sensed by sensor 827 after the first condenser 201 is not below a predetermined humidity level, it is determined that the humidity should be decreased and pass through a next condenser 202. Therefore the control unit 825 will leave the first bypass valve 1029 open allowing the air stream to pass to the second condenser 202. A sensor 827 after the second condenser 202 then determines that the relative humidity is below the predetermined humidity level. If it is decided that passing the air stream through another condenser 203 does not add much benefit, then control unit 825 operates the bypass valve 1029 between the second condenser 202 and the third condenser203 causing the air stream to be redirected through a connection conduit 1033. The air stream then bypasses the last condenser 200 since no further condensation is required for this air stream. In this manner, the control unit can adjust various parameters of the system, such as adjusting air flow rate. It can adjust the number of evaporators that the air stream will pass through, the number of condensers it will pass through, the temperature of the coolant, the pressure in the evaporator 500 and the pressure surrounding the condensers 201, 202, 203. By adjusting these parameters, the system can optimize the collection of moisture from the atmosphere, the amount of potable water purified from salt water, waste water or other contaminated water.

[0098] Figure 11 shows a schematic plan view of an embodiment of the system according to the present invention employing the multiple condensers 200. Figure 12 shows a schematic elevational view of an embodiment of Figure 11. This embodiment will be described with respect to Figures 11 and 12. In this embodiment, an evaporator 1100, similar to that of Figure 5, receives incoming air into a heating chamber 1102 which may be an area enclosed by a greenhouse-like structure 1121. Heating chamber 1102 may also be a chamber heated by solar light focused by lenses or by mirrors reflecting light. The air inside this heating chamber 1102 is heated and is then drawn as an air stream 25 downward into a passageway 1241 between an outer wall 1243 of the evaporator 1100 and a baffle 1103 by a fan 1101. The air stream 25 then passes over the surface 21 of non-potable water 23 causing evaporation of water vapor into the air stream 25 to create moist air 9.

[0099] Air stream 25 then passes through a separating convolution 1245 which causes droplets to hit the walls of the separating convolution 1245 and drop the water droplets of non-potable water which are swept into the air stream 25 as it passes over the non-potable water 23.

[00100] The resulting air is now moist air 9 carrying a significant amount of water vapor. This moist air 9 is then passed over a plurality of condensers each similar to condensers 200 and 300 of Figure 3. Each of these condensers 200, 300 is cooled with a coolant 1135.

[00101] A coolant device 1105 receives and cools the coolant 1135 and passes this coolant 1135 through the condensers 200, 300. The coolant 1135 should be of a temperature which is below the dew point of the moist air 9. As the air passes over the condensers 200, 300, the water vapor in the air condenses and is collected as potable water 5. The condensers 200, 300 may be housed within a greenhouse-like structure 1123.

[00102] For clarity, sensors for temperature, pressure, humidity, air velocity and other physical parameters, a connected control unit and connections between the sensors, control unit and other elements including the fan 1101 and coolant device 1105 are not shown here for clarity, but exist in at least one of these embodiments. Also, the solar voltaic array, wind turbines and battery storage are not shown in this figure, but are assumed to be in the functional embodiment.

[00103] Figure 13 shows a schematic plan view of an embodiment of the system according to the present invention employing the multiple condensers of Figure 10. In this embodiment, the evaporator 1100 and the fan 1101 function in the same manner as described in connection with Figures 11 and 12. However, this embodiment passes the moist air 9 by the condensers until the humidity level drops to a predetermined level then is directed by a bypass valve 1029 to a bypass conduit, bypassing the remaining condensers. This reduces the amount of air pressure drop and reduces the fan horsepower required.

[00104] Figure 13 shows condensers 201, 202, 203, 204, 205, 206, 207 and 208 having their coolant lines connected in series. The coolant from coolant device 1105 first passes through condenser 208 then through condenser 207, then through condenser 206 ... and then through condenser 201 and back to the coolant device 1105.

[00105] Due to this arrangement, the coldest condenser is condenser 208 and the warmest one is condenser 201 with the others having successively warmer temperatures moving from condenser 208 to condenser 201. Temperature sensors measure the coolant temperature as well as the air temperature between the condensers which is sent to a control unit. The control unit operates the elements of the systems and for example, would cause the coolant unit to reduce the coolant temperature so that the coolant at each condenser is below the dew point of the surrounding air stream.

[00106] The moist air 9 enters and passes by condenser 201, then 202, then 203 ... then through 208. The moist air 9 loses moisture and cools as it moves past condenser 201, 202 ... then 208. This then is a countercurrent thermal arrangement which maximizes condensation.

[00107] Driving airflow past the condensers requires power. At times, the amount of vapor that can be extracted does not warrant the energy required to extract it. Therefore, in this embodiment, there are humidity (and other) sensors between the condensers. When the humidity drops below a certain predetermined level, a bypass valve, such as that shown in Figure 10 may be activated to cause the air stream 25 to be directed into a bypass conduit 1031 and bypass at least one of the condensers.

METHOD

[00108] Figures 14, 15 and 16 together are a flowchart illustrating the functioning of an embodiment of the current invention being a method of efficiently creating potable water from non-potable water. The process starts at 1401. In step 1403 one or more evaporators are provided. One evaporator would be similar to the embodiment of Figures 4, 6 and 7, and multiple evaporators would be similar to the embodiment of Figure 9.

[00109] These evaporators have a larger surface area than depth to maximize the surface area to mass ratio, as illustrated in Figure 11. They also have an air flow passageway from the heating chamber through the evaporation chamber and out an air flow exit as shown in Figures 5 and 12. Optionally, as indicated later, additional heating device and additional heating may be provided to the heating chamber 501 of the evaporators 500, to increase evaporation of non- potable water 23.

[00110] In step 1405, the non-potable water is provided to the evaporation chamber from below. In step 1407, a physical parameter of at least one of the heating chamber, the evaporation chamber and the air flow exit are monitored by appropriate sensors. These physical parameters may be temperature, air pressure, relative humidity and air stream velocity.

[00111] In step 1409, the control unit controls the air flow device, which may be a fan or blower that is positioned at or near the air flow exit. The control device reads the monitored temperatures, pressures, relative humidity and air steam velocity and creates an air stream having a velocity causing it to reduce the air pressure in the evaporator drawing an air stream from the heating chamber through the evaporation chamber and out of the air flow exit evaporating water vapor into the air stream. The air flow device also directs the air stream from the air flow exit past condensers. The condensers have at least one surface held a temperature below the dew point of the air stream. The control unit calculates the dew point based upon the air stream temperature and relative humidity.

[00112] In the embodiments having multiple evaporators, in step 1411, the relative humidity exiting a condenser is monitored. If it is less than a predetermined relative humidity, the air stream is routed through another evaporator. The process is repeated either until the relative humidity exceeds the predetermined level, or there are no additional evaporators to further process the air stream.

[00113] In still another embodiment, the air stream exiting the evaporator does not exceed the required water content; the control unit may slow the air flow rate, or activate additional heaters which heat the air stream.

[00114] In step 1413, a contaminant sensor is provided in the air flow exit that can measure at least one contaminant in the air stream and provide the measurements to the control unit. In step 1415, the control unit determines if the amount of contaminants is below a safe acceptable level. If so, the processing continues at step 1417, if not, process continues at "A" of Figure 16.

[00115] If the contaminants are above the acceptable level, in step 1601, optionally, an alarm, notification, or corrective message is provided to a user. Also, optionally, in step 1603, the air stream will be directed to a direction other than to the condenser, stopping the contaminated air stream from condensing into the potable water.

[00116] Also, optionally, in step 1605, the control unit can slow the velocity of the air stream, preventing more contaminants from being swept up into the air stream. After step 1605, processing continues at "B" of Figure 14. [00117] In step 1417 the operation of air flow device may be adjusted to adjust the air pressure in the evaporator. In still another embodiment, there is an air flow valve at the air flow exit of the evaporator. This can be adjusted to also increase or decrease the air pressure within the evaporator. This is under the control of the control unit.

[00118] In step 1419, at least one condenser is provided in the air stream. In step 1421, optionally a vessel may be provided which encloses the one or more condensers. This vessel has an air flow inlet and an air flow outlet. It may optionally have an air flow valve on the air flow outlet which may be adjusted by the control unit. Processing continues at "C" of Figure 15.

[00119] Therefore, in step 1501, when the control unit partially closes the air flow valve, the air pressure within the vessel increases, and similarly, when the control unit partially opens the air flow valve, the air pressure in the vessel reduces.

[00120] In step 1503 the air stream is directed to the condenser and the potable water is collected in step 1505. If there is an embodiment having more than one condenser, then the humidity is measured in step 1507. In step 1509, if the measured humidity is below a predetermined humidity level, processing ends at step 1511. If the measured humidity is greater than a predetermined level, then the air stream is directed through a next condenser, if one exists. This process continues until either there are no more condensers to use or the measured humidity of the air stream exiting the condenser is below the predetermined level. This architecture causes the moisture to be continually run through condensers to extract water vapor which was not extracted by the previous condensers. This allows for an adjustable amount of condensation capacity to adjust for changes in ambient temperatures.

[00121] Please note that the embodiment of Figure 1 may be varied to employ multiple condensers such as those shown in Figure 10. In this embodiment, the adjustable condenser capacity will adjust for the differences in the ambient air temperature and relative humidity.

[00122] Similarly, the use of multiple evaporators in various embodiments shown allows for the interactive adjustment to adjust to changing sunlight and temperature conditions.

IMPLEMENTATION

[00123] The amount of water evaporated from a body of water in contact with circulating air can be calculated with the following equation:

E = k A (xs- x) where:
E = amount of evaporated water (kg/h)
k = (25 + 19 v) = evaporation coefficient (kg/m<2>h)
v = velocity of air above the water surface (m/s)
A = water surface area (m<2>)
xs= humidity ratio in saturated air at the same temperature as the water surface (kg/kg)
x = humidity ratio in the air (kg/kg)

[00124] It was therefore determined that by using a 60m by 60m evaporator, the water surface area is 3600 sq. meters at a temperature of 140 Degrees F. (60 deg. C), and an air flow velocity of 3.5 miles per hour (1.56 m./sec), the saturated humidity ratio xs would be 0.421 kg/kg. The humidity ratio x would be 0.0285 kg/kg. In an air volume of 5400 m3, there would be 14,469,250 kg. of water evaporated each hour. If the air velocity were increased to 5 mph (2.235 m/sec), this amount of water evaporated would then jump to 17,837,710 kg. each hour.

[00125] To detail the effects of air velocity and temperature on units designed to attain a potable water volume of 5.0 million gallons per day (MGD), assuming an evaporator efficiency of 60% and operating at 60 deg. C. and assuming condensers with a 60%> water vapor removal efficiency, below is the water removal by stages for a 2-stage and a 3-stage condenser section:

[00126] 2-stage condenser section (at 60 deg. C)
Input Output
Stage 1 2.16 1.29
Stage 2 1.29 0.78
Total 2.07
2,070,000

3-stage condenser section (at 60 deg. C)
Input Output
Stage 1 2.16 1.29
Stage 2 1.29 0.78
Stage 3 0.78 0.47
Total 2.54
2,536,804

Now assuming an evaporator efficiency of 60%> and at 80 deg. C. and assuming condensers with a 60% water vapor removal efficiency, below is the water removal by stages for a 2-stage stage condenser section:

2-stage condenser section (at 80 deg. C)
Input Output
Stage 1 5.24 3.14
Stage 2 3.14 1.89
Total 5.03
5,029,233

It is apparent that a 2-stage unit operating at 60 deg. C does not provide enough flow; using two 3 -stage units will provide the desired flow. Now to compare this unit to the 2-stage unit operating at 80 deg. C; while twice the water is produced so that only a single 2-stage unit is required to attain the desired 5 MGD output, the operating air temperature cannot be naturally attained and will need continuous additional energy inputs to attain the higher operating air temperature. If energy costs are the limiting factor in system design, the more efficient and sustainable method to attain the five million gallons per day is to use two 3 -stage units operating at 60 deg. C rather than one 2-stage unit operating at 80 deg. C. However, if the higher energy costs can be absorbed into the cost of the produced water, the lower capital costs of the single 2- stage unit becomes the preferred selection.



Water Harvester Having Micro-line Pattern
KR101492823

Disclosed is a water collector and, specifically, to a water collector having a fine line pattern comprising a base substrate, and a micro-channel in the form of a groove consisting of a line pattern in the surface of the base substrate, and capable of collecting water by collecting moisture in the air. According to the present invention, groove walls on both sides of the micro-channel have hydrophobic properties for mobility of a water drop, and at least one between the groove bottom side of the micro-channel and the upper lateral side of a channel wall forming a groove wall of the micro-channel has hydrophilic properties for condensation of water. The present invention has an effect of continuously condensing water in the surface of a water collector by ensuring smooth movement of a water drop due to geometrical characteristics, thereby the water collecting amount can be significantly increased.




ATMOSPHERIC WATER HARVESTER
US8627673

A method and a system are provided for producing water from atmospheric air by contacting the air with an aqueous hygroscopic material in a contacting chamber and allowing a portion of the water from the air to be adsorbed into the aqueous hygroscopic stream. The adsorbed water is then subsequently separated from the hygroscopic material to provide a clean water stream and a reconstituted hygroscopic stream.

FIELD OF THE INVENTION

[0002] The invention relates to atmospheric moisture harvesting and improvements in the efficiency of condensing water from air and in apparatus relating thereto. More particularly, the invention provides improved energy efficient extraction of water from air, particularly in outdoor settings and over a range of relative humidity.

BACKGROUND OF THE INVENTION

[0003] Atmospheric water harvesting is intended to produce water in the general vicinity of its place of use. Producing potable water near its place of use removes the requirement for either temporary or fixed water delivery systems such as pipelines and canals or temporary delivery systems such as bulk motorized water tankers. Production of high-quality water at or near its place of use is superior to transporting bottled drinking water, which requires substantial consumption of energy for delivery and waste disposal. Water harvesters are also superior environmentally because water bottle disposal is not an issue; water bottles are reused in conjunction with water harvesting. In addition, the water produced from suitably designed and operated water harvesters is pure and suitable and safe for drinking with very little treatment.

[0004] Water harvesting has not generally been regarded as a replacement for conventional piped water supplies because of its relatively higher cost and lower volumes. In present water systems, there is an effective “waste” of public high quality water that is used for low-quality uses, such as flushing toilets and watering lawns.

[0005] Conventional water supplies are running short because of increased demand and local overuse of natural water supplies. In addition, the cost of conventional water supplies is increasing significantly. One of the drivers of increased water cost is the incorporation of desalinated water, which is relatively expensive to produce using current technologies, in the basic supply. Perceptions about the quality of public water supply has led to bottled water being used increasingly as a regular personal drinking water source, even though it is much more expensive than public water supply.

[0006] In atmospheric water harvesting, condensation of water is achieved by providing and maintaining a chilled surface upon which water from moist air condenses. This is well known as a byproduct of chilling air, as in air conditioning systems in which chilling the air is the objective or in air dehumidification systems in which the objective is to achieve relative dryness of the exhaust air. However, water produced as a byproduct in these systems is more expensive to produce than that which is produced in a water harvester apparatus that is optimized for energy efficient water production by not overcooling air or water. In addition, byproduct water quality is generally not suitable for drinking, and can be dangerous, without additional treatment that is not provided for by an apparatus that does not have water production as a primary objective.

[0007] Water harvesting apparatus that has been specifically designed to produce water from air already exists (but without the efficiency and sophistication of this invention) which allows the production of water of the same or superior quality as bottled water but without the delivery or environmental waste issues and in quantities that are suitable for personal or family use on a regular and extended basis. Water harvesting provides high quality potable water without the continued cost of producing bottles directly in proportion to the quantity of water delivered, at a lower cost than bottled water.

SUMMARY OF THE INVENTION

[0008] The present invention provides improved apparatus and methods for condensing water from air. These improvements involve, but are not limited to, an improved water condenser, improved condenser airflow control, a variable speed air impeller, forced air or conductive cooling of all heat-producing parts of the system, new intake air controls, and provision for system-controlled on/off switching for the compressor. The apparatus is robustly designed and constructed, is resistant to common handling vibration and shock, and is meant to be moved by hand locally although it may also be fixed. The apparatus is intended for use either outdoors or indoors in a semi-autonomous mode, and where air quality is generally good. Water is pumped from a removable collection tank underneath the evaporator into which water has flowed by gravity, either directly or through a water treatment system to the user. Although the water exiting the water harvester has the character of distilled water and is very pure, for prolonged drinking of this water alone, some of the produced water should be remineralized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention will now be described in greater detail in connection with the Figures, in which:

[0010] FIG. 1 is schematic plan view of a first embodiment of an atmospheric water harvester according to the invention;

[0011] FIGS. 2a and 2b are schematic side views of two alternative orientations, respectively, of a heat exchanger/evaporator used in an atmospheric water harvester according to the invention;

[0012] FIGS. 3 and 4 are schematic plan views of second and third embodiments, respectively, of  an atmospheric water harvester according to the invention, which second and third embodiments are generally similar to the first embodiment shown in FIG. 1;

[0013] FIGS. 5 and 6 are schematic plan views of a fourth embodiment of an atmospheric water harvester according to the invention illustrating the atmospheric water harvester in two different operational configurations;

[0014] FIG. 7 is a schematic end view illustrating a variant of the embodiment of an atmospheric water harvester shown in FIGS. 5 and 6; and

[0015] FIG. 8 is a schematic plan view illustrating a variant of the embodiment of an atmospheric water harvester shown in FIGS. 5 and 6.



DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0016] FIG. 1 shows a first embodiment 100 of an atmospheric water harvester (AWH) according to the invention. The apparatus for drawing in and exhausting air and refrigeration causes water vapor to be condensed into liquid water within an enclosed apparatus so that it can be collected. The apparatus 100 may be placed out-of-doors, where it is surrounded by moist air. Ambient air 102 is drawn into the AWH 100 under suction and expelled under pressure. This AWH 100 includes an airflow system having an intake 105; an air filter 110; and air passages 116, 120 upstream from an impeller or fan 125. The impeller/fan 125 is responsible for drawing air into and forcing it through the apparatus 100 and into an exhaust chamber 135, from which the air exits through vents 138 (venting air is indicated by dashed-stem arrows) in the external vented wall 137 of the high-pressure exhaust chamber 135. The refrigeration system in general includes an evaporator (cooling member) 140 in which liquid refrigerant is allowed to vaporize, thereby causing the evaporator 140 to become cold and cooling the air passing across it so as to condense water from the air; and a compressor 150, in which the refrigerant gas from the evaporator 140 is compressed into a liquid by the combination of higher pressure and cooling of the refrigerant by air forced through a condenser 145.

[0017] Ambient air 102 is drawn in through the filter assembly 110, which may include more than one filter or type of filter, into the pre-evaporator air passage 116. Water is condensed from the air on the evaporator/heat exchanger 140 as the air is pulled through it. Condensation on the evaporator is the key process of atmospheric water harvesting. The condensation process is made as efficient as possible by using a high-thermal-transfer heat exchanger for the evaporator, for instance, a narrow-bore PF<2 >heat exchanger manufactured by the Modine Manufacturing Company. In order to prevent aluminum or other metals from the evaporator from being dissolved in condensing water, a coating is applied to the evaporator 140. The coating also may have antibacterial properties. Among, but not limited to, examples of this type of coating are a silver ion-containing epoxy available from Burke Industrial Coatings and another (Alcoat 5000 or similar) available from Circle-Prosco that also offers corrosion protection and may assist shedding of water from the condensing surface of the evaporator 140.

[0018] Regarding the compressor 150, a fixed or a variable speed compressor may be used. In one configuration of an AWH according to the invention, a fixed speed compressor, which is the simplest type and is most commonly used in refrigeration apparatus, is used. Such compressors are cycled on and off to minimize their running time. They are commonly operated along with a temperature-sensing device 155 that measures and controls the system superheat, which is the difference between the temperature of the gas entering the compressor 150 and the evaporation temperature of the liquid refrigerant within the evaporator 140. This device 155 (e.g., a thermostatic expansion valve (TXV or TEV), amongst other types of electronic and mechanical devices) is located between the condenser 145 and the evaporator 140. It controls temperature in the evaporator 140, in which vaporization of the refrigerant is directly related to cooling potential, by metering the flow of fluid refrigerant through the system. In an alternate configuration, a variable speed compressor 150 is used, which runs almost continuously but only as fast as necessary to maintain the desired pressure differential between the evaporator 140 and the condenser 145. A temperature-sensing device 155 that measures and controls the system superheat may be used with this sort of variable-speed compressor as well. In either of these configurations, a cut-off switch (not shown here), which is operated by sensors that detect freeze-up on the evaporator, turns off the compressor to allow ice to melt before restarting.

[0019] In the AWH embodiment 100 shown in FIG. 1, the evaporator 140 is in a vertical orientation, as shown in FIG. 2a. Water (black, single stem arrows) 158 formed on the upper evaporator surfaces flows down over the subjacent evaporator surfaces, which has the effect of amalgamating the water into rivulets as well as droplets as it flows from the evaporator 140 to the subjacent water collector 163. Because rivulets are more coherent water masses with higher mass to surface area ratios, they are less liable to lose water to the airstream moving at about a 90 degree angle across the flowing condensed water. Additionally, the water passing from the evaporator 140 to the water collection tank 163 may be only very slightly affected by air flow, which does not impinge toward the water collection tank 163.

[0020] With an alternate orientation of the evaporator as shown in FIG. 2b, water is removed from a horizontally oriented evaporator (also labeled 140) by forced air moving in the same direction as the condensed water separating from the evaporator 140. Water droplets 146 flow directly downward (single-stem black arrows) under the combined influence of gravity and forced air into the water collection tank 163. Water is more rapidly removed following condensation, which may have the result of reducing overcooling of already condensed water and allowing better heat transfer than in the case of coalescing water flowing over the evaporator. This is because water on the evaporator 140 acts as an insulator against heat transfer between the evaporator surface and the moist air 114. This horizontal orientation minimizes run-off of amalgamated or rivulet/coalesced water on the evaporator surface in favor of keeping most of the water in the form of droplets until it leaves the evaporator. However, droplets 146 have to cross the exhaust air path 118 and may be entrained in the air. Angled evaporators (not illustrated) would have attributes intermediate between upright or vertical and horizontal evaporators.

[0021] Water that has condensed on the evaporator 140 flows downward by gravity into a water collection region tank 163 beneath the evaporator and then into a removable water collection tank (not shown) that is from five to ten gallons or greater in capacity. Multiple tanks allow users to carry water from the water harvester. Alternatively, water may be pumped from the collection tank by a pump 167, located in the body of the AWH, through an industry-standard replaceable water filter 170 that is located in a compartment 175 that is isolated from the airflow passages within the apparatus. Treated water 190 that has passed through the water treatment system 170 remains under pressure after passing through the filter and exits from ports (not shown) at either or both the top and sides of the apparatus 100. (A straight-through water filter body without a filter may be used to produce water that is to be used for industrial purposes or that is otherwise not required to be treated to drinking water standards.)

[0022] Air exiting from the evaporator on which water has condensed then passes into an air passage 120 under suction caused by the fan/impeller 125. The air from the fan/impeller 125 then passes through a downstream air passage 130 and through the vaned condenser 145, where the air cools the compressed refrigerant that is being pumped to the condenser 145 from the compressor 150. After heat exchange warms it, the exhaust air passes into an exhaust chamber 135 from which it is exhausted through louvers in the walls of the AWH 100, the approximate locations of which are shown by arrows.

[0023] In a suitable configuration of the AWH 100, the impeller or fan 125 is capable of running at variable speed, which is controlled by varying electrical current or voltage. This allows the impeller or fan to force air through the apparatus at different velocities to optimize water production on the evaporator with respect to the electrical energy consumed. A variable speed impeller or fan allows the airflow over the evaporator to be varied, optimizing water production by, for instance, increasing fan speed for high humidity air or preventing or remediating unintended freeze-up where slower airflow could otherwise allow the air to reach a dew point below freezing. (Slowly moving air can be cooled to lower temperatures and has a greater likelihood of reaching dew points below freezing, regardless of the original air temperature.) Alternatively, the fan or impeller may be fixed speed, which may be less efficient under a wide range of input air temperature and humidity conditions but less expensive to implement and not significantly more expensive to operate under consistently humid conditions such as may be found on tropical, low-lying, smaller islands.

[0024] Sealed electronic controls and computer systems that control the refrigeration and airflow system for all embodiments of this invention are integrated in a control pad (not shown) that is located in the top cover of the water harvester for easy operation. In order to prevent overheating of the electronic control pad, the bottom surface of the electronic control pad is a conduction heat exchanger that is exposed to the cold airflow stream upstream and/or downstream from the condenser. Thus, heat that may be produced within the pad or by heating of the pad externally by heat exchange with ambient air or heating by the sun may be removed and the pad kept within operating temperature conditions.

[0025] In the embodiment 100, the compressor 150 is located within the exhaust air chamber 135. Where a compressor is used that is designed to be cooled internally, for instance using refrigerant discharge inside the compressor, there is no need for other cooling of the compressor. With that type of compressor, it is possible to insulate it with noise-absorbing material for quieter operation. The air within this chamber is slightly over-pressured with respect to ambient air outside the apparatus, which allows for distribution of air within the chamber 135 in the direction of sidewall vents. Air vents that form a large proportion of the side of the enclosure are located generally in the exterior sidewall 137 of the exhaust chamber 135 (exhaust air shown by black arrows but actual vents may be widespread in the wall) in order to allow air to vent from the apparatus.

[0026] Two further embodiments 200, 300 will be described with reference to FIGS. 3 and 4, respectively, in which there are slight variations in the handling of air within the AWH following extraction of water from it. In these embodiments 200, 300 (as well as in another embodiment 400, as described below), similar system components are similarly numbered, but increased to the corresponding hundreds series to “match” the embodiment number 200, 300, 400. Unless otherwise described, the similarly numbered components are the same as or generally similar to those described above and may have similar attributes.

[0027] Where an AWH must be operated in very hot ambient temperatures, or where a compressor that requires external cooling is used, forced-air cooling may be provided by controlling airflow in two general manners. These are shown in FIG. 3, in which an embodiment 200 uses existing exhaust for cooling of the compressor 250, and in FIG. 4, in which an embodiment 300 uses a supplemental supply of ambient air for cooling the compressor 350. FIG. 3 shows airflow around the compressor 250 from the central part of the exhaust chamber 235 created by locating louvered sidewall vents 295 “downstream” from the compressor 250. This configuration forces air to pass the compressor 250 in exiting from the exhaust chamber 235. In the alternate embodiment 300 shown in FIG. 4, an internal partition 311 isolates the compressor 350 from the exhaust chamber 335. In this configuration, vents 313 in the outer hull of the AWH 300 allow air to be pulled in by suction into the air passage 320 upstream from the impeller 325.

[0028] The three embodiments 100, 200, 300 that have been described above will work best in high relative humidity (RH) conditions. In general, where RH is high, particularly where temperature is also high and relatively large amounts of water are dissolved in the air, condensation on the evaporator takes place by reducing the temperature of the humid air to the point where condensation initiates. Where intake air is at a high humidity, for instance in excess of 85% RH, water will begin to condense with relatively little energy consumed by chilling. The sensible heat of the humid air (which is the term applied to heat associated with temperature change) must be removed to lower the temperature of the air slightly and bring the air to 100% RH locally, at which point condensation is initiated. As condensation proceeds, the latent heat (which is that required to cause the water vapor to condense to liquid water) is removed by heat exchange on the evaporator. Following the initiation of condensation, both sensible heat and latent heat are removed from the air being processed in the AWH as the air temperature is further reduced slightly and water is condensed and extracted. When RH is low, on the other hand, it is beneficial to be able to remove sensible heat before the air reaches the evaporator so that the cooling potential of the evaporator continues to remove a minimum of sensible heat and a maximum of latent heat, which has the effect of maintaining the energy efficiency of water production. (High humidity ambient air requires very little additional cooling to initiate condensation.) The delivery of air to the evaporator at approximately 90-99% RH, which is the general range for humid ambient air, is the primary objective for the most economic water production through condensation.

[0029] A variable pre-cooling embodiment 400 of an AWH, which is configured to operate well under low as well as high ambient RH conditions and preferably at RH points in between, is illustrated in FIGS. 5 and 6. Most notably in comparison to the embodiments 100, 200, 300 described above, the embodiment 400 includes a variable flow geometry thermal economizer section 417 located upstream of the impeller 425 and its inlet air passageway 420. The thermal economizer section 417 is suitably housed within a forward extension of the AWH housing and includes an air-to-air heat exchanger 456 located between the evaporator 440 (i.e., downstream from the evaporator) and the impeller 425 (i.e., upstream of the impeller). Preferably, the heat exchanger 456 is directly connected to the evaporator 440 and the impeller entry air passageway 420, or is connected via ducting to those components, such that air does not seep out from between the evaporator and the heat exchanger or from between the heat exchanger and the impeller. A preferred air-to-air heat exchanger 456 is fabricated from thin-walled tubes (e.g., as available from Cesarroni Technologies); from thin-walled corrugated plastic plate (e.g., as available from Innergy Tech, AB Segerfroejd, or Greenbox); or from corrugated metal plate (e.g., as available from Xetex and Des Champs Technology). In general, such air-to-air heat exchangers include two sets (at least) of interleaved flow passageways that are typically arranged perpendicularly to each other. In the AWH embodiment 400, the heat exchanger 456 is arranged with 1) a first set of heat transfer flow passageways (not illustrated specifically) oriented longitudinally, i.e., generally aligned with the main or overall direction of flow through the AWH 400; and 2) a second set of heat transfer flow passageways (not illustrated specifically) that are oriented transverse to the first set of heat transfer flow passageways, i.e., laterally as in the embodiment 400 shown in FIGS. 5 and 6 or vertically.

[0030] Upstream of the heat exchanger 456, the air intake of the AWH 400, i.e., the entrance to the thermal economizer section 417, is configured to regulate the amount (if any) of air that flows through the second, transverse set of heat exchanger flow passageways. To that extent, a motorized sliding panel 446, mounted in a support or frame 433, is provided near the entrance to the thermal economizer section 417, and an airway partition 438 extends from a lateral mid-location—suitably but not necessarily the center—of the panel support or frame 433 to an end of the evaporator 440. Suitably, the panel 446 extends vertically from the top to the bottom of the thermal economizer section entrance; laterally, assuming the airway partition 438 abuts the frame 433 at the lateral center of the AWH 400, the panel 446 is slightly wider than half the width of the thermal economizer section entrance.

[0031] With this arrangement of the AWH intake, when the panel 446 is all the way to one side of the entrance to the thermal economizer section 417 (i.e., to one side of the airway partition 433) as shown in FIG. 5, a first inlet aperture 402 is formed on the opposite side of the airway partition 433. When the apparatus 400 is in this operational configuration, air enters the thermal economizer section 417 through the first inlet aperture 402 and flows through the transverse (e.g., lateral) set of air passageways through the air-to-air heat exchanger 456. The air then turns and flows through the evaporator 440, which cools/chills the air to condense moisture out of it, before the air flows through the longitudinal set of air passageways through the heat exchanger 456 and on to the impeller. Because the air flowing through the longitudinal set of heat exchanger air passageways has been cooled by the evaporator 440, it will absorb sensible heat from the air flowing through the transverse set of heat exchanger air passageways, thus pre-cooling the incoming air before it reaches the evaporator 440. This allows a greater percentage of the evaporator work to be directed to removing latent heat from the incoming air and thus improves water production efficiency.

[0032] On the other hand, as noted above, it is relatively easy to condense moisture from ambient air that has high RH. Therefore, it becomes less important or beneficial to pre-cool the air before it passes across the evaporator 440. In this case, the panel 446 may be moved all the way across the entrance to the thermal economizer section 417, to the opposite side of the airway partition 433, which opens up a second inlet aperture 403 (i.e., a bypass inlet) as shown in FIG. 6. When the apparatus 400 is in this operational configuration, air enters the thermal economizer section 417 through the second inlet aperture 403 and flows immediately over evaporator 440, then down to the fan/impeller 425 through the longitudinal set of heat exchanger air passageways, without first having flowed through the transverse set of heat exchanger air passageways for pre-cooling. This improves operational efficiency in terms of amount of water produced per unit of electricity consumed. In particular, air density increases with humidity, and resistance to flow (i.e., frictional drag) increases with air density. Therefore, by shortening the overall airflow distance, and in particular by bypassing the portion of the flow course passing through the transverse set of heat exchanger airflow passageways, airflow drag is reduced. This, in turn, reduces operational load on the fan or impeller 425 and hence the cost to drive the fan or impeller for a given volumetric flow rate of air through the AWH 400. Alternatively, for a given amount of electricity consumed, the fan or impeller can be run faster (assuming it has that capability), which allows more water to be produced in a given period of time and at a given operating cost.

[0033] In practice, the panel 446 may be positioned at various points between the two endpoints shown in FIGS. 5 and 6. Depending on the position of the panel 446, the relative sizes of the first and second inlet apertures 402, 403 will vary, which regulates the amount of air flowing through the transverse set of heat exchanger airflow passageways and hence how much pre-cooling of the incoming air is provided. Suitably, the position of the panel 446, and hence the relative sizes of the inlet apertures 402, 403, is controlled automatically by a computer controller (not shown), which receives information on ambient conditions from on-board temperature and humidity sensors (not shown). Using pre-programmed maps or lookup tables, and/or using sensors that measure internal humidity levels at the evaporator so as to provide feedback-based control, the controller adjusts the position of the panel 446 such that the intake air is cooled to the point that 90% to 99% RH air is passing across the evaporator and/or until, at some point, the pre-cooling potential is at a maximum. From that point to lower temperatures and RH, an increasing amount of sensible heat has to be removed from the incoming air by the evaporator 440, which means that increasing electricity must be used to produce relatively smaller amounts of water. With such an automatic configuration of the AWH, the speed of the fan/impeller 425 may also be adjusted automatically (assuming it has variable speed capability).

[0034] In a simpler implementation, automatic control over the position of the panel 446, and hence the sizes of the intake apertures 402, 403, may be omitted. In that case, it may be preferable for the AWH 400 to be configured with springs, cams, detents, etc. (not shown) such that the panel 446 stably assumes only the position shown in FIG. 5 or the position shown in FIG. 6, but not positions in between. The user would then manually move the panel to one side or the other depending on humidity existing generally at the time the AWH is being operated.

[0035] Furthermore, in the embodiment 400 of an AWH illustrated in FIGS. 5 and 6, the sizes of the two air intake apertures 402 and 403 are directly linked to each other and always vary inversely to each other as the position of the panel 446 changes. For finer control and optimization of efficiency (water produced per unit of electricity, water produced per unit of time, or water produced per volumetric unit of airflow), on the other hand, it may be desirable for the sizes of the air intake apertures to be independently controllable (preferably by computer). To that end, the air intake apertures may be formed as separate, louvered openings 402', 403', as illustrated in FIG. 7, sphincter openings, etc. (A variable speed fan/impeller is particularly suitable for use with such an embodiment to fine-tune operation of the AWH as much as possible.)

[0036] Alternatively, instead of controlling the amount of airflow through each of the inlets 402', 403' by varying the size of their openings, it is possible to regulate the relative amounts of airflow by controlling the speed of the air flowing through each opening. To that end, a variable speed fan or impeller 472, 473 can be provided in association with each opening 402', 403', as shown in FIG. 8. Such variable speed fans or impellers could be provided in addition to the variable speed fan or impeller 425 or, alternatively, instead of the fan or impeller 425.

[0037] Various attributes of the embodiments 100, 200, 300 of AWH's described above (e.g., variable speed refrigeration compressor) may be incorporated into the embodiment 400 of an AWH as well.

[0038] Reverting to more general discussion applicable to any of the embodiments disclosed herein, unwanted mixing between intake and exhaust air has the potential to reduce the humidity of the intake air, which would have the effect of increasing energy use and decreasing water production. The intake and exhaust are located on generally opposite sides of the apparatus to separate them as much as possible without using intake or exhaust pipe extensions. In still air, exhaust will generally tend to be propelled away from the apparatus while intake air will be drawn from the ambient air at the other end. Where a water harvester is operated outdoors, changing wind direction and velocity may be anticipated. Shift of wind direction will have an impact upon the potential for mixing intake and exhaust air, particularly when the wind is blowing from the exhaust end and toward the intake end of the water harvester. Optimum conditions for minimum mixing of intake and exhaust air occur when the wind is blowing generally on the intake and away from the exhaust.

[0039] A manual switch may be provided on the control panel (not shown) to initiate a timed cycle in which the air system operates but the condenser system is turned off. This allows air to be passed through the unit without water being condensed from the air. This provides for drying of the internal air courses and their surfaces (including the evaporator and condenser). At the initiation of the cleaning/drying cycle, dilute chlorine spray from a hand-pump rechargeable container is sprayed into the intake air stream in sufficient quantities so that all internal air passages, including the main condenser and water collection area, are sufficiently exposed to allow for effective sterilization of the system. The unit continues to run, which has the effect of drying the internal surfaces and leaving the unit dry. If it is to be operated again in a relatively short time or if it is to be stored in a dry, climate-controlled location, packing in an air-tight container may not be necessary. Where the unit may be off for more than a short time, it should be packed in a sealed manner.

[0040] Provision may be made for quick-fitting a backup hand pump so that water may be filter-treated or removed from the water harvester under pressure if the pump 167 fails. It is also possible to recover the water directly from the removable water tank by removing it and pouring the water out manually.

[0041] The apparatus is wheeled and has handles suitable for pulling or lifting, even on ground that is not flat or smooth. It is designed and fabricated to be robust and to be operated out of doors without regard for weather conditions. All embodiments of the water harvester are weather-proofed, with sealed electronics, louvered intakes, screening as part of the filter assembly 110 (all embodiments) and on intakes and exhausts. The apparatus is suitable for placement by hand, without mechanized lifting or towing equipment. It can be left in one location over a period of time and can be manually brought under cover for protection in advance of major storms and redeployed manually.

[0042] The foregoing disclosure is only intended to be exemplary of the methods and apparatus of the present invention. Departures from and modifications to the disclosed embodiments may occur to those having skill in the art. For example, while an air-to-air heat exchanger as disclosed and described may be preferred, other forms of heat exchangers such as heat pipes, a fluid loop recirculation system, or an inverse vapor compression refrigeration system running in tandem with the “primary” refrigeration section may be implemented. Furthermore, the evaporator of a vapor compression-based refrigeration system is but one type of cooling device that may be used to cool the incoming air. Other cooling devices such as thermoelectric cooling devices could also be used. The scope of the invention is set forth in the following claims...



ATMOSPHERIC WATER HARVESTERS WITH VARIABLE PRE-COOLING
US7954335

An atmospheric water harvester includes a cooling member over which humid air flows to condense moisture from the atmosphere. The cooling member may be the evaporator of a conventional, gas vapor-based refrigeration circuit. If a gas vapor-based refrigeration circuit is used, the compressor of the circuit may be variable speed. A fan or impeller used to move air through the system may also be variable speed. Preferred embodiments are reconfigurable between at least two operational configurations such that to varying degrees the incoming air may be pre-cooled, before it passes over the cooling member, by heat exchange with colder air that has already flowed over the cooling member.

FIELD OF THE INVENTION

[0003] The invention relates to atmospheric moisture harvesting and improvements in the efficiency of condensing water from air and in apparatus relating thereto. More particularly, the invention provides improved energy efficient extraction of water from air, particularly in outdoor settings and over a range of relative humidity.

BACKGROUND OF THE INVENTION

[0004] Atmospheric water harvesting is intended to produce water in the general vicinity of its place of use. Producing potable water near its place of use removes the requirement for either temporary or fixed water delivery systems such as pipelines and canals or temporary delivery systems such as bulk motorized water tankers. Production of high-quality water at or near its place of use is superior to transporting bottled drinking water, which requires substantial consumption of energy for delivery and waste disposal. Water harvesters are also superior environmentally because water bottle disposal is not an issue; water bottles are reused in conjunction with water harvesting. In addition, the water produced from suitably designed and operated water harvesters is pure and suitable and safe for drinking with very little treatment.

[0005] Water harvesting has not generally been regarded as a replacement for conventional piped water supplies because of its relatively higher cost and lower volumes. In present water systems, there is an effective “waste” of public high quality water that is used for low-quality uses, such as flushing toilets and watering lawns.

[0006] Conventional water supplies are running short because of increased demand and local overuse of natural water supplies. In addition, the cost of conventional water supplies is increasing significantly. One of the drivers of increased water cost is the incorporation of desalinated water, which is relatively expensive to produce using current technologies, in the basic supply. Perceptions about the quality of public water supply has led to bottled water being used increasingly as a regular personal drinking water source, even though it is much more expensive than public water supply.

[0007] In atmospheric water harvesting, condensation of water is achieved by providing and maintaining a chilled surface upon which water from moist air condenses. This is well known as a byproduct of chilling air, as in air conditioning systems in which chilling the air is the objective or in air dehumidification systems in which the objective is to achieve relative dryness of the exhaust air. However, water produced as a byproduct in these systems is more expensive to produce than that which is produced in a water harvester apparatus that is optimized for energy efficient water production by not overcooling air or water. In addition, byproduct water quality is generally not suitable for drinking, and can be dangerous, without additional treatment that is not provided for by an apparatus that does not have water production as a primary objective.

[0008] Water harvesting apparatus that has been specifically designed to produce water from air already exists (but without the efficiency and sophistication of this invention) which allows the production of water of the same or superior quality as bottled water but without the delivery or environmental waste issues and in quantities that are suitable for personal or family use on a regular and extended basis. Water harvesting provides high quality potable water without the continued cost of producing bottles directly in proportion to the quantity of water delivered, at a lower cost than bottled water.

SUMMARY OF THE INVENTION

[0009] The present invention provides improved apparatus and methods for condensing water from air. These improvements involve, but are not limited to, an improved water condenser, improved condenser airflow control, a variable speed air impeller, forced air or conductive cooling of all heat-producing parts of the system, new intake air controls, and provision for system-controlled on/off switching for the compressor. The apparatus is robustly designed and constructed, is resistant to common handling vibration and shock, and is meant to be moved by hand locally although it may also be fixed. The apparatus is intended for use either outdoors or indoors in a semi-autonomous mode, and where air quality is generally good. Water is pumped from a removable collection tank underneath the evaporator into which water has flowed by gravity, either directly or through a water treatment system to the user. Although the water exiting the water harvester has the character of distilled water and is very pure, for prolonged drinking of this water alone, some of the produced water should be remineralized.

[0010] Preferred embodiments are reconfigurable between at least two operational configurations such that to varying degrees incoming air may be pre-cooled, before it passes over a cooling member, by heat exchange with colder air that has already flowed over the cooling member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will now be described in greater detail in connection with the Figures, in which:

[0012] FIG. 1 is schematic plan view of a first embodiment of an atmospheric water harvester according to the invention;

[0013] FIGS. 2a and 2b are schematic side views of two alternative orientations, respectively, of a heat exchanger/evaporator used in an atmospheric water harvester according to the invention;

[0014] FIGS. 3 and 4 are schematic plan views of second and third embodiments, respectively, of an atmospheric water harvester according to the invention, which second and third embodiments are generally similar to the first embodiment shown in FIG. 1;

[0015] FIGS. 5 and 6 are schematic plan views of a fourth embodiment of an atmospheric water harvester according to the invention illustrating the atmospheric water harvester in two different operational configurations;

[0016] FIG. 7 is a schematic end view illustrating a variant of the embodiment of an atmospheric water harvester shown in FIGS. 5 and 6;

[0017] FIG. 8 is a schematic plan view illustrating a variant of the embodiment of an atmospheric water harvester shown in FIGS. 5 and 6;

[0018] FIGS. 9 and 10 are schematic views (either plan or side elevation; either orientation would be acceptable) of a fifth embodiment of an atmospheric water harvester according to the invention illustrating the atmospheric water harvester in two different operational configurations;

[0019] FIGS. 11 and 12 are schematic views (either plan or side elevation; either orientation would be acceptable) of a sixth embodiment of an atmospheric water harvester according to the invention illustrating the atmospheric water harvester in two different operational configurations; and

[0020] FIGS. 13 and 14 are schematic diagrams illustrating so-called “split-condenser” refrigeration systems with the condensers arranged in parallel and in series, respectively, that can be incorporated into any of the atmospheric water harvester embodiments disclosed herein.

[ Figures 1-8 : See
US8627673 above ]

       

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0021] FIG. 1 shows a first embodiment 100 of an atmospheric water harvester (AWH) according to the invention. The apparatus for drawing in and exhausting air and refrigeration causes water vapor to be condensed into liquid water within an enclosed apparatus so that it can be collected. The apparatus 100 may be placed out-of-doors, where it is surrounded by moist air. Ambient air 102 is drawn into the AWH 100 under suction and expelled under pressure. This AWH 100 includes an airflow system having an intake 105; an air filter 110; and air passages 116, 120 upstream from an impeller or fan 125. The impeller/fan 125 is responsible for drawing air into and forcing it through the apparatus 100 and into an exhaust chamber 135, from which the air exits through vents 138 (venting air is indicated by dashed-stem arrows) in the external vented wall 137 of the high-pressure exhaust chamber 135. The refrigeration system in general includes an evaporator (cooling member) 140 in which liquid refrigerant is allowed to vaporize, thereby causing the evaporator 140 to become cold and cooling the air passing across it so as to condense water from the air; and a compressor 150, in which the refrigerant gas from the evaporator 140 is compressed into a liquid by the combination of higher pressure and cooling of the refrigerant by air forced through a condenser 145.

[0022] Ambient air 102 is drawn in through the filter assembly 110, which may include more than one filter or type of filter, into the pre-evaporator air passage 116. Water is condensed from the air on the evaporator/heat exchanger 140 as the air is pulled through it. Condensation on the evaporator is the key process of atmospheric water harvesting. The condensation process is made as efficient as possible by using a high-thermal-transfer heat exchanger for the evaporator, for instance, a narrow-bore PF<2 >heat exchanger manufactured by the Modine Manufacturing Company. In order to prevent aluminum or other metals from the evaporator from being dissolved in condensing water, a coating is applied to the evaporator 140. The coating also may have antibacterial properties. Among, but not limited to, examples of this type of coating are a silver ion-containing epoxy available from Burke Industrial Coatings and another (Alcoat 5000 or similar) available from Circle-Prosco that also offers corrosion protection and may assist shedding of water from the condensing surface of the evaporator 140.

[0023] Regarding the compressor 150, a fixed or a variable speed compressor may be used. In one configuration of an AWH according to the invention, a fixed speed compressor, which is the simplest type and is most commonly used in refrigeration apparatus, is used. Such compressors are cycled on and off to minimize their running time. They are commonly operated along with a temperature-sensing device 155 that measures and controls the system superheat, which is the difference between the temperature of the gas entering the compressor 150 and the evaporation temperature of the liquid refrigerant within the evaporator 140. This device 155 (e.g., a thermostatic expansion valve (TXV or TEV), amongst other types of electronic and mechanical devices) is located between the condenser 145 and the evaporator 140. It controls temperature in the evaporator 140, in which vaporization of the refrigerant is directly related to cooling potential, by metering the flow of fluid refrigerant through the system. In an alternate configuration, a variable speed compressor 150 is used, which runs almost continuously but only as fast as necessary to maintain the desired pressure differential between the evaporator 140 and the condenser 145. A temperature-sensing device 155 that measures and controls the system superheat may be used with this sort of variable-speed compressor as well. In either of these configurations, a cut-off switch (not shown here), which is operated by sensors that detect freeze-up on the evaporator, turns off the compressor to allow ice to melt before restarting.

[0024] In the AWH embodiment 100 shown in FIG. 1, the evaporator 140 is in a vertical orientation, as shown in FIG. 2a. Water (black, single stem arrows) 158 formed on the upper evaporator surfaces flows down over the subjacent evaporator surfaces, which has the effect of amalgamating the water into rivulets as well as droplets as it flows from the evaporator 140 to the subjacent water collector 163. Because rivulets are more coherent water masses with higher mass to surface area ratios, they are less liable to lose water to the airstream moving at about a 90 degree angle across the flowing condensed water. Additionally, the water passing from the evaporator 140 to the water collection tank 163 may be only very slightly affected by air flow, which does not impinge toward the water collection tank 163.

[0025] With an alternate orientation of the evaporator as shown in FIG. 2b, water is removed from a horizontally oriented evaporator (also labeled 140) by forced air moving in the same direction as the condensed water separating from the evaporator 140. Water droplets 146 flow directly downward (single-stem black arrows) under the combined influence of gravity and forced air into the water collection tank 163. Water is more rapidly removed following condensation, which may have the result of reducing overcooling of already condensed water and allowing better heat transfer than in the case of coalescing water flowing over the evaporator. This is because water on the evaporator 140 acts as an insulator against heat transfer between the evaporator surface and the moist air 114. This horizontal orientation minimizes run-off of amalgamated or rivulet/coalesced water on the evaporator surface in favor of keeping most of the water in the form of droplets until it leaves the evaporator. However, droplets 146 have to cross the exhaust air path 118 and may be entrained in the air. Angled evaporators (not illustrated) would have attributes intermediate between upright or vertical and horizontal evaporators.

[0026] Water that has condensed on the evaporator 140 flows downward by gravity into a water collection region tank 163 beneath the evaporator and then into a removable water collection tank (not shown) that is from five to ten gallons or greater in capacity. Multiple tanks allow users to carry water from the water harvester. Alternatively, water may be pumped from the collection tank by a pump 167, located in the body of the AWH, through an industry-standard replaceable water filter 170 that is located in a compartment 175 that is isolated from the airflow passages within the apparatus. Treated water 190 that has passed through the water treatment system 170 remains under pressure after passing through the filter and exits from ports (not shown) at either or both the top and sides of the apparatus 100. (A straight-through water filter body without a filter may be used to produce water that is to be used for industrial purposes or that is otherwise not required to be treated to drinking water standards.)

[0027] Air exiting from the evaporator on which water has condensed then passes into an air passage 120 under suction caused by the fan/impeller 125. The air from the fan/impeller 125 then passes through a downstream air passage 130 and through the vaned condenser 145, where the air cools the compressed refrigerant that is being pumped to the condensor 145 from the compressor 150. After heat exchange warms it, the exhaust air passes into an exhaust chamber 135 from which it is exhausted through louvers in the walls of the AWH 100, the approximate locations of which are shown by arrows.

[0028] In a suitable configuration of the AWH 100, the impeller or fan 125 is capable of running at variable speed, which is controlled by varying electrical current or voltage. This allows the impeller or fan to force air though the apparatus at different velocities to optimize water production on the evaporator with respect to the electrical energy consumed. A variable speed impeller or fan allows the airflow over the evaporator to be varied, optimizing water production by, for instance, increasing fan speed for high humidity air or preventing or remediating unintended freeze-up where slower airflow could otherwise allow the air to reach a dew point below freezing. (Slowly moving air can be cooled to lower temperatures and has a greater likelihood of reaching dew points below freezing, regardless of the original air temperature.) Alternatively, the fan or impeller may be fixed speed, which may be less efficient under a wide range of input air temperature and humidity conditions but less expensive to implement and not significantly more expensive to operate under consistently humid conditions such as may be found on tropical, low-lying, smaller islands.

[0029] Sealed electronic controls and computer systems that control the refrigeration and airflow system for all embodiments of this invention are integrated in a control pad (not shown) that is located in the top cover of the water harvester for easy operation. In order to prevent overheating of the electronic control pad, the bottom surface of the electronic control pad is a conduction heat exchanger that is exposed to the cold airflow stream upstream and/or downstream from the condenser. Thus, heat that may be produced within the pad or by heating of the pad externally by heat exchange with ambient air or heating by the sun may be removed and the pad kept within operating temperature conditions.

[0030] In the embodiment 100, the compressor 150 is located within the exhaust air chamber 135. Where a compressor is used that is designed to be cooled internally, for instance using refrigerant discharge inside the compressor, there is no need for other cooling of the compressor. With that type of compressor, it is possible to insulate it with noise-absorbing material for quieter operation. The air within this chamber is slightly over-pressured with respect to ambient air outside the apparatus, which allows for distribution of air within the chamber 135 in the direction of sidewall vents. Air vents that form a large proportion of the side of the enclosure are located generally in the exterior sidewall 137 of the exhaust chamber 135 (exhaust air shown by black arrows but actual vents may be widespread in the wall) in order to allow air to vent from the apparatus.

[0031] Two further embodiments 200, 300 will be described with reference to FIGS. 3 and 4, respectively, in which there are slight variations in the handling of air within the AWH following extraction of water from it. In these embodiments 200, 300 (as well as in another embodiment 400, as described below), similar system components are similarly numbered, but increased to the corresponding hundreds series to “match” the embodiment number 200, 300, 400. Unless otherwise described, the similarly numbered components are the same as or generally similar to those described above and may have similar attributes.

[0032] Where an AWH must be operated in very hot ambient temperatures, or where a compressor that requires external cooling is used, forced-air cooling may be provided by controlling airflow in two general manners. These are shown in FIG. 3, in which an embodiment 200 uses existing exhaust for cooling of the compressor 250, and in FIG. 4, in which an embodiment 300 uses a supplemental supply of ambient air for cooling the compressor 350. FIG. 3 shows airflow around the compressor 250 from the central part of the exhaust chamber 235 created by locating louvered sidewall vents 295 “downstream” from the compressor 250. This configuration forces air to pass the compressor 250 in exiting from the exhaust chamber 235. In the alternate embodiment 300 shown in FIG. 4, an internal partition 311 isolates the compressor 350 from the exhaust chamber 335. In this configuration, vents 313 in the outer hull of the AWH 300 allow air to be pulled in by suction into the air passage 320 upstream from the impeller 325.

[0033] The three embodiments 100, 200, 300 that have been described above will work best in high relative humidity (RH) conditions. In general, where RH is high, particularly where temperature is also high and relatively large amounts of water are dissolved in the air, condensation on the evaporator takes place by reducing the temperature of the humid air to the point where condensation initiates. Where intake air is at a high humidity, for instance in excess of 85% RH, water will begin to condense with relatively little energy consumed by chilling. The sensible heat of the humid air (which is the term applied to heat associated with temperature change) must be removed to lower the temperature of the air slightly and bring the air to 100% RH locally, at which point condensation is initiated. As condensation proceeds, the latent heat (which is that required to cause the water vapor to condense to liquid water) is removed by heat exchange on the evaporator. Following the initiation of condensation, both sensible heat and latent heat are removed from the air being processed in the AWH as the air temperature is further reduced slightly and water is condensed and extracted. When RH is low, on the other hand, it is beneficial to be able to remove sensible heat before the air reaches the evaporator so that the cooling potential of the evaporator continues to remove a minimum of sensible heat and a maximum of latent heat, which has the effect of maintaining the energy efficiency of water production. (High humidity ambient air requires very little additional cooling to initiate condensation.) The delivery of air to the evaporator at approximately 90-99% RH, which is the general range for humid ambient air, is the primary objective for the most economic water production through condensation.

[0034] A variable pre-cooling embodiment 400 of an AWH, which is configured to operate well under low as well as high ambient RH conditions and preferably at RH points in between, is illustrated in FIGS. 5 and 6. Most notably in comparison to the embodiments 100, 200, 300 described above, the embodiment 400 includes a variable flow geometry thermal economizer section 417 located upstream of the impeller 425 and its inlet air passageway 420. The thermal economizer section 417 is suitably housed within a forward extension of the AWH housing and includes an air-to-air heat exchanger 456 located between the evaporator 440 (i.e., downstream from the evaporator) and the impeller 425 (i.e., upstream of the impeller). Preferably, the heat exchanger 456 is directly connected to the evaporator 440 and the impeller entry air passageway 420, or is connected via ducting to those components, such that air does not seep out from between the evaporator and the heat exchanger or from between the heat exchanger and the impeller. A preferred air-to-air heat exchanger 456 is fabricated from thin-walled tubes (e.g., as available from Cesarroni Technologies); from thin-walled corrugated plastic plate (e.g., as available from Innergy Tech, AB Segerfroejd, or Greenbox); or from corrugated metal plate (e.g., as available from Xetex and Des Champs Technology). In general, such air-to-air heat exchangers include two sets (at least) of interleaved flow passageways that are typically arranged perpendicularly to each other. In the AWH embodiment 400, the heat exchanger 456 is arranged with 1) a first set of heat transfer flow passageways (not illustrated specifically) oriented longitudinally, i.e., generally aligned with the main or overall direction of flow through the AWH 400; and 2) a second set of heat transfer flow passageways (not illustrated specifically) that are oriented transverse to the first set of heat transfer flow passageways, i.e., laterally as in the embodiment 400 shown in FIGS. 5 and 6 or vertically.

[0035] Upstream of the heat exchanger 456, the air intake of the AWH 400, i.e., the entrance to the thermal economizer section 417, is configured to regulate the amount (if any) of air that flows through the second, transverse set of heat exchanger flow passageways. To that extent, a motorized sliding panel 446, mounted in a support or frame 433, is provided near the entrance to the thermal economizer section 417, and an airway partition 438 extends from a lateral mid-location—suitably but not necessarily the center—of the panel support or frame 433 to an end of the evaporator 440. Suitably, the panel 446 extends vertically from the top to the bottom of the thermal economizer section entrance; laterally, assuming the airway partition 438 abuts the frame 433 at the lateral center of the AWH 400, the panel 446 is slightly wider than half the width of the thermal economizer section entrance.

[0036] With this arrangement of the AWH intake, when the panel 446 is all the way to one side of the entrance to the thermal economizer section 417 (i.e., to one side of the airway partition 433) as shown in FIG. 5, a first inlet aperture 402 is formed on the opposite side of the airway partition 433. When the apparatus 400 is in this operational configuration, which provides a maximum amount of pre-cooling, air enters the thermal economizer section 417 through the first inlet aperture 402 and flows through the transverse (e.g., lateral) set of air passageways through the air-to-air heat exchanger 456. The air then turns and flows through the evaporator 440, which cools/chills the air to condense moisture out of it, before the air flows through the longitudinal set of air passageways through the heat exchanger 456 and on to the impeller. Because the air flowing through the longitudinal set of heat exchanger air passageways has been cooled by the evaporator 440, it will absorb sensible heat from the air flowing through the transverse set of heat exchanger air passageways, thus pre-cooling the incoming air before it reaches the evaporator 440. This allows a greater percentage of the evaporator work to be directed to removing latent heat from the incoming air and thus improves water production efficiency.

[0037] On the other hand, as noted above, it is relatively easy to condense moisture from ambient air that has high RH. Therefore, it becomes less important or beneficial to pre-cool the air before it passes across the evaporator 440. In this case, the panel 446 may be moved, for example, all the way across the entrance to the thermal economizer section 417 to the opposite side of the airway partition 433, which opens up a second inlet aperture 403 (i.e., a bypass inlet) as shown in FIG. 6. When the apparatus 400 is in this operational configuration, which provides a minimum amount of pre-cooling (for example, no pre-cooling at all) to the net airflow flowing through the airflow passageway before it flows across the evaporator 440, air enters the thermal economizer section 417 through the second inlet aperture 403 and flows immediately over evaporator 440, then down to the fan/impeller 425 through the longitudinal set of heat exchanger air passageways, without first having flowed through the transverse set of heat exchanger air passageways for pre-cooling. This improves operational efficiency in terms of amount of water produced per unit of electricity consumed. In particular, air density increases with humidity, and resistance to flow (i.e., frictional drag) increases with air density. Therefore, by shortening the overall airflow distance, and in particular by bypassing the portion of the flow course passing through the transverse set of heat exchanger airflow passageways, airflow drag is reduced. This, in turn, reduces operational load on the fan or impeller 425 and hence the cost to drive the fan or impeller for a given volumetric flow rate of air through the AWH 400. Alternatively, for a given amount of electricity consumed, the fan or impeller can be run faster (assuming it has that capability), which allows more water to be produced in a given period of time and at a given operating cost.

[0038] In practice, the panel 446 may be positioned at one or more points between the two endpoints shown in FIGS. 5 and 6, which provides for at least one, and suitably a plurality, of intermediate pre-cooling operational configurations between the maximum pre-cooling operational configuration and the minimum pre-cooling operational configuration. Depending on the position of the panel 446, the relative sizes of the first and second inlet apertures 402, 403 will vary, which regulates the amount of air flowing through the transverse set of heat exchanger airflow passageways and hence how much pre-cooling of the incoming air is provided. Suitably, the position of the panel 446, and hence the relative sizes of the inlet apertures 402, 403, is controlled automatically by a computer controller (not shown), which receives information on ambient conditions from on-board temperature and humidity sensors (not shown). Using pre-programmed maps or lookup tables, and/or using sensors that measure internal humidity levels at the evaporator so as to provide feedback-based control, the controller adjusts the position of the panel 446 such that the intake air is cooled to the point that 90% to 99% RH air is passing across the evaporator and/or until, at some point, the pre-cooling potential is at a maximum. From that point to lower temperatures and RH, an increasing amount of sensible heat has to be removed from the incoming air by the evaporator 440, which means that increasing electricity must be used to produce relatively smaller amounts of water. With such an automatic configuration of the AWH, the speed of the fan/impeller 425 may also be adjusted automatically (assuming it has variable speed capability).

[0039] In a simpler implementation, automatic control over the position of the panel 446, and hence the sizes of the intake apertures 402, 403, may be omitted. In that case, it may be preferable for the AWH 400 to be configured with springs, cams, detents, etc. (not shown) such that the panel 446 stably assumes only the position corresponding to the maximum pre-cooling operational configuration (e.g., the position shown in FIG. 5) or the position corresponding to the minimum pre-cooling operational configuration (e.g., the position shown in FIG. 6), but not positions in between, thus giving the AWH 400 just two operational configurations in practice. The user would then manually move the panel to one side or the other depending on humidity existing generally at the time the AWH is being operated.

[0040] Furthermore, in the embodiment 400 of an AWH illustrated in FIGS. 5 and 6, the sizes of the two air intake apertures 402 and 403 are directly linked to each other and always vary inversely to each other as the position of the panel 446 changes. For finer control and optimization of efficiency (water produced per unit of electricity, water produced per unit of time, or water produced per volumetric unit of airflow), on the other hand, it may be desirable for the sizes of the air intake apertures to be independently controllable (preferably by computer). To that end, the air intake apertures may be formed by flow-restricting devices such as separate, louvered openings 402', 403', as illustrated in FIG. 7, sphincter openings, etc. (A variable speed fan/impeller is particularly suitable for use with such an embodiment to fine-tune operation of the AWH as much as possible.) In this case, one or more intermediate pre-cooling configurations of the AWH can be obtained via intermediate sizes for either or both of the air intake apertures.

[0041] Alternatively, instead of controlling the amount of airflow through each of the inlets 402', 403' by varying the size of their openings, it is possible to regulate the relative amounts of airflow by controlling the speed of the air flowing through each opening. To that end, a variable speed fan or impeller 472, 473 can be provided in association with each opening 402', 403', as shown in FIG. 8. In that case, the different operational configurations of the AWH would correspond to the different speeds of the fans, with maximum speed of one fan and minimum speed of the other fan defining one operational configuration limit value for the overall AWH (i.e., a maximum pre-cooling configuration); minimum speed of the one fan and maximum speed of the other fan defining another operational configuration limit value (i.e., a minimum pre-cooling configuration); and intermediate fan speed settings for either or both of the fans defining a theoretically infinite number of potential intermediate pre-cooling operational configurations of the AWH. Such variable speed fans or impellers could be provided in addition to the variable speed fan or impeller 425 or, alternatively, instead of the fan or impeller 425.

[0042] Various attributes of the embodiments 100, 200, 300 of AWH's described above (e.g., variable speed refrigeration compressor) may be incorporated into the embodiment 400 of an AWH as well.

[0043] In the embodiment 400 of an AWH described above, the various operational configurations of the apparatus are determined by the relative configurations of the airflow passageways in the device, as defined by the position of the panel 446 and/or by the size of the inlet openings. (In the embodiment 400, the size of the inlet openings is defined by the position of the panel 446 as shown in FIGS. 5 and 6; in the other referenced AWH configurations (e.g., inlets having louvers or other types of flow restrictors), on the other hand, the size of the inlet openings is independent.) Alternatively, the different operational configurations of the AWH may be defined by different operating speeds of inlet fans. In each of these embodiments, the operational configuration of the AWH is defined by attributes of the AWH that affect the relative amounts of air flowing through the two sets of passageways in the air-to-air heat exchanger, and hence the amount of pre-cooling that is achieved.

[0044] As an alternative to that approach to controlling the amount of pre-cooling that is achieved, it is possible, by using the appropriate type of heat-exchanger, to control the pre-cooling by varying the position of the heat exchanger itself. This illustrated in the embodiments 500 and 600 shown in FIGS. 9-10 and 11-12, respectively, in which heat pipes are exemplarily used as the heat exchangers. (Heat pipes are preferred due to their relatively simple construction and due to the fact that they are completely passive, stand-alone devices in that they require no other apparatus (e.g., compressors, circulation pumps, etc.) or electrical input to work.)

[0045] (Heat pipes are fairly simple and efficient devices that can be used to transfer heat from one region to another. Essentially, a heat pipe consists of a sealed, partially evacuated tube made from heat-conducting material (e.g., metal) that has a small amount of a working refrigerant fluid contained inside of it. (The particular working fluid is selected depending on the temperatures of the environment in which the heat pipe will be used.) One end of the tube is disposed in the region where cooling is required (i.e., where heat needs to be removed), and the other end of the tube is disposed in the region where heat is to be discharged. In the region to be cooled, the working fluid will be in liquid form. As the working fluid absorbs heat from the region to be cooled, it boils or vaporizes, and a vapor pressure differential causes the vaporized fluid to move toward the opposite end of the heat pipe. At that opposite end of the heat pipe, heat is discharged from the working fluid, e.g., by dumping the heat into a heat sink, blowing cooling air across the end of the heat pipe, etc., which causes the working fluid to condense back into liquid form. In its simplest form, the heat pipe is empty except for the working fluid; in that case, the condensed working fluid may flow back to the heat-absorbing region due to gravity. In other forms, the heat pipe includes wicking material of some sort, and the condensed working fluid flows back to the heat-absorbing region due to capillary action.)

[0046] In the AWH embodiment 500 illustrated in FIGS. 9 and 10, a fixed-configuration airflow passageway 520 extends through the AWH from inlet 502 to outlet 504. The airflow passageway 520 is configured such that at least a segment of a downstream portion of the airflow passageway 520 is in proximity to at least a segment of an upstream portion of the airflow passageway. For example, as illustrated in FIGS. 9 and 10, the airflow passageway 520 may have a U-shape, in which case approximately half of the airflow passageway 520 (i.e., the portion to the left of the dividing wall 521 as shown in the figures) lies in proximity to the other approximate half of the airflow passageway 520 (i.e., the portion to the right of the diving wall 521 as shown in the figures). Evaporator (cooling member) 540 is located within the airflow passageway 520 and suitably extends all the way across it, as illustrated, so that all air flowing through the airflow passageway 520 must flow across/through it. (No other components of the refrigeration system in the embodiment 500 are illustrated, but they may be configured and located as per any of the embodiments described above.) One or more fans/impellers may be located at any suitable location to propel air through the airflow passageway 520. For example, fans 572, 573 may be provided at the inlet 502 and the outlet 504, respectively. The fan(s) may be single speed or variable speed depending on the desired sophistication of the system.

[0047] Furthermore, as noted above, the AWH embodiment 500 illustrated in FIGS. 9 and 10 uses heat pipes as the heat exchanger. In the embodiment 500, the heat exchanger 556 consists of an array of parallel, generally straight-tube configuration heat pipes. The heat exchanger 556 is repositionably mounted (e.g., by means of a pivot 557) so that it can be moved between a first position as shown in FIG. 9 and a second position as shown in FIG. 10, which two positions of the heat exchanger 556 define two operational configurations of the AWH embodiment 500. The first heat exchanger position (FIG. 9) is used when maximum pre-cooling of the incoming air is desired or required; the second heat exchanger position (FIG. 10), on the other hand, is used when minimum (e.g., no) pre-cooling of the incoming air is required or desired. As shown in FIG. 9, when the heat exchanger 556 is in the first position, one portion of it 559 (i.e., the portion having the heat-absorbing portions of the constituent heat pipes) extends into, and suitably all the way across, the portion of the airflow passageway 520 that is located upstream of the evaporator 540, and another portion 561 of the heat exchanger 556 (i.e., the portion having the heat-discharging portions of the constituent heat pipes) extends into, and suitably all the way across, the portion of the airflow passageway 520 that is located downstream of the evaporator 540.

[0048] Thus, when the heat exchanger 556 is in the first position (and, accordingly, the AWH 500 is in its first, maximum pre-cooling operational configuration), relatively warm incoming air will pass over or across the heat-absorbing portion 559 of the heat exchanger 556, thereby causing the working fluid inside the heat exchanger heat pipes to vaporize; that vaporization removes heat from the incoming air and hence pre-cools it before it passes across the evaporator 540. Furthermore, as it passes across the evaporator 540, the air being treated will be cooled even further as moisture condenses out of it. The cooled air then continues to flow downstream from the evaporator 540 and passes over or across the heat discharge portion 561 of the heat exchanger 556. The cooled air absorbs heat from the heat discharge portion 561, thus allowing the working fluid inside the heat pipes to condense back into a liquid, and carries the absorbed heat away with it as it exits the AWH 500 via outlet 504.

[0049] On the other hand, when pre-cooling of the incoming air is needed or desired to a lesser extent (e.g., if it is not needed or desired at all), the heat exchanger 556 is moved (e.g., pivoted) from the first position shown in FIG. 9 to the second position shown in FIG. 10 such that the AWH 500 is converted to its second, minimum pre-cooling operational configuration. (This may be accomplished either manually or automatically under computer control.) When it is in the second position, the heat exchanger 556 will reside essentially within either the downstream portion of the airflow passageway 520 relative to the evaporator 540 (as shown in FIG. 10) or the upstream portion of the airflow passageway 520 relative to the evaporator 540 (not shown). (The precise position of residence is less important than the fact that the heat exchanger should be so positioned/located as to have minimal impact on airflow, especially downstream from the evaporator 540.) Accordingly, the heat exchanger 556 will not extend between upstream and downstream portions of the airflow passageway; no heat transfer will take place from the former to the latter via the heat exchanger 556; and no pre-cooling will occur.

[0050] Another reconfigurable, generally similar embodiment 600 of an AWH is illustrated in FIGS. 11 and 12. In this embodiment, the fixed-configuration airflow passageway 620 is suitably straight and extends from inlet 602 at one end to outlet 604 at the opposite end. Evaporator (cooling member) 640 is located within the airflow passageway 620 and suitably extends all the way across it, as illustrated, so that all air flowing through the airflow passageway 620 must flow across/through it. (No other components of the refrigeration system in the embodiment 600 are illustrated, but they may be configured and located as per any of the embodiments described above.) One or more fans/impellers may be located at any suitable location to propel air through the airflow passageway 620. For example, fans 672, 673 may be provided near the inlet 602 and the outlet 604, respectively. The fan(s) may be single speed or variable speed depending on the desired sophistication of the system.

[0051] In the AWH embodiment 500 described above, the heat exchanger 556 is straight and the airflow passageway 520 is curved (e.g., U-shaped) so that when the heat exchanger 556 is in the first position it can extend between upstream and downstream portions of the airflow passageway 520 relative to the evaporator 540. Conversely, in the AWH embodiment 600, the airflow passageway 620 is essentially straight and the heat exchanger 656 is curved (e.g., U-shaped or C-shaped) so that part of it can be disposed upstream of the evaporator 640 and part of it can be disposed downstream of the evaporator 640 simultaneously. Thus, in the AWH 600, the heat exchanger 656—again exemplarily constructed using heat pipes—has a heat-absorbing portion 659 and a heat discharge portion 661 that are connected by means of bridge portion 663.

[0052] The first heat exchanger position (FIG. 11) is used when pre-cooling of the incoming air is desired or required; the second heat exchanger position (FIG. 12), on the other hand, is used when less (e.g., no) pre-cooling of the incoming air is required or desired. As shown in FIG. 11, when the heat exchanger 656 is in the first position, one portion of it 659 (i.e., the portion having the heat-absorbing portions of the constituent heat pipes) extends into, and suitably all the way across, the portion of the airflow passageway 620 that is located upstream of the evaporator 640, and another portion 661 of the heat exchanger 656 (i.e., the portion having the heat-discharging portions of the constituent heat pipes) extends into, and suitably all the way across, the portion of the airflow passageway 620 that is located downstream of the evaporator 640.

[0053] Thus, when the heat exchanger 656 is in the first position (and, accordingly, the AWH 600 is in its first, maximum pre-cooling operational configuration), relatively warm incoming air will pass over or across the heat-absorbing portion 659 of the heat exchanger 656, thereby causing the working fluid inside the heat exchanger heat pipes to vaporize; that vaporization removes heat from the incoming air and hence pre-cools it before it passes across the evaporator 640. Furthermore, as it passes across the evaporator 640, the air being treated will be cooled even further as moisture condenses out of it. The cooled air then continues to flow downstream from the evaporator 640 and passes over or across the heat discharge portion 661 of the heat exchanger 656. The cooled air absorbs heat from the heat discharge portion 661, thus allowing the working fluid inside the heat pipes to condense back into a liquid, and carries the absorbed heat away with it as it exits the AWH 600 via outlet 604.

[0054] On the other hand, when less (e.g., no) pre-cooling of the incoming air is needed or desired, the heat exchanger 656 is moved translationally (e.g., slid) from the first position shown in FIG. 11 to the second position shown in FIG. 12 such that the AWH 600 is converted to its second, minimum pre-cooling operational configuration. (This may be accomplished either manually or automatically under computer control.) When it is in the second position, either or both (as illustrated) of the heat-absorbing and the heat-discharging portions of the heat exchanger 656 will reside entirely outside of the airflow passageway 620 and will offer no impediment to smooth airflow. Accordingly, the heat exchanger 656 will not extend between upstream and downstream portions of the airflow passageway; no heat transfer will take place from the former to the latter via the heat exchanger 656; and no pre-cooling will occur.

[0055] Reverting to more general discussion applicable to any of the embodiments disclosed herein, unwanted mixing between intake and exhaust air has the potential to reduce the humidity of the intake air, which would have the effect of increasing energy use and decreasing water production. The intake and exhaust are located on generally opposite sides of the apparatus to separate them as much as possible without using intake or exhaust pipe extensions. In still air, exhaust will generally tend to be propelled away from the apparatus while intake air will be drawn from the ambient air at the other end. Where a water harvester is operated outdoors, changing wind direction and velocity may be anticipated. Shift of wind direction will have an impact upon the potential for mixing intake and exhaust air, particularly when the wind is blowing from the exhaust end and toward the intake end of the water harvester. Optimum conditions for minimum mixing of intake and exhaust air occur when the wind is blowing generally on the intake and away from the exhaust.

[0056] A manual switch may be provided on the control panel (not shown) to initiate a timed cycle in which the air system operates but the condenser system is turned off. This allows air to be passed through the unit without water being condensed from the air. This provides for drying of the internal air courses and their surfaces (including the evaporator and condenser). At the initiation of the cleaning/drying cycle, dilute chlorine spray from a hand-pump rechargeable container is sprayed into the intake air stream in sufficient quantities so that all internal air passages, including the main condenser and water collection area, are sufficiently exposed to allow for effective sterilization of the system. The unit continues to run, which has the effect of drying the internal surfaces and leaving the unit dry. If it is to be operated again in a relatively short time or if it is to be stored in a dry, climate-controlled location, packing in an air-tight container may not be necessary. Where the unit may be off for more than a short time, it should be packed in a sealed manner.

[0057] Provision may be made for quick-fitting a backup hand pump so that water may be filter-treated or removed from the water harvester under pressure if the pump 167 fails. It is also possible to recover the water directly from the removable water tank by removing it and pouring the water out manually.

[0058] The apparatus may be wheeled and has handles suitable for pulling or lifting, even on ground that is not flat or smooth, or it may be operated essentially fixed in place (as on a pedistal or platform, with no provision for hand moving. It is designed and fabricated to be robust and to be operated out of doors without regard for weather conditions. All embodiments of the water harvester are weather-proofed, with sealed electronics, louvered intakes, screening as part of the filter assembly 110 (all embodiments) and on intakes and exhausts. The apparatus is suitable for placement by hand, without mechanized lifting or towing equipment. It can be left in one location over a period of time and can be manually brought under cover for protection in advance of major storms and redeployed manually.

[0059] Furthermore, when a water harvester operates in very hot ambient conditions, the heat load on the refrigeration system as a whole may become very large—especially when it is performing a large amount of work. In that case, the ability to keep the refrigerant within an optimal range of operating temperatures may be exceeded at high heat loads if, as in the embodiments described above, there is essentially just a single stream of air passing through the AWH, with the air that passes over the evaporator being the same air and the only air that subsequently passes over the condenser to cool it. Therefore, to accommodate operation in hotter environments, any of the embodiments of an AWH illustrated herein and described above may be configured with a so-called “split condenser” refrigeration system. Such refrigeration systems are generally known and include multiple condensers (e.g., two), with additional, separate forced-air system(s) being provided to remove heat from the additional condenser(s) beyond the “primary” condenser. This supplements the cooling of the condenser by removing additional heat from the refrigerant stream and enhances total system heat rejection. The bias in the system toward greater heat rejection also helps to ensure that liquid refrigerant within the refrigeration system does not spontaneously begin to vaporize in an unintended manner.

[0060] FIG. 13 illustrates a split condenser refrigeration system that could be implemented in any of the AWH embodiments described above, with the condensers X45a and X45b arranged in parallel. (“X” is used as the first character of the reference numerals to indicate that the components could be as used in any of the AWH embodiments.) The refrigeration system includes the “primary” condensing unit X45a that operates directly with the water condensation system X15 (consisting of an evaporator and possibly other heat exchangers) and a compressor X50 (which may be implemented as more than one compressor operating in tandem). An impeller or fan X25 drives air through the primary system. (Open-stemmed arrows show airflow through the system and solid arrowheads on the refrigerant circulating system show flow direction.) Additional system heat rejection is achieved via “secondary” condensing unit X45b connected in parallel with the primary condensing unit X45a. In a parallel system, it possible to turn the secondary system on and off, which has the effect of reducing demand on the compressor, by opening or closing the upstream valve X88 (upstream with respect to the secondary condensing unit X45b) and the downstream valve X90, which valves link the secondary system to the primary recirculation refrigeration system. A separate fan X92 drives a supplemental airstream X94 across the secondary condensing unit X45b. Being able to close off the additional heat rejection capability is desirable in conditions of low system load (e.g., lower temperature and higher humidity) and to prevent unwanted refrigerant migration when portions of the system are turning on and off while operating in a low-demand mode. There are also technical improvements to system performance that can be achieved by bypassing the secondary condenser X45b during low load, though it adds system control complexity.

[0061] FIG. 14 illustrates a split condenser refrigeration system that could be implemented in any of the AWH embodiments described above, with the condensers X45a and X45b arranged in series. The primary condenser X45a, the water condensation system X15, the fan or impeller X25, and the airflow for the primary system are the same as in FIG. 13. The overall recirculation refrigeration system, however, consists of just a single loop that runs from the compressor X50 through first one condenser X45b and then the other condenser X45a. FIG. 14 shows the compressed refrigerant being passed first through the additional heat-rejecting condenser X45b and then through the primary condenser X45a. Although the order in which the refrigerant fluid passes through the two condensers could be reversed, our experience is that greater system performance is achieved by removing heat from the vicinity of the primary refrigeration system. There may also be a subcooler (not shown) associated with the primary condenser that ensures the refrigerant is liquid when it reaches the metering device that controls input of the refrigerant into the evaporator. Serial operation also requires fewer sensors, valves, and a simpler control system.

[0062] The foregoing disclosure is only intended to be exemplary of the methods and apparatus of the present invention. Departures from and modifications to the disclosed embodiments may occur to those having skill in the art. For example, while an air-to-air heat exchanger or heat pipes as disclosed and described may be preferred, other forms of heat exchangers such as a fluid loop recirculation system or an inverse vapor compression refrigeration system running in tandem with the “primary” refrigeration section may be implemented. Furthermore, the evaporator of a vapor compression-based refrigeration system is but one type of cooling device that may be used to cool the incoming air. Other cooling devices such as thermoelectric cooling devices could also be used. The scope of the invention is set forth in the following claims...



ATMOSPHERIC MOISTURE HARVESTING
US2010307181

The invention relates to atmospheric moisture harvesting. In particular, the invention capitalizes on the recognition that the air outside of a building usually has higher relative humidity than the air inside of the building. Therefore, the present invention relocates and/or modifies the configuration of an atmospheric moisture harvester such that more-moisture- laden, higher-relative-humidity outdoor air flows over the cooled water condensation surface of the atmospheric moisture harvester as the source for water to be delivered and consumed safely inside a dwelling or building. This increases the efficiency of atmospheric moisture harvesting and, at the same time, maintains the ability to access water obtained by the atmospheric moisture harvester from inside the building, thereby fostering ease of use.

FIELD OF THE INVENTION

[0002] The invention relates to atmospheric moisture harvesting, i.e., extracting water from the air for human consumption.

BACKGROUND OF THE INVENTION

[0003] Atmospheric moisture harvesting to obtain drinking water is known. In this process, air containing water vapor is passed over a cooled or chilled surface, and moisture contained within the air condenses on that surface. The condensed water is then collected and, typically after some form of treatment to kill germs (e.g., ultraviolet irradiation, exposure to ozone, etc.), it is suitable for human consumption.

[0004] To the best of my knowledge, where atmospheric moisture harvesters have been used to obtain drinking water, the conventional practice has been to install them and use them indoors or to produce water outdoors and deliver it there also.

SUMMARY OF THE INVENTION

[0005] The present invention capitalizes on the recognition that the air outside of a building usually has higher relative humidity than the air inside the building. This is due to the fact that buildings are usually climate-controlled, e.g., air-conditioned, which reduces the relative humidity of the air inside of them. Therefore, the present invention relocates and/or modifies the geometric layout or configuration of an atmospheric moisture harvester such that more-moisture-laden, higher-relative-humidity outdoor air flows over the cooled water condensation surface of the atmospheric moisture harvester as the source for water to be consumed. This increases the efficiency of atmospheric moisture harvesting. At the same time, the present invention maintains the ability to access the water obtained by the atmospheric moisture harvester from inside the building, thereby fostering ease of use.

[0006] Thus, according to the invention, an arrangement for atmospheric moisture harvesting has a building with an interior and an exterior and an atmospheric moisture harvester with a condensing surface over which air can flow; an air inlet; an air outlet; and a water outlet. The atmospheric moisture harvester's air inlet is in communication with the building's exterior such that outside air can flow over the condensing surface, and the atmospheric moisture harvester's water outlet is in communication with the building's interior such that water obtained from the outside air by means of the atmospheric moisture harvester can be accessed from inside the building.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention will now be described in greater detail in connection with the Figures, in which:

[0008] FIG. 1 is schematic illustration of a first embodiment of an atmospheric moisture harvesting arrangement according to the invention;

[0009] FIG. 2 is schematic illustration of a second embodiment of an atmospheric moisture harvesting arrangement according to the invention, which is a variant of the first embodiment illustrated in FIG. 1;

[0010] FIG. 3 is schematic illustration of a third embodiment of an atmospheric moisture harvesting arrangement according to the invention; and

[0011] FIG. 4 is schematic illustration of a fourth embodiment of an atmospheric moisture harvesting arrangement according to the invention.



DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0012] FIG. 1 shows a first embodiment 100 of an atmospheric moisture harvesting arrangement according to the invention. In this embodiment 100, an atmospheric moisture harvester 102 is located entirely outside of a building, the interior of which is labeled as 104, the exterior of which is labeled as 106, and an exterior wall of which is labeled as 108.

[0013] The atmospheric moisture harvester 102 suitably is configured according to any of the embodiments of atmospheric moisture harvesters disclosed in co-pending application Ser. No. 12/418,077 filed May 11, 2009 and entitled “Atmospheric Water Harvesters with Variable Pre-Cooling” (either with or without pre-cooling of the air before the air passes over the condensing surface), the entire contents of which are incorporated by reference. Alternatively, the atmospheric moisture harvester 102 may be configured with pre-cooling that is not variable. As illustrated by the double-stemmed arrows, outdoor air enters the atmospheric moisture harvester 102 through an inlet 110; the air is cooled as it passes over a condensing surface 112, which causes moisture in the air to condense into liquid form; and the air exits the atmospheric moisture harvester through an outlet 114. Assuming the atmospheric moisture harvester 102 is constructed in accordance with the embodiments disclosed in the above-referenced co-pending application, or as a generally similar device that has non-variable pre-cooling, the condensing surface 112 will be the surface of an evaporator in a vapor compression cycle-based refrigeration circuit. As illustrated by the dashed line 116, the atmospheric moisture harvester 102 is suitably powered by electricity from the building's electrical system. Additionally, controls for the atmospheric moisture harvester 102 are suitably located inside the building, and control signals are also represented by the dashed line 116.

[0014] As further illustrated in FIG. 1, liquid water that is obtained from the outside air by means of the atmospheric moisture harvester 102 exits the atmospheric moisture harvester 102 via water outlet 117 and passes into the interior 104 of the building via a conduit 118, e.g., a pipe. The water may be pumped from the atmospheric moisture harvester 102 into the building; alternatively, depending on the relative vertical positioning of the components in the arrangement 100, the water may simply flow into the building due to gravity.

[0015] In the embodiment 100 illustrated in FIG. 1, it is anticipated that the atmospheric moisture harvester 102 may be sized to produce on the order of about 20 gallons of water per day for an average family home. Therefore, a water treatment/reservoir unit 120 is located inside the building to store that water, and the water treatment/reservoir unit 120 receives the water flowing from the atmospheric moisture harvester 102. The water treatment/reservoir unit 120 may include one or more means such as a UV-based bacteriostat, an ozone generator, a chlorinator, etc., by means of which germs that may have entered the water can be neutralized. Additionally or alternatively, the water treatment/reservoir unit 120 may include various water filtration devices to remove particulate matter from the water, or that/those filtration device(s) may be provided directly in the atmospheric moisture harvester 102. (To obtain economies of scale, two or more atmospheric moisture harvesters 102 can be run in parallel, with a single, common air intake/air filtering mechanism serving all atmospheric moisture harvesters 102 in the group and all atmospheric moisture harvesters 102 in the group delivering water to a single, common water treatment/reservoir unit 120.)

[0016] When it is needed, water is withdrawn from the water treatment/reservoir unit 120, e.g., via a tap or spigot 122. Depending on the relative vertical positioning of the water inlet to and water outlet from the water treatment/reservoir unit 120 and/or whether there is pressurization in the system, the water may need to be pumped out of the water treatment/reservoir unit 120 or, alternatively, it may flow out of the water treatment/reservoir unit 120 due to gravity.

[0017] A second embodiment 200 of an atmospheric moisture harvesting arrangement according to the invention, which arrangement 200 is similar to the arrangement 100 illustrated in FIG. 1, is illustrated in FIG. 2. The embodiment 200 is generally identical to the embodiment 100, with the only difference being that the water treatment/reservoir unit 220 is located outside of the building instead of inside the building. Thus, the water outlet 217 from the atmospheric moisture harvester 202 is in indirect communication with the interior 204 of the building (e.g., via the water treatment/reservoir unit 220), in contrast to being in direct communication with the interior of the building as in the first embodiment 100. The two embodiments are otherwise identical, and the same reference numerals are used to identify the same components but are increased by 100 to a 200 “series” of reference numerals.

[0018] A third embodiment 300 of an atmospheric moisture harvesting arrangement according to the invention is illustrated in FIG. 3. In this embodiment 300, components that are essentially the same as those illustrated in FIGS. 1 and 2 and described above have correspondingly similar reference numerals, but in the 300 “series” of reference numerals. In the third embodiment 300, the atmospheric moisture harvester 302 extends through the wall 308 of the building. One portion, which houses the condensing surface 312, is located outside of the building so that outside air can flow easily across the condensing surface 312 as illustrated by the double-stemmed arrows, and the other portion, which has the water outlet 317, is located inside the building. The atmospheric moisture harvester 302 may be mounted in a window in a manner similar to that in which a window-unit air conditioner is mounted, or it may be mounted in some other opening in the wall 308 that is specifically configured to accommodate the atmospheric moisture harvester 302.

[0019] In this third embodiment 300, the atmospheric moisture harvester 302 is significantly smaller than the atmospheric moisture harvesters 102 and 202 employed in the first and second embodiments 100 and 200, respectively. Thus, the atmospheric moisture harvester 302 is foreseen as producing on the order of about five to ten gallons of water per day, and that amount of water can be stored in a reservoir (not shown) that is in the atmospheric moisture harvester 302, per se. Germicidal means and filtration means (not shown) are also housed within the atmospheric moisture harvester. Furthermore, depending on the vertical positioning of the water outlet 317 and the tap or spigot 322, water may be pumped out of the reservoir or it may flow out of the reservoir due to gravity.

[0020] Finally with respect to this third embodiment 300, although the atmospheric moisture harvester 302 is powered by electricity from the building's electrical system as in the above-described embodiments and as indicated by the dashed line 316, because the portion of the atmospheric moisture harvester 302 with the water outlet 317 is located inside the building and is therefore easily accessible, a control panel 324 may be provided directly on the atmospheric moisture harvester 302. Therefore, the dashed line 316 represents the flow of electricity to the atmospheric moisture harvester 302 but not the flow of control signals to or from the atmospheric moisture harvester.

[0021] Finally, a fourth embodiment 400 of an atmospheric moisture harvesting arrangement according to the invention is illustrated in FIG. 4. The fourth embodiment 400 is substantially similar to the third embodiment 300. Unlike the third embodiment 300, however, in the fourth embodiment 400, the atmospheric moisture harvester 402 is located entirely inside the building, which might be desired in order to limit access and/or possible damage to the atmospheric moisture harvester 402 or to reduce weatherproofing requirements. Therefore, to facilitate such an arrangement, an inlet duct 426 is provided to convey air from outside of the building to the inlet 410 in the atmospheric moisture harvester 402, and an outlet duct 428 is provided to convey the air from the outlet 414 in the atmospheric moisture harvester 402 back to the exterior of the building once that air has passed over the condensing surface 412. (In FIG. 4, the inlet and outlet ducts 426 and 428 are external to the atmospheric moisture harvester 402; it is possible, of course, for the ducting to be provided inside the atmospheric moisture harvester 402 as a component thereof.) Otherwise, the fourth embodiment 400 of an atmospheric moisture harvesting arrangement is essentially the same as the third embodiment 300.



Solar Atmospheric Water Harvester
US2008314058

The atmospheric water harvester (2) shown in FIG. (1) comprises a centrally located flue in the form of a tower 4 and a surrounding heating enclosure (6) for collecting incident solar energy to heat air which enters its periphery (8). With heating of the air in the heating enclosure (6), an updraught is created within tower (4) as the air from the heating enclosure (6) returns to the atmosphere from the open end of the tower A base structure (10) housing a plurality of wind turbines is provided around the base of the tower. As the heated air flows from the heating enclosure (6) into the tower it is harnessed to rotate the wind turbines. Each wind turbine (20) is provided with associated water collection apparatus (94) comprising a refrigeration system for cooling condensation surfaces to, or below, the dew point of the air to effect the condensation of water from the air onto condensation surfaces of the water collection apparatus for collection. The refrigeration system comprises a compressor (46) for compressing a refrigerant vapour for the cooling of the condensation surfaces and which is driven by the wind turbine (20).

FIELD OF THE INVENTION

[0001] The present invention relates broadly to condensing moisture from the atmosphere to provide a source of water and more particularly, to an atmospheric water harvester that utilises solar energy to drive production of the water.

BACKGROUND OF THE INVENTION

[0002] Changing climate patterns and global population increases means that water shortage is a significant issue. Methods and equipment to reduce water usage and produce drinking water are therefore being considered by organisations and governments throughout the world.

[0003] One of the problems with many of the currently available water production alternatives is that they require electrical energy to power drinking water generating equipment. This is particularly true with conventional water desalination plants employing reverse-osmosis technology. These alternatives have two main drawbacks, namely they generate pollution including greenhouse gases and are expensive to operate.

[0004] Over the last 15 to 20 years environmentally friendly solar tower power stations have been proposed for generating electricity from solar energy as an alternative to fossil fuel and nuclear power stations. These typically comprise a central tower structure surrounded by a heating enclosure for heating atmospheric air employing radiant solar energy. The heating enclosure opens into the lower region of the tower. Air that enters the heating enclosure is heated by the solar energy and the tower is of a height such that the temperature differential created between the heated air in the heating enclosure and the atmosphere at the top of the tower is sufficient to create an updraft within the tower as the heated air returns to the atmosphere. Electricity is generated by harnessing the updraft to drive one or more wind turbines. Solar tower power stations of this type can potentially be utilised to generate 200 MW of electric power or more depending on the dimensions of the heating enclosure and tower, and the intensity of available solar energy.

SUMMARY OF THE INVENTION

[0005] In a first aspect of the present invention there is provided an atmospheric water harvester, comprising:

[0006] a heating enclosure adapted to receive air from the atmosphere and be heated by solar energy to effect heating of the air;

[0007] a flue for return of the air from the heating enclosure to the atmosphere, the flue opening to the atmosphere at a sufficient height relative to the heating enclosure to create a draught within the flue;

[0008] at least one wind turbine arranged to be driven by the air returning to the atmosphere via the flue from the heating enclosure; and

[0009] at least one water collection apparatus comprising at least one condensation surface, and a refrigeration system for cooling the condensation surface to, or below, a dew point of the air to effect the condensation of airborne moisture onto the condensation surface for collection, the refrigeration system including a compressor for compressing refrigerant vapour and a condensor for condensing the compressed refrigerant vapour into liquid refrigerant, and the wind turbine being arranged to drive the compressor.

[0010] Typically, the condensation surface is arranged for contact with the air heated in the heating enclosure as the air returns to the atmosphere via the flue, the airborne moisture being condensed from the heated air. Alternatively, the condensation surface may be arranged for contact with further air from the atmosphere other than the air heated within the heating enclosure, the airborne moisture being condensed from the further air.

[0011] Typically also, the wind turbine is coupled to the compressor for driving the compressor. Preferably, the wind turbine incorporates a gear box that couples an output shaft of the wind turbine to the compressor. However, any other suitable coupling for mechanically coupling the wind turbine to the compressor for operation thereof may be utilised. In another embodiment, the wind turbine is coupled to an electric generator for generating electricity to power operation of the compressor.

[0012] Preferably, the water collection apparatus further comprises water collection means for collecting water condensed onto the condensation surface from the airborne moisture. Typically, the water is collected from the condensation surface by the water collection means by gravity. Preferably, the water collection means comprises a holding reservoir that receives the water from the condensation surface.

[0013] Preferably, the refrigeration system further comprises an evaporator for evaporation of the liquid refrigerant into refrigerant vapour to effect the cooling of the condensation surface. Most preferably, the condensation surface is a surface of the evaporator.

[0014] In a particularly preferred embodiment, the condensor is arranged for contact with air flowing from the condensation surface for cooling of the condensor to facilitate the condensing of the compressed refrigerant vapour into the liquid refrigerant.

[0015] Preferably, the atmospheric water harvester also comprises air flow control means for controlling flow rate of the air flowing into contact with the condensation surface to enhance the efficiency of the condensation of the airborne moisture onto the condensation surface.

[0016] Preferably, the air flow control means incorporates at least one adjustable air inlet operable to allow the air to flow to the condensor by-passing contact with the condensation surface such that the flow rate of the air flowing into contact with the condensor is adjusted compared to the flow rate of the air flowing into contact with the condensation surface. This allows increased air flow to the condensor to cool the condensor for condensing of the compressed refrigerant vapour, substantially without increasing the flow rate of the air to the condensation surface and thereby adversely affecting condensation of water from the air onto the condensation surface.

[0017] Preferably, the heating enclosure will comprise a plurality of radially directed heating chambers disposed around the tower and which open to a base region of the flue, each heating chamber being respectively provided with one or more air inlets for entry of the air from the atmosphere.

[0018] Typically, the, or each, wind turbine is arranged in a central region of the heating enclosure in which the flue is disposed. The wind turbine(s) generally incorporate blades rotatable about a turbine rotation axis. The turbine rotation axis may be vertical, horizontal or inclined at an oblique angle, respectively. In one or more embodiments, a wind turbine may be arranged within a lower region of the flue. Alternatively, the atmospheric water harvester may comprise a plurality of wind turbines, the wind turbines being radially orientated with respect to the central region of the heating enclosure and circumferentially spaced apart from each other. In a particularly preferred embodiment, each wind turbine is arranged to be driven by air flowing from a corresponding one of the heating chambers, respectively.

[0019] The flue may comprise a shaft, pipe, chimney, tower or other structure through which the air heated in the heating enclosure returns to the atmosphere. The flue may be substantially vertical or extend upwardly from the heating enclosure at an oblique angle. In a particularly preferred embodiment the flue will comprise a tower.

[0020] In a preferred embodiment the at least one water collection apparatus is disclosed at a position within the heating enclosure at which the average velocity the air returning to the atmosphere, whilst in use, is within a range of between 2.0 m/s and 3.5 m/s.

[0021] In another preferred embodiment the at least one water collection apparatus is disclosed at a position within the heating enclosure at which the average temperature of the air returning to the atmosphere, whilst in use, is substantially equal to, or no more than 5[deg.] C. greater than, an ambient temperature of air at a periphery of the heating enclosure.

[0022] The wind turbine may be mechanically coupled to the compressor by means of a rotatably mounted drive shaft extending from the turbine to the compressor. Alternatively, the turbine may be electrically coupled to the compressor by means of an electrical generator driven by the wind turbine so as to generate electricity that is conducted via conductors extending between the turbine to the compressor. In another embodiment the refrigeration system is disposed adjacent the wind turbine such that, in use, the refrigeration system is driven by the turbine to produce chilled gases that are communicated along at least one thermally insulated pipe from the refrigeration system to the condensation surface.

[0023] All publications mentioned in this specification are herein incorporated by reference in their entirety. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed anywhere before the priority date of this application.

[0024] Throughout this specification, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps, unless the context of the invention indicates otherwise.

[0025] In order that the nature of the present invention may be more clearly understood, preferred forms thereof will now be described, by way of example only, with reference to a number of preferred embodiments with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

[0026] FIG. 1 is a schematic side view of an atmospheric water harvester embodied by the present invention;

[0027] FIG. 2 is a schematic plan view of the atmospheric water harvester of FIG. 1;

[0028] FIG. 3 is a schematic partial cross-sectional view of the atmospheric water harvester of FIG. 1;

[0029] FIG. 4 is a schematic partial side cross-sectional view of a further atmospheric water harvester embodied by the present invention;

[0030] FIG. 5 is a schematic partial cross-sectional view of yet another atmospheric water harvester embodied by the present invention;

[0031] FIG. 6 is a schematic diagram of a refrigeration system of water collection apparatus of an embodiment of the present invention;

[0032] FIG. 7 is a schematic side view taken through B-B of FIG. 6;

[0033] FIG. 8 is a schematic diagram showing further water collection apparatus embodied by the present invention;

[0034] FIG. 9 is a schematic side view of another wind turbine of an embodiment of the present invention;

[0035] FIG. 10 is a schematic view showing water collection apparatus housed in the wind turbine of FIG. 9;

[0036] FIG. 11 is a schematic view showing operation of the refrigeration system of FIG. 6;

[0037] FIG. 12 is a schematic diagram of the refrigeration system of the water collection apparatus of FIG. 6;

[0038] FIG. 13 is a schematic side view of an alternative embodiment of an atmospheric water harvester;

[0039] FIG. 14 is a schematic side plan view of the embodiment shown in FIG. 13 with the omission of the roof of the heating enclosure so as to illustrate the interior of the heating chamber; and

[0040] FIG. 15 is a graph of the average air flow velocity versus distance from the outer periphery of the heating enclosure.



DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0041] The atmospheric water harvester 2 shown in FIG. 1 comprises a centrally located flue in the form of a tower 4 and a surrounding heating enclosure 6 for collecting incident solar energy to heat air which enters its periphery 8. With heating of the air in the heating enclosure 6, an updraught is created within tower 4 as the air from the heating enclosure 6 returns to the atmosphere from the open end of the tower. A base structure 10 housing a plurality of wind turbines is provided around the base of the tower. As the heated air flows from the heating enclosure 6 into the tower it is harnessed to rotate the wind turbines. As will be described further below, each wind turbine is provided with associated water collection apparatus comprising a refrigeration system for cooling condensation surfaces to, or below, the dew point of the air to effect the condensation of water from the air onto condensation surface(s) of the water collection apparatus for collection. The refrigeration system comprises a compressor for compressing a refrigerant vapour for the cooling of the condensation surfaces and which is driven by the wind turbine. A plan view of atmospheric water harvester 2 is shown in FIG. 2.

[0042] As shown in FIG. 3, the tower 4 is buttressed about its base by reinforced concrete and is supported by reinforced concrete foundations 14. The tower itself is fabricated from steel plate. The heating enclosure 6 has a canopy 16 held aloft by internal supporting walls. The canopy may be formed from any suitable material that permits ingress of solar energy into the interior of the heating enclosure. To enhance retention of heat within the enclosure, the internal walls supporting the canopy may be lined with corrugated zinc coated sheet metal. The heating enclosure thereby acts as a "greenhouse" for heating of the air to generate the updraught through the tower 4 to drive the wind turbines.

[0043] In the embodiment shown in FIG. 3, the heating enclosure 6 is divided into radial heating chambers 18 that fan outwardly from around the base 16 of the tower. Each heating chamber 18 houses a wind turbine 20 and opens into the tower 4 at one end and to the atmosphere via opposite respective openings defined in the periphery 8 of the heating enclosure 6. The heating chambers act to funnel air heated by the incident solar energy through respective confusor 22 regions thereof to each turbine. To minimise turbulent air flow resulting from passage of the air through the blades of the turbines, each heating chamber 18 is further provided with a diffusor region 24, the cross-sectional area of which increases with distance from the corresponding wind turbine 20 into the base of the tower. To minimise drag and turbulence, an arcuate exhaust passageway 26 is provided through the concrete buttress 12 for feeding the heated air from each heating chamber into the tower 4, respectively. The heating chambers 18 may be provided with heater beds to assist heating of the air, that are operable in times of low solar energy input or for night operation when solar energy is not available. The heater beds will typically comprise a plurality of heaters spaced apart along the length of each heating chamber. The heaters may be electric or gas fired and be automatically operated by a central monitoring system in response to decreases in air temperature detected by temperature sensors located within the heating chambers and/or the tower. Remotely controlled shutters can also be provided that are operable to partially or fully close the air inlet opening and corresponding exhaust passageway 26 of each heating chamber to enable the air to be heated to the necessary temperature prior to entering the tower 4. In this way, the flow of air from the heating chambers into the tower can be controlled to maintain the updraught through the tower and maximise efficiency of the atmospheric water harvester 2. That is, in times of lower solar energy availability, different ones of the turbines can be operated by controlling the flow of air through selected one(s) of the heating chambers 18 while others are closed to allow the air to reach a sufficient temperature, to maximise the production of water from the atmosphere for the prevailing atmospheric conditions and available solar energy. Controlling the updraught through the tower is particularly desirable in embodiments where a wind turbine is arranged within the lower throat region of the tower, as exemplified in FIG. 4.

[0044] A solar tower power station with a solar heating enclosure of the type described above with discrete heating chambers radiating outwardly from a central tower as outlined above is, for instance, described in U.S. patent application Ser. No. 10/341,559. That disclosure also exemplifies the structural detail of the heating enclosure and its contents are herein incorporated in their entirety. In some embodiments, the tower 4 may comprise a constricted region in which the wind turbine is arranged. The constriction within the tower provides a venturi type effect in which the air flowing up the tower is accelerated through the constriction. An arrangement of this type is for instance described in International Patent Application No. PCT/CA01/00885. As also described in International Patent Application No. PCT/EP2004/010091, the tower may be reinforced by one or more spoked reinforcement structures, each comprising wire cable spokes that are tensed between an outer pressure ring of the tower and an inner anchoring hub disposed in a transverse cross-sectional plane of the tower, respectively. However, it will be understood by persons skilled in the art that any suitable known such solar tower and heating enclosure arrangements may be employed.

[0045] Typically, the tower of an atmospheric water harvester 2 embodied by the present invention will be of a height to create an updraught sufficient to drive the wind turbine(s) 20 of the water harvester. Typically, the tower will have a height of at least 200 meters, more preferably a height of 400 meters or 500 meters and most preferably, a height of 800 meters or 1,000 meters or more. The diameter of the tower will normally be at least 50 meters, 75 meters or 100 meters or more. Most preferably, the tower will have a diameter of about 130 meters or more.

[0046] The heating enclosure 6 will typically have a canopy area of at least about 1,000 hectares, more preferably at least about 2,000 hectares and most preferably, a canopy area of at least about 4,000 hectares. The canopy 16 of the heating enclosure may, for instance, be provided by glass, polycarbonate sheeting, plastic film or a combination of the foregoing. Generally, the heating enclosure will be circular in form with a diameter of at least about 1,000 meters, more preferably at least about 2,000 meters or 3,000 meters and most preferably, a diameter of about 3,500 meters.

[0047] In the embodiment shown in FIG. 4, the output shaft 28 of the wind turbine 20 is rotatably supported within the tower 4 as indicated by the numeral 30 such that the blades 32 of the wind turbine are mounted in the throat of the tower for being rotated about turbine axis 34 with flow of the air from the surrounding heating enclosure 6 into the tower 4, as indicated by the arrows. In some embodiments the wind turbine further comprises a housing 36 in which the refrigeration system of the water collection apparatus is housed for condensing water from the air from the heating enclosure which enters the housing through air inlet 38 from the heating enclosure 6 before exiting the housing through air outlet 40 to the tower.

[0048] Rather than a single centrally located wind turbine, the embodiment of the atmospheric water harvester shown in FIG. 5 is provided with a plurality of wind turbines driven by heated air passing from corresponding respective heating chambers 18. While only two wind turbines are shown in FIG. 5, an atmospheric water harvester of this type will normally have a plurality of wind turbines equidistantly spaced circumferentially around the base of the tower for being driven by the passage of the heated air flowing from respective heating chambers into the tower. The housing 36 of each turbine houses a refrigeration system as described above for condensing water from the passing air. In a particularly preferred embodiment, thirty-six wind turbines are arranged around the tower, one wind turbine to each heating chamber, respectively.

[0049] The condensing of the water from the heated air will now be described with reference to FIGS. 6 to 12. Turning firstly to FIG. 6, the refrigeration system of the water collection apparatus disposed within housing 36 of a wind turbine 20 comprises an evaporator 42, a condenser 44 and a compressor 46. As can be seen, the compressor is coupled to the output shaft 28 of the wind turbine by a gear box 48. However, as will be readily apparent to persons skilled in the art, any suitable coupling for transferring rotational kinetic energy of the output shaft 28 to the compressor 46 may be used. For example, rather than a gear box, hydraulic couplings, including hydrostatic couplings, may be used.

[0050] The evaporator 42 is provided with a plurality of spaced apart fins through which the air from the heating enclosure flows and which provide condensation surfaces for the condensation of water from the air upon the condensation surfaces being cooled to, or below, the dew point of the air by the refrigeration system.

[0051] In order to assist in the optimisation of operational efficiency, the interior of the housing 36 is divided into separate compartments to which the air entering the housing is directed by air flow control means. More particularly, heated air from the heating enclosure 6 flowing into the housing 36 through air inlet 38 initially enters air intake chamber 50 from where it flows to evaporator 42 through compressor chamber 54 housing compressor 46. The flow of air from the air intake chamber 50 to the compressor chamber 54 is regulated by dampers of the air control means in the form of air intake valves 52. From the compressor chamber 54, the air flows into contact with the condensation surfaces of the evaporator 42 prior to entering condensor chamber 56 in which the condensor 44 is located. As the air contacts the condensation surfaces of the evaporator, heat is drawn from the air and water condenses on the condensation surfaces from where it flows under gravity into water collection means in the form of a funnel 58 which directs the water to a holding reservoir comprising a tank. From the tank, the water is pumped to an external storage reservoir.

[0052] The cooled air from the evaporator 42 then flows into contact with the condenser 44, drawing off heat from the condensor. This in turn cools refrigerant vapour within the condenser, facilitating the condensing of the refrigerant vapour into liquid refrigerant. The warmed dry air flowing from the condensor then exits the housing 36 of the wind turbine and flows into the tower 4 of the atmospheric water harvester. A hinged by-pass damper 60 of the air control means regulates the flow of air from the air intake chamber 50 into the condensor chamber 56 as will be further described below.

[0053] The air flowing through the housing 36 therefore serves two primary functions, namely providing a source of moisture which condenses onto the condensation surfaces of the evaporator for collection and secondly, to cool the condensor 44 for condensation of the refrigerant vapour of the refrigeration system into liquid refrigerant for effecting cooling of the evaporator upon being allowed to subsequently expand. The passage of the air through the compressor chamber also serves to cool the compressor 46 and its coupling to the output shaft of the wind turbine.

[0054] A wind turbine 20 typically requires a wind speed of at least about 6-7 m/s before it will rotate. Generally, a wind speed of at least about 2.0 m/s through the housing 36 of the wind turbine is required to create turbulent air flow therethrough for efficient condensation of water from the air and cooling of respective components of the refrigeration system. Water can, therefore, be effectively condensed from the air whenever there is sufficient wind generated by the flow of heated air from the heating enclosure 6 into the tower 4 to rotate the wind turbine. However, the flow of air through the evaporator 42 should be limited to about 3.5 m/s and preferably about 2.5 m/s to allow sufficient contact of the air with the condensation surfaces of the evaporator for condensation of the water. Accordingly, the air intake valves 54 and by-pass damper 60 are generally operated to limit air flow through the housing to this speed. Typically, the air will pass through a filter 62 prior to entering the evaporator as indicated in FIG. 11.

[0055] Rather than the compressor 46 being mechanically driven by rotation of the output shaft 28 of the wind turbine, embodiments may be provided in which the output shaft rotates an alternator 66 that generates electric power for driving the compressor 46.

[0056] A yet further wind turbine that may be employed in an atmospheric water harvester embodied by the present invention is shown in FIG. 9. This wind turbine is provided with a rotor 64 having wind vanes rather than blades as does the wind turbine of FIG. 6. This wind turbine also differs from that shown in FIG. 6 in that the air entering the housing of the wind turbine is less affected by the rotation of the rotor 64 and primarily arises from the natural flow of air passing from the heating enclosure 6 into the tower 4. In contrast, the exhaust air from the wind turbine shown in FIG. 6 is directed into the air inlet 38 of that wind turbine and so is substantially more turbulent. Air flow through the housing of the wind turbine of FIG. 9 is shown in FIG. 10.

[0057] The refrigeration system may be either a single pressure or dual pressure system, and provides sub-cooled liquid refrigerant to the evaporator for evaporation therewithin to effect the cooling of the condensation surfaces of the evaporator for condensation of the water from the passing air. The resulting heated refrigerant vapour is drawn from the evaporator 42 and passed to the condensor 44 for condensation to liquid refrigerant as described above. To enhance thermal efficiency, heat is drawn from the compressed liquid refrigerant by the cool condensed water collected from the evaporator via a heat exchanger 72 as shown in FIG. 11.

[0058] More specifically, as shown more clearly in FIG. 11, the heated refrigerant vapour is drawn through suction loop 68 from the lower region of the evaporator 42 to the compressor 46. The suction loop 68 traps and holds any liquid refrigerant which might pass from the evaporator, thereby preventing the liquid refrigerant from entering and potentially damaging the compressor. The refrigerant vapour is compressed and thereby heated in the compressor, prior to being discharged through hot gas loop 70 to the top of the condenser 44. The hot gas loop 70 traps any liquid refrigerant draining back from the condensor to the compressor 46.

[0059] Air flowing to the condenser 44 from the evaporator cools the high pressure hot refrigerant vapour in the condenser such that the refrigerant vapour condenses. The condensed liquid refrigerant is then cooled by the condensed water passing through heat exchanger 72. The cooled liquid refrigerant subsequently drains from the bottom of the condenser 44 into reservoir 74, prior to passing from the reservoir through a filter 76 which removes any contaminants and moisture from the liquid refrigerant. From the filter 76, the refrigerant travels along conduit 78, incorporating a sight glass 80 which allows a visual check for the presence of any moisture or bubbles in the liquid refrigerant.

[0060] The conduit 78 then feeds the now dry, cooled liquid refrigerant to a thermostatic expansion valve 82. As the liquid refrigerant passes through the valve, the pressure of the liquid refrigerant decreases. The resulting low pressure cold liquid refrigerant with some flash gas is fed from the expansion valve 82 into the evaporator 42 where the liquid refrigerant evaporates back into refrigerant vapour, drawing in heat from the condensation surfaces of the evaporator. The cooled condensation surfaces in turn draw heat from the air flowing into contact with the condensation surfaces effecting cooling of the air and condensation of the moisture therefrom onto the condensation surfaces.

[0061] As described above, for efficient operation the flow rate of the air is adjusted by the air control means to optimise condensation of water per unit volume of the ambient air flowing through the evaporator 42, and to maintain sufficient air flow to the condenser for heat transfer from the condenser to the air for achieving the condensing of the refrigerant vapour in the condenser. As will be understood, the refrigeration system is operated to cool the condensation surfaces of the evaporator without freezing the condensed water.

[0062] For any given prevailing atmospheric conditions, there is a specific humidity value measured in grams of water vapour per kilogram of the air. For example, a specific humidity of between 4.5 and 6 grams of moisture per kilogram of air correlates to a dry bulb temperature of between 1[deg.] C. and 6.5[deg.] C. In use, the water collection apparatus is operated to condense water from the ambient air entering the housing 36of a wind turbine such that the specific humidity of the air flowing from the evaporator to the condensor is reduced to a specific humidity correlating with a selected reference dry bulb temperature. The selected dry bulb temperature will typically be in the above temperature range and usually, will be in a range of from about 3.5[deg.] C. to about 5.5[deg.] C. and preferably, will be about 5[deg.] C. or below.

[0063] Turning now to FIG. 12, a temperature sensor 84 is provided for measuring the dry bulb temperature of the air passing from the evaporator 42 to the condensor 44. This temperature is compared by an automatic operation control system 86 with the selected reference dry bulb temperature which has been manually set in the control module. If the dry bulb temperature measured by the temperature sensor 84 increases above the set reference dry bulb temperature, the operation control system operates actuator 88 such that air intake 54 partially closes, thereby decreasing air flow through the evaporator 42. This in turn lowers the dry bulb temperature of the air leaving the evaporator.

[0064] As the flow rate of the air leaving the evaporator is decreased, the amount of cooled air from the evaporator available for cooling the condensor 44 also decreases. This results in a rise in the pressure of the refrigerant vapour in the condensor above the optimum pressure for the fixed refrigeration capacity of the refrigeration system. The pressure of the refrigerant vapour in the condensor is measured by a pressure sensor 90. In response to the increased pressure measured by the pressure sensor, the operation control system 86 operates actuator 92 to open. This increases the flow rate of air flowing to the condensor while simultaneously substantially maintaining the flow rate of the air A to the evaporator. The increased flow rate of air to the condensor removes heat from the condensor such that the pressure of the refrigerant vapour in the condensor reduces to the optimum pressure for condensation of the compressed refrigerant vapour.

[0065] The operation control system 86 continues to monitor the dry bulb temperature of the air leaving the evaporator 42 and the pressure of the refrigerant vapour in the condensor 44 is respectively measured by temperature sensor 84 and pressure sensor 90. If the dry bulb temperature sensed by the temperature sensor decreases below the set reference dry bulb temperature, the operation control system 86 operates to increase the speed of air flowing through the evaporator and decreases the flow of air by-passing the evaporator through by-pass damper 60.

[0066] The monitoring is repeated at regular intervals to ensure optimum efficiency of the apparatus and thereby, maximum condensation of water from the air. The provision of such timing circuits is well within the scope of persons skilled in the art. For different latitudes or atmospheric conditions, the reference dry bulb temperatures set in the controller 86 may be adjusted. The operation control system may comprise a central computerised control system that monitors the operation of each of the water collection apparatus, or control modules each of which monitors the operation of water collection apparatus associated with at least one wind turbine 20.

[0067] The level of water collected in the holding tank from the condensation surfaces of the evaporator is monitored by float switches or other suitable water level sensing arrangements. Suitable such systems are for instance described in International Patent Application No PCT/AU2004/001754, the contents of which are also expressly incorporated herein in their entirety. When sufficient water accumulates in the holding tank, it is pumped from the holding tank to an external storage reservoir which may be in the form of an open dam or a larger tank from where the water can be pumped to consumers.

[0068] While the water will normally be condensed from the heated air flowing to the tower from the heating enclosure 6 as shown in the accompanying figures, other embodiments may be provided wherein air is ducted to the water collection apparatus associated with the wind turbine(s) through conduits from exterior of the heating enclosure without being heated within the heating enclosure with the air that flows from the heating enclosure to the tower. Similarly, the exhaust air from the water collection apparatus may be returned to the atmosphere via return conduits or otherwise be expelled into the tower for return to the atmosphere. In such embodiments, the air may be drawn through the inlet conduits by fans arranged within the housing(s) of the wind turbine(s) or by rotors arranged within the housings that are coupled or otherwise driven by the wind turbine(s) or the draught within the heating chamber.

[0069] In the embodiment illustrated in FIGS. 13 and 14 the water collection apparatuses 94 are remote from the wind turbines. More particularly, the water collection apparatuses 94 are disclosed at positions within the heating enclosure 6 at which the average velocity of the air returning to the atmosphere, whilst in use, is within a range of between approximately 2.0 m/s and 3.5 m/s. In contrast, the wind turbines 20 are generally disposed at positions of maximum average air speed velocity so as to maximise their power output. The average air velocity profile that arises within the heating enclosure due to the escaping of air from the tower 4 generally increases from a minimum at or near the periphery 8, through to a maximum at or near the tower 4. An example of such an average air velocity profile is illustrated in the graph of FIG. 15. From this graph it can be seen that each of the water collection apparatuses 94 in this preferred embodiment are disposed at a radial distance from the outer periphery 8 of between approximately 11% and 21% of the total radius of the heating enclosure 6 so as to ensure that the average air velocity to which the water collection apparatuses 94 are exposed is within the optimum range of between approximately 2.0 m/s and 3.5 m/s. It will be appreciated, however, that alternative embodiments may have differing average air velocity profiles to that shown in FIG. 15. Hence, the optimum positioning of the water collection apparatuses 94 within such alternative embodiments should be determined with reference to the average air velocity profile that is applicable to the particular embodiment.

[0070] If it is desired to minimise the amount of refrigerating effort required to cool the air to at or below the dew point, it is generally preferable to minimise the temperature of the air incident upon the condensation surfaces. Hence, in some embodiments (not illustrated) the water collection apparatuses are positioned within the heating enclosure with this in mind. A typical air temperature profile generally increases from a minimum air temperature at or near the periphery of the heating enclosure, through to a maximum air temperature at or near the tower 4. It therefore follows that positioning the water collection apparatuses at or proximate to the periphery of the heating enclosure is optimum if it is desired to reduce the incident air temperature. In this way it is possible to ensure that the average temperature of the air that is incident upon the condensing surface is no more than approximately 15[deg.] C. or 110[deg.] C. or preferably 5[deg.] C. greater than, or substantially equal to, the ambient temperature of the air that enters at the periphery of the heating enclosure.

[0071] The embodiments described in the preceding two paragraphs entail a physical separation of the wind turbines 20 from the condensation surfaces of the water collection apparatuses 94. In the embodiment illustrated in FIGS. 13 and 14, the wind turbines 20 are mechanically coupled to the water collection apparatuses 94 by means of rotatably mounted elongate drive shafts 96 extending from each wind turbine 20 to a respective refrigeration system 98 associated with a respective water collection apparatus 94. In an alternative embodiment the wind turbines are electrically coupled to the compressors of the water collection apparatuses by means of an electrical generator driven by the wind turbine so as to generate electricity that is conducted via conductors extending between the turbine to drive the compressor. In yet another alternative embodiment, the refrigeration system is disposed adjacent the wind turbine such that, in use, the refrigeration system is driven by the wind turbine to produce chilled gases that are communicated along thermally insulated pipes that extend from the refrigeration system to the condensation surface.

[0072] Preferred forms of solar atmospheric water harvesters embodied by the present invention therefore provide at least one of a number of advantages including:

the utilisation of solar energy as a power source for the production of water;
the air leaving the water collection apparatuses is dehumidified as compared to the air entering the heating enclosure, thereby assisting to lessen corrosion problems within the heating chamber and tower;
the avoidance of air pollution associated with coal or other fuel fired power stations; and
the production of large quantities of replenishable potable water.

[0077] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. Accordingly, the specific embodiments illustrated are preferred and not limiting. For example, rather than a flue comprising an upright tower as shown in the accompanying figures, an embodiment may be provided in which the flue is in the form of a heat outlet pipe which follows the upward slope of a hill or mountainside, the pipe being supported at regular intervals along its length up the hill or mountainside by mounts to which the pipe is secured by brackets. The pipe may also be formed from a material transparent to at least some solar energy or, for instance, have a transparent side facing the sun, for facilitating further heating of the air within the pipe by incident solar energy as the air flows upwardly within the pipe. As will be understood, the heating enclosure 6 may also be situated on the side of a hill or inclined ground to maximise exposure of the canopy 16 of the enclosure to incident solar energy. Alternatively, or as well, the canopy may have a number of inclined surfaces, each being disposed to maximise the surface area of the heating enclosure exposed to the incident solar energy at different times during the day, respectively. For instance, an eastern side of the canopy may be inclined to face the rising sun during morning hours while a western side of the canopy has an opposite inclination so as to face the sun in the latter part of the afternoon.



Apparatus and method for harvesting atmospheric moisture
US6945063

An atmospheric water harvester extracts water from high relative humidity air. The temperature of the surface of a condensation member is lowered in the presence of moist air to promote condensation of water vapor on its surface, and the water so obtained by condensation is collected. The atmospheric water harvester includes a photovoltaic member that generates electricity to power the refrigeration of the condensation member. At least as much electrical power is produced as is used to condense the water vapor so that no additional sources of electrical power are required. Each atmospheric water harvester (or array of harvesters) is rapidly installed and then operated in an unattended state for considerable periods of time. Arrays of autonomous atmospheric water harvesters can be installed as free-standing units or as roofs on either new or existing buildings.

2. FIELD OF THE INVENTION

[0002] In general, the invention relates to "harvesting" water from the atmosphere.

3. BACKGROUND OF THE INVENTION

[0003] Provision of water is a problem where rainfall is scarce, strongly seasonal, or where there are relatively small catchment areas and little natural local water storage. This is particularly true for remote locations such as oceanic islands and for coastal areas where the fresh water table is relatively shallow or not well developed because of subsurface geological conditions.

[0004] On oceanic islands, for example on Bermuda in the central Atlantic Ocean, water is provided mainly by rain catchment on most buildings, including virtually all private homes. Water is stored locally in cisterns into which the run-off flows directly. Because the water is derived from rainwater run-off from roofs, there is often both biological and sediment contamination. When rainfall is sparse, the collection of water is insufficient for demands and where populations are high, water rationing is common. Low rainfall also increases the level of pollution. In addition, where roofs are of such a size that not enough water can be captured directly from run-off for local use, for instance from roofs of factories on Saipan in the western Pacific, water must be provided from another source.

[0005] Similarly, the capture of rainwater and pumping of shallow wells for human use, including industrial purposes, in localities where there is a very thin fresh water groundwater layer on top of a saline-saturated substrate substantially degrades the environment on many of these islands and related localities. Capture of rainwater prevents it from recharging fragile groundwater systems.

[0006] Water companies in most of the United States plan water requirements based on an average water use for an individual in an urban environment of about 100 gallons per day. Where water supplies are restricted, such as in most of the Caribbean Islands for instance, 50 gallons per day represents average per capita total water use. In arid areas or where water infrastructure is poor, average per capita consumption (for all purposes) is commonly below 10 gallons per day, even when water supplies are normal. Natural water resources often do not meet local demands now, and population growth is increasing. Thus, new sources of fresh water for human consumption are required now.

[0007] In addition, relatively smaller amounts of high quality potable water are required from time to time where natural or man-made disasters render water and electrical infrastructure unusable, or in remote locations where distributed water supplies are required and no water infrastructure exists.

SUMMARY OF THE INVENTION

[0008] One source of fresh water that has not previously been drawn upon in any known significant manner is the atmosphere, especially in those areas near warm seawater where the atmosphere contains significant volumes of water vapor. In these areas, the amounts of water in the atmosphere that can be recovered is related to both the initial relative humidity and the temperature to which this warm, moisture-laden air can be cooled so that water condenses. Where relative humidity is high, considerable amounts of water are held in the air.

[0009] Table 1 shows two examples of the amount of water contained in warm air at about sea level, which examples are typical of most tropical and sub-tropical regions near large bodies of water. Where the temperature of the fully saturated air is higher, more water is present as vapor, and where colder temperatures can be reached during the condensation phase, more water may be recovered.

TABLE 1

1  2  3  4
Air Temperature,  Relative  Water Content/  Water Content/
[deg.] F.  Humidity, %  100 m<3 >air, g  100 m<3 >air, liters
80  100  2531  2.54
Cooled To:     Water Condensed  Water Condensed
70  100  686  0.69
60  100  1204  1.21
50  100  1591  1.59
40  100  1876  1.88
Air Temperature,  Relative  Water Content/  Water Content/
[deg.] F.  Humidity, %  100 m<3 >air, g  100 m<3 >air, liters
80  80  2027  2.04
Cooled To:     Water Condensed  Water Condensed
70  100  182  0.18
60  100  700  0.70
50  100  1087  1.09
40  100  1372  1.37

[0010] Water content and production potential for 80% and 100% relative humidity. More cooling is required to produce water from air in which the relative humidity is less than 100%. The amount of water condensed listed in columns 3 and 4 relates only to condensed water vapor removed when the humid air temperature is lowered to the indicated levels. Remaining air is saturated with water vapor at the temperature to which the air has been cooled.

[0011] The present invention provides a new method and apparatus for obtaining high quality water, of distilled water character and in which virtually no dissolved solids are present, by using a light-weight, self-contained, passive system for harvesting atmospheric moisture when relative humidity is high. In locations where there is high relative humidity throughout the diurnal cycle, water may be condensed and collected according to the invention both during the day as well as at night, whenever relative humidity is high enough. Even in locations where the air tends to have low relative humidity during the heat of the day, the relative humidity usually rises during the night and will often be at near 100% humidity for long periods of the diurnal cycle. This condition prevails even in most semi-arid and arid regions. At these times of high relative humidity, water may be collected according to the invention using autonomous atmospheric water harvesters.

[0012] Apparatus according to the invention, referred to as an "autonomous atmospheric water harvester," includes two main parts, namely 1) one or more water vapor condensation and collection members each having a surface upon which water is condensed and collected, and 2) an energy-gathering member such as a photovoltaic panel that produces electricity to power condensation-driving refrigeration. Additionally, the apparatus includes a frame to secure the photovoltaic member and the one or more condensation members firmly in place. An air passage is formed between the energy-gathering member (photovoltaic member) and the condensation member, and additional air passages are formed between condensation members where there are more than one condensation member.

[0013] High relative humidity air passes through the air passage or passages, where it is cooled. Water vapor from the chilled air, which becomes supersaturated with moisture, thus condenses onto the condensation member. The condensed water flows under the force of gravity off the condensation member and is collected in a separate container.

[0014] Electricity used to power the cooling (i.e., refrigeration) necessary to condense the water vapor is produced by the apparatus itself, which can operate in a stand-alone, essentially unattended mode for long periods of time. Where it is needed or desired to store electrical energy, batteries or fuel cells are used for each autonomous atmospheric water harvester or group of harvesters. Moreover, surplus electrical energy produced during sunlight hours (i.e., electrical energy in excess of that required for cooling and condensation) may be added into an existing electrical grid, from which grid electricity later may be drawn when no electricity is being produced by the water harvesters. Where no electrical grid exists to absorb large quantities of electrical energy, local energy storage systems or methods for storing the excess electricity in the form of potential energy, e.g., pumping water into towers or up-hill reservoirs (hydroelectric pump storage), may be employed.

[0015] The purpose of the water harvester is not to dramatically reduce the temperature of the air passing through the apparatus (as in an air conditioning unit) or to primarily dry the air (as in an air dehumidifier), but to only chill the air sufficiently to condense the required amounts of water from relatively humid air. The air exiting the water harvester may be only slightly chilled and may still contain considerable moisture. Thus, the water harvester constitutes a third, and new type of apparatus for the treatment of air, which is designed to achieve the objective of condensing water from air.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will now be described in greater detail in connection with the drawings, in which:

[0017] FIG. 1 is a generalized perspective view of an autonomous atmospheric water harvester according to the invention;

[0018] FIG. 2 is a generalized end view of an autonomous water harvester having two condensation members;

[0019] FIG. 3 is a diagrammatic view of a planar disposition of cooling coils above the condensation member, which is also cooled by its proximity to the coils;

[0020] FIG. 4 is a generalized perspective view of a dendritic drainage system incised in the surface of a condensation member upon which condensation takes place directly;

[0021] FIG. 5 is a generalized perspective view of corrugations and fins on the refrigerated surface of a condensation members;

[0022] FIG. 6 is a generalized view of the underside of three water harvesters joined in an array, with provision for grouping refrigerant circulation and electrical-energy gathering into a single system;

[0023] FIG. 7 is a generalized perspective view of an array of water harvesters with screened air passages with a fan assembly in the joined apex;

[0024] FIG. 8 is a diagrammatic perspective view of a fan assembly employed in the array illustrated in FIG. 7; and

[0025] FIG. 9 is a diagrammatic perspective view of a portable water harvester according to the invention.



DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0026] Preferably, an autonomous atmospheric water harvester according to the invention condenses atmospheric water vapor to yield liquid water while producing at least sufficient electrical power for its own operation.

[0027] In one embodiment, as shown in FIG. 1, an autonomous atmospheric water harvester 100 according to the invention has a rigid, panel-type photovoltaic member 110, a panel-type condensation member 115, and a frame or support member 118 on each side (nearside shown in phantom for clarity) that hold the members securely in place with respect to each other and that give the entire autonomous atmospheric water harvester a box-section configuration having substantial physical strength. The side frame members are also used to affix multiple autonomous atmospheric water harvesters together and/or to supports.

[0028] The panel-type members of the harvester are illustrated in FIG. 1 as flat for diagrammatic simplicity. It should be understood, however, that a variety of surface configurations may be used to facilitate the condensation, collection, and removal of the harvested water. The water produced by condensation should be essentially pure and suitable for potable use after relatively little treatment, e.g., light chlorination. Because the product water is essentially distilled water, it will be necessary or desirable to add salts or mix a certain proportion of seawater with it so that the water is suitable for continuous human or animal consumption.

[0029] Where a water- and weather-proof abutting connection is required between two or more water harvesters, a cap-type sealer strip 144, which has inert and long-lived properties similar to silicone rubber, may be fitted over the edges of the frame member 118 which extend above the photovoltaic member 110 so that adjacent harvesters may be joined together in side-to-side fashion. The sealer strip may be held in place by friction, with glue, or some other means such as bolts or snap-clips. Other means of sealing adjoining panels, such as adhesive or O-ring sealing, may also be used.

[0030] The ends 122, 124 of each autonomous atmospheric water harvester 100 are open so that an air passage 120 is formed through the harvester assembly. Moist air from the ambient air mass surrounding the autonomous atmospheric water harvester flows or is caused to flow across exposed, refrigerated apparatus or the refrigerated face of the condensation member 115. As the moist air flows through the harvester, i.e., across the condensation member 115, water vapor condenses out of it and accumulates on the surface of the condensation member 115. Therefore, materials such as metals that maintain electric charge are used within the air passage to retard the establishment and growth of microorganisms, so long as no hazardous material residue is added to the product condensed water.

[0031] The ends of the air passage 120 are preferably screened to keep larger animals, e.g., birds and bats which could roost in the air passage, out of the air passage 120. The screens are removable so that they can be removed for periodic cleaning of the air passage.

[0032] Water harvesters are arranged in a tilted position so that water that condenses or gathers on the condensing surface flows, under the influence of gravity, to the lower end 124 of the harvester. At the lower end 124, water is collected by a catch trough or physical barrier 126 that causes the water to flow laterally along the panel such that it can be transported away from the condensation member by a pipe 138.

[0033] Electrical energy to power the requisite cooling is generated by the photovoltaic member 110, which is the uppermost part of the autonomous atmospheric water harvester 100. In addition to water obtained via condensation and collection of atmospheric moisture, water is also obtained from rainwater run-off. A catch-trough 128 is located at the lower end of the photovoltaic member 110 to catch rainwater as it flows down along the surface of the photovoltaic member 110, and rainwater caught by the barrier 128 is removed to storage through piping 134.

[0034] The amount of rainwater run-off obtained or captured using the atmospheric water harvester 110 will be at least as large as that obtained from any roof of the same size as the harvester, and this water, which is likely to be polluted with material washed from the roof, can be used for all non-potable purposes or treated to potable quality water standards. This run-off water is kept separate from the water collected by the condensation member 115 because the rainwater may be polluted with matter such as dust, pollen, and bird excreta that falls onto the surface of the member 110. The photovoltaic member 110 shelters the condensation member 115 from matter falling from or generally settling out of the air, thereby helping to preserve the quality of the water produced by condensation of water vapor.

[0035] Insulation 112 is affixed to the back of the photovoltaic member 110 so that as the photovoltaic member 110 warms due to its direct exposure to sunlight, it is substantially prevented from warming air in the airway 120, which would otherwise make the condensation member less efficient when water is being produced by condensation during the day. In the embodiment shown in FIG. 1, there is only a single condensation member 115. In this embodiment, the condensation member 115 may also have a layer of insulation on its exterior (i.e., lower) surface to help isolate the cooling region from unwanted heat that would decrease overall efficiency.

[0036] Although only one condensation member 115 and one air passage 120 are shown in FIG. 1, more than one condensation member may be provided, which would form more than one air passage. Thus, in another embodiment 100' as shown, for example FIG. 2, the addition of a second condensation member 125 that forms a second airway 130 increases the water production capability of the harvester 100'. In addition, where a condensation member (e.g., condensation member 115 in FIG. 2) has air passages on both sides, both sides of the condensation member may have cooling surfaces or coils (illustrated in more detail below) on which water is condensed. Water condensing on coils located along the lower surface of the condensation member 115 will drip onto the condensation member below it, from which it is collected. Thus, the more air passages and condensation members an autonomous atmospheric water harvester has, the greater the potential for water production. Thus, assuming electric power, the ambient humidity of the moist air, and the structure carrying the harvester or group of harvesters is adequate, increased water production can be achieved by producing water from more than one condensation and water collection surface.

[0037] The number of cooling members and air passages-for instance, the number of harvesters to be joined along a common air passage axis, thereby forming a longer, compound airway, or the number of harvesters to be joined side-by-side-and the required airflow that will yield optimal water harvesting for particular installations is a function of the area to be covered and the local atmospheric conditions. In circumstances where a maximum amount of water condensation is required, as many condensation members and air passages as is desirable and practical may be employed.

[0038] A presently preferred system for cooling the condensation member 115 is conventional refrigeration. Conventional refrigeration devices operate using a vapor- or a vapor-liquid cycle to absorb heat from one region and disperse it in another region. In such systems, a refrigerant is compressed, thereby generating heat that is dispersed in air remote from the area in which refrigeration is required. The compressed refrigerant is then circulated through pipes or other conduits to the area where cooling is required, where pressure within the refrigeration system conduits is reduced. The refrigerant expands and vaporizes, cooling as it does so. The cooled refrigerant is then circulated through the region in which cooling is desired. This cooled refrigerant is warmed via heat exchange with the region, and the region is cooled.

[0039] In an autonomous atmospheric water harvester, the area in which chilling is required is the area within the air passage or air passages 120, 130, at the surface of each condensation member or immediately adjacent to it, so that the water vapor in the moist air passing through a given air passage condenses and can be collected for use as fresh water. In one cooling system configuration, as illustrated in FIG. 3, exposed cooling coils 150 are arranged in a plane above the condensation member 115 but near enough to it so that the surface of the condensation member may also be somewhat chilled. The cooling coils 150 are held in place by supports 153. The refrigerant course leading to the cooling coils 150 is embedded in the condensation member 115, and connections with other harvesters are made between fixed connector points within the condensation members.

[0040] In this configuration, water condenses on the cooling coils and drips onto the upper surface of the condensation member 115, where the water gathers through coalescing of drops of water and flow of the collected water to the lower end of the member. The gathering water is diverted by the collector trough or barrier 126 into a removal pipe 138, through which it is removed for storage.

[0041] Alternatively, cooling coils may be disposed in more than one plane or in a more complex fashion, e.g., within multiple air passages 120, 130 of a multiple air passage assembly. In such a configuration (not illustrated), the coils are sized and located to create optimum conditions of air flow and heat exchange. Water is collected in the same manner described above.

[0042] In another configuration of the cooling system for a water harvester, the entire cooled fluid circulation system is miniaturized and embedded in a material having a high degree of thermal conductivity, which are known in the art. This is done in a fashion similar to some refrigeration systems designed for aircraft and spacecraft, where weight and size are important considerations and where physical protection of the refrigeration pipe system is important. Refrigeration apparatus such as these are also very durable and capable of long-term operation in unmaintained situations.

[0043] In such a cooling system configuration, illustrated in FIG. 4, a cooled flat panel 115' has small diameter pipes on the order of a centimeter or less in diameter carrying the refrigerant that are embedded beneath the surface of the condensation member to provide a refrigerated surface 158 on which condensation can take place. Embedding the refrigerant pipes provides a number of benefits. For example, the temperature of the chilled surface 158 of the refrigerated member 115' as a whole can be controlled by redirecting fluid using constrictor control valves to meet heat local sink demands. In addition, physical protection is provided by the material into which the refrigerant conduits are embedded.

[0044] Other means of refrigeration may also be employed. Thermoelectric coolers (TECs), for instance, are solid state heat pumps that utilize the Peltier effect, which is a solid-state method of heat transfer through dissimilar semiconductor materials. TECs may have particular application where light weight is a primary requirement. These would also be used where flat or complex surfaces were desired to be cooled, as circulated refrigerant is more difficult to use in those applications. Magnetocaloric effect (MCE) refrigeration exploits the magnetic properties of certain materials that warm when they are magnetized and cool when they naturally demagnetize. That method may also be used when cooling a surface is required because, like TECs, no circulating refrigerant is used or needed. However, because the surface alternately warms and cools as it is magnetized and demagnetized, condensation would be intermittent or cyclical rather than continuous. Thermoacoustic coolers (TACs) or pulse tube coolers can also be employed. They are gas-filled variable diameter tubes in which acoustic energy (instead of mechanical compression) is used to drive the compression and expansion of the circulated refrigerant.

[0045] Hydrophilic materials such as special polymers that attract water molecules (e.g., nylon or rayon) may be used on the surface 158 of the member 115' where condensation takes place. When droplets form directly on the surface, they increase in size and mass by coalescing with other water droplets and by direct condensation of water vapor onto their surfaces. Thus, the droplets gain mass and merge into streams that flow under the influence of gravity.

[0046] To assist this movement of water, a dendritic system of micro-channels 165 that increase in cross-sectional area down the slope of the condensation member 115' is engraved into the surface 158 of the condensation and water gathering member 115'. Ideally, hydrophobic materials that repel water molecules (e.g., Teflon) are used to line the surfaces of the micro-channels to promote rapid water flow from the upper end to the lower end of the condensation member 115'.

[0047] Furthermore, as illustrated in FIG. 5A, cooling member surfaces are preferably either corrugated, e.g., as at 160 or, as illustrated in FIG. 5B, finned, e.g., as at 162. This increases the surface or heat transfer area and thus increases the rate of condensation and accumulation of water.

[0048] In another cooling system configuration (not illustrated), one or more planar or more complexly arranged exposed refrigeration coils and a refrigerated surface of the condensation and water gathering member are combined. This maximizes refrigeration within the air passages.

[0049] Because the air cools and water condenses from it as the air moves through the air passage, the temperature of the cooling coils and/or the condenser member surfaces may be controlled to form local cooling zones, where different temperatures are maintained. This helps distribute the cooling load more equally and of improves the efficiency of water production by not overcooling some of the air and by facilitating condensation occurring generally equally along the length of the air passage for best water production. Additionally, optimizing temperatures, distribution of water production, and air flow will lead to the lowest energy costs per volume of water produced.

[0050] As illustrated in FIG. 6, groups of autonomous atmospheric water harvesters, termed "arrays," can be joined together to form a single structural entity. For example, three water harvesters H1, H2, H3 share a single refrigeration system that circulates refrigerant through the array 200 of water harvesters as a whole. Harvesters are designed so that connections between them can be established quickly and securely with prefabricated connecting sections for both conventional gas/fluid refrigerant distribution line 199 and return 191 (where these are used).

[0051] The underside of each condensation member of an individual water harvester H1, H2, or H3 that is part of the array 200 has built-in "female" receptors (similar to small fueling points on aircraft and racing cars) that contain their own self-sealing mechanisms for secure, quick-fit connections between the condensation members and the distribution system. These receptors are small depressions into which the "male" connectors of prefabricated electrical and refrigeration connections are inserted. In the refrigerant distribution system, butt-end connectors 197 having a male fitting on one end 198 and a female fitting on the other end 199 allow an essentially continuous pipe configuration to be established rapidly at any array installation, where any number of individual water harvesters are assembled into an array. For refrigerant return, the return line 191 mates with female socket connectors 195 on the underside of the condensation members by a male fitting 193. Unused connectors are self-sealing so that the absence of a connector does not impede operation where a water harvester is to operate independently (i.e., by itself) or at the periphery of an array of harvesters. Different lengths of prefabricated refrigeration system piping are made so that in large arrays, the fewest butt-end connectors are used, as leaks are most likely to occur at mechanical joints.

[0052] In addition, a prefabricated electrical energy wiring system includes control cable harnesses 170 that plug into electrical and control sockets 176 in the underside of each photovoltaic member. The prefabricated electrical harnesses 170 have plugs 173 in the connector cable system that fit into the female sockets 176 in each photovoltaic member in the array. Alternatively, each photovoltaic member may have a short, permanent fitted electric cable extending from about the same position as the female socket 176 shown on FIG. 6, which cable plugs into an electric cable with waterproof sockets (not shown). Electricity produced by the photovoltaic members is conditioned in an industry standard regulator and control device 179 used for controlling the output of photovoltaic panels. These regulators can also be linked with an electrical grid 181. Electricity is provided for operation of control and other equipment (not shown). The control system 179 operates and powers the condenser pumps 185 and heat exchanger 187 of the refrigeration system.

[0053] It may be required to store electricity to operate the control systems of the panels when the photovoltaic members are not generating electrical power. Electricity produced in excess of that required to recharge the control batteries or capacitor assembly may be stored. Where there is need for excess electricity to be stored locally (e.g., where electrical energy is required at night when the photovoltaics do not produce electricity), larger or higher energy density batteries may be located in the immediate vicinity of an array or group of arrays of autonomous atmospheric water harvesters. The excess electrical energy may be stored at a location remote or removed from the locations of the condensation water harvesters.

[0054] A water harvester can be pre-set to operate at particular temperatures on a time-of-day basis. For instance, where local environmental conditions such as the diurnal cycle of relative humidity and ambient temperature can be predicted, operation of the refrigeration system can be pre-set on a calendar basis, much like most heating and air conditioning systems in homes and buildings. However, in order to optimize chilling of the condensation member, a suite of sensors to measure parameters such as temperature, relative humidity, wind, water flow, and water levels can be linked to a computer or manual control (not shown) to provide for precise control over the refrigeration process. This will allow the temperature of the condensation member to be changed in response to changing conditions to optimize condensation and conserve energy.

[0055] It is not necessary (or practical) to remove all moisture from a given volume of treated air, i.e., by reducing the temperature to the point where virtually no moisture remains. Also, because of the relatively short time that the moist air will be in the air passage where it can be cooled, it is more practical to reduce air temperature by no more than a few tens of degrees. For instance, Table 1 above shows the significant amounts of water that may be condensed from water vapor while still leaving substantial amounts of water vapor in the moist air. Thus, the temperature of the condensation panel should not be kept too cold, as this will waste energy due to diminishing returns.

[0056] Moisture-laden air may be moved through the airway 120 either by gravity or by propulsion, for instance by fans. In particular, depending on the amount of moisture removed from the air and the temperature of the air in the airway following removal of that moisture, the air may be either more or less dense than the surrounding, ambient moist air. As a result, the treated air may move automatically either up or down in the inclined air passage due to such density differences. Such natural airflow is not, however, as dependable as forced airflow where a constant airflow is desired. Thus, small air-thrusters may be used to propel the air regardless of the density contrast with ambient moist air.

[0057] An ideal application for an array of panels is for use as a roof. Using arrays of panels on roofs of buildings provides a number of benefits over a conventional roof and conventional water and electricity provision. A roof comprised largely of an array of autonomous water harvesting panels will be strong and provide shelter, electricity, and water all at the same time and as part of the same investment.

[0058] An example of a thruster assembly for use where water harvesters are part of a peaked roof is shown in FIG. 7. An upper shroud assembly 208 with screened outlets is located above the apex of two harvesters such as would be found in a peaked roof. The thruster assembly consists of a metal or plastic shroud assembly that covers the top of the harvesters. Air A drawn into the lower end 124 of a water harvester passes through the air passages and out the top end 122 of the air passage and then upward through fan assembly 215.

[0059] The shroud 208 keeps rainwater and other material from falling into the interior spaces and air passages. In addition, the shroud supports the fan assembly 215. Although the fans are illustrated in FIG. 8 as being held in a vertical orientation in the fan assembly 215, with fan motors 220 mounted on the lower side of the fan assembly 215, a number of different orientations for the fans are possible. Fan blades 217 propel the air A while operating, and when the fans are not operating, the air passages ventilate naturally. A downward-facing air exit gap 222 (FIG. 7) is screened, similarly to the screening at the lower entry to the air passage 205 and for the same reasons.

[0060] In another configuration (not shown), instead of exhausting the cooled air directly into the surrounding air mass from the shrouded hood at the apex as shown in FIG. 7, the air may be ducted through an insulated air pipe that carries the chilled air away from the air gathering assembly. This chilled air may be used, for instance, as input into an air conditioning system. Although the air within an air conditioning system tends to be mainly recirculated within the air conditioned space, it is good practice for health reasons and to keep the oxygen levels normal to introduce outside air during air conditioning.

[0061] Water harvesting apparatus according to the invention is designed for strength, reliability, and durability as well as for optimum photovoltaic and water condensation. Individual autonomous atmospheric water harvesters may be free-standing, but they are more likely to be deployed as groups or arrays of water harvesters. Harvesters and arrays of harvesters operate in a passive mode in that they can be deployed for continued use without excessive maintenance or control. Each array may be autonomous with respect to its operation in that it produces at least the electrical energy that it requires to produce condensed water. Where the electricity that is generated by the photovoltaic members exceeds that required to operate the harvesters, the energy may be put into an existing electrical grid for use elsewhere or from which the harvesters can be powered later, when they are not producing electricity.

[0062] An example of the relationship between electricity that can be generated photovoltaically and the relative amount of water that may be condensed can be derived for any location. Two examples of the electricity and water production at typical high solar insolation locations at which atmospheric water harvesting is practical have been calculated (taking into account the efficiencies of the photovoltaic members, the heat energy of condensation, and well known efficiency and energy consumption of conventional refrigeration) and are shown in Table 2.

TABLE 2

Guam  Hawaii
Days/  Elec. Prod'n<2>  Elec. Prod'n<2>  Water Prod'n<3>  Elec. Prod'n<2>  Elec. Prod'n<2>  Water Prod'n<3>
Month  Month  (kWh/Mo)  (kWh/Day)  (Gal,/Day)  (kWh/Mo)  (kWh/Day)  (Gal,/Day)
Jan.  31  142  4.6  1.9  120  3.9  1.6
Feb.  28  130  4.6  1.9  126  4.5  1.9
Mar.  31  164  5.3  2.2  135  4.4  1.8
Apr.  30  152  5.1  2.1  128  4.3  1.8
May  31  145  4.7  1.9  132  4.3  1.8
Jun.  30  137  4.6  1.9  137  4.6  1.9
Jul.  31  131  4.2  1.8  132  4.3  1.8
Aug.  31  128  4.1  1.7  141  4.5  1.9
Sep.  30  127  4.2  1.8  135  4.5  1.9
Oct.  31  138  4.5  1.9  125  4.0  1.7
Nov.  30  128  4.3  1.8  112  3.7  1.6
Dec.  31  135  4.4  1.8  119  3.8  1.6
Total  365 days  1,657/yr        1,542/yr
Annual

[0063] Electricity generation and water production based on a 1.0 kW photovoltaic system. This system uses (10) 100 Watt modules for a total area of 100 ft2. Site No. 1-Guam: Latitude=13.550 N, Longitude=144.830 W. Site No. 2-Hilo, Hawaii: Latitude=19.720 N, Longitude=155.070 W. DOE/NREL PVWATTS computer model (2000) was used to calculate a first approximation of electric energy production; the solar insulation data for the two sites are included in the model's database. Energy cost: 2,400 Watts/Gal for water production (600 Wh/Qt=632 Wh/L). Actual water production will be lower depending on efficiencies of particular systems. Water saturated air is assumed (See Table 1 for effect of undersaturation during chilling).

[0064] When these calculations are extrapolated to a larger array, for instance as might be used to cover the roof of buildings, the amount of water that could be produced could be significant. Given a panel array surface of, for instance, 1,000 square feet, or about the size of the roof of a bungalow that would be occupied by a single family, about 40 kVh of electricity can be produced each day in each of the locations represented in Table 2 and in other regions having similar relative humidity and air temperatures. Integrated high quality water and electricity production using the integrated water harvester concept will have the greatest impact where population is widely scattered, and infrastructure for both water and electricity production is poor.

[0065] Another preferred embodiment of atmospheric water harvesters is as small, portable, self-powered, stand-alone units. These are for use where relatively small amounts of at least sustenance levels of high quality potable water are required and/or where the time to install water harvester units for water production can be very short, such as immediately following a natural disaster. Emergency supplies of potable water are almost always a priority immediately following typhoon, hurricane, earthquake, some terrorist activities, etc., (i.e., following natural or man-made disasters), where water and electrical systems are rendered unusable, often for substantial periods or time. For instance, typhoons affecting the American island possessions in the Southwest Pacific Ocean in 2002 created immediate need for potable water, which was only met by supplying bottled water by air freight in the near-term. Because bottled water is suitable for only one-time use as drinking water, the water to meet the disaster relief situation has to be flown or shipped in for often considerable periods of time. Waste bottles also create a waste or pollution issue, especially in a fragile environment such as an oceanic island.

[0066] In emergency situations, the amounts of water used to sustain human life can be much smaller than normal water use. The U.S. Department of Defense, for instance, recommends 1-3 gallons of water per soldier per day, but accepts 1 gal/day per person as a minimum in constrained circumstances. This provides a rough guide to the minimum water production required for atmospheric water harvesters used in a disaster relief situation

[0067] Portable water harvesters according to the invention are unitary and self-contained apparatus in that they contain the means to produce electrical energy and means to extract water from the air using this energy, They have a maximum of integral controls and are designed to be simply deployed so that they automatically extract atmospheric moisture and produce potable water in an efficient manner. As illustrated in FIG. 9, stand-alone water harvesters 300 consist of a case or housing 303 which, in a preferred embodiment, is molded high impact plastic or other material which has been designed specifically for strength, light weight, and durability and which forms the frame within and upon which all other components of the apparatus and its supports and connections are fixed. The case is special also with respect to its stand-alone nature and the requirements for operating in a variety of conditions. This embodiment is shown with its long axis parallel to the ground, but other embodiments may stand with their long axis vertical. Other embodiments may be more equi-dimensional or proportioned differently where either weather conditions or other physical constraints (such as a maximum size to suit deployment in restricted spaces) may be important.

[0068] This portable water harvester is preferably employed in an upright or slightly inclined position, so no provision for collection of rainwater is made. The sole purpose of the apparatus is to produce potable water by extracting atmospheric moisture. The water harvester is meant to be located so that its front (i.e, the side visible in FIG. 9) always faces generally sunward. Consequently, the rear of the apparatus will be shaded to some extent. The water harvester may be moved and tilted during the day in order to allow its front to face the sun more directly. Easily and quickly attachable feet or props to hold the apparatus in an upright or inclined position, e.g., steel wire braces 305 and their receiving holes 306 formed in the case 303, are provided so that setup of the apparatus on even, uneven, or sloping ground is facilitated. Ring eyelets 308 are provided in the upper part of the apparatus to allow lines to be attached to each end or the top of a free-standing water harvester to further secure it in an upright position.

[0069] Energy for the operation of the portable water harvester is provided by photovoltaic panels 310 supplied with the water harvester. A primary design aim is that the power required to produce a certain quantity of water (which can be different from place to place or for different electricity requirements) is produced by the apparatus. External power may be used, but it is not required. These photovoltaic panels may be integral with the case 303 and folding and affixed to the front of the water harvester case, e.g., by hinges as shown; flexible panels fixed to the case (not illustrated); or free-standing from the case and connected by wire (not illustrated). Additional photovoltaic panels may be located on the front face of the case, but they are not shown in FIG. 9 since front face access panels by means of which access is gained to the interior of the water harvester are not shown (i.e., as if removed from the water harvester unit) in FIG. 9 for better illustration of internal components. Both integral and free-standing photovoltaic panels may be employed simultaneously. Where photovoltaic panels optimized for use with water harvesters are not integral parts of the structure of the water harvester, they are also supplied along with the water harvester.

[0070] Where no provision is made for storage of electricity, or where no other source of electricity is available, electricity generation and water production are carried out only during the day. Where other sources of electricity are available, or where it is desirable to produce additional electricity to be stored rather than to use all of the electricity produced by the supplied photovoltaics for just extraction of water, sockets 315 for power output and power sensors and regulators (not shown) are provided for electrical connection and are located in the electrical and control housing 324 Power input connectors 319 are also provided, e.g., for use where other sources of power are available. Where other sources of power are available, this will allow operation of the apparatus during those times of the diurnal cycle when the relative humidity is high but sufficient sunlight may not be available to provide the required amounts of electrical energy. This housing 324 also contains computer control apparatus that apportions energy from any source and regulates moisture extraction according to predetermined algorithms embedded in a micro-controller. Provision exists for rapid replacement of controller (ROM chips) so that water harvesters can be reprogrammed easily for different areas that have different sunlight and atmospheric conditions.

[0071] In one configuration, variable speed fans 328 are provided at the upper rear of the case 303, in a cut-out portion 330, and draw air into the apparatus from the rear, shaded area of the case at a rate determined by the controller. These air intakes may be screened (not shown) to keep out insects and dust. The relative humidity of the cooler air from the shaded side of the apparatus is likely to be higher than warmed air from the front, sunny side of the water harvester. The ideal or operational aim for air flow (i.e., the optimal flow rate) is to only ingest as much air as can be fully chilled over a particular time, so that excess air is not chilled and so that all the air that is passed through the apparatus is chilled only to the extent necessary to produce a desired amount of water. Thus, minimal power is required to maintain the optimal airflow, even where conditions such as air temperature, relative humidity, and available power change, as they naturally do during diurnal cycles.

[0072] The air is brought by the fans into the air equilibration chamber 331 in order to allow the air to be spread uniformly along the top, and then through an air diffuser 332, which allows uniform air flow through the separated airways below. The diffuser can be a coarse porous material or a metal or plastic strip which has slits or holes 322 (indicated by dashes in its upper surface on FIG. 9) through which the air can pass. The air (arrows) then passes downward through airways 338 formed between condensation panels 341 (three of which are shown, for illustration), where the air is chilled. Condensation thus forms on the condensation panels 341. (Theoretically, a single panel 341 could be used, with airways formed between the single panel 341 and the walls of the case 303.) The air is then exhausted to the side and front of the case through an exhaust 344 that is smaller than the air intakes, which causes the exhaust speed of the air to be greater than the intake speed of the air so that the exhaust can be deflected away from the rear of the case, where the air intakes are placed.

[0073] Alternatively, in another configuration, a fan assembly having one or more fan motors located inside the case near the exhaust port blow air out through the exhaust port, thus causing air to flow into the case through air intakes located at the upper rear portion of the case. This lay-out permits the air intakes to be narrow slits and the air space in the air equilibration chamber above the diffuser to be narrower so that a larger surface area coverage of condenser plate assemblies can be fitted within the case.

[0074] In yet another configuration, fans for moving air can be placed at any point, and the air is preferably caused to move upwardly from the lower part of the apparatus through the airways bounded by condensation surfaces. This has the advantage of exposing the most highly saturated air to the lower part of the condensation panels, from where condensed water may collect and flow immeditely into the water collector and minimize its flow down the collector panels. Rapid collection of the condensed water will remove it from the airstream quickly and will preclude minor reabsorbtion of the water by the air where slight temperature and humidity variations may develop in the airways.

[0075] Where heat is produced as a byproduct of the refrigeration system, this heat has to be dissipated. Regardless of the locations of the motive electrically driven fans 328 in this preferred mode of operation, chilled air (arrows) that moves through the airways 338 and across the condensation panels 341 is then used to cool the heat exchangers of the electrically driven compressors or other refrigeration apparatus 348 in order to enhance the overall thermodynamics and performance. Because the air that has been chilled and subjected to water condensation will be cooler than the ambient air outside the apparatus, the overall efficiency of the condenser/refrigerator system is enhanced by passing this chilled air over heat exchangers that will more efficiently remove the heat than would be the case if the air were not chilled. Because the condensed water will also be cooled and removed from the water harvester, however, additional cooling air will need to be drawn from outside the apparatus and passed through a small but efficient heat exchanger (not shown, hidden by electrical and control box 324).

[0076] Chilled water is produced by condensation on condensation panels 341, which are optimized for light weight, durability, and performance. These are single- or double-sided and are spaced to form airways between the panels that are optimized for a relatively low volume of input air. Water that condenses on the panels 341 flows under the effect of gravity down the condensation surfaces and is collected in an integral water collector 351 in the base of the apparatus. This water collector is a small tank from which water is drained from the apparatus to water storage apparatus outside of the water harvester through a drain 354. The surface of the condensation panels are coated with hydrophobic and hydrophyllic materials that promote condensation (causing water to condense) and to then bead up and flow along the surfaces. A water deflector 362, which is placed over components in the lower part of the apparatus to shelter them from the dripping condensed water, allows water from the overhead condensation panels to flow into the water collector 351.

[0077] Portable water harvesters may be specially optimized for disaster relief situations. In this embodiment of the portable water harvester, it is designed to have a long shelf life so that they can be stored for considerable periods of time without significant deterioration prior to rapid deployment. They are sized to meet storage and emergency air transport requirements and are designed and packaged to provide for local deployment under primitive conditions where this may be done by hand over rough ground.

[0078] Portable atmospheric water harvesters can also provide substantial water under conditions where the use of the water is periodic. The production of water is semi-continuous, within the diurnal cycle, while use of the water may take place over shorter periods of time. A water harvester that produces water over the period of a week but where the demand for water is possibly for only a few hours of a few days, for instance, will result in quantities of water well above the subsistence level for the periods of time over which the water is required.



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