Donald ERICKSON
ISAAC Solar Icemaker
ISAAC Solar Ice Maker
The ISAAC Solar Icemaker
is an Intermittent Solar Ammonia-water Absorption Cycle. The ISAAC
uses a parabolic trough solar collector and a compact and
efficient design to produce ice with no fuel or electric input,
and with no moving parts.
The ISAAC Solar Icemaker operates in two modes. During the day,
solar energy is used to generate liquid ammonia refrigerant.
During the night, the generator is cooled by a thermosyphon and
ice is formed in the evaporator compartment as ammonia is
reabsorbed to the generator.
The daily ice production of the ISAAC is about 5 kg per square
meter of collector, per sunny day. The construction of the ISAAC
Solar Icemaker involves only welding, piping and sheet metal work,
and there are no expensive materials. It is estimated that, when
produced in-country where wages are low and transportation costs
can be minimized, the 11 square meter
ISAAC can be produced for less than $7,000. When produced
in-country, the creation of urban employment is an additional
advantage of ISAAC technology.
The characteristics of the ISAAC which make it particularly well
suited to provide refrigeration to unelectrified rural communities
are:
1. It is solar thermally powered, avoiding expensive diesel fuel
or photovoltaics.
2. Low cost construction requires only welding, piping and sheet
metal work.
3. Very low maintenance.
4. The quantity of ice is sufficient to support small scale
businesses while maintaining sustainability in fragile
environments, or provide low cost household refrigeration.
The ISAAC design was developed by Energy Concepts Company. Over
forty systems have been built and twenty installed in seven
countries. The ISAAC is on display in Annapolis, Maryland and at
Sandia National Lab, Albuquerque, New Mexico. ISAAC is now being
distributed and commercialized by Solar Ice Co.
Providing Jobs to Remote
Communities - By Providing Ice
The ISAAC Solar Icemaker makes enough ice at low cost to support
many small scale businesses in rural unelectrified areas.
Enterprises using ISAAC will be environmentally sustainable
because no fuel is required. They will be economically sustainable
because the cost of producing the ice by the ISAAC is sufficiently
less than the value of the ice that it can easily be recovered by
a micro-enterprise.
Ice is of major economic importance. In rural communities of
developing countries, there is frequently a shortage of ice to
support business activities. The result is loss of revenue, jobs,
and substantial food spoilage.
Three important community needs for electricity are:
* lights
* communications and entertainment
* refrigeration.
Lights, communication and entertainment require modest amounts of
electricity and are affordable even at the high cost of
electricity from emergency generators, diesel mini-grids or
photovoltaics.
When refrigeration is needed also, the amount of electricity
required from the power system increases drastically. Thus it is
usually omitted to keep costs down. An ISAAC Solar Icemaker
supplies refrigeration without the intermediary step of
electricity and at a much lower cost. Thus ISAAC Solar Icemakers,
in combination with mini-grids and/or photovoltaics, are a good
method of supplying remote community needs.
For example, ISAAC can provide domestic refrigeration. An ISAAC
produces six blocks of ice each day, weighing ten kilograms each.
If an icebox requires five kilograms of ice per day to stay cool,
then one ISAAC will be able to supply domestic refrigeration to
twelve households. The cost of a standard electric refrigerator,
plus the constant requirement of expensive electricity, would be
much higher.
The Absorption Cycle was invented in 1846 by
Ferdinand Carré for the purpose of producing ice with heat
input. It is based on the principle that absorbing ammonia in
water causes the vapor pressure to decrease. Absorption cycles
produce cooling and/or heating with thermal input and minimal
electric input, by using heat and mass exchangers, pumps and
valves.
An absorption cycle can be viewed as a mechanical
vapor-compression cycle, with the compressor replaced by a
generator, absorber and liquid pump. The absorption cycle enjoys
the benefits of requiring a fraction of the electrical input,
plus uses the natural substances ammonia and water, instead of
ozone depleting halocarbons. The absorption cycle enjoyed
widespread use from the 1920’s as gas powered
refrigerators/ice-makers.
The basic operation of an ammonia-water absorption
cycle is as follows. Heat is applied to the generator, which
contains a solution of ammonia water, rich in ammonia. The heat
causes high pressure ammonia vapor to desorb the solution. Heat
can either be from combustion of a fuel such as clean-burning
natural gas, or waste heat from engine exhaust, other industrial
processes, solar heat, or any other heat source. The high
pressure ammonia vapor flows to a condenser, typically cooled by
outdoor air. The ammonia vapor condenses into a high pressure
liquid, releasing heat which can be used for product heat, such
as space heating.
The high pressure ammonia liquid goes through a
restriction, to the low pressure side of the cycle. This liquid,
at low pressures, boils or evaporates in the evaporator. This
provides the cooling or refrigeration product. The low pressure
vapor flows to the absorber, which contains a water-rich
solution obtained from the generator. This solution absorbs the
ammonia while releasing the heat of absorption. This heat can be
used as product heat, or for internal heat recovery in other
parts of the cycle, thus unloading the burner and increasing
cycle efficiency. The solution in the absorber, now once again
rich in ammonia, is pumped to the generator, where it is ready
to repeat the cycle.
An absorption cycle can use a variety of working
pairs. The working pair is made up of a refrigerant, typically
ammonia or water; and a solution which absorbs the refrigerant.
Other working pairs include lithium-bromide-water;
TriDroxide-water; and Alkitrate-water. Tridroxide and Alkitrate
are Energy Concepts patented working pairs with specialty
applications in industry.
Absorption cycles can operate at high efficiency
by utilizing advanced cycles, using generator-absorber heat
exchange, multiple pressures, and multiple effects. These cycles
use extensive internal heat recovery to require less prime fuel
input to produce the same thermal output. High efficiency
operation, plus benefits of environmentally friendly
refrigerants, clean-burning fuels, and few moving parts
requiring maintenance make absorption a very good choice for
consumers.
Absorption cycles can produce a variety of thermal outputs. In
common commercial use today are gas-fired absorption chillers,
which produce chilled water for space cooling applications. The
absorption cycle can produce low temperature cooling for ice
production or cold storage. Turbine inlet cooling is a very
efficient use of absorption cooling, boosting turbine efficiency
by up to 15%. Many other applications exist in industry, where
waste heat is available and cooling is required. Advanced cycles
can also produce electrical or shaft power by producing steam or
high pressure vapor to power a turbine/generator pair.
Publications -- ISAAC™
SOLAR
ICEMAKER
Pierpont, J. P. "Energy Concepts Rises From Ashes To
International Market." Baltimore Business Journal.
February 1989.
"What’s New: News in Brief." Maryland Business Weekly: The
Baltimore Sun. December 18, 1989.
"Hot Refrigeration" Environmental Protection Week. June
1990.
"Solar Refrigeration Brings Ice to Developing Countries." Solar
Industry
Journal. Second Quarter. 1990.
Maier, Timothy A. "Solar-Powered Refrigerator Heats Up Energy
Concepts." Baltimore Business Journal. November 1990.
Erickson, Donald C. "Isaac Solar Absorption Icemaker." Soltech
91
Erickson, Donald C. "Isaac Solar Refrigerator." Environment-Friendly
Technologies
for the 21st Century. Proceedings of the Japanese Assocition
of Refrigeration Absorption Heat Pump Conference. Tokyo.
September 1991.
Erickson, Donald C. and Jorgensen, Paul. "Solar Absorption
Ice-Making in a Mexican Fishing Village." Hawaii 1992.
Erickson, Donald C. "Solar Icemakers in Maruata, Mexico." Solar
Today. July/August 1994.
ThermoSorber™
The ThermoSorber™ is a
gas-fired heat pump which supplies air conditioning or
refrigeration at the cold end, and which uses all the reject
heat (gas heat plus cooling duty ) to heat hot water. The high
temperature glide achieved with the GAX absorption cycle makes
it possible to heat hot water to 160°F, thus meeting the needs
of commercial users. The hot water is normally the primary
product, with the cooling in a supplementary role. This ensures
high year round utilization and short paybacks. This appliance
reduces the utility bill for hot water and cooling by more than
half, compared to the most economic commercially available
equipment.
US6584801
Absorption Cycle with
Integrated Heating System
Abstract -- An absorption
system powered by low temperature heat for producing at least one
of refrigeration and power is disclosed, wherein a low-pressure
drop heat reclaimer 1 reclaims heat from the source into a heating
agent, which in turn supplies heat to the absorption cycle
desorber 5 via internal coils 7. The extra temperature
differential normally present in closed cycle heating systems is
avoided by using the absorption working fluid as the heating
agent, in an integrated system.
US6269644
Absorption Power Cycle with
Two Pumped Absorbers
Abstract -- An absorption
power cycle is disclosed which achieves a closer match to heat
source temperature glide, and also lower heat source exit
temperatures, and hence higher conversion efficiencies, in
practical equipment. Referring to FIG. 7, two separate absorbers
(725 and 706) are provided, each with a pumping path for a
different concentration absorbent liquid to a different
temperature location within counter-current high-pressure desorber
721. Heat source 710 heats the high-pressure desorber 721 and
superheater 724 in parallel, and subsequently heats
intermediate-pressure desorber 761. Dotted lines in the figures
signify vapor.
US5309985
Stationary Continuous
Multimodular Trisorption Heat Pump
Abstract -- Apparatus and
process are disclosed for sorption heat pumping at high efficiency
in a smooth and continuous manner using a multiplicity of
stationary triplex sorption modules. The hermetically sealed
trisorption modules, each of which contains at least two solid
sorbents, are free of pumps, valves, restrictors, or any similar
devices for flow control of refrigerant or sorbent. The apparatus
contains no moving parts beyond a small number of control and
motive devices for the heat transfer fluids. The preferred
refrigerant is ammonia and the preferred sorbents are the solid
type with monovariant equilibrium, e.g., BaCl2, SrCl2, CaCl2,
MnCl2, FeCl2 and SrBr2. The apparatus is preferably adapted for
residential or small-scale commercial space-conditioning
applications, and operates at double-effect efficiency in both the
heating and cooling modes without inter-module heat transfer.
US5279359
Rotary Trisorption Heat Pump
Abstract -- Apparatus and
process are disclosed for sorption heat pumping at high efficiency
in a smooth and continuous manner using a multiplicity of
intermittent cycle triplex sorption modules. The hermetically
sealed trisorption modules, each of which contains at least two
solid sorbents, are free of pumps, valves, restrictors, or any
similar devices for flow control of refrigerant or sorbent. The
preferred refrigerant is ammonia and the preferred sorbents are
the solid type with monovariant equilibrium, e.g., BaCl2, SrCl2,
CaCl2, MnCl2, FeCl2 and SrBr2. The apparatus is preferably adapted
for residential or small-scale commercial space-conditioning
applications, and operates at double-effect efficiency in both the
heating and cooling modes without inter-module heat transfer.
US5272891
Intermittent Sorption Cycle
with Integral Thermosyphon
Abstract -- Intermittent
sorption cycles with fixed heat supply and removal and comprised
of a generator/absorber (4), a condenser (2), and a
receiver/evaporator (10) are adapted and simplified so as to
require at most only two control valves (8) and (15) for their
operation. With an integral thermosyphon (6) for absorption heat
removal, only a single refrigerant charge is necessary. The two
valves are advantageously combined into a single three-way ball
valve, and key gravity drains (14) and (17) are provided.
Applications include hot water heating, solar refrigeration, and
steam generation.
US5653116
Triple-Effect Absorption
Cycle with Condensate-to-Solution Sensible Heat Exchanger
Abstract -- A
triple-effect cycle is disclosed which avoids the two primary
limitations of currently known triple-effect cycles:
super-atmospheric pressures and/or low pressure absorbers that
operate without mass transfer enhancers. The cycle is comprised of
two hermetic loops-one a conventional LiBr double-effect loop, and
the other a single-effect loop which overlaps the high pressure
portion of the double-effect loop, and exchanges heat with it at
three locations. Referring to FIG. 3, the latent heat exchanges
are with absorber 302, condenser 304, and evaporator 305 of the
single-effect loop. Sensible heat losses are reduced by
incorporating inter-loop condensate-to-solution sensible heat
exchanger 314. The inter-loop CSSHX also applies to other
triple-effect cycles.
US5771710
Thermosyphon Cooled Absorber
for Air Cooled Absorption Cycles
Abstract -- The absorption
step of a continuous absorption cycle apparatus (refrigerator or
heat pump) is externally cooled by an air-cooled thermosyphon
having hot end 107 (FIG. 1), air-cooled end 115, and reservoir
123. The absorption step is further recuperatively cooled by
internal fluids, in absorber heat exchanger 108 and/or GAX 109.
Thus the absorber is highly compact and the cycle is highly
efficient. A hotter hermetic thermosyphon can advantageously
supply additional cooling.
US5660049
Sorber with Multiple
Cocurrent Pressure Equalized Upflows
Abstract -- A sorber for
sorbing a vapor into (absorber) or out of (desorber) a liquid
sorbent comprised of a sequential plurality of highly effective
and intensified locally cocurrent sorptions, but with
non-cocurrent flow of vapor and liquid between the individual
sorptions. The structure containing the locally cocurrent upflow
is preferably comprised of enhanced heat transfer surface, making
the sorption diabatic, further enhancing the intensification, and
improving the sorption efficiency. Referring to FIG. 12 , vertical
cylinders (70) and (71) form an annular space within which
desorption occurs, powered by external heat source (72) and
internal heat recuperation (77). The liquid portion of the annulus
is divided into multiple compartments by folded rectangular fin
(73). The space above fin (73) allows pressure equalization of all
compartments. Each compartment is divided by insert (80) into
separate vapor-liquid riser channels and a liquid downcomer
channel. The sorbent liquid flow sequentially through the
compartments via flow ports (74). The same high effectiveness
sequential liquid recirculating cocurrent upflow desorption can
also be accomplished in a horizontal cylindrical annulus, in plate
fin exchangers, and in other geometries.
US5713216
Coiled Tubular Diabatic
Vapor-Liquid Contactor
Abstract -- A non-diabatic
vapor-liquid contact device is disclosed which achieves high heat
transfer effectiveness without sacrificing mass transfer
effectiveness. Referring to FIG. 2, a helical coil of crested
tubing 84 is contained within the annualr space between shrouds 82
and 83. Liquid flows downward through the annulus, and vapor flows
countercurrently upward. The mass exchanging fluids pass through
the space between tube crests and the shroud, achieving very
effective mixing. Heat transfer fluid is flowed through the tubing
via connections 87 and 88. The heat and mass transfer is
preferably additionally enhanced by interspersing contact media
with the coiled tubing, either longitudinally or radially.
US5798086
Intensified Locally
Cocurrent Tray Contactors
Inventor(s): ERICKSON DONALD C [US]
Abstract
-- An intensified means of multicomponent fluid multistage
vapor-liquid contact is disclosed. The contactor achieves the
thermodynamic advantages of global countercurrency, the tray
efficiency advantages of tray crosscurrency, and the point
efficiency advantages of local cocurrency with liquid
recirculation. Referring to FIG. 6, each tray has multiple
compartments formed by compartment dividers 62, 63, and 64, and
each compartment has a channel divider 69, 66, 67 which forms
separate locally cocurrent riser channels and liquid downcomer
channels.
