Michael BERNITSAS, et al.


( Vortex-Induced Vibrations for Aquatic Clean Energy )

Vortex Hydro Energy

2512 Carpenter Road Suite #101-C
Ann Arbor
MI 48108
Phone: (734) 223-4223
Fax: (734) 944-4072

VIVACE (Vortex Induced Vibrations for Aquatic Clean Energy)

A novel approach to extract energy from flowing water currents. It is unlike any other ocean energy or low-head hydropower concept. VIVACE is based on the extensively studied phenomenon of Vortex Induced Vibrations (VIV), which was first observed 500 years ago by Leonardo DaVinci in the form of “Aeolian Tones.” For decades, engineers have been trying to prevent VIV from damaging offshore equipment and structures. By maximizing and exploiting VIV rather than spoiling and preventing it, VIVACE takes this ‘problem’ and transforms it into a valuable resource for mankind.

Vortex Induced Vibrations (VIV) result from vortices forming and shedding on the downstream side of a bluff body in a current. Vortex shedding alternates from one side to the other, thereby creating a vibration or oscillation. The VIV phenomenon is non-linear, which means it can produce useful energy at high efficiency over a wide range of current speeds.

VIVACE devices have many potential advantages, which improve installation survivability in the hostile underwater environment and enable low-cost power production by decreasing capital cost and minimizing maintenance.

High energy density - permits low cost energy to be produced from relatively small installations - requiring up to 50 times less ocean acreage than wave power concepts.

Simple and rugged moving parts - allows for robust designs that can operate for long periods in the underwater environment with minimal maintenance.

Low dependence on ocean/river conditions - application of non-linear resonance permits useful energy to be extracted over a wide range of current speeds.

VIVACE and other renewable energy technologies also face regulatory hurdles. Again, VIVACE is advantaged by salient benefits over other technologies.

Non-obtrusiveness - installations can be positioned beneath the surface, thereby avoiding interference with other uses, such as fishing, shipping and tourism.

Compatibility with marine life - VIVACE utilizes vortex formation and shedding, which is the same mechanism fish use to propel themselves through the water.

Prototype, funded by the U.S. Department of Energy and the Office Naval Research, is currently operating in the Marine Hydrodynamics Laboratory at the University of Michigan. This device has met and often exceeded expectations; thereby, providing strong evidence to proceed to the next scale, a multi-kilowatt field demonstration.

Video :--

'Fish Technology' Draws Renewable Energy from Slow Water Currents

Michael Bernitsas, professor in the Department of Naval Architecture and Marine Engineering, stands before a prototype of his VIVACE hydrokinetic energy device.
Credit: Scott Galvin

Slow-moving ocean and river currents could be a new, reliable and affordable alternative energy source. A University of Michigan engineer has made a machine that works like a fish to turn potentially destructive vibrations in fluid flows into clean, renewable power.

The machine is called VIVACE. A paper on it is published in the current issue of the quarterly Journal of Offshore Mechanics and Arctic Engineering.

VIVACE is the first known device that could harness energy from most of the water currents around the globe because it works in flows moving slower than 2 knots (about 2 miles per hour.) Most of the Earth's currents are slower than 3 knots. Turbines and water mills need an average of 5 or 6 knots to operate efficiently.

VIVACE stands for Vortex Induced Vibrations for Aquatic Clean Energy. It doesn't depend on waves, tides, turbines or dams. It's a unique hydrokinetic energy system that relies on "vortex induced vibrations."

Vortex induced vibrations are undulations that a rounded or cylinder-shaped object makes in a flow of fluid, which can be air or water. The presence of the object puts kinks in the current's speed as it skims by. This causes eddies, or vortices, to form in a pattern on opposite sides of the object. The vortices push and pull the object up and down or left and right, perpendicular to the current.

These vibrations in wind toppled the Tacoma Narrows bridge in Washington in 1940 and the Ferrybridge power station cooling towers in England in 1965. In water, the vibrations regularly damage docks, oil rigs and coastal buildings.

"For the past 25 years, engineers—myself included—have been trying to suppress vortex induced vibrations. But now at Michigan we're doing the opposite. We enhance the vibrations and harness this powerful and destructive force in nature," said VIVACE developer Michael Bernitsas, a professor in the U-M Department of Naval Architecture and Marine Engineering.

Fish have long known how to put the vortices that cause these vibrations to good use.

"VIVACE copies aspects of fish technology," Bernitsas said. "Fish curve their bodies to glide between the vortices shed by the bodies of the fish in front of them. Their muscle power alone could not propel them through the water at the speed they go, so they ride in each other's wake."

This generation of Bernitsas' machine looks nothing like a fish, though he says future versions will have the equivalent of a tail and surface roughness a kin to scales. The working prototype in his lab is just one sleek cylinder attached to springs. The cylinder hangs horizontally across the flow of water in a tractor-trailer-sized tank in his marine renewable energy laboratory. The water in the tank flows at 1.5 knots.

Here's how VIVACE works: The very presence of the cylinder in the current causes alternating vortices to form above and below the cylinder. The vortices push and pull the passive cylinder up and down on its springs, creating mechanical energy. Then, the machine converts the mechanical energy into electricity.

Just a few cylinders might be enough to power an anchored ship, or a lighthouse, Bernitsas says. These cylinders could be stacked in a short ladder. The professor estimates that array of VIVACE converters the size of a running track and about two stories high could power about 100,000 houses. Such an array could rest on a river bed or it could dangle, suspended in the water. But it would all be under the surface.

Because the oscillations of VIVACE would be slow, it is theorized that the system would not harm marine life like dams and water turbines can.

Bernitsas says VIVACE energy would cost about 5.5 cents per kilowatt hour. Wind energy costs 6.9 cents a kilowatt hour. Nuclear costs 4.6, and solar power costs between 16 and 48 cents per kilowatt hour depending on the location.

"There won't be one solution for the world's energy needs," Bernitsas said. "But if we could harness 0.1 percent of the energy in the ocean, we could support the energy needs of 15 billion people."

The researchers recently completed a feasibility study that found the device could draw power from the Detroit River. They are working to deploy one for a pilot project there within the 18 months.

This work has been supported by the U.S. Department of Energy, the Office of Naval Research, the National Science Foundation, the Detroit/Wayne County Port Autrhority, the DTE Energy Foundation, Michigan Universities Commercialization Initiative, and the Link Foundation. The technology is being commercialized through Bernitsas' company, Vortex Hydro Energy.

The paper is called "VIVACE (Vortex Induced Vibration for Aquatic Clean Energy): A New Concept in Generation of Clean and Renewable Energy from Fluid Flow."

Technical Papers and Presentations

M.M. Bernitsas, K. Raghavan, Y. Ben-Simon, E. M. H. Garcia, “VIVACE (Vortex Induced Vibration Aquatic Clean Energy): A New Concept in Generation of Clean and Renewable Energy from Fluid Flow”, Journal of Offshore Mechanics and Arctic Engineering, ASME Transactions, in press; also invited paper, Proceedings of the 25th International Conference on Offshore Mechanics and Arctic Engineering (OMAE ’06), Paper #92645, Hamburg, Germany, June 4-9, 2006.

M.M. Bernitsas, Y. Ben-Simon, K. Raghavan, E. M. H. Garcia, “The VIVACE Converter: Model Tests at Reynolds Numbers Around 10^5", Journal of Offshore Mechanics and Arctic Engineering, ASME Transactions, in press; also invited paper, Proceedings of the 25th International Conference on Offshore Mechanics and Arctic Engineering (OMAE ’06), Paper #92652, Hamburg, Germany, June 4-9, 2006.

VIVACE: A New Concept for Harnessing Hydrokinetic Energy
CITRIS and Ocean Engineering Seminar - University of California, Berkeley

Reynolds Number Effect on Vortex Induced Vibrations
Raghavan, K., Bernitsas, M. M., and Maroulis, D., (2007), "Effect of Reynolds Number on Vortex Induced Vibrations," IUTAM Symposium, Hamburg, Germany. (Invited Paper)

VIVACE Technology Progress & Path Forward
U.S. Department of Energy Presentation

Raghavan, K., Bernitsas, M. M., and Maroulis, D., (2007b), "Effect of Bottom Boundary on VIV for Energy Harnessing at 8x10^3 < Re < 1.5x10^5", Journal of Offshore Mechanics and Arctic Engineering, ASME Transactions, submitted; also invited paper, Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering (OMAE ’07), Paper #29727, San Diego, California, June 10-15, 2007.

Bernitsas, M. M., Raghavan, K., and Maroulis, D., (2007a), "Effect of Free Surface on VIV for Energy Harnessing at 8x10^3 < Re < 1.5x10^5", Journal of Offshore Mechanics and Arctic Engineering, ASME Transactions, submitted; also invited paper, Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering (OMAE ’07), Paper #29726, San Diego, California, June 10-15, 2007.

Bernitsas, M. M., Raghavan, K., and Duchene, G., (2007), "Induced Separation and Vorticity Using Roughness in VIV of Circular Cylinders at 8x10^3 < Re < 1.5x10^5," OMAE2008 - June 15-20, 2008, Estoril, Portugal.

Raghavan, K., and Bernitsas, M. M., (2007), "Enhancement of High Damping Viv through Roughness Distribution for Energy Harnessing at 8x10^3 < Re < 1.5x10^5," OMAE2008 - June 15-20, 2008, Estoril, Portugal.

Bernitsas, M. M., and Raghavan, K., (2007), "Reduction/Suppression of VIV of Circular Cylinders through Roughness Distribution at 8x10^3 < Re < 1.5x10^5," OMAE2008 - June 15-20, 2008, Estoril, Portugal.

Tapping the Vortex for Green Energy

by Alexis Madrigal

A bane of Big Oil's offshore rigs could become a boon for renewable energy.

By tapping the natural motion of slow-moving water, a new hydrokinetic generator could open vast new swaths of the ocean for energy production.

When ocean currents flow over any kind of cylinder, like the long cables that hold drilling platforms in place, small vortices are created. They eventually spin away, or shed, causing vibrations that over time can destroy an oil rig's moorings.

Now, a University of Michigan engineer who long worked on suppressing this phenomenon, has developed a prototype energy-harvester that can capture the mechanical energy it creates.

"About four years ago, it dawned on me that we should enhance the vibrations and try to harness the energy," said ocean engineer Michael Bernitsas, who has founded Vortex Hydro Energy to commercialize his idea. "No one has ever thought of patenting this idea, even though vortex induced vibrations were first observed in 1504 by Leonardo da Vinci."

Energy experts consider the movement of water in oceans a vast untapped source of clean energy  that could provide up to 10 percent of U.S. demand (pdf). A variety of schemes have been proposed to capture this mechanical energy, usually involving turbines to capture fast-moving water generated by tides or a strong current. But few projects have progressed beyond the science project stage. The most advanced is a Pelamis Wave Power project off the coast of Portugal, which provides a mere 2 megawatts of power.

One major problem is that most underwater turbines require the water to be moving very fast. One study suggested that hydrokinetic projects only made economic sense in currents moving at over six knots, which are highly rare. It's all the ocean's other currents, which are generally under 3 knots, that Bernitsas sees as his technology's main advantage.

"There is a huge amount of hydrokinetic energy in currents but a lot of that we cannot harness with the present technology and that's where my device comes in, to extract energy at speeds down to 1 knot," said Michael Bernitsas, who has founded Vortex Hydro Energy to commercialize his idea. "It taps into a new energy source."

That idea has attracted some name-brand backers. The National Science Foundation, the U.S. Navy, and the Department of Energy have together contributed about $2 million to Vortex to further develop the concept.

Schematic Prototypes of the device — known as Vortex Induced Vibrations Aquatic Clean Energy — are essentially round cylinders a few inches across suspended in water on a spring. The vortices generated by water flow move the cylinder up and down. The VIVACE system converts that mechanical energy into electricity via rotary or linear generators.

In the future, Bernitsas wants to create modular 50 kilowatt units, like the artist's rendering seen above. They could be strung together for larger applications into power plants producing as much as a gigawatt of power.

The engineers are working on making the basic system components more efficient, too. The cylinders of the early designs have sprouted tails, which allow them to use more of the energy in the vortices. It's an idea that the engineer has borrowed from whales, fish, tadpoles and other creatures that move in liquid, which he says all have a bluff, or not slender, body followed by a tail.

"The muscle power the fish have is not enough to support the speed at which they are going," he said. "So, if you study more carefully, there are lots of things going on. A fish will curve its body, collect a vortex, shed it, and collect one on the other side and shed that, alternating on the two sides of its body."

The design of the system allows it to take much more energy out of the water than turbine-based systems. In technical terms, the energy density of the system is higher. For example, in a three-knot current, the VIVACE gets 50 watts per cubic meter of water, while the Pelamis system, considered the world leader in ocean energy, gets 21.

The innovative nature of the idea, however, is no guarantee of commercial success.

"I think that it's at a very, very early stage of development," said Roger Bedard, an analyst at the Electric Power Research Institute in Palo Alto, California, and world expert on ocean energy.

And Bernitsas' system would be subject to the United States' regulatory process, which was designed with large hydroelectric dam projects in mind, and that has hampered all hydrokinetic energy technology development.

"You have to go through 20 to 25 different regulatory agencies in this country," Bedard said.

Governmental risk frightens potential investors. Erik Straser of the Silicon Valley-based venture capital firm Mohr Davidow Ventures, sees potential regulatory and technical issues, too.

"This seems like it would be have some issues with permitting," Straser wrote in an e-mail to "I think that and reliability will be the key issues to deployment and efficacy."

Bernitsas believes that his technology is much more environmentally friendly than other marine projects, so he's looking forward to working with regulators.

Still, the tide could be turning, no pun intended, for marine and hydrokinetic projects. The recent Wall Street bailout bill included tax credits for these projects, which could stir investor interest.

For now, Bernitsas isn't focused on large-scale production just yet. The first ready-to-use prototype, slated for splash down in the Detroit River, will be ready in about a year.

"We're where cars were 100 years ago," Bernitsas said. "Hopefully it won't take us 100 years to get where we need to be."

( 11 April 2008 )

Harnessing River Whirlpools Puts Energy on Tap

by Jim Giles

Whirlpools created by currents as they flow over obstacles are powerful enough to tear apart bridges and offshore rigs. So why not use them as a source of renewable power?

Previous attempts to harness energy from the flow of the world's rivers and oceans have had limited success, at best. Tidal flow can only be tapped at certain times of day, while underwater turbines are only viable if they are mounted in rapid currents.

Now researchers led by Michael Bernitsas at the University of Michigan, Ann Arbor, are preparing for the first outdoor trials of a technology that makes use of the slow-moving currents down rivers and across the ocean.

When water flows over an underwater obstacle, whirlpools or vortices form alternately above and below it. The vortices create a tugging effect, so the result is an alternating force that yanks the object up and down (see Diagram). It is these oscillations that can have devastating consequences for rigs and bridges, but Bernitsas has now created a device that turns them into usable amounts of electricity.

In his lab, he took a cylinder 10 centimetres in diameter and 91 centimetres long with the same average density as water and suspended it horizontally in a bath. Then he generated currents of between 0.5 and 1.0 metres per second - speeds that are common in rivers. The vortices generated by the flow moved the cylinders up and down, and by attaching the cylinders to springs that turn an electric generator he was able to convert the motion into 10 watts of electrical energy. Bernitsas calls the technology Vortex Induced Vibrations Aquatic Clean Energy, or VIVACE, and plans to commercialise it with his company Vortex Hydro Energy.

He has also come up with an idea for squeezing more energy from VIVACE. At the Offshore Mechanics and Arctic Engineering conference in Estoril, Portugal, in June this year, he will show how roughening the surface of the cylinders allows them to capture more energy. The idea was inspired by the fact that fish that use energy from vortices to help propel themselves forward also have rough skin.

VIVACE's big test will come next year, when the team plans to deploy a larger version in the Detroit river. They expect it to generate 3 kilowatts, enough to power lights on a nearby pier, and claim that still larger versions could produce megawatts of power at a cost of around 5 cents per kilowatt-hour. This would make it competitive with coal and gas-fuelled generators.

These projections are contested, however, by commentators who point out that the performance has yet to be tested in the fluctuating current of a real river. They also have doubts about the claimed cost of the power it produces, since it is not yet clear how much the system will cost to maintain. "It is very new and very different to existing devices," says Walter Musial of the National Renewable Energy Laboratory in Golden, Colorado. "There are a lot of questions still to be answered."


Applicant(s):  UNIV MICHIGAN [US]
Classification: - international:  F03B13/12; F03C1/00; F03B13/00; F03C1/00 ;- European:  F03B17/06
Also published as:  EP1812709

Abstract -- A converter for producing useable energy from fluid motion of a fluid medium. The converter includes a support structure, at least one movable element immersed in the fluid medium and supported externally on the support structure such that the movable element can move relatively to the structure in response to the fluid motion by vortex induced motion, galloping or combination thereof, and at least one power device supported on the support structure and coupled to the movable element. The power device converts motion of the movable element to useable energy.

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