Will water vortices provide the next renewable energy?

Prototype, VIVACE underwater energy collector

T. Boone Pickens may well have been right: Oil dependence is almost certainly “one emergency we can’t drill our way out of.” But if a University of Michigan engineer knows half of what he thinks he knows about water power, the solution to the world’s energy needs doesn’t have much to do with the billionaire oilman’s much-advertised vision of an endless line of windmills stretching from Texas to Canada.

The real answer may be a cylinder continuously moving up and down in an 8,000-gallon water tank in the Naval Architecture and Marine Engineering Building on the University of Michigan’s North Campus in Ann Arbor.

As Professor Michael M. Bernitsas sees it, the cylinder-based device he invented is a short step away from a commercially viable version that might be the key to a cheap, inexhaustible supply of clean energy to power the entire world, even regions far removed from sources of water.

The device is nicknamed VIVACE, short for Vortex Induced Vibrations for Aquatic Clean Energy. It’s pronounced “Vee-VAH-chay,” after the term for music played in a lively, spirited manner.

A prototype of Bernitsas’ invention could be set up in about a year – or sooner – for an underwater field test in the Detroit River. The major hurdle now is neither creative nor technical; it’s a matter of getting clearances from some two dozen federal and state agencies. The six-month-long field test – to be conducted in water 44 feet deep at a site near Detroit’s Renaissance Center — will have to demonstrate that the system is safe, has no technical issues and poses no threat to nesting fish or other aquatic life.

“We’re where cars were 100 years ago,” says Bernitsas, 56. “Hopefully it won’t take us 100 years to get where we need to be.”

Actually, he says, securing permits for the VIVACE test should be relatively easy, since it is considered a scientific instrument.

“I do not see the regulatory agencies as a problem,” adds Bernitsas, who explained his invention in a series of e-mails to Michigan Messenger recently. “They are helpful in identifying environmental issues that we have to look into. In my opinion we are living with the consequences of decisions we made 100 years ago to go with fossil fuels and other decisions we did not make since then, and now that we see these consequences, we are more careful.”

According to Bernitsas, the VIVACE system is more eco-friendly than any other technology. It will, he says, eventually be able to produce energy that is cheaper than wind or solar power; cleaner than gasoline, coal or natural gas; safer than nuclear power; and more practical than existing water power technologies.

“I believe that the energy problem we face as a planet needs us to look at every energy source that we can develop with a cost-competitive and sustainable (renewable and environmentally compatible) technology,” says Bernitsas. “We really need to have as many successful technologies as possible.”

The response of the scientific community to VIVACE has been “very positive across the board,” says Bernitsas, since he and his colleagues described the system in the November issue of the Journal of Offshore Mechanics and Arctic Engineering.

“Most encouraging is that environmentalists who visit my lab love the idea and give us lots of useful suggestions,” he says. “Actually all environmentalists that have visited our lab have been very enthusiastic.”

Another reason for optimism, in Bernitsas’ estimation, is that continuing test results also have been “most encouraging,” compared to the 2-year-old results reported in the journal.

Despite the positives, not all wave energy experts have jumped on the VIVACE bandwagon.

“I have no comment about their design other than, let’s put it in the water and try it and use an independent organization for review of the test results,” Roger Bedard, analyst at the Electric Power Research Institute in Palo Alto, Calif., was quoted by the Web site livescience.com.

‘I think that it’s at a very, very early stage of development,’ he was quoted by the Web site dailydevice.com.

“Indeed it is,” Bernitsas acknowledges. “We have tested many models for three years, but we will be 100-percent sure when we have the prototype completed and launched near the end of 2009.”

Bernitsas and his co-inventor, Kamaldev Raghavan, have one patent approved and two more pending through the university. The prototype hydrokinetic generator on campus for VIVACE was funded by grants from the National Science Foundation, the U.S. Navy, the U.S. Department of Energy and the Detroit/Wayne County Port Authority. The grants totaled $1 million through the university for research and another $2 million for development through Vortex Hydro Energy, a spin-off company founded by Bernitsas.

VIVACE is designed to harness power from even slow-moving rivers and ocean currents. Bernitsas got the idea from his experience with the very destructive phenomenon of vortex-induced vibrations and by observing the way fish swim by utilizing vortices, or eddies. The system is based on a phenomenon first observed more than 500 years ago by Leonardo da Vinci.

“The muscle power that fish have is not enough to support the speed at which they’re going,” says Bernitsas, a professor of naval architecture at the U. of M. “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.”

Bernitsas says the device, like fish, takes advantage of the changes in water speed caused when a current flows past an obstruction. The vortices formed in the water flow can move objects up and down or left and right.

In concept, VIVACE consists of a system of cylinders positioned horizontally and perpendicular to the water flow. As water flows past, the vortices push and pull the cylinders up and down. The mechanical energy in the vibrations is then converted into electricity by a generator. The current version of VIVACE is one cylinder attached to springs; future versions are expected to have a fishlike tail and scales, which have already been tested in the Marine Renewable Energy Lab at the university.

The prototype for the Detroit River field test will operate seven or eight cylinders, each of them about 10 inches in diameter and a bit more than two yards long. The device itself is expected to cost about $25,000, but Bernitsas projects the entire development process of building, testing, launching, etc. at above $1 million.

Besides ensuring that marine life can live with VIVACE, the test will aim to confirm the energy output results produced in the U. of M. lab, in addition to gauging the device’s durability, resistance to fouling, robustness in dealing with variable current speeds, and the functioning of adoptive controls.

A second field test is expected to be run in an undetermined ocean environment.

The technology can generate electricity in water flowing at a rate of less than 1 knot – a knot is a bit more than 1 mile an hour — meaning it could operate on most waterways and sea beds around the globe. Electricity can be sent to other locations through power grids, just as it is now.

Existing technologies that use water power, relying on the action of waves, tides or faster currents created by dams, are far more limited in locations where they can be used; they also cause greater obstructions when they are built in rivers or the sea. Turbines and water mills need an average current of 5 or 6 knots to be financially viable, while most of the Earth’s currents are slower than 3 knots.

The vibrations produced by vortices can cause damage to structures built in water, like docks and oil rigs. But because the parts in VIVACE are designed to harness the hydrokinetic energy, the technology is not destructive. Oscillations are slow, mimicking fish motions, and thus less likely to be harmful to aquatic life than are dams or water turbines. And because the installations can be positioned far below the surface of the sea, there would be less interference with shipping, recreational boat users, fishing and tourism.

As Bernitsas explains: “About four years ago, it dawned on me that we should enhance the vibrations and try to harness this powerful and destructive force in nature. This is a totally new method of extracting energy from water flow. No one has ever thought of patenting this idea, even though vortex-induced vibrations were first observed in 1504.”

When Da Vinci recorded the phenomenon after detecting sounds produced by fluctuations in air pressure, he named it “Aeolian Tones.” The eddies causing the acoustic vibrations are analogous to those produced on the downstream side of a rock in a river.

“There is a huge amount of hydrokinetic energy in currents,” says Bernitsas, “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. It taps into a new energy source.”

Cylinders arranged over a cubic meter of the sea or river bed in a flow of 3 knots can produce 51 watts. This amount of energy per used fluid space (where all space between cylinders is accounted for) is higher than similar-sized turbines or wave generators, and the amount of power produced can increase sharply if the flow is faster or if more cylinders are added. This energy density is still small compared to fossil fuels, however.

A “field” of cylinders built on the sea bed over a 1-kilometer-by-1.5-kilometer area, and the height of a two-story house, with a flow of just 3 knots, could generate about 500 megawatts, enough power for around 500,000 homes. Just a few of the cylinders, stacked in a short ladder, could power an anchored ship or a lighthouse.

Systems could be sited on river beds or suspended in the ocean. Bernitsas and his colleagues say that generating power in this way would potentially cost only around 5.5 cents per kilowatt hour, compared to about 6.6 cents for wind energy and between 14.6 and 45.2 cents for solar power. They say the technology would require up to 50 times less ocean acreage than wave power generation.

Although there have been many projects proposed to harness wave energy, only a few actually are operating, among them the Pelamis Wave Project off the coast of Portugal, a system that generates 2 megawatts of power, enough to supply about 2,000 homes.

A renowned expert in the study of underwater structures, Bernitsas has a doctorate in ocean engineering from Massachusetts Institute of Technology. He is professor and lab director at the U. of M. Department of Naval Architecture and Marine Engineering, where he served as chair for nine years. He is also chief technology officer and interim CEO of Ann Arbor-based Vortex Hydro Energy. He is a fellow of the American Society of Mechanical Engineers and the Society of Naval Architects and Marine Engineers, and he was awarded the Blakely Smith Medal in 2003.

(Dave Good is veteran journalist and a member of the copy editing team supporting Michigan Messenger and the rest of the Center for Independent Media sites.)