'Fish Technology' Draws Renewable Energy From Slow Water Currents

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. 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.
Journal reference:
. VIVACE (Vortex Induced Vibration for Aquatic Clean Energy): A New Concept in Generation of Clean and Renewable Energy from Fluid Flow. Journal of Offshore Mechanics and Arctic Engineering, December 2008
Adapted from materials provided by University of Michigan.

Dam The Red Sea And Release Gigawatts

Damming the Red Sea could solve the growing energy demands of millions of people in the Middle East and alleviate some of the region's tensions pertaining to oil supplies through hydroelectric power। Equally, such a massive engineering project may cause untold ecological harm and displace countless people from their homes.

In the Inderscience publication International Journal of Global Environmental Issues, Roelof Dirk Schuiling of Utrecht University in The Netherlands and his colleagues discuss the costs and benefits of one of the potentially most ambitious engineering projects ever.
Present technology allows us to shift and shape the earth on a relatively large scale and to control lakes and reservoirs for hydroelectric power generation. In the near future, however, it might be possible to build dams large enough to separate a body of water as large as the Red Sea, from the world oceans. A similar macro-scale engineering project is already planned for the Strait of Hormuz at the entrance of the Persian Gulf. This seawater barrier will exploit the evaporative cycle and influx of seawater to generate vast quantities of electricity.
Geochemical engineer Schuiling suggests that a dam Bab-al-Mandab could be used to stem the inflow of seawater into the highly evaporative Red Sea with the potential of generating 50 gigawatts of power. By comparison, the Palo Verde nuclear power plant, the largest nuclear station in the US has an output of just 3.2 gigawatts.
"Such a project will dramatically affect the region's economy, political situation and ecology, and their effects may be felt well beyond the physical and political limits of the project," says Schuiling.
Schuiling and his colleagues point out that the cost and timescales involved in creating such a hydroelectric facility are way beyond normal economical considerations. It is inevitable that such a macro-engineering project will cause massive devastation of existing ecologies. However, it will also provide enormous reductions in greenhouse gas emissions as well as offering a viable, sustainable alternative to fossil fuels for future generations. The ethical and environmental dilemmas are on an international scale, while the impact on ecology, tourism, fisheries, transport and other areas could have effects globally.
The researchers point out that the precautionary principle cannot be applied in making a decision regarding the damming of the Red Sea. "If the countries around the Red Sea decide in favor of the macro-project, it is their responsibility to limit the negative consequences as much as possible," they conclude.
Adapted from materials provided by Inderscience Publishers.

Marine Bacteria Can Create Environmentally Friendly Energy Source

Bacteria in the world's oceans can efficiently exploit solar energy to grow, thanks to a unique light-capturing pigment. This discovery was made by researchers at University of Kalmar in Sweden, in collaboration with researchers in Gothenburg, Sweden, and Spain. The findings are described in an article in the journal Nature."It was long thought that algae were the only organisms in the seas that could use sunlight to grow," says Jarone Pinhassi, a researcher in Marine Microbiology at Kalmar University College. These microscopic algae carry out the same process as green plants on land, namely, photosynthesis with the help of chlorophyll.In 2000 scientists in the U.S. found for the first time that many marine bacteria have a gene in their DNA that codes for a new type of light-capturing pigment: proteorhodopsin.Proteorhodopsin is related to the pigment in the retina that enables humans to see colors. It should be possible for this pigment to enable marine bacteria to capture solar light to generate energy, but until now it had not been possible to confirm this hypothesis.Last year researchers from Kalmar collected 20 marine bacteria from different ocean areas and mapped their genomes. Several of them proved to contain the pigment proteorhodopsin. This made it possible to run a series of experiments that clearly show that growth in bacteria with this pigment is stimulated by sunlight, because the pigment converts solar energy to energy for growth. In other words, the scientists had found a new type of bacterial photosynthesis that takes place in the seas.It's easier to understand the importance of understanding new mechanisms in marine bacteria to making efficient use of solar energy if we consider the fact that one liter of natural sea water contains roughly a billion bacteria. The activity of these bacteria is of great importance to the carbon cycle, through, for example, the amount of carbon dioxide they produce, and also to how the solar energy that reaches the earth is channeled through the nutrition cycle."Bacteria in the surface water of the world's oceans swim in a sea of light," says Jarone Pinhassi. "And it is shouldn't be too surprising that evolution has favored microorganisms that can use this rich source of energy. This type of protein may also play a role in commercial and environmental perspectives, for the development of artificial photosynthesis for the environmentally friendly production of energy."Note: This story has been adapted from a news release issued by Swedish Research Council.

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