A yellow cylinder that floats inside a doughnut bobbing in the waves, just a mile offshore from Kaneohe Bay Marine Corps Base in Hawaii, the United States, marks the latest phase of a wave energy research programme to power the countrys shore-side military bases and reduce dependence on fossil fuel. The PowerBuoy which resembles an ocean buoy is being developed by Ocean Power Technologies to convert the wave energy to electrical power. It is 3.65 m in diameter, 15.85 m in length and 17 tonnes in total weight. About 4 m of the device floats above water. It has a maximum rated power output of 40 kW.

As the PowerBuoy bobs with the rise and fall of the waves, a piston-like structure moves inside its spar. This movement drives a generator on the ocean floor, producing electricity that is sent to the shore by an underwater cable. The company hopes to develop a 100 MW system using an array of PowerBuoys to lower the cost of generating electricity to US$0.03 to US$0.04 per kilowatt-hour.

Source: www.starbulletin.com

Sea Generation Ltd. in the United Kingdom is on track to begin full operation of its giant 1.2 MW SeaGen tidal energy system, following the replacement of two rotor blades on the second of its two turbines. The second turbine is now running under test mode, while the first has been generating power into the local grid, at varying levels up to its maximum of 600 kW.

The blade replacement operation also demonstrated the benefits of SeaGens design that allows the rotors to be raised out of the water, so that it can be maintained a small service vessel. When fully operational, the tidal systems twin rotors with 16 m diameter will operate for up to 18-20 hours per day to produce enough clean electricity to power around 1,000 homes.

Source: www.gizmag.com

A University of Michigan (UM) engineer has built a machine that works like a fish to turn potentially destructive vibrations in fluid flows into clean, renewable power. VIVACE, for Vortex Induced Vibrations for Aquatic Clean Energy, is the first known device that could harness energy from water currents slower than 2 knots. While conventional turbines and water mills need an average of 5-6 knots to operate efficiently, most of the currents are slower than 3 knots.

VIVACE is a unique hydrokinetic energy system that relies on vortex induced vibrations undulations that a rounded or cylinder-shaped object makes in a flow of fluid. The object puts kinks in the currents speed as it skims by, causing to form vortices 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. Both in water and air, these vibrations have damaged bridges, cooling towers, docks, oil rigs, coastal buildings, etc.

Prof. Michael Bernitsas of the UM Department of Naval Architecture and Marine Engineering says that VIVACE copies aspects of fish technology. Fish curve their bodies to glide between the vortices shed by the bodies of the fish in front of them. Their muscle power alone cannot propel them through the water at the speed they go, so they ride in each others wake. The working prototype in Prof. Bernitsas lab is just a sleek cylinder attached to springs and hanging horizontally in a tank across a water flow of 1.5 knots. The vortices push and pull the cylinder, creating mechanical energy, which the machine converts into electricity.

Source: www.sciencedaily.com

In China, a collaboration between Chuan Shiyu Machinery and the Institute of Electric Engineering of the Chinese Academy of Sciences has recently worked out a display unit to demonstrate the feasibility of wave power generation principle that is completely different from the conventional wave power generation theory. The new method of power generation uses a megnetohydrodynamic generator, which works by creating a solid mechanical resistance to the waves. The method is claimed to enjoy several merits, such as high conversion rate, large power density, compact structure, lower cost and enhanced mobility.

Source: www.most.gov.cn