Buoy turns waves into electricity


POSTED: Sunday, November 16, 2008

It's described as a small yellow cylinder floating inside a 12-foot-diameter doughnut bobbing in the waves just a mile offshore from Kaneohe Bay Marine Corps Base.





Oahu PowerBuoy

        » Location: Kaneohe Bay
» Diameter: 12 feet
» Length: 52 feet
» Length above water: 13 feet
» Weight: 17 tons
» Manufacturer: Ocean Power Technologies
» Deployed: June 2007 and October 2008
» Purpose: Convert wave energy to electricity
»Maximum output: 40 kilowatts
Source: Ocean Power Technologies

But it's actually the latest phase of a wave energy research program to find renewable energy to power the country's shore-side military bases and reduce dependence on foreign oil.

The program initially was sponsored by the Office of Naval Research in 2001 and is being developed by Ocean Power Technologies, a New Jersey company. Since 2004, the company has anchored “;PowerBuoys”; - which resemble ocean buoys - in Kaneohe Bay, converting the energy from ocean waves to electrical power.

Inside the PowerBuoy's spar, a pistonlike structure moves as the buoy bobs with the rise and fall of the waves. This movement drives a generator on the ocean floor, producing electricity that is sent to the shore by an underwater cable.

The company has said that if it can develop a 100-megawatt system using an array of PowerBuoys, the cost of generating electricity can be lowered to 3 to 4 cents a kilowatt hour. That would make it slightly cheaper than electricity generated by fossil fuels and cheaper than wind- or solar-energy systems. An environmental impact assessment on a six-buoy array concluded that the project would have no significant impact on Kaneohe Bay's seabed; fish, organisms and mammals; vegetation; and sea quality.

Brian Cable, program manager, said the project is still in the research and development stage. Congress has allocated $1 million to $2 million each year since 2001 to investigate the potential of using wave energy as a reliable source of electrical power for Navy and Marine Corps bases.

Cable said the latest PowerBuoy was anchored to the limestone bottom of Kaneohe Bay on Oct. 28 about one mile from the Marine Corps Base's runway in about 100 feet of water.

Ocean Power officials said the power produced will be monitored by its facilities in Pennington, N.J. - 5,000 miles away - via radio link and the Internet.

Cable said the first buoy was larger - 15 feet in diameter, 90 feet in length and weighing 20 to 30 tons. It was tethered to the ocean floor for one month both in 2004 and again in 2005. It generated about 20 kilowatts a day.

A second buoy was smaller - 12 feet in diameter and 52 feet long. It was anchored in the bay in June 2007 for a month. It was re-stationed at Kaneohe Bay late last month and will generate about 40 kilowatts in a day.

A fact sheet provided by the Navy says Hawaii was chosen because it has, on average, some of the highest recorded wave power in the world.

Since it launched its first 40-kilowatt PowerBuoy, Ocean Power has landed larger-scale wave power development deals with utilities in the United States, Spain and Australia.

In October, the company announced a $2 million contract from the U.S. Department of Energy to support the launch of a PowerBuoy off the Oregon coast, part of a project with utility Pacific Northwest Generating Cooperative meant to produce up to 50 megawatts.

In February, Hawaii state officials and representatives of Oceanlinx, an Australian renewable-energy company, unveiled what was called a “;commercially viable wave-energy project”; that would place two wave-powered turbine platforms in the waters near the Pauwela Lighthouse on Maui.

The platforms would generate 2.7 megawatts of power and reduce carbon emissions from traditional power generation by up to 2,000 tons a year, officials said.

The company is performing preliminary site work, such as environmental assessments, and expects to have the generators in place by 2009.