Dec. 1, 2011 - When they named our planet Earth, they named it wrong. They should have named it Ocean. Oceans dominate our world, and the energy they contain -- in the form of moving water -- could provide up to 15,000 megawatts of renewable energy here in the United States by 2030, according to the report, "U.S. Marine and Hydrokinetic Renewable Energy Roadmap," published Nov. 1, 2011, by the Ocean Renewable Energy Coalition. "More than 70 percent of our planet is covered with oceans. Why compete with land resources, which have precious uses already?" asked Sean O'Neill, president of the organization that authored the report, the Washington, D. C.-based Ocean Renewable Energy Coalition.
At least 15 companies in the United States are designing and testing technologies to capture the power of the oceans. O’Neill thinks electricity generated from waves, tides, deep-water currents and offshore wind farms could power 15 million homes in the States by 2030.
Here are five new ocean power projects coming online or being tested in waters off the coasts of the United States that could help deliver renewable electricity.
Windmills Under New York’s East River
Windmill-like turbines from New York-based Verdant Power are being installed under the city's East River to harness power from the motion of the tides. According to the company's president, Trey Taylor, the Free Flow systems have two main advantages over other energy-generating structures, such as hydroelectric dams. First, the underwater turbines require very little civil engineering and infrastructure construction, which makes them cheaper.
Second, the system allows the water to flow naturally, dramatically reducing disruptions in the water column and on the sea floor. The turbine heads turn in a full circle, so they can capture energy from the tide flowing in and out.
The amount of power produced is a function of the size of the blades and the speed of the current, and the design of the turbine installation depends on the specifics of the site.
“We can take no more than 15 percent of the energy out of the water current. We have to allow a significant distance between rows so the water current can regain speed,” said Taylor.
Verdant Power plans to install its first commercial tidal power system in 2012 in the East River, which is technically a tidal strait that connects the New York Bay to the Long Island Sound. The relatively shallow side will use turbine blades of five feet each, so that the turbines spin six to eight feet below the surface, depending on the state of the tide. Verdant plans to install a field of 10 units with three turbines each, producing a total of 1 MW.
Tidal Turbines in Maine’s Bay of Fundy
Another way to generate power from tides comes from Portland, Maine-based Ocean Renewable Power Company. Their Turbine Generator Unit uses horizontal, spiral turbines that have a low profile, which lets them function well in shallow waters. These turbines use a cross-flow design, meaning that the turbine sits perpendicular to the flow of the water.
"With cross-flow technology, the turbines always rotate the same direction, no matter if you are in ebb or flow tide," said the company's CEO, Chris Sauer.
Sauer described the unit as a rugged turbine that can be used in tidal systems, rivers and deep water currents alike. ORPC will install their first commercial tidal system in the Bay of Fundy in March 2012. These large tidal turbine units are 92 feet long, 14 feet wide and sit on a support frame, 10 feet above the sea floor. The units produce 0.13 MW each.
Turbines Harnessing Gulf Stream Power
Ocean Renewable Power Company is also testing prototypes for use in the Gulf Stream. Like a powerful river flowing through the ocean, the Gulf Stream current could provide as much electricity as 10 nuclear power plants. Along Florida’s coast, the ocean is 1,000 to 1,200 feet deep. If the turbines installed in these waters could harness just 1/1000 of the current, they could power 7 million homes in Florida.
PowerBuoys Floating Along Oregon’s Coast
Above the surface, these buoys from Pennington, N.J.-based Ocean Power Technologies capture the power of waves. As the waves toss the PowerBuoy up and down with the surf, the motion moves a piston inside a metal tower up and down. The piston drives a generator.
The PowerBuoy design can be scaled up or down, depending on the site. For utility projects, which they call wave farms, the PowerBuoy stands 150 feet tall and weighs 220 tons. Each of these systems can currently produce 0.15 MW of power.
The company is currently updating their design to make the technology more efficient and their new prototype produces 0.5MW.
“One of the ways that we’re going to get more power is to increase the size of that float. It’s difficult to do that and still retain the structural strength and stability of the device; that’s where a lot of the engineering innovations have to go,” said Robert Lurie, the vice president of business development for Ocean Power Technologies.
The company, which has installed projects in Spain and Scotland, plan to install the first 10 devices in a commercial, grid-connected project in 2012, just off the coast of Reedsport, Ore. PowerBuoys can also be used to provide a power source out in the open ocean, for example, to generate power for off-shore platforms or ocean-observing scientific buoys.
Searays Riding Waves in Puget Sound
Wave energy is also being harnessed in Puget Sound, off the coast of Oregon. There, Corvallis, Ore.-based Columbia Power will be testing a commercial scale prototype called the Searay, which is moored to the floor and has two wings that bob up and down in the waves.
A vertical column beneath the surface houses a generator for each wing. As the water moves the device up and down, the generator captures the motion and turns it into electricity. Because the device has the freedom to move in big waves, it's durable and can withstand the high forces of water, said Reenst Lesemann, the company’s CEO.
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