Governors' Wind Energy Coalition

Ocean Power Technology’s PB150 wave generator lies horizontally on a dock before deployment off the coast of Scotland. When operational, the device is righted and submerged with just the yellow portion above water. Photo courtesy of Luther Pendragon Ltd.

The sea’s heaving, rolling waters are an often overlooked source of renewable energy, but companies are now harnessing the motion of the ocean to feed electricity into the grid.

The potential is enormous, experts say.

“The predictions are that oceans could generate at least 10 percent of the world’s energy usage,” said Belinda Batten, director of the Northwest National Marine Renewable Energy Center at Oregon State University. Wave and tidal generators could supply power to areas that lack power lines and transformer substations, like isolated coastal villages, islands and offshore drilling platforms, she added.

Larger-scale devices could also feed into metropolises and provide power to utilities. That’s the idea behind the PB150, a 150-kilowatt buoy generator developed by Ocean Power Technologies Inc. (OPT). The buoy itself is a long, narrow stalk. The bottom is a pie tin-shaped heave plate, which keeps the main spar relatively stationary in the water while a three-point mooring system keeps the buoy from drifting. At the water line is a yellow and black doughnut-shaped float, which bobs up and down with the motion of the water.

Reliably harnessing this movement is challenging, especially in water conditions that range from placid currents to tsunami and hurricane waves. Generators have to withstand these conditions and function without servicing for long periods of time, since preparing a boat and working underwater is a costlier endeavor than jumping into a truck and driving to a wind turbine

Last week, OPT announced that it took a major step in this direction with the successful testing of a new power takeoff, a device that converts energy from one form to another. The apparatus survived a variety of wave conditions and will be deployed off the coast of Reedsport, Ore., later this summer.

“Job one has got to be surviving out there in very fierce storms and other wave conditions that come their way,” said Charles Dunleavy, CEO of OPT

Dunleavy envisions arrays of these devices bobbing in the ocean 2 to 4 miles offshore in 160-foot-deep water, barely visible from land. An underwater power station then aggregates the energy from the wave farm and sends it along a cable to the shore, ready for a utility to use. Dunleavy said OPT is aiming for a production volume of 400 buoys per year with a levelized energy cost of 15 cents per kilowatt-hour.

Caution remains in uncharted energy territor

Despite these advances, ocean energy generation is still behind wind and solar in terms of sophistication. From buoys to underwater turbines to salinity gradient generators, no particular strategy has yet emerged as the defining way to generate power from the ocean, making it riskier for investo

Robert Thresher, a research fellow at the National Renewable Energy Laboratory in Golden, Colo., compares the ocean energy market to the wind industry a generation ago.

“This is like the early days of wind when the actual costs were uncertain,” said Thresher, noting that as wind turbines were scaled up and more were produced, costs came down. “The early [ocean energy] devices are like the early wind turbines in the ’80s. They work, but they’re not as efficient as they could be. From a technology point of view, there’s a lot room for evolution.”

Wave energy in particular has some advantages over other energy sources. “You can predict the waves with more accuracy than the wind,” said Luis Vega, manager for the National Marine Renewable Energy Center at the University of Hawaii. Being able to predict when you have power is very useful for utilities, since it allows them to schedule electricity and buy power when it’s cheaper, which in turn lowers costs for consumers.

But ocean energy is uncharted territory, and regulators are trying to be cautious about how these generators will affect marine ecosystems on large scales.

“The biggest challenge by far is the environmental impact statement, all the work you have to do to convince licensing agencies to go into the ocean with these devices,” said Vega. Conservationists want to make sure no wildlife is harmed by the generators, fishermen want to make sure their catch isn’t scared away, and boaters want clear waters to sail.

Will the U.S. part the waters?

These risks also have to be extrapolated decades into the future to cover the operating lifetime of buoys and underwater turbines. Nonetheless, researchers said it’s high time the United States gets involved in this sector and take the lead in ocean energy.

“The United States have a really good opportunity right now to develop these devices ourselves and build supply chains,” Batten said. “Otherwise, we’ll see the same thing happen with ocean energy that happened with wind,” she added, referring to how Americans initially led in wind technology development but lost their prominence to overseas developers.

Batten also said ocean energy is in its infancy and still waiting for a particular technology and a company to blaze the trail.

“I think it’s too early to say who’s going to eventually be the industry leader. There may be multiple devices,” she said. “It’s just an exciting time to be in the middle of this industry.”