Offshore wind energy on and beyond the horizon

The United States Department of Energy recently released a document that outlines a scenario wherein wind energy meets 20% of the nation's electricity demand by the year 2030. That would mean bringing close to 300,000 megawatts of wind energy online over the next 22 years.

According to the scenario, 54,000 (or roughly 20%) of that total would come from offshore wind resources -- most generated by winds off the Northeast and Mid Atlantic coasts. The U.S. offshore wind energy resource is vast. Its potential for addressing climate change is enormous. While Department of Energy officials feel that the offshore wind goals can be met without major technological breakthroughs, it's clear that constructing wind farms in ocean (and Great Lakes) waters still poses considerable engineering challenges. Hopefully the next Administration will support an R&D budget that will accelerate the deployment wind energy projects off the U.S. coasts.(GW)

Offshore Wind May Power the Future

Not only are offshore winds stronger but landlubbers have fewer objections to turbines almost invisible from the coast

By Emily Waltz

Scientific American Online

October 20, 2008

The waters of the Jersey Shore may soon become home to the nation's first deepwater wind turbines. New Jersey officials recently announced the state would help fund an initiative by Garden State Offshore Energy to build a 350-megawatt wind farm 16 miles (26 kilometers) offshore. The state wants by 2020 many more of these parks, at least 3,000 megawatts worth, or about 13 percent of the state's total electricity needs.

"This is probably the first of many ambitious goals to be set by states," says Greg Watson, a senior advisor on clean energy technology to the governor of Massachusetts. "Three thousand megawatts is significant. With that you're able to offset or even prevent fossil fuel plants from being built."

The federal government is about to open up to wind energy development vast swaths of deep ocean waters, and states and wind park developers are vying to be the first to seize the new frontier. Wind parks in these waters can generate more energy than nearshore and onshore sites, they don't ruin seascape views, and they don't interfere as much with other ocean activities.

New Jersey's plan was prompted, in part, by new federal rules that will greatly expand the territory in which developers can build offshore wind parks. Until now, such projects were only allowed in shallow state waters—those within 3.5 miles (5.6 kilometers) of shore. The new rules would allow them in federal waters, known as the outer continental shelf, which extend to the edge of U.S. territory about 230 miles (200 nautical miles, or 370 kilometers) out. These are the same waters where the hotly debated oil and gas drilling has been proposed, but the sites are unlikely to overlap, say wind developers.

The U.S. Department of the Interior's Minerals Management Service, the federal agency with jurisdiction, plans to finalize the rules by the end of the year. The agency says it will lease plots of the shelf to developers of wind parks and other renewable energy projects, such as ocean current and wave-harvesting technologies. States are chipping in on wind park development projects in the hope that the energy from these complexes will feed into state grids and help meet renewable energy requirements.

Some groups say the rules leave too many barriers for developers to overcome. "Are these waters really open?" asks Sean O'Neill, founder of the Ocean Renewable Energy Coalition. O'Neill says the leases may be prohibitively expensive and the environmental review process too extensive.

Which way the wind blows
But opening up the shelf may be the only way a viable offshore wind industry can develop in this country. Wind projects in state waters are visible from shore and can interfere with shipping routes and recreation. Turbines often have to be smaller and fewer to minimize these impacts, leading to less profitable projects. And prior to the new federal rules, no one knew who was in charge.

These obstacles have delayed, and in some cases nixed, many projects—and so far, not a single offshore wind turbine is operating in the U.S. Organizers of Cape Wind, an offshore wind park to be built more than five miles (eight kilometers) from Cape Cod, Mass., have been battling public opposition and regulatory hurdles for more than seven years.

Leasing the outer continental shelf may solve some of these problems and open a tremendous energy resource. Researchers at the National Renewable Energy Laboratory (NREL) in Golden, Colo., estimate that the wind in this territory could generate nearly 1000 gigawatts—a little more than the current U.S. electrical capacity.

The figure is enticing because nearly 80 percent of the population lives in coastal states. In some of the most densely populated areas, particularly in the Northeast, there is not enough space for large onshore wind farms. Offshore wind parks can get much closer to some of these coastal cities without having to run long transmission lines over rocky terrain and through urban areas. "I think a lot of people would like to bring the energy from wind farms in the Midwest to the cities in the east, but those links aren't easy to make," says Walter Musial, an engineer at NREL.

Europe has far surpassed the U.S. in offshore wind with more than two dozen wind parks in its waters. But nearly all are built within nine miles (14 kilometers) from coastlines—a distance still visible from shore—and in depths less than 60 feet (18 meters). Researchers must tackle some turbine design challenges before wind parks can move into deeper waters.

Building for depth
A common design for shallow depths is a simple pole driven into the seafloor, called a monopile. The deeper the water, however, the longer and more wobbly the pole. Beyond 65—possibly 100—feet (20 to 30 meters) deep, monopiles are no longer suitable. "At some depth you have to switch technologies," Musial says.

Researchers are experimenting with new designs such as underwater tripods and lattice structures called jackets, which provide extra support. Engineers for the Beatrice Wind Farm in the North Sea near Scotland are leading the way with two turbines in water 138 feet (42 meters) deep and more than 15 miles (24 kilometers) from shore. German developer Alpha Ventus plans to build in the next few months a dozen turbines with both tripod and jacket technologies.

Engineers say these designs could hold up in depths of as much as 200 feet (60 meters). To go any deeper, the best option is likely a floating structure similar to that used by the oil industry. Wires would anchor the platforms to the seabed. But unlike an oil platform, the floating wind turbine would have to better restrain the sea's pitch, roll and heaving motions. Commercial development of these structures is likely a decade away, says Musial, although some private developers in Europe say they are working on prototypes.

The depths of the U.S. outer continental shelf vary: Off of California's coast, for example, it gets deep fairly quickly compared with the east coast shelf. To get to a point where turbines are barely visible, wind parks must be built at least 14 or so miles (22.5 kilometers) from shore, says George Hagerman, a marine renewable energy researcher at Virginia Polytechnic Institute.

Offshore costs can be prohibitive, particularly without tax credits and incentives. Turbines and transmission lines are more expensive. Boats have to make long trips to and from the wind park. And some of the equipment to build in deep waters doesn't yet exist. In Europe, an offshore wind park costs nearly twice as much per megawatt as an onshore wind park, according to the European Wind Energy Association in Brussels. The question, says Paolo Berrino at the association, is whether greater wind generation efficiency offshore will outweigh the additional costs.

"Going into deeper water is not something we're comfortable doing yet," says Jim Lanard a spokesperson for Bluewater Wind, a company that has proposed a wind park 13.2 miles (21.2 kilometers) from the Delaware shore that will employ monopiles to depths of about 75 feet (23 meters). "The first offshore wind parks cannot fail because it will send a signal to the industry and the government that [the] U.S. offshore wind industry is not ready for prime time. So we are taking a conservative approach with technologies proven in Europe."