by Dan Bihn, Enerdynamics Instructor
Today wind turbines generate about 3% of electricity in the United States — all of it onshore. Europe gets about 6% of its electricity from wind. But nearly 4 GW of its 900 GW of installed wind capacity now comes from turbines mounted on the seabed miles offshore. This is an impressive statistic considering the first commercial-scale offshore turbine was installed in 2001 and the real push for offshore didn’t really kick off until 2007.
Offshore wind isn’t easy and it isn’t cheap. Electricity and water don’t mix. Steel and saltwater don’t mix. And few things mix well with hurricanes. Not surprisingly the International Energy Agency (IEA) estimates that offshore wind costs two to three times more than onshore wind.
So why would anyone want to put a 300-foot-tall wind turbine 20 miles out to sea?
The main reason is that is where strong, consistent, unobstructed winds are closest to coastal population centers. This results in wind output that more resembles a baseload power plant than a variable resource. And there are other advantages: no need to buy land (try that 20 miles from New York City); no one is around to complain about their views being ruined (a 400-foot structure is completely over the horizon 25 miles offshore); and the length of wind turbine blades isn’t constrained by trucking limits on the autobahn or the interstate.
Initial offshore wind development in the U.S.
While the U.S. doesn’t have any commercial offshore wind turbines as of 2012, the idea isn’t new here. Since 2001, a group of developers has been proposing an ambitious 468 MW wind farm off the coast of Cape Cod — a project called Cape Wind. The plan is to build 130 3.6-MW turbines four to 11 miles offshore. The tips of the 182-foot blades will reach 440 feet above the water, making them visible onshore.
Being visible is the problem — and the source of local and regional opposition from the late Ted Kennedy to former Massachusetts Governor Mitt Romney. While the project is still officially in play, it seems unlikely it will be constructed. Time will tell.
But the idea of offshore wind in the U.S. is far from dead. In 2010, the U.S. Department of the Interior (whose jurisdiction extends to the offshore exterior) launched the “Smart from the Start” initiative to promote the construction of 10 GW of offshore wind by 2020 and another 44 GW by 2030.
A total of 10 GW of offshore wind along the Atlantic seaboard probably means 10 to 30 wind farms. Each could potentially construct its own underwater transmission line. Surprisingly, underwater transmissions lines can be cheaper than traditional overhead lines — especially when those overhead lines need to go through heavily populated areas.
But it may be more economical to aggregate the power from these future farms and use a single system to bring that power back to shore. This is exactly what Google and financial heavyweight Marubeni are proposing. It’s called the Atlantic Wind Connection — a high-voltage DC superhighway with floating substations. The 230-mile offshore transmission system would span the U.S. mid-Atlantic seaboard from New Jersey to Virginia, bringing 7 GW of proposed offshore wind power to the Atlantic seaboard. On May 15, 2012, the Department of the Interior moved its permit to the next stage.