An Answer for Offshore Wind?


We US-based Treehuggers have been following the battle over the Cape Wind Project in Nantucket Sound for several years now, and the fight between wind energy advocates and homeowners determined to keep the Sound free of offshore wind turbines continues to drag on. MIT's Technology Report notes that such battles may quickly become irrelevant as GE and the US Department of Energy have announced a partnership to develop larger wind turbines that will be able to not only generate more power, but may be able to do it offshore at distances that wouldn't bother even the most diehard NIMBYist.

MIT researchers recently demonstrated the feasibility of "tension-leg" platforms, a technology that oil companies have recently adopted for deep-water rigs. The wind turbines and towers would be assembled at a shipyard and placed on top of large floating cylinders (see images). The canisters would be ballasted on the bottom with high-density concrete to keep the structure from tipping over, and the whole turbine assembly would be tugged out to sea.

There, four steel cables would be attached to the platform, anchoring it to the sea floor. First, though, some water would be allowed into the cylinder, causing the structure to sink more into the water. Once the cables are attached, the water is pumped back out again, allowing the turbine to rise, tightening the cables, and preventing the turbine from bobbing up and down, yet allowing some lateral movement that would help cushion the impact of storm waves on the tower. (The blades themselves would be high enough to avoid even waves from hurricanes.) The cable tension can be adjusted for different weather conditions, says Paul Sclavounos, professor of mechanical engineering and naval architecture at MIT.

Based on wind-speed measurements, researchers at MIT, led by Stephen Connors, director of the Analysis Group for Regional Electricity Alternatives, calculated that large turbines located far offshore could ultimately cost less per power generated than either land-based turbines or near-offshore ones, even factoring in extra costs, such as much longer underground electricity transmission cables. The upside: much more fast and steady wind, which would allow the turbines to generate power at 50 percent capacity on average throughout the year, compared with 30 percent or less with on-land turbines.

Offshore wind farms could also have the advantage of being close to big cities, unlike wind farms in remote areas, which require significant power grid upgrades to transport the power to places where it's needed. "I personally see this as the endgame," says GE's [Jim] Lyons. "We'll see gigawatt-scale projects delivering clean energy to the East Coast."

As GE and the USDE are shooting for a 2009 completion date, the bluebloods and windpreneurs will still have plenty of time to squabble over Cape Wind. By that point, assuming the project's engineers overcome the numerous technological challenges of building such large turbines, we may be able to have both our unspoiled views and green power from offshore wind farms. :: MIT Technology Review via The Energy Blog