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There's a Wind Turbine On the Horizon With Blades the Size of Trump Tower
merbs writes: Imagine a stretch of open ocean, populated by a swath of wind turbines with skyscraper-sized blades, whipping into the gusts like enormous palm trees. The vision is partly terrifying, partly inspiring, and being taken entirely seriously by the federal government and one of our top research laboratories. [Sandia National Labs, in an effort led by the University of Virginia] has unveiled the preliminary design for a new offshore wind turbine with 650-foot turbine blades. That, as its announcement points out, is twice the size of an American football field. It's also roughly the size of Trump Tower in New York.
Generally, bigger is better in wind turbines. Power generated is proportional to swept area, more mass means cleaner power which leads to more efficiency, and yes, larger, heavier turbine blades are more survivable in weather events. Modern turbines automatically self-furl as required, in much the same way that modern helicopter blades will auto-gyro in the event of an engine failure, and the mechanisms that do this work better if they are bigger.
All that being said, weather can destroy literally anything less than planet-sized. But if weather brings down a modern windmill, the damage done by the weather event itself is likely to dwarf the damage done by the failure of the turbine and tower - unlike the failure of a large hydro dam, for example. And afterwards you can rebuild it with very few worries about the kind of large-scale, long-lasting contamination that other forms of power production (such as coal or fission) create during a weather event failure.
Really only solar has a comparably benign failure mode in weather events - basically if you get hit by a flying chunk of solar panel or wind turbine blade, that's how you can get hurt, which is why some people prefer such things to be set up well offshore or in deserts.
The NASA ones are using the swept diameter for size, while the article quoting 650 ft is talking about the length of a single blade, i.e. radius. So these are about four times the linear dimension of the largest built NASA wind turbine, which is probably why it also produces about 16 times as much power.
Well, Trump certainly does have a history with offshore wind farms. He and his lawyers managed to delay the implementation of a wind farm project off the coast of Scotland for several years. It finally went ahead after he lost three successive court judgements.
His objection was that the turbines would spoil the view from his golf course.
Mega installation which require mega capital which allow power companies to centralize production, control distribution, and charge consumers.
It is more efficient and less prone to failure to have distributed production with small scale wind turbines, photovoltaic, etc. on peoples' homes. But then, well, where's the profit to the established interests?
It's not more efficient. It may be more desirable for several reasons, but with wind turbines for efficiency (power produced per dollar spent) you want the big and high up. This especially applies if you are building them offshore as is proposed in this case, because buildign the base and getting there to do maintenance are high costs that depend on the number of turbines, not the power produced.
It's also not less prone to failure, at least for some definitions of failure, in that the wind is much steadier out at sea an a few hundred meters up. A professional maintenance and inspection regime also helps.
Yes, larger turbines spin at lower rpm but the tip speed is about the same regardless of size. There are physical limitations.
Actually I didn't some checking and found a paper titled Optimal Tip Speed Ratio [PDF]. The tip speed ratio is the tip speed/wind speed. The paper says:
For grid connected wind turbines with three rotor blades the optimal wind tip speed ratio is reported as 7, with values over the range 6-8.
So the optimal tip speed depends on the wind speed but for practical reasons the tip speed may be limited to non-optimal values.