Try to wrap your head around this: A slender tower stretches 100 meters above the waves. Blades, each one of them nearly 60 meters long, face down the briny spray as they turn about a 250-metric-ton nacelle at the top of the tower, which houses the turbine generator and everything else needed to produce electricity.

Now double the size of everything, and make it five times as heavy.

That’s the problem that will eventually face builders of offshore wind farms. In general, bigger—more megawatts per turbine—is better. So wind farm operators have been demanding higher-power offshore turbines, and manufacturers have been delivering. The most powerful turbine yet installed, an 8.8-megawatt machine from Vestas Wind Systems, went up off the coast of Scotland in April, and bids for some upcoming North Sea wind farms were made with the expectation that 13- to 15-MW turbines would be available by the middle of the next decade. Such turbines could power about 9,000 homes while the wind is blowing. But though bigger might be better, without some equally big changes in the wind turbine’s core technologies, bigger quickly becomes ludicrous.

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