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Photo: Michael Ross, RER Renewable Energy Research
The tiny Aegean island of Bozcaada-- not too far from the ancient city of Troy-- is a showcase for renewable energy technologies. In the main settlement, solar thermal systems adorn nearly every rooftop, and at the far end of the island, megawatt-class Enercon turbines tower over a PV-powered lighthouse.
Coastal areas, and points jutting into large water bodies, often enjoy favourable wind regimes. With few obstructions to wind flow, average wind speeds tend to be higher and turbulence is minimal.
I walked to this wind farm with a friend who had never been close to a wind turbine. He asked, as we approached, whether the turbines were noisy-- he had heard complaints along those lines. I told him that he could make up his own mind. We walked under the turbines, and, clearly impressed, he noted that there was barely a whisper as the blades passed overhead.
Over the last two decades, considerable effort has been expended on eliminating gear box noise and reducing aerodynamic noise. Aerodynamic noise-- the noise of the blades passing through the air-- increases with increasing wind speed, a fortuitous correlation: higher wind speeds also generate higher levels of background noise that mask the turbine's faint whisper.
The Enercon wind turbines used in this windfarm are direct drive machines: they have no gearbox, the rotational speed of the rotor varies in response to wind conditions, and the output of the turbine is fed onto the grid via an inverter. The inverter is an electronic device that synthesizes an AC waveform compatible with the grid waveform. Because it is synthesized, the output waveform can include reactive as well as active power. Reactive power can support weak grids, and may have been one reason why Enercon turbines were chosen for this island, located at the terminus of an undersea cable.
Created 2005/08/11 Updated 2005/08/31 ©2005 RER Renewable Energy Research