Better wind turbines

A more efficient generator could convert more of the wind's energy into electricity.

By Consulting Specifying Engineer Staff November 14, 2008

According to a story in the MIT Technology Review , ExRo Technologies , a startup based in Vancouver, British Columbia, has developed a new kind of generator that’s well suited to harvesting energy from wind. It could lower the cost of wind turbines while increasing their power output by 50%.

The new generator runs efficiently over a wider range of conditions than conventional generators do. When the shaft running through an ordinary generator is turning at the optimal rate, more than 90% of its energy can be converted into electricity. But if it speeds up or slows down, the generator’s efficiency drops dramatically.

This isn’t a problem in conventional power plants, where the turbines turn at a steady rate, fed by a constant supply of energy from coal or some other fuel. But wind speed can vary wildly. Turbine blades that change pitch to catch more or less wind can help, as can transmissions that mediate between the spinning blades and the generator shaft. But transmissions add both manufacturing and maintenance costs, and there’s a limit to how much changing the blade angle can compensate for changing winds.