Technology Review reports that a variable electric generator can improve the efficiency of a wind turbine because it can harvest electric power over a wider range of wind speeds.
ExRo Technologies, a startup based in Vancouver, BC, 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 percent.
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 percent of its energy can be converted into electricity. But if it speeds up or slows down, the generator’s efficiency drops dramatically.
Randall Parker comments, “If the cost delta for this generator design is small enough then the 50% boost in electric power could greatly improve the economics of wind electric power. The generator works by switching in more magnetic coils as turbine speed increases.”
ExRo’s new design replaces a mechanical transmission with what amounts to an electronic one. That increases the range of wind speeds at which it can operate efficiently and makes it more responsive to sudden gusts and lulls.
Here’s the company’s description of their Variable Input Electric Generator (VIEG):
Rather than layering individual legacy machines one on top of the next, the VIEG uses a series of coils, configured in “balanced stages”.The magnetic balancing allows the use of permanent magnets, yet still reduces cogging torque to a bare minimum, which allows the VIEG to operate at extremely low wind speeds (near zero).As available energy increases, the VIEG matches generator resistance to source energy by electronically adding generator stages. Conversely, the VIEG is able to drop stages as available energy (wind speed) drops, cycling up and down without hesitation and without mechanical friction.The need for a gearbox is eliminated, and a single VIEG generator scales up and down with available energy in a way that would take almost 70 individual generators to match.
Parker surmises that, by changing the threshold, such technology could reduce the problem of intermittency since wind power would decay more slowly. Would this also tend to make load balancing easier? He asks, “Anyone know if this intuition is correct?”
