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Prof: Use wind turbines as flywheels to smooth output

Revolutionary thinking

A team of Wisconsin-based academic engineers have come up with a novel idea for smoothing out wind turbines' erratic power output in gusty conditions. In essence, the Milwaukee team's idea is to use the turbine itself as a giant flywheel to siphon off energy spikes and so offer more consistent output.

The research was led by assistant professor Adel Nasiri of the Power Electronics and Motor Drives Lab at the University of Wisconsin-Milwaukee. The paper, Wind power smoothing using rotor inertia aimed at reducing grid susceptibility, is published in the International Journal of Power Electronics.

According to the Milwaukee boffins, "the output power of wind turbines fluctuates. These power fluctuations make the wind power undispatchable. Furthermore, they can cause frequency deviations and power outage particularly when wind power penetration is significant [that is, when there is a large amount of wind power on the grid]".

Thus, according to the engineers, any power grid intending to use large amounts of wind normally needs to use expensive power storage units and/or backup generation to smooth out short-term spikes and troughs in output. But they believe that a useful amount of this can be avoided, by letting the turbine spin faster during gusts - so storing energy in the same way as a rotating flywheel - and only extracting as much power as the grid would like to have. Then, should a lull follow, the energy stored in the fast-spinning windmill can be extracted to bridge the gap.

It seems unlikely that this technique would be able to cope with the days-long calms which some critics of wind power have pointed out as the main weakness of the idea. The potential of wind turbines to fail catastrophically when spun too fast might also be a factor of concern. Nonetheless, the idea of dual-purposing the actual generating turbine itself as a storage flywheel is certainly an elegant one.

Full details of the research are available here. ®

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