Priya has found that a gentle breeze of 16 kilometres per hour can generate a constant power of 7.5 milliwatts, which is more than enough to keep an electronic sensor running. [...]
The first trials of completely wireless sensor networks used photovoltaic cells for power. But these did not always work, since a spate of cloudy days could cause a node to shut down. "The idea failed because light isn't available everywhere and all the time," says Priya. [...]
We don't think that the point is to argue that these mini wind turbines are better than solar panels, but that in some cases they might be more appropriate or cost-effective.
The piezoelectric generator is much more efficient way of converting wind energy on a small scale than the conventional generators that create energy for the national power grid from wind turbines.
A conventional generator that used a 10-centimetre turbine would convert only 1% of the available wind energy directly into electricity. A piezoelectric generator ups that to 18%, which is comparable to the average efficiency of the best large-scale windmills, says Priya.
::Mini windmills power wireless networks, via ::Digg