El Hierro is now the first island in the world to be self-sufficient in electricity from renewable sources. There are be six modern windmills on the ridge where the wind generally tries to blow your hair off, and most of the time, they’ll provide the electricity direct to the island’s power grid.
It’s not too hard to see the catch. “Generally” isn’t enough. Nobody wants to wait for a windy day to switch the kettle on. They want their cup of tea now.
So when the windmills generate more electricity than the demand, the excess will be used to pump water uphill to a reservoir in a natural volcanic crater. Then when the windmills can’t keep up with the demand, the water will be released to run downhill through turbines into another lake near the port of Estaca to generate the extra energy. This should smooth out the bumps nicely.
Up until now, most of the island’s electricity came from a diesel-fired power station. That will be on standby for the first year, while they make sure that everything really does work reliably, and then moth-balled. After that, the whole island will run on clean energy.
Of course it helps that the population is only about 10,500, and the winters are fairly mild. But ti’s still impressive.
More details (in English) at http://www.goronadelviento.es/index.php?accion=articulo&IdArticulo=121&IdSeccion=104