Catalyst could power homes on a bottle of water, produce hydrogen on-site

[Wood]

With one bottle of drinking water and four hours of sunlight, MIT chemist Dan Nocera claims that he can produce 30 KWh of electricity, which is enough to power an entire household in the developing world. With about three gallons of river water, he could satisfy the daily energy needs of a large American home. The key to these claims is a new, affordable catalyst that uses solar electricity to split water and generate hydrogen.

http://www.physorg.com/news187031401.html

Not exactly free energy (it needs the solar panels + the catalyst) but it should be cheap and quite clean.