Great question! Your question was actually the first that I'd heard of such a thing, so I had to do quite a bit of the old research to get up to speed. The idea originated at the University of Cambridge with a group of savvy architecture graduate students, who have lovingly named their process "algaetecture". From the Greenbang.com website: the design "uses in-built algae tubes and a photo bio-reactor to generate hydrogen. A glazing system and water pool are incorporated into the design to mitigate -- reflect and cool -- the sunlight the algae need to survive." According to the same article the house produces 4100 kilowatt-hours "of hydrogen and biomass per year -- enough to drive an electric MINI E car from London to Beijing and back twice over."

I've linked the Algaetecture homepage below, as well as the greenbang.com article and a wired.co.uk article.

Thanks for enlightening me....er... no pun intended.