VIDEO: Which green X Prize finalist gets your vote?
Three YouTubers are competing to win a $25,000 (£16,546) prize for eco innovation. The winner of the "What's your Crazy Green Idea?" contest, organised by the X Prize Foundation, will be decided by a public vote.
Ideas include pitting communities against one another to win cash by cutting energy use, a project to invent non-toxic batteries and an ambitious bid to make all US homes produce their own electricity.
133 contestants submitted their vision for the X Prize, which were whittled down to three by a panel that scored them on creativity, impact and viability. Voting closes 30 November 2008.
Here's one of the finalists with "the capacitor challenge", looking at batteries made from eco materials.