First, cars that run on water and air. Now, here's a go-kart that zips along on compressed O2. Considering that air is (still) free, this project by mechanical engineering students from Canada's Dalhousie University is on the right track. The air-powered vehicle apparently compares favorably against electric-powered carts. In test laps, the students managed three rounds or just under 2 minutes going full out at 43kmh on two tanks. But the air-powered go-kart still has some ways to go, literally. It runs out of air quickly, according to its makers. Nothing that time and refinements won't improve. And in the name of cheap, sustainable energy, we say bring it on!