When it comes to clean energy, you would think that we had most of the sources covered. But Laurence Kembell-Cook, director of Pavegen Systems, thinks we might have overlooked something – kinetic energy. Kembell-Cook is working on a system that could turn high-traffic walkways into electrical generators. The Pavegen system harvests energy from footsteps on its tiles, converts it into electricity and stores it in a lithium polymer battery that's then used to provide electricity. Make no mistake, this isn't designed to power houses. Instead, it's intended for low-power applications such as street lights, displays, speakers, alarms and billboards. A tile in a busy area can generate 2.1 watts of electricity per hour, so obviously there'd need to be a lot of them to provide a meaningful amount of electricity. In a big city with a lot of walkers it could work. The tiles themselves are built, for the most part, from recycled rubber, with some marine grade stainless steel in there as well. They are waterproof, designed to take a battering (each tile should survive at least 20 million steps), and can be retrofitted to existing infrastructure. Want to see Pavegen in action? The first commercial installation will be at the London 2012 Olympics, where the tiles will light the crossing between the Olympic Stadium and Westfield Stratford City Shopping Center.