It's an alarmingly simple concept that claims to be the world's first application: Netherlands-based company Natuurcafé La Port installed a power generator into a revolving door. Fantastic, but it took us this long? The door is the entrance to the Driebergen-Zeist railway station, where it's predicted to generate 4600 kwh of energy a year—or somewhere around what the average house needs annually, depending who you talk to. Not bad at all. Sure, it's probably not enough to power all of thos