Here's an electric bike that doesn't need plugging in.. or swapping out batteries. As the name suggests, the Solarbike has solar cells built into both sides of the party typical bicycle wheels, using cells (and a design) that's apparently "shadow optimized": The inventor is based in Copenhagen, so it's certainly an issue that needed tackling. Power drawn in from the solar cells when the bike isn't moving is stored inside an on-board battery, then when you're in transit, power comes both from the Thermos-shaped attached to the bike frame and what ever trickles in from the solar cells. As Treehugger puts it, improvements solar cell tech improvements in last decade has made this design at least tenable -- because the wheels are facing out sideways, not getting solar rays head-on, it makes the task of absorbing light a little bit more difficult.