This build uses a custom 3D-printed / hand assembled case from RPi hacker Cottonpickers, which comes attached to the back of a 300mA solar panel. The case includes a… 4 × AA NiMH rechargeable batteries provide reserve power.
Från http://blog.makezine.com/2012/12/11/how-to-solar-powered-raspberry-pi-ftp-server/