Then, charging, you'd want at a bare minimum, a 10Watt solar panel. That, at an average of 6 hours usable sunlight each day, could possibly keep you running. Get a few dark stormy days though, and you'd run out of juice I think.

Could be fun. I'm tempted to co-host my Pi in Austria now that I'm looking at using Arduinos for my project instead. (Order of magnitude less current drain and instant start, which is awesome)