SolarSheat

http://www.yoursolarhome.com/solarsheat1500G.html

These are solar "sheets" (notice the play on words that they've used for their name...) that are used like space heaters. They are pretty expensive space heaters, $1500+ for one, but if your need to be solar powered is greater than your need to not speand money, these are for you...Oh, did we meantion that they do not work at night? Seems like you should be able to create your own version for less $$$.