I'm considering building a little solar-powered garage ventilation system. My garage faces SSW and gets very hot on a summer afternoon. There is no energy savings involved in this, and I'm probably willing to pay about $100 just to screw around with a solar cell and fan. If I do this, I'll do some before and after data logging of temperatures in the garage. Solar cells are pretty expensive for low wattage models - high cost per watt due to loss of economy of scale. Here's a decent looking site a quick google found: http://www.mrsolar.com/page/MSOS/CTGY/wattsort They have a few that look to be reasonable options: 3 watt: SC-3-12 - $45 ($15/watt)(9.5"x5.5") 8 watt: Photon8 - $60 ($7.5/watt)(9.5"x13.5") 12 watt: GSE-12 - $95 ($8/watt)(18"x16.5") I'm a little unclear on voltage ratings: one 12V panel has a rated voltage of 18.7 - I guess that won't burn out a DC fan motor? I would think I can overspeed it by quite a bit without hurting it. Here's a popular PC cooling fan fan company: http://www.thermaltakeusa.com/Products.aspx?C=1164 A possibility: A2368 - 78CFM, 4.6W, 120mm - $13 Grainger has some DC fans: one is 12V, 6W, 108 CFM. That's a good possibility, though it is expensive. I'm not sure it is well matched to my panel possibilities, but if I assume I'll never get more than 75% of rated power out of a panel, I could pair two of those fans with a 12W panel. Still looking for other fans, though. My garage is about 18'x12'x8', or 1728 ft^3. 1 air change an hour would be 30 CFM, 2 air changes, 60 CFM, etc. The panel would probably be mounted vertically to not interfere with the door opening, but that's probably ok since the problem is at its worst late in the afternoon, when the sun gets low and blasts against the door. Thoughts...?