I thought it was cool because it used solar energy to heat a space. If you recirculate the air in the garage through the box. The box being large enough to produce enough BTU's. Using a low CFM fan. The air coming back into the garage would be getting warmer as long as there were no cold infiltration.
I drink enough stuff out of cans <img src="/forums/images/graemlins/cheers.gif" alt="" />, that next year I will try the little experiment. With the number of years I have in the HVACR field. I think getting a heat gain would not be too hard.
I know your thinking I could just find enough materials in the trade to build a cheap heater. But I am up for a getto challenge. <img src="/forums/images/graemlins/mrt.gif" alt="" />