On a corner in McPherson Square, home of the OccupyDC movement is a homemade solar powered heating unit that is heating up a four man tent. I just had to stop the other morning and learn more about this.
There wasn't anyone hanging around the sustainability tent, but they had left a notebook of information that I leafed through. The photographs showing the unit in various stages of construction was interesting and there was a parts list included. Seems like the total cost of the parts was less than $50.00.
It's built from some scrap 6x8 lumber, a "recycled" window, a sheet of Styrofoam, a recovered space blanket, some abandoned dryer hose and about a hundred aluminum soft drink cans -- painted black.
The contraption captures the sunlight which warms up the air inside the frame. The law of thermodynamics forces the hot air through the dryer hose at the top where it's blown into the tent. Then there's a hose that leads from the bottom of the tent back into the solar-powered-heating-thingy and the whole process is repeated.
I don't know about you, but it seems to me to be a pretty good demonstration of how cheap solar energy can be, once we get the greedy, candy-ass yuppies out of the way and let the unemployed, long-haired, drum playing hippies show them how to do it.