Here is a picture of our homemade solar air heater. We tried it out on the wood shed and it really heats up the air on a sunny day. The solar panel runs a computer fan inside the top portion of the unit to blow the hot air out and the cool air is drawn in from the bottom through 3" dryer duct.
This experimental unit works but I would recommend a second fan or a stronger fan to really move the air through the unit.
The principle is that the sun hits the panel and heats up the air inside the beer cans . The box is insulated with foil backed foam and the beer cans are caulked together with the bottoms cut out and the tops cut to slow the moment of air so it has opportunity to heat up. This unit has 120 beer cans in 10 rows of 12 . The box is made of plywood and the cover is plexiglass. The overall size is 30 x 72 inches. The cans and background were painted flat black with high heat stove paint. It took two spray cans to cover and one can of expanding foam to fill in all the gaps and seal the lower end of the can towers. The tops of the cans are connected to the upper manifold with sliced pool noodles and all was sealed with the expanding foam. I plan to install this box in a south facing exterior wall by removing an exterior door that never gets used. It will effectively heat a 200-400 sq ft area of our ranch bungalow that is farthest from the wood stove thus giving us a more consistent heat and reducing the amount of wood we will use in a winter. I suspect that two 240 can panels can reduce the need for any additional heat source on clear sunny winter days. Significant gains in the units performance can be had by tilting the bottom of the unit to match the angle of the sun. Consider building a small experimental model for your home or room by making a box the size of a window that you can remove temporarily. Imagine what could happen if this was your siding? I think this is the best use for coor's light anyway. Another example of appropriate technology for the masses. What if we could all reduce our energy demand by 20%? Try it and be amazed! This idea came from a clever inventor in Newfoundland and he now sell the units through his company called Sol- Air.