Homemade “Steel Can” Solar Air Heater. made with STEEL CANS. produces consistent flow of hot (140F+) air. video provides full instructions on how to build it. this thing moves a LOT of hot air. air enters through vents at the bottom of collector and is heated as it’s pulled up through all seven columns of cans. the fan also draws heated air from the airspace surrounding the cans. all the cans are either soup or vegetable cans.