Build Your Own Soda Can Solar Heater. Perfect for heating a Greenhouse or a small garage
The basic premise of the project is to build a simple box out of some 2x4s, stack a hundred or two black-painted soda cans inside with some adhesive, and stick a vacuum hose on the end to direct heat into your house. You'll also need to drill a hole in the bottom of each can to direct the heat through the box, so a drill press or something similar would come in handy (since you will have to do it 180 times). Other than that, you shouldn't need any other fancy tools.P
It won't heat your whole house, but it will do a pretty good job keeping your garage, greenhouse, or other small area warm.