However you can take advantage of the sunny days of winter and use solar power from the sun to produce heat in your garage. Particularly if you live in hilly or mountainous areas, where the sun can reflect the suns rays as you could build a solar furnace to collect some of that sunshine that bounces off the snow or that just beams down. Solar powered furnaces have in the past recorded to reach temperatures of up to 110 degrees. So if you have a lot of scrap laying around in your basement, then put it to good use.

You can start with some 2x4's and plywood to make a simple box. It helps if you build your box to the dimensions of the material that you are going to be fitting in there, in this case you should use aluminum cans because they're easy to get hold of and to fit into your home made box. 50 cans in 5 columns of 10 will funnel air upwards.

Before putting your cans in the box, be sure to seal the edges with wood glue to ensure that any of the heat that the box produces does not escape.

So you may have already thought, “How can air climb the columns of cans when there's no hole at the bottom of the can?” Answer: drill press and 3/4-inch bit. Times 45.

The last five cans, the bases of each column, will sit on the bottom of the box and thus will be unable to draw air from underneath, so I poked holes in the sides of each of the five. Stack the cans with liberal doses of adhesive caulk. Give them enough time to dry. Once they have dried paint each column with black BBQ paint to absorb the suns heat, make sure that the paint is matt, as it absorbs more heat like this, BBQ paint is also very good because it keeps from flaking off the cans.

At the top, you can then drill an outlet hole. Leave an inch or two of space between the tops of the columns and the top of the box to permit air to flow out of the columns. Drill out the outlet hole based on the diameter of a wet-dry vacuum hose that you could find laying in your basement, about 1-1/2 inches in diameter.

At the bottom you can use another wet-dry vacuum attachment; the rectangle shaped end that you use on the carpet, this will disperse the incoming air more evenly. Screw it in at each ends, then glue the seal. Then you can start to glue the columns in place. Remember to have drilled your inlet hole in the bottom. You can drill an inlet hole at the base for each column if you have time, this way the air can simply pass over the cans (there's about 1/2 to 3/4 of an inch between the cans and the upper edge of the 2×4 frame) and all the air would be forced to pass though them picking up all of the absorbed heat.

You can then make a frame for your solar powered furnace using anything strong enough to hold it up towards the sun, you may wish to attach a thermometer to it to see how quickly it heats up and to what temperatures it can reach. Once it has been out side all day you can then bring it inside your garage and the heat that has been preserved by the solar heater shall radiate through your chosen space to heat up.