DIY: Aluminum Solar Heater

Decide which end of the box will be the top of the heater; it’s a matter of personal preference. Use a ruler to draw two lines across the top, each extending from a front corner to the opposite back corner. The result is an "X" shape consisting of two lines intersecting in the middle of the box top.

Slot a circle cutter into the chuck of a drill. Use a cutter that matches the diameter of the flexible piping. Tighten the chuck around the cutter, and remove the chuck key. Squeeze the trigger to make sure the cutter spins without wobbling.

Drill a hole through the top of the box where the lines intersect. Smooth the edges with glass paper.

Use the circle cutter to drill a line of holes through the back of the box, just above the base. Smooth the edges of the holes. The result is a series of holes forming a line across the back of the box, through which cool air will enter the base of the heater.

Lay the box, face down, on a sheet of Perspex. Draw around it, then use a fine-tooth saw to cut the Perspex to size. The result is a Perspex cover for the box.

Rest the box on its back. Lay empty aluminum drink cans, side by side, across the width of the box. Record the number of cans. Place the cans, end to end, from the bottom of the box to the top. Record the number of cans.

Multiply the number of cans used across the width of the box by the number of cans used along the height of the box. The result is the number of aluminum cans required to fill the box. For example, if the box is 20 cans wide and 8 cans high, you need 160 cans -- 20 x 8 = 160.

Don strong gloves. Fit a circle cutter to the drill, with a diameter about 2/3 of the diameter of the aluminum cans. Drill a hole through the top and bottom of each can. Drill an additional hole in the side of enough cans to form the bottom row across the heater box.

Paint the can exteriors and the box interior with matte black paint. Allow the paint to dry.

Glue the cans together, using sealant, to form columns of the correct length to fit in the box. Fill the box with columns of cans, side-by-side, with each column starting with a can with a hole in the side. Make sure that the holes face outward from the box.

Run sealant around the top edges of the box, then press the Perspex sheet into place. Allow the sealant to set. Push a flexible pipe into the hole in the top of the heater. Secure it with sealant.

Place the heater box the correct way up, where sunshine falls on the front. Adjust the position until warm air emerges from the flexible pipe attached to the top of the aluminum solar heater.