A ROUGH GUIDE TO CONSTRUCT A PASSIVE SOLAR AIR HEATER

Transcription

1 A ROUGH GUIDE TO CONSTRUCT A PASSIVE SOLAR AIR HEATER The passive solar air heater is an inexpensive way to generate heat without any carbon emissions. The project was undertaken by a group of volunteers in early December of The construction took approximately two and a half days, with installation taking another half day. This should serve as a rough guide to help you build your own passive solar air heater. Throughout the design and construction process, we consulted resources like YouTube in order to get best practices from others who have undertaken the same project. Materials Used 1 1/2in foam insulation (Styrofoam SM) Glue for Styrofoam SM 1 tube clear silicon 2in deck screws 1 1/2 roof screws (with rubber washer) Tin flashing roll 24in wide-24ft Tin for outside of 4'x8'x6" box 1 can matt black BBQ high temp spray paint 4in vent pipe 4ft Inexpensive thermostat Angle iron for mounting on wall dryer vent (with flaps) Hi temp silicone Computer fan 2 5/8" plywood Approx. 175 beer or pop cans Solar charger Preparation of Cans We used a drill press in order to remove the drinking side of the pop cans.

2 One person needed to hold the cans while the other person operated the drill. Wearing gloves with good grip is advisable, as the cans will heat up. We found that certain major brands seemed to be more structurally stable than the no-name brands of cans. After the drinking side of the can had been removed, the cans were washed.

3 In order to prepare the cans for installation into the box, they should be clean of any beverage residue and the tabs must be removed. In order to quickly dry the cans, we placed them on baking sheets and let them dry in the oven set on a medium setting. After the cans are dry, they should be lightly sanded (we will be painting them later and the mat black paint will better adhere to the exterior). The bottom of the cans is then punctured in a pin-wheel style design. We used chisels in order to achieve the desired pattern. The pin-wheel pattern causes the air to rotate and generate heat as it rises. After the cans have been cleaned, opened and punctured with the pin-wheel pattern, they should be attached together using a high-temp silicone adhesive. The cans should be stacked in columns that fit the dimensions of your solar heater; in our case, we used 12 rows of 16 cans.

4 The silicone adhesive should be generously applied so that the seal is air tight as to prevent hot air from escaping. Once glued together, the cans will need 24 hours for the silicone to cure. We assembled the rows of cans on corrugated sheets of fiberglass. The ridges hold the cans in place so they can dry. Because we built our solar air heater outside and in the winter, we used a blow dryer to assist in the drying process.

5 Once the cans are solidly glued together, the cans should be spray-painted matt black in order to better generate heat. Construction of the box, the header and footer We cut the ply-wood to our desired dimensions and assembled the pieces using 1 ¾ inch screws.

6 The ends of the box are bowed; be sure that both the top and bottom mirror each other. Essentially, the solar air heater is an insulated box. You can make yours to whatever dimensions you require. We constructed ours to suite the exterior of the building, with dimensions of 4 x 8. The box has both an insulated header and footer which act as the air intake and exhaust chambers.

7 Both the header and footer require a hole for the air intake and exhaust. This should be about the same size as a vent for a household dryer, which is what we used. Your intake exhaust valves will correlate to the particulars of where your solar air heater will be installed. Once the simple box has been constructed, the pieces for the header and footer should be installed. To contract the header and footer pieces, cut two pieces of the ply-wood so they will sit flush in the larger box. Use the drill press to drill holes for the cans. They should be roughly the same size as the rim of the pop cans. These holes will both keep the cans in place and direct the air from the intake chamber into the columns of cans. The holes for the cans should be evenly spaced, reflecting the dimensions of your solar air heater. Insulation of the box The box needs to be insulated so the warmed air cannot escape. We insulated the box by covering the back and sides with ¾ foam insulation. We then covered the insulation with aluminum flashing this not only gave the solar air heater an esthetically pleasing appearance, but also serves to protect the insulation and the wood from any ill effects associated with the high heat of the air.

8 The aluminum flashing we used came in rolls that measured approximately 12 in width; we sealed the seams using metallic tape. We also covered the nails with the metallic tape, in order to prevent any leakage. Once the aluminum cans are installed in the box, it needs to be sealed shut. We were able to secure a heavy duty piece of bullet-proof glass (Lexan), but Plexiglas works well. However, be aware that it can lose colour and change shape over time; Lexan is more durable.

9 We drilled holes in the Lexan to accommodate the screw placements. We then screwed the Lexan to the box, again using 1 ¾ decking screws. The solar air heater is now complete; all that is left is to install it in your desired location. A location that is south-facing is ideal, as the more direct sunlight it receives, the more heat will be generated. Nonetheless, any amount of sunlight will work and cause the passive system to activate.