Introduction
Air collectors can be installed on a roof or an exterior (south facing) wall for heating one or more rooms. Although factory-built collectors for on-site installation are available, do-it-yourselfers is better way to go if you have time.
The collector has an airtight and insulated wood frame and a black painted aluminum sheet for absorbing heat with black soda or beer cans and glass in front of it. Solar radiation heats the aluminum which, in turn, heats the air in the cans. An electrically powered fan or blower pulls air from the room through the collector, and blows it back into the room.
Roof-mounted collectors require ducts to carry air between the room and the collector. Wall-mounted collectors are placed directly on a south-facing wall, and holes are cut through the wall for the collector air inlet and outlets.
Simple “window box collectors” fit in an existing window opening. They can be active using a fan, or passive. In passive types, air enters the bottom of the collector, rises as it is heated, and enters the room.
Before Building the Solar Air Heater
First you will need 72 large soda or beer cans (“tall boy”), the cans will be laid down in 8 x 9 grid. The moment you acquire the cans we suggest you stack on top of one another 8 cans. After you are done stacking, measure the height of the 8 cans, than measure the width of a single can. The reason for this is since all cans differ by few mm, we cannot present you with exact dimension for the casing, and therefore you will need this measurement for the fabrication of the case for the cans.
You will need enough plywood to construct a frame for the tin cans. The measurements of the inside of the case will be: the height of the 8 tin cans stacked on top of one another + 1”, and the width of a single can x 9. With these measurements you can fabricate tight enough casing which should just fit the tin cans. Just to get an idea how the casing should look when it’s done take a look at the first image in the next chapter.
You will also need an aluminum sheet that will lie inside the casing which the soda cans will be attached to, and a glass or Plexiglas to cover the casing once the cans are inside it.
And finally you will need matt black paint to paint the tin cans and the aluminum sheet, and silicone to attach the cans to the aluminum sheet and the Plexiglas or glass to the casing.
Building a Solar Air Heater
Step 1: Building the Case
First of all make a box out of plywood. Set the dimensions of the width of the interior of the box exactly the same as the width of 9 tin cans next to each other, and the height as 8 cans on top of each other plus one inch.
For increased efficiency, you should insulate the box to prevent heat escaping through the plywood. If so, size your box so that the cans and insulation will fit snuggly.
Step 2: Drilling the Cans
For the air to pass through a column of cans, holes must be drilled into them. Since there is already a hole at the top of each can for drinking, you will only need to drill a hole through the bottom of the cans.
The bottom and top can of each column a 1/2 to 1 inch hole is drilled in the side. This is done so the air can flow from column to column. Take a look at the images below so you can see the arrangement of the cans and the size of the holes.
Step 3: Building the Can Columns and Painting
The cans of each column are glued together using silicon adhesive and painted using black paint to help them absorb the sun’s energy.
The inside of the box must also be painted with the same paint before the columns of cans are glued into position using silicon adhesive. The outside of the box should be treated with preservative, varnish, or paint to help it survive the elements for many years.
Step 4: Sealing the Solar Heating Box
Ideally the whole unit will be sealed with a sheet of tempered glass. This glass is very strong and resilient to heat. However, tempered glass is also very expensive. Therefore Plexiglas can be used, but it will degrade far more quickly.
A hole at the top of the box is drilled so it acts as the hot air outlet and can be connected to the building/room to be heated using an insulated pipe.
Step 5: Mounting a Fan (Not mandatory)
A PV Electric Solar Panel could be used to power a small fan to drive air through the snake. The final temperature achieved would be lower, but having a large quantity of 30 degree Celsius air entering a room is much better than a much smaller quantity of 50 degree Celsius air.
Step 6: Mounting
You will mount the Solar Air Heater on a south wall or the roof facing the south. On the top of the solar air heater you should drill a hole from which an insulated pipe will come out and will go in the room through a wall. This pipe will bring the hot air inside the room. The same thing should be done with the bottom of the solar collector. The difference between the top and bottom pipe is that the top pipe is used to bring hot air inside the room while the bottom pipe is used to bring cold air inside the collector. If you decide to mount a fan on the collector it should be mounted only at the top pipe.