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Solar air heater
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Solar Air Heaters
Solar air heaters are systems that collect solar energy and transfers the heat to passing air, which is either stored or used for space heating. The collectors are often black to absorb more of the sun's energy and a conductive material, often metal, acts as a heat exchanger. There are many different designs and systems may include fans to increase the flow rate of air. Alternatively, a passive collector can be built whereby the hot air rises and draws fresh air through the bottom. Fans can often increase the performance of the system, but require additional parts and adds complexity. Solar air heaters can compliment traditional indoor heating systems by providing a free and clean source of heat (after initial costs). While clouds effect the energy output of the system, the metal will store energy on a hot day and will reduce the impact of momentary cloud cover. To achieve best results, the system should be unshaded and facing the general direction of the sun (south for the northern hemisphere, north for the southern hemisphere)
breakdown of energy consumption
IN 2000, space heating accounted for 40% of total energy consumption in the UNited Kingdom
How to calculate energy gain and efficiency.
Two basic forms of solar air heaters
Beer can and snake methods. both are easy and effective.
The simplest and made of widely available products is the pop can...
Solar ”Can” Air Heater
This simple small passive solar heater, made from recycled aluminum drink cans, can be used to heat an insulated garage or small room. A larger heater or a number of similar heaters can be used to heat larger spaces, or to heat smaller spaces to a higher temperature.
The box is built from 2″ x 4″ studs and a sheet of plywood, measured to tightly hold 5 rows of 10 black-painted aluminum drink cans. The inside of the box is sealed using caulk to prevent hot air from escaping. Cold air is drawn in from a hole at the bottom of the box and heated air emerges from the top passing through a pipe into the space to be heated. A Plexiglas sheet is glued to the top of the box to let sunlight in but not let the hot air escape.
This solar space heater works by drawing the air to be heated into the bottom can of a column of cans. The air is then heated inside the cans by the sun’s energy and the hot air within them rises upwards (thanks to convection) to be fed into a pipe which re-enters the building to be heated.
For the air to pass through a column of cans, holes must be drilled into them. There is already a hole at the top of each can out of which the drink is poured. That just leaves holes at the bottom of each can to be drilled. In the bottom can of each column, a 1 inch hole is drilled in the side.
The cans of each column are glued together using caulk or silicon adhesive and painted using black paint to help them absorb the sun’s energy. Barbecue,fireplace or stove paint is excellent for this as it will not flake off. Make sure it has a totally matt finish.
The inside of the box must also be painted with the same paint before the columns of cans are glued into position using caulk or silicon adhesive. The outside of the box should be treated with preservative, varnish, or paint to help it survive the elements for many years.
Ideally the whole unit will be sealed with a sheet of tempered glass. However, tempered glass (unless you can find and recycle a sheet) is also very expensive. Therefore Plexiglas (plastic) can be used, but it will degrade far more quickly and become opaque blocking out the sunlight.
A hole at the top of the box acts as the hot air outlet and can be connected to the building/room to be heated using an insulated pipe.
Required Improvements to this Design
“Snake” the cans together so the air travels farther and has more opportunity to take the heat from the aluminum cans.
Add a fan to both the intake and output sides of the unit, to move more air.
Insulate the box - bottom, sides and ends. One inch rigid foam is easy to work with.
Keep the input and output pipes short and super insulated.
Glass window, 70 x 192 cm (2.3 x 6.3 feet).
Insulation, 2 cm or ~ 1 inch thick 70 x 192 cm for the back of the unit. Cheap at home depot
Exterior construction wood 2 x 4s ~ 18 feet or two lengths of 6.5 feet and 2 of 2.5 feet
Backing of unit. thin layer of plywood
Mat Black Paint/engine enamel, either spray paint or brush paint
~200 pop cans
computer fans or a larger one
power source (solar panel)
3 tubes of silicon for gluing together the cans and the unit
Possibly Aluminum "L" or corner Trim to keep the glass in place. Stainless steel would work too
Screws and such
saw or drill to create inlet and outlet holes
double pane glass window.
Styrofoam or cardboard
optional tape to seal Styrofoam seams
Great stuff spray foam
flat black spray paint
Nails and screws
lots of pop cans
skills and knowledge required
Solar data (maps)
angle and tilt of unit
technical specs (schematic)