Build a Simple Solar Air Heater

By Gary Reysa
Published on December 1, 2006
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The author and the south face of his Montana home equipped with a simple solar air heater.
The author and the south face of his Montana home equipped with a simple solar air heater.
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Side-view diagram of the solar air heater shows the air flow pattern.
Side-view diagram of the solar air heater shows the air flow pattern.
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The author, Gary Reysa, checks airflow.
The author, Gary Reysa, checks airflow.
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Front-view diagram of the solar air heater panel.
Front-view diagram of the solar air heater panel.
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The solar collector is built from these simple materials.
The solar collector is built from these simple materials.
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This close-up through the polycarbonate shows the absorber screen, the foam sealer molding, screws with EPDM washers, battens and a bottom vent.
This close-up through the polycarbonate shows the absorber screen, the foam sealer molding, screws with EPDM washers, battens and a bottom vent.

After walking into my workshop one December morning and feeling a bone-chilling 10 degrees, I decided to install a heating system. Given the rising costs of propane and my family’s environmental concerns about using nonrenewable fossil fuels, a solar solution seemed fitting.

I’m a retired aircraft engineer, but you don’t need a similar background to tackle this project. In fact, a solar air heater built into new construction or added to an existing building can be an easy and inexpensive heating solution. Following the simple principles and plan outlined here, you can heat your workshop, barn or even your home with free heat from the sun. If it works here in Bozeman, Mont., it’s bound to work wherever you are.

I reviewed many solar collector concepts and decided to install a thermosiphon air collector on the south wall of the workshop. The elegant, simple thermosiphon design uses only the buoyancy of heated air to create circulation through the collector, eliminating the cost, maintenance and power consumption of fans, sensors and controllers commonly used in other collector designs. On a sunny day, in a cold climate like ours, this simple system can produce heat equivalent to burning about $2 worth of propane (equivalent to about $3 for natural gas).

To minimize costs, I integrated the collector with the structure and used readily available materials. It cost me about $350 and took only one trip to the hardware store. I built and installed it in about three working days. Follow the suggestions below, and you may be able to do it faster!!

How It Works

The thermosiphon collector consists of clear, corrugated polycarbonate panels fastened to 2-by-6-inch studs. The clear panels admit sunlight, and an absorber suspended inside the collector captures the sun’s heat energy. The air around the absorber warms, expands and rises, creating a convection current. Vents at the top and bottom of the collector allow air to circulate through it. Cool air enters the lower vents from the interior, is heated by the absorber, rises to the upper vents and returns to the interior. Air circulation continues as long as the sun shines on the collector.

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