Most active solar heating systems use liquid – water or an anti-freeze solution – to heat the home. Yet solar air heating offers more possibilities than you might think. Active or passive, solar air heater collectors can be placed directly on an exterior wall or in a window and directly heat the living space. Not only that, they can be very cheap. According to the Department of Energy, “A simple window air heater collector can be made for a few hundred dollars.”

The Definition

A room solar air heater consists of an airtight, insulated metal frame and a black metal plate with glazing to absorb solar radiation. Essentially, a fan pulls air from the room into the collector, where it is heated by the sun, and then redistributes it into the room.

The Benefits

• Solar air heater collectors can directly heat a certain room or pre-heat air passing through a heat recovery ventilator.
• They produce heat earlier and later in the day than liquid systems. Therefore they work hard longer to heat living space, although they are not as efficient as liquid systems.
• Also, solar air heaters do not freeze and small leaks are not a significant problem. Leaks will reduce efficiency, but a major breakdown of the system will not occur.

The Possibilities

• On the Roof. Solar air heater collectors can be placed on the roof like a typical solar collector. They can, however, be hidden quite well in cases where heating a single room is desired. For example, a tile roof could have paths for air flow built into it in order to harness the heat absorbed by the tiles themselves. Ducting is required to transfer heated air from the roof to the room or rooms to be heated.
• On the Wall. Wall air heater collectors, as you might imagine, are placed on the exterior of a south-facing wall. Holes are then cut in the wall to allow heated air to flow in and out of the room.
• In the Window. Window collectors can be active or passive. In a passive situation, air enters through the bottom of the collector. It then rises as it is heated and enters the room at the top. A damper should be used to keep room air from entering the collector during the night. These simple systems, which you could build for a few hundred bucks, do not provide an exceptional amount of heat because the collector is so small. Nonetheless, these window collectors can be very beneficial in the right climate.

Posted on October 10th in Going Solar by Dan.