The $350 DIY Solar Heater

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Solar power seems to be the energy source of choice for the do-it-yourselfer, and today we came across another project that allows you to cut your utility bills and produce green heat for a relatively small investment: the $350 solar heater. Gary Reysa of BuildItSolar.com takes the home handyperson through detailed steps to create a thermosiphon air collector ready for installation on the south-facing wall of a home or building. According to Gary,

The thermosiphon collector consists of clear, corrugated poly carbonate panels fastened to vertical 2 by 6s. The clear panels, on the building’s south face, admit sunlight. An absorber—in this case, two layers of black metal window screen—suspended inside the collector captures the sun’s heat energy. The air around the mesh expands and rises as it warms, creating a convection current. Vents located at the top and bottom of the collector allow air to circulate and become heated. Cool air enters the lower vent, is heated by the absorber, and rises through to the upper vents that exit into the building’s interior. This circulation of air continues as long as the sun shines on the collector. At night, as air in the collector cools to outside temperatures, airflow tries to reverse. Air in the collector sinks through the bottom vents and attempts to pull the warmed air from the building through the top vents. Use of flapper valves on the top vents helps prevent this reverse circulation and keeps the heat inside.
He estimated that he built his own heater in three eight-hour days with materials found in one trip to the hardware store. Perhaps the only downside to his design is the size: at 20 feet x 8 feet (6.1 x 2.4 m), the collector requires a large wall space for installation. On the upside, he built his in Montana; as he notes, "If it works here, it's bound to work wherever you are!" ::EnergyRefuge.com via Hugg