Solar active air heater, 100% PV powered featuring fifty two square feet of collector space. Home made, on the cheap with scrap and salvaged items!


    After a lot of reading and the decision to build an active solar air panel, the next obvious step was the design, and which construction materials to use. Since this was my first, I did not want to have a lot invested in the project, and I also did not want to cut any holes in the house or siding! So the design height and width was determined by the material at hand. The basic design guidelines for the panel, came from The Complete Handbook of Solar Air Systems . The size of the panel is 16 feet long and 45 inches tall, with a collector space of 14 feet by 45 inches.  Being that I did not want to cut any holes in the house, I built a 12 inch plenum on each side that cover the basement windows. Two six inch ducts feed the inlet and outlet from the windows. You can see some of the details in the photos.

This was built from scrap materials,

except for the insulation, screws and caulking, and paint.

        Materials used;
  • 10 ft sections of metal wall stud plate normally used for constructing walls in commercial buildings.
  • Metal suspended ceiling wall track.
  • 9 inch aluminum siding removed from a house being torn down.
  • The windows were removed from a sun porch, another house that was being torn down.
  • Dow Tuff-R foil backed insulation.


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    The framing was built using the wall stud plate. The ceiling wall track was used to support the sides and center of the collector plates which were made from the aluminum siding. Also the outside is covered with the aluminum siding. You gotta love Ollie's, my favorite closeout store. They got a load of caulking in made by Tremco, at $0.99 a tube, could not pass it up. I used Tremco Specrtra I, a black silicon based construction sealant, and Tremco black butyl rubber construction sealant. I use Tremco products at work, it is great stuff. It takes a lot longer to cure, but it remains much more pliable as the temperature drops.

    The design is in which the air passes behind the collector plate, with a 1 inch air space. I split it into an upper an lower chamber, with a channel between the chambers made from ceiling wall track, and it also serves as a center support for the collector plates. You can see the first piece of aluminum attached on the left side of the first photo below. Using calculations from  The Complete Handbook of Solar Air Systems, it was easy to calculate the need CFM for the blower. But, being that the design was not exact, I wanted to experiment. I purchased a larger CFM blower than was required, and a blower speed control  so I could experiment  with different fan speeds.


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    Above you can see the inside of the inlet air plenum. On the lower left is the six inch inlet and also air diverters which split the air between the upper and lower chambers. At the top corner of the plenum is an air diverter to ease the air around the corner. On the hot (right) side I mounted the thermostat switch in the corner air diverter. The Thermostat turns on at 110 degrees, and off at 90 degrees cycling the blower.  The panel is sitting on three 1/4" steel brackets towards the middle, and a piece of angle iron at the extreme left and right ends. The top and sides are attached to the house with four small aluminum brackets and screws.  The panel frame was mounted first, then the windows attached, then the aluminum covering on the outside.





The completed Solar Air Panel is powered by two used 20 watt Siemans (now Shell Solar) PV panels  located to the left.






    The fan in the photo below has been changed from what I originally had. It is attached directly to the 6" duct. My calculated CFM requirements are 130, but due to the distance of the 25' of 6" duct that feeds a dedicated vent in the living room, I used a single 200 cfm 6" 12vdc 1.6 amp fan. My wife came home one day to find me sawing a hole in the living room floor for the duct work, and commentated "I don't even want to know what in the world you are up to." Inside the control panel below, I used a small 12vdc low power relay to cycle the fan because it would be difficult to get back in the panel to replace the thermal sensor inside the panel. The thermal sensor activates the relay at 100 degrees and off at around 90 degrees. To keep the fan at a constant speed when the sun is behind a cloud, I used a low cost solar charge controller from Green Energies, connected to a few small gel batteries. The two 20 watt PV panels provide around 2.5 amps in full sun, plenty to run the fan and top off the batteries!


    The chart below shows some temperatures from 01/2009. It could probably make more heat in the late afternoon if the panel was tilted toward the south-west a bit more. As the sun's angle changed with the winter season, I saw temperatures peak as high as 150 degrees from the end of January on.