Building a Simple Solar Air Heating Collector

Air enters at the lower right and makes its way
around the baffles to exit on the upper left.

First of all I decided to go with four baffles instead of two to provide a longer run and greater temperature rise. I put the collector on the southeast side of the addition I built onto my small shop last spring. This gets a lot of good direct morning sun. This helps to start heating things up quick.

I have another wall mounted TAP on the back south facing wall designed like the one you have on your shop though not as big. It starts to kick in good after the active one is shaded. The addition I'm heating is approximately 200sq.ft. and is yet to be insulated.

Photo 1: Layout of collector on the wall.

Photo # 1: I marked my level and plumb lines for the inside measurements of the frame. I'm using 2x4's for the frame. Making sure that the first vertical line is plumb and also that the first horizontal line is square with the vertical. I'm sure you know that you'll be sorry if they're not. The little tool in the photo is a Dremel tool I used to cut out the inlet and outlet ports. A jigsaw will work just as well. I like the dremel tool because it cuts such a nice circle.

Photo 2: Cutting the inlet and exit vent holes.

Photo # 2: For this collector I cut 5.25"(13.3cm) inlet and outlet holes because the fan I'll be using has a 5"(12.7cm) diameter blade.

Photo 3: Installing the collector frame on the wall.

Photo # 3: The frame is 39.75"(1meter) x 64.25"(1.63 meters) inside measurements because of the glass I have on hand. I used 4"(10.16cm) ex. decking screws counter sunk 1"(2.54cm) to attach the first vertical frame member to an existing stud behind the wall, for the horizontal one I put screws in every stud I could hit. One vertical member didn't land on an inside stud so I attached it from the inside using 2"(5.08cm) sheet rock screws. I primed all frame parts before attaching them then filled all screw holes with caulking.

Photo 4: Installing the absorber and baffles.

Photo # 4: I then used 1/2"(1.27cm) R-MAX foil faced insulating board inside the frame for the absorber. I then installed the baffles which are 5" shorter than the inside vertical measurement, and 7 7/8"(20.2cm) on center. I sprayed the inside with Rustoleum high heat flat black paint (with a spray gun). After the paint had dried I caulked all cracks and seams with 100% silicone caulk. Do not skimp on caulking for your collector, you'll be sorry.

Photo 5 -- Finished Collector

Photo # 5: Glass installed, turning vane at bottom right to help the air have a smooth entry. The glass I used had a 7/8" frame around it with enough room for me to drill pilot holes for screws to attach it to the frame. I then caulked all around the exterior of the metal. The funny looking white lines you see behind the glass is weather stripping to make a good seal on the baffles. The only fan I had on hand to power this with was (believe it or not) a microwave fan which turned out to work very well. The length of run through the baffles is 26' 8" (8.12meters). The collector glass comes out to be 40" x 64" (17.77sq.ft.) Collector is 3"(7.62cm) deep making for 4.4cu.ft volume.

Performance:
I have not run a smoke test on it yet and do not have a meter to check the air volume output of the collector. But, I can tell you this much. Early in the mornings, at 9:00am I turn it on and in about an hour the temperature in the building is up by 15F degrees. By noon the collectors output is 50F degrees warmer than the intake air, I've checked this for several days and it is constant.

The collector was not expensive to build at all. Less than $40 and is simple and easy. One note: glass can be costly, I got mine from Habitat for Humanity for $10. So it pays to scrounge around.

One thing about this collector that surprises me is that even after it is shaded for up to two hours the exit vent air is around 20F degrees warmer than the intake air. I didn't realize that reflective ground radiation would play this big of a part on the collector.

Greg

March 21, 2008

This is another illustration of how simple solar heating can be. For only about $2 per square foot for materials and a few hours of labor The collector makes a significant contribution to heating his addition.

Greg's Solar Air Collector

Construction:

The collector was not expensive to build at all. Less than $40 and is simple and easy. One note: glass can be costly, I got mine from Habitat for Humanity for $10. So it pays to scrounge around.

One thing about this collector that surprises me is that even after it is shaded for up to two hours the exit vent air is around 20F degrees warmer than the intake air. I didn't realize that reflective ground radiation would play this big of a part on the collector.