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Glen and Ronny's Solar Heater Project 2007-2009

Construction:

The main box is made from 1x6s with Luan backing. The dimensions are 12 feet long by 30 inches wide.
 
 
Tried to make it as square as possible with my extremely limited carpentry skills. Glued everything together with Liquid Nails and used outdoor deck screws.
 
 
Used corner braces to make it a little sturdier. Sealed every joint you can imagine with silicone.
 
 
Used 1X4s to edge the top.
 
 
Used more 1X4s to connect the Luan joints.
 
 
Attached 4 screw eyes for a dual purpose. The first reason was so I could hang it up on the garage wall in the warm months. The second reason was to have points where I could stake it to the ground. Have yet to use them. The complete solar heater turned out to be pretty heavy, sits nicely along the garage wall (on the floor), and seems to have enough weight to hold itself in place.
 
 
Glued and siliconed in one layer of 3/4" and one layer of 1/2" polyiso insulation along the back wall.
 
 
Cut out the holes for the inlet and outlet ducting.
 
 
Fit the 3 inch, 90 degree bend duct elbows.
 
 
Glued and siliconed in 3 layers of 3/4" polyiso on the sides. Spacers were temporary to hold the insulation in place while the glue/silicone set.
 
 
Roughed in the 3 inch flexible aluminum ducting. Used duct connecters and aluminum tape to connect them. The idea to use aluminum ducting came to me after seeing other peoples projects using aluminum cans. It just seemed a lot easier than connecting cans together. Also I figured that the round shape and corrugations would provide more surface area as well as providing air flow turbulence.
 
 
Routed the 1X4 top edge trim to hold the polycarbonate glazing, attached with glue and sealed with silicone.
 
 
Sanded and painted with high temperature black barbecue grill paint.
 
 
Spray painted the ducting with more high temperature paint.
 
 
Mounted the snap switch in the outlet elbow. The switch connects at 110 degrees and disconnects at 90 degrees.
 
 
Attached the ducting to the box with silicone. Space is 3/4 inches between ducting. Used 1 by wood as spacers to keep it even.
 
 
Attached UV protected, twinwall polycarbonate glazing to the box with silicone. Left some room for expansion and contraction.
 
 
This part was interesting. Had the heater leaning against the house while trying to figure out how to duct it through the window. With no fan running, within 30 - 45 minutes the temperature climbed to over 200 degrees, the polycarbonate bowed, expanded and popped loose. So I ended up resealing and trimming it with some moulding.
 
 
Here is the input and output ducting through my window. The window piece is polyiso insulation trimmed in automotive weatherstripping. The output ducting is insulated with foil coated bubble wrap. Looked a long time for a fan. One of the shortfalls of this design is a very long ducting run with extreme bends. Apparently HVAC design people highly recommend against this! Anyway, I needed a strong cheap fan and after much searching found a 175 CFM rated marine bilge fan that fit the bill. It is connected to a transformer normally used for flat screen monitors. The setup seems to work well and only uses 48 watts, but it's a little noisy.
 
 
This is the well camouflaged view from a little further back. The inlet has a 1/4 inch screen over the end and picks up cold air from near the floor. The white outlet hose is high temperature industrial and aims the warm air into the main living area.
 
 
The view from outside. For our lattitude in Oklahoma the tilt angle should have been 51 degrees. It's a bit higher but seems to be ok.
 
 
 
This was a nice little project for me and my son that seemed to take on a life of its own. We installed it on 12/31/07 and tested it on 1/1/08. It was very exciting to finally see the thing in action. It kept the house at a nice 68 degrees while it was running with the central heating turned off. We will probably keep the "normal" heat on and use this system as a supplemental heat source. Measured the airflow with a 30 gallon trash bag and the output at the outlet is 40 CFM. It could probably be more efficient with more airflow and a cooler output, but the warm air feels great!

Performance:

Time Conditions Inlet Outlet Outside
09:00 Sunny/Clear, not in sun yet. 56.6 65.1 29.5
09:49 Sunny/Clear, Fan on, 3/4 of heater in the sun. 65.1 110.0 33.9
10:00 Sunny/Clear, Turned off central heat in house.
10:15 Sunny/Clear, heater almost in full sun. 66.0 133.0 34.8
10:30 Sunny/Clear, heater in full sun. 68.0 137.9 34.8
10:45 Sunny/Clear 66.5 141.5 35.2
11:00 Sunny/Clear 68.9 144.6 36.1
11:15 Sunny/Clear 68.3 147.4 36.5
11:30 Sunny/Clear 69.6 148.7 36.5
11:45 Sunny/Clear 68.7 150.0 38.6
12:00 Sunny/Clear 68.3 151.7 38.6
12:15 Sunny/Clear 68.7 151.3 40.2
12:30 Sunny/Clear 68.5 152.9 43.0
12:45 Sunny/Clear 68.7 152.7 46.0
13:00 Sunny/Clear 68.7 151.7 46.0
13:15 Sunny/Clear 68.9 152.2 46.0
13:30 Sunny/Clear 68.5 151.8 44.0
13:45 Sunny/Clear 69.0 149.5 44.4
14:00 Sunny/Clear 68.9 146.3 43.0
14:15 Sunny/Clear 68.7 143.2 41.9
14:30 Sunny/Clear 68.7 140.5 43.5
14:45 Sunny/Clear 68.5 137.4 44.2
15:00 Sunny/Clear 68.7 131.3 44.0
15:15 Sunny/Clear 68.3 128.3 45.0
15:30 Sunny/Clear 68.7 121.6 45.1
15:45 Sunny/Clear 68.5 117.8 45.8
16:00 Sunny/Clear 68.0 111.7 44.0
16:15 Sunny/Clear 68.0 103.4 42.0
16:30 Sunny/Clear 67.6 95.0 42.0
16:37 Fan turned off for the 1st and last time.

Update:

01/04/08....Woke to 30 - 40 mph winds and the solar heater disconnected and laying face down :(  No real damage only a few minor scratches.

01/05/08....Reconnected and now firmly staked down.  Still pumping out heat!!

01/15/08....Still working nicely, but was not satisfied with the airflow and fan noise.  Hooked up a 465 cfm blower from Grainger today. The output of the heater is now 60 cfm, 50% higher! It is also much much quieter.  Getting great heat from this design, but airflow is still a challenge.  Surprisingly sample readings show the temperatures are almost exactly the same as before.  The fan does turn off once or twice in the beginning and end of the sun day now.
 

 

02/09/08....New fan is working great.  On typical 30-50 degree days, at midday the heater room is typically about 75 degrees, the adjacent rooms in the main living area are 71-72 degrees and the bedrooms on the outskirts are about 69-70 degrees.  The house heat never kicks in on sunny days from about 10 a.m. to at least 5 or 6 p.m. Although the design is far from perfect, it is doing exactly what I wanted it to, my house is comfortably warm during the day without using any gas.
 
 

 

04/30/09....At the end of winter 2008 built a simple cover out of 1X2's and luan, painted it white, screwed it to the face of the heater and unplugged the blower. Planted some giant zinnias in front of it. They seemed to like the reflected light. Planted the seeds from the dried flower heads from 2008 and they are already growing like crazy! Oh yeah, season 2008-2009, the heater performed well without a hitch.