solar heat on the cheap***

[Frankn]

When I built my house, I designed it to be solar. It has been 13+ years since I built it and I decided it was time to finish the solar heat . I have been heating the slab floor with a hot water heater. The roof is aluminum on perlins so I will use this as the back of the solar panels. The top,bottom and sides will be 1X4 pressure treated lumber in a 4'X8' configeration. I will use 20 1/2" copper pipes. The big problem is the glazing that covers it. I can't find it locally and shipping is hundreds. Anyone know where I can get it within reasonable driving distance from Maryland? If I can't get it , I will go with black 6 mil poly to cover it. That will heat the frame up like an oven.

 

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[dances for eels]

Are you talking about polycarbonate glazing? Are the copper pipes going outside on the metal roof and then going to tie back to the pipes in the floor or to some heat exchanger?

 

[Frankn]

eels, Yes, the double walled,hollow 1/4" thick polycarbonate. The thick walled 1/2" copper tubeing will lay on a peace of 6 mil black poly ethalene on the aluminum roof. They will be incased in a pressure treated 1X4 frame that will be 8'X10'. The tubes will go thru the roof and attach to PEX tubing that will go to a heat exchange tank. the tank will be app. 3'high, 3'deep, and 6'long. It will also have a coil to preheat the sanitary hot water. I already have thr 2k' of PEX in the slab. I have 3 zone valves controlled by seserate thermostats. I use a regular water pump to circulate the hot water in the floor.

 

[dances for eels]

That's where I thought you were going with your system. Do you have an idea of the approximate temperature to expect the water in the roof copper would reach and what if you had nothing on the outside but could run the copper against the underside of the metal parallel to the purlins amd keep them in good contact with the metal? I wonder what that temperature would be? Have you had the chance to make a mock-up section as a test.

 

[Frankn]

No mockup. This is an experiment in motion. I am just going by the basic rules of physics. The roof is AL and the coils are copper so I don't want any direct contact because of the corrosion factor "chemical reaction".
Coils on the inside will not work The AL roof reflects heat. If you touch it in full sunlite it is not hot, but hold your hand about a foot away and you get the heat. I am going to try an oven effect with black 6mil poly as the cover. It will be fully sealed except for safety vents on the lower end. The roof is a 4-12 pitch shed roof. That gives me an area of 50'X35'. I will add more units as required, but I want to leave plenty of room for solar electric panels later.
I will start with one frame with 10 or 20 tubes, a 3'x3'x6' storage tank and a circulator pump. I will monitor the incoming temp rise and tank rise for starters. I have already cut out the frame and will start assembling it. The frame is already groover for the glazing, so I can add it later if the 6mil poly doesn't work out. One end of the frame will be removeable. Copper is expensive. So far I have the T's for a 10 tube setup so I can start on the top and bottom manifolds. Sweating joints isn't my favourite thing, but I can handel it.

 

[Frankn]

Well, the frame is finished, that is fully assembled on the ground. It has to be painted and two mounting arms mounted, then placed on the roof. I am a slow worker because I am usually working on several projects at the same time. I will photograph it when it is on the roof.

 

[Frankn]

I just finished painting the frame and supportr, but the next 4 days are supposed to have rain. Might start on the swetting. Got enough t's to make a ten tube manifold fro both ends.