A Homemade Solar Water Heater
(Page 2 of 4)
September/October 1979
By William J. Weber
A plumber friend gave me an old water heater to use for our storage tank, and I was able to "scavenge" all the black plastic pipe and odd fittings I'd need to connect all my units, and plenty of nails as well. Still, try as I might, I couldn't get around shelling out hard cash for my wood and copper materials.
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The lumber costs weren't too severe. In fact, I bought all the wood I needed for the box's sides and support pieces, plus two sheets of styrofoam insulation and one of pegboard Masonite, for a very reasonable $25.59 (see the accompanying bill of materials).
Our project did require one "killer expense," though: copper. I didn't want to spend any money I didn't have to, but I also figured that the outlay for our conducting medium was no place to cut corners. Copper is incredibly efficient at absorbing and releasing heat. And any less expensive collector material would have given us a "temporary gain but a permanent drain."
So, to build the manifold, I bought three 20-foot lengths of three-quarter-inch copper pipe, two rolls of 50-50 solder, one can of flux and numerous fittings. That added up to an admittedly not inexpensive $75.72. (Of course, half-inch pipe and parts would have cost less, but such smaller diameter lines are too restrictive for good thermosiphon flow.)
I also paid $45 for a large 12-gauge copper sheet, which became the main "heat catcher" inside the box. This material is commonly sold in a 36-inch width, so, rather than cut off two inches of copper to meet my 34-by-90-inch requirement, my local sheet metal salesman kindly bent a one-inch border along each side, which made the piece both more rigid and easier to fasten.
To Work, To Work
At last we were ready to build. We made the 34-by-90-inch (measured on the inside) frame from two 12-feet long 2-by-6's. This rectangle had 2-by-2's spiked along its sides and 2-by-4's at its ends to support the collector plate. An extra 2-by-4 was nailed across the middle of the box as a brace. Then we covered the frame's "bed" with a piece of one-eighth-inch pegboard Masonite and two sheets of heat-holding Styrofoam insulation.
Next we started on the main task: welding our copper pieces together. The first stage of this "penny metal" work involved constructing the pipe manifold, a "jail-door" structure that had four "bars" inside a frame-fitting rectangle. (Since each interior pipe section had to be fastened to the top and bottom pipe lines by three-quarter-inch T's, we did a lot of cutting and soldering at the manifold's ends.)
