Solar Collectors(metal And Fabrication Content)
Q: Has anybody built there own solar panels? I googled around and found some info but wanted to hear from RCMs. I also posted to alt.solar.thermal and alt.energy.homepower and got no replies. I have a bunch of sheet copper and thought I could braze or solder it to 3/8 tubing and paint it black, place in an insulated box .....The goal is to supply my domestic hot water or at least reduce the amount of fuel oil we use. As always I'd like to do most of this myself but if building panels doesn't make sense (efficiency wise) then I'd look to fabricate and install whatever else I could. (more time then money)Also if anyone has experience with heat exchangers that too would be helpful.
A: I played around with some things about 20 years ago, just piddling during a winter, and found that painting a common red brick black in color raised it's temperature 9 degrees when compared to a red brick placed next to it on wood blocks in the direct sun. In Mother Earth News at the time, the statement was made that a dark green color was actually the most heat absorbent color to use. That's about as deep as I got into it. Finding black body info. is hard , I think it's because solar people want the edge from proprietary info. Something turns copper or was it aluminum black , maybe sulfuric acid? Don't know if it will hurt the pipe , but its best to stain it somehow. Maybe anodize it flat black. I tried engine paint once and it didn't last long , but then I was focusing about 25 suns on it and what ever water boils @ 300 psi. That was one scary experiment. Try looking for redrock web site from alt.thermal it has tons of info. in it. My (commercial) 4x10 collectors use 3/8 tubing for the 10' direction, but a dozen or more in parallel, all fit into 1" (domestic) or 1.5" (pool) headers at the ends. If you're thinking of a single serpentine tube, 3/8 will waste serious pumping energy. You'll also want to think about layout for getting the air out initially, and draining the water out for freeze protection. Or plan to use a heat exchanger at the other end, and antifreeze. Also remember that steam is serious power - if your pump stops and your system doesn't thermosyphon, it _will_ exert awesome force somewhere... And you can't just switch off the sun to solve the problem...
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