Originally Posted by
rreidnauer
. . . Second, these are flat-plate collectors. I don't recommend them, especially if you live anywhere there is less the 98% sunny skies. They suffer from two problems which reduce their efficiency. First problem, the flat glass front. Almost every photo on their website reflects the problem, literally!!! Notice the glare on the panels. That is reflected light that never gets collected. It's not bad if the sun is directly in front of the panel, but as angle increases, energy absorption decreases exponentially. Second problem, the collector itself. It's just black tubing under glass. The problem occurs when a cloud or any form of shadow reduces light input. Heat energy of the fluid being pumped through the panels is actually radiated back out of the panel. There are supposed coatings to help reduce this from happening, but it can't be avoided. Essentially, when a cloud passes by, you go negative production.
I strongly recommend evacuated tube collectors. They suffer neither of the problems of flat-plate collectors, as they are able to collect energy at an angle as efficiently as if directly forward, and being that they are vaccuum tubes, heat energy can't be released back when shaded. (that, and the fact that the fluid never enters the collector tubes to start with) Efficiency all around is higher. . .
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