A Homemade "Factory" Solar Collector

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The glazing seals are a matter of choice. We've found that ethylene-propylene diene monomer (EPDM) gaskets have admirable resistance to weather, sunlight, and chemicals, and are also flexible even in extreme temperatures. Some gaskets are grooved to accept glazing, while others are flat and can be cut or folded to fit. (Silicone sealant can be used as well, but it's obviously a messier proposition.)

As for the isocyanurate insulation board, it can easily be cut to size with a utility knife and a steel straightedge. Because of the frame design, you'll find it easiest to slip the side boards into the partially assembled box. Then, after the hardboard and the precut bottom panel are installed, the surfaces can be painted black, the absorber plate fitted in place, and the frame completed.

The absorber can be either purchased as a complete unit or made up yourself from fintubes (at about a 30% saving). Ideally, the header tubes should have appropriately spaced tees pulled off of them . . . either by the component supplier or by you, using a unibit and an extractor tool. Short of that, the fintube risers can be brazed directly to holes in the headers, but this method invites potential leakage through mechanical and thermal stress. You may also use solder joints (as we did for our testing), but they'll be subject to stress problems as well . . . and will make your collector unsuitable for use with potable water, forcing you to use it with a heat transfer medium, and closed-loop plumbing, to heat your household supply.

Naturally, the absorber plate must be coated black and mounted, and the headers appropriately capped and plumbed through the frame. (The frames come with mounting clamps for just about any application.)

TRIAL WITHOUT ERROR

LIST OF MATERIALS

(2)13' 4" corner key frame sections w/caps

(8)corner keys

(7)1/2" X 4-1/2" X 96" unpainted copper fintubes

(2)3/4" X 33-1/2" copper header tubes w/caps
    1/2" X 22' EPDM rubber gasket
    3' X 8' fiberglass-reinforced plastic glazing
    1" X 4' X 8' foil-faced isocyanurate insulation board
    1/4" X 3' X 8' tempered hardboard

(2)1/8" X 3/4" X 3' aluminum angle supports
    13 oz. Thurmalox black solar collector paint

(4)1/2" conduit clamps w/ 1/4" X 1-3/4" bolts and nuts

(26)No. 6 X 314" ovalhead sheet metal screws

We can't speculate on how this panel might function at your specific site, but we can provide you with its performance data taken from tests made at our North Carolina location. We assumed that this panel would most likely be used in a closed-loop system, with a heat exchanger incorporated into the domestic hot water storage tank, so that's how we set it up. To assure accurate and consistent readings, we used fixed thermocouples to establish temperatures, and an insolation meter to determine the amount of sunlight available to the absorber surface on a Btu-per-square-foot-per-hour basis. The panel was fastened to a permanent mount, and the data were recorded during the same two-hour period each midday.

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