A Homemade "Factory" Solar Collector

(Page 3 of 3)

May/June 1985
By the Mother Earth News editors 
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In order to keep the "fluke factor" to a minimum, we took 47 separate readings and averaged the results. A typical entry noted the date, time, water inlet and outlet temperatures (from which we established the differential, or delta-T), the ambient temperature, the water flow rate, and the number of Btu per hour available in insolation.

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Given the formula:

we merely had to plug in the values to determine how effectively our homemade device converted water to hot water. So, for example, the standard 1/2-gallon-per-minute flow delivered by our circulating pump figures out to 30 gallons an hour, or — by weight — 250 pounds per hour. This times an average deltaT (16.33°F) yields 4082.5, which divided by 22 (the square foot surface area of the aperture) gives us 185.56 . . . the number of Btu gained per square foot per hour. By comparing this to the number of Btu actually available over the same period through insolation, we can ascertain the collector's percentage of efficiency — in this case 65%.

So what's the bottom line? In dollars and cents, the cost of building this panel from premanufactured parts came to just over $200, which puts it in the $10-per-square-foot range. In comparison, a typical factory-made collector may cost twice that . . . a factor that should, of course, be balanced against its quality and long-term performance. As for efficiency, many manufacturers refrain from making claims, because they can't be responsible for installation practices. The final decision is yours, and — as is often the case — you'll probably get what you pay for . . . but you can choose to spend either your money or your time!

EDITOR'S NOTE: The Solar Components Corporation catalog is available from the address above at a cost of $1.00 to those who make reference to this article. Another component supplier, Solar Usage Now (Box 306, Bascom, OH 44809), also has a catalog, which is available for $7.95.

COMING UP

A couple of MOTHER's staffers have been working on a hot air collector designed for the home-builder. We'll be running a full report on that in an upcoming issue!

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  • Don Posey 5/17/2009 8:12:43 AM

    A couple of tips:

    A glazier (window manufacturer) may be able to supply some of the "channel" type materiel for the frames, as they are used in the construction of patio doors, windows, etc. Just a thought. Sheet metal shops can be a godsend when special parts are needed. They seem to have been forgotten by most of us, yet are plentiful if you look! Your A/C contractor may have a sheet metal shop that can do fabrications for you rather inexpensively.

    Also keep in mind that this article appears to have been written in 1985, so mfr's mentioned may no longer exist.

    Modern designs incorporate a small PV panel to power a low voltage DC pump (El Sid, etc) for circulation of water or heating fluid. If you don't want 2 frames, incorporate the PV panel into the frame as well. 1 Frame for both solar units.

    For those concerned about thermal loss overnight, I recommend connections to the panel be made with galvanic (or insulated) unions These are unions with a built in insulator to inhibit transference of current to prevent galvanic corrosion, and are readily available at a PROPER plumbing supply house. They are typically used when connecting copper fittings to steel pipes or some other dis-similar metal. They would serve as a thermal barrier as well, being insulated as they are. Of course a check valve is the primary recommendation-it's practically mandatory....

    For the gent looking for tanks....Ruud appears to be a supplier to a couple of Solar Tank Kit mfrs. I intend to contact Bradford-White however and see if they offer any.
    You could simply purchase a water heater and convert it. Right now, that appears to be the cheapest route, because once you say "Solar", the $$$ signs pop into the salesperson's head!

    The three big Wtr Htr mfrs in the US: Rheem/Ruud, A. O. Smith, and Bradford White. There are many others, but these are the big three, and provide tanks for many other brands (Sears, Kenmore, etc).

    Just

  • Mike in Beatty 1/6/2009 8:32:45 PM

    I'm building flate plate solar collectors, and as Jim Todd stated, I can't find any aluminum frame materials as described in this article. Am looking at steel framing studs as an alternate. Most flanged aluminum in 4 inch widths is about $80 for a 10 foot piece.
    Any ideas welcome to construct a collector frame. No wood.

  • Jim Todd 9/3/2008 1:56:32 PM

    Does anyone have any sources for the "corner key frame sections" and corner keys? I checked both Solar Components Corp. and Solar Usage Now and can't seem to find anything.

    Thanks,
    Jim

  • John K. Rupp Jr. 6/28/2008 6:00:29 PM

    This is the first time I've read any article from Mother earth. Presently I'm gathering info for a solar hot water, to heat my house with oil back up, since my heater is only 3 years old. My water storage tank will have a electric back up with 1 heat exchanger. I'm having a hard time finding the hot water storage tank. So looking up kalwall- Sun-lite panels I came across Mother earth. Thank you for the info.

    John Rupp

  • John K. Rupp Jr. 6/28/2008 5:59:08 PM

    This is the first time I've read any article from Mother earth. Presently I'm gathering info for a solar hot water, to heat my house with oil back up, since my heater is only 3 years old. My water storage tank will have a electric back up with 1 heat exchanger. I'm having a hard time finding the hot water storage tank. So looking up kalwall- Sun-lite panels I came across Mother earth. Thank you for the info.

    John Rupp

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