Letter 23142

Solar selective coating  

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I am fabricating flat plate solar water heaters. I need a selective coating to apply to the plate, to absorb as much energy and emmit as little energy as possible, and to withstand temps up to 220F. Need a black mate selective coating. I know Thurmalox was a brand to use but I don't find any more info specific to this application. Please help with your info in this.

Thank U,

Jesus Bermudez
Varnier - San Diego, California, USA

Your library will have a whole shelf of books on this subject, Mr. Bermudez. I browsed one some years ago and recall that three good coatings, best first, were black chrome plating, black oxided copper, and regular nickel chrome plating. At that time the author found no black paint that was worthwhile.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

In approximately 1980, a friend and I built a flat roof mounted water solar system on a roof 30'(N/S) x 60'(E/W) consisting of 14 - 4'x 8' copper "selective surface" collectors purchased from Phelps Dodge Copper Co. This building was a laundromat, and had a 3,000 gal insulated storage tank in the building. It was a total drain back system, thus no anti-freeze was ever needed even in cold temperature extremes (-30 F). An effecient heat exchanger allowed us to heat all incoming city water to above 120 degrees for up to 4 weeks at a time in the summer without using any additional heat source, and pre-heated water in winter to between 70 and 90 degrees, even on cold sunny days in January. The whole array (14) collector insulated boxes were built as one unit and faced south, in summer at a 35 degree angle with the roof, and in winter were raised to a 65 degree angle. We were located 17 miles north of the 45th paralel in Northestern Wisconsin. I now live in New Ulm MN, and have a laundromat which I would like to do the same thing with, but cannot seem to find the same type of collector panels to build a similar system. My thanks in advance for any help in locating a solar supply company that I can buy individual components and build my own sytem once again.

Norman L Edlebeck
Laundromat Owner - New Ulm, MN, USA

I believe that Olymco does black chrome plating of solar collectors, and has done so since the era you mention.

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