SUNSHINE POWER
(Page 4 of 5)
May/June 1971
By the Mother Earth News editors
Our second design principle: USE THE M.I.T. PACKAGE SHAPE A, AS SMALL AS PRACTICAL.
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What about the design of the collector itself? The least expensive approach is to absorb the sun's energy with a black surface. Expensive focusing collectors (as used for solar cooking) are not needed in house heating because the collector surface is large and the desired temperature change—compared to cooking—is not great. One of the simplest designs (and owner built) was that used by Harry E. Thomason in Washington, D.C. His two houses were pictured and described in the February 1965 Popular Mechanics.
Thomason converted an existing roof into a collector by first laying down insulation, then blackened sheets of corrugated aluminum and finally . . . 840 square feet of glass! (Possibly Thomason would today cut costs by substituting black plastic sheeting-the composter's friend—for the sheets of aluminum in the sandwich—Ed.)
To transfer the heat down into storage—water tanks surrounded by bins filled with 50 tons of fist-sized rocks—Thomason in stalled a perforated pipe along the apex of the collector/roof. A light downward flow of water from the pipe and across the metal was sufficient to move the heat.
Another oft-quoted design is The Dover House by Dr. Maria Telkes (architect, Eleanor Raymond). The sun-trap sandwich chosen in this case was blackened metal sheeting overlaid by double plates of glass. Circulating air behind the metal carried the heat off to storage and distribution (See fig. 1).
In these two designs we can see many of the contrasts possible (and practical) in solar heat design. Let's look at them in more detail (see Dover vs. Thomason comparison chart).
Each of these plans has some advantages. The Telkes plant had no running costs, except electricity for the fan. Neither system produces smoke, soot, or fumes. There is no stoking, refueling, cleaning or repair, and no wasting of valuable fossil fuel. A further advantage is that air (used in the heat transfer) can't freeze; several water-based systems have had to add anti-freeze substances.
On the other hand, Thomason's water-storage system could doubtedly be cheaper (especially if you have labor at hand to dig, and you're into gathering stone like Scott Nearing did). small commune or large family could probably gather 50 tons of rocks eventually—and it'd sure make plowing a lot easier.
A possible compromise to consider would be the use of a by of both these methods . . . a smaller amount of Glauber's salt than the Dover house, within a larger bin of crushed rock. You should get some of the advantages of both and, undoubtedly some of the disadvantages. It's better than burning all that oil, though.
If you're going to use heated air to warm the house, you might as well use air all the way because—if you use water—you'll need expensive pumps. Although both the Thomason and Dover houses use electricity to drive fans, etc., it might be possible to arrange a "no moving parts" system of heat "chimneys" to move the air . . . just as the Model T. Ford cooling system moved water. The idea has been used for cooling desert houses; perhaps it can also be used to move heating air (Yes. Wendell Thomas has successfully applied the idea to two homes in the mountains of North Carolina. We'll describe his system soon in MOTHER—Ed.) In any case, if you must use a fan, the electricity doesn't have to be bought from a high-pollution generating plant. Wind-powered and methane gas-powered generators can be set up on the homestead. Ken Kern shows solar-tempered houses in which wind-powered generators provide the fan power.
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