THERE'S A SOLAR HEATED HOUSE ALIVE AND WELL IN PRESCOTT ARIZONA

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Last January, during the most severe test that the system has yet had to face, air was supplied to the house from the bins at an average temperature of 78° F and at a volume of 1,500 cubic feet per minute.

Given the above inputs from the storage units to the living space, we found that-by running the fans continuously throughout the night we could maintain a house temperature of 68°. And what happens when-due to long spells of overcast weather-we pull so much from our stored heat reserve that there's no longer enough left to warm the building? The radiant-heat ceiling panels-which are set to kick on whenever living space temperatures drop to 60°simply take over automatically until the insulated bin of rocks is recharged.

And the primary system plus backup does work! From December 1 to April 1 this past winter (minus several weeks when the Grieves were gone), the solar heating system provided over 70% of the house's heating needs. The cost of operating the two one half horsepower motors 22 hours a day averaged $16.20 a month versus the $70.00-to $100.00 a month bill that the radiant heating system alone runs up.

Interestingly enough, by the way, we've found that we experience a "heat lag" phenomenon with our solar system. That is: We can charge the storage bins for six hours straight and raise the temperature of the air passing from the insulated boxes to the house only a few degrees. Then, for the first several hours after switching to the house heating mode, we find that the air passing from the bins to the living space will actually continue to rise in temperature! Still later-by morning, on an all-night run-the temperature of the supply air will have dropped off only a few degrees from its level at the beginning of the heating cycle.

With summer approaching, we're now looking forward to reversing the operation of the solar system so that we can use it to cool the Grieve house. By running the collector/bin circuit at night instead of during the day warmth should be extracted from the stored rocks, drawn through the rooftop
collector, and radiated to the sky. The resulting "cool" left. in the insulated boxes can then be circulated throughout the residence on the following day.

The coming hot season should give us a chance to try another idea: One major drawback of our )ow-angle (11° instead of the nearly ideal 60°) roof mounted collector is that-as the sun climbs higher and higher in the sky-the unit provides more and more heat just when our house requires less and less. We're going to have a very hot roof in the summer, in other words, just when we don't want it.

To counteract this, we plan to use ventilators and a greenhouse type shading compound to cool our collector and reflect away a portion of the sun that strikes the unit. The shading compound is sprayed on in the spring and floated off in the fall with a mixture of water and laundry detergents.

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