A Homemade Solar Lumber Kiln

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SOLAR PANEL CONSTRUCTION

Most literature on solar theory recommends that collectors be slanted to the degree of latitude of the building site, plus 15°. Using that formula, I estimated that 40° would be close to optimum here in southeastern Ohio. But since the sun crosses on a lower arc in winter than it does in summer, I figured I wouldn't be able to hit the correct angle on a year-round basis anyway, so I simply set the collectors at 45°. (Solar panels work more efficiently when slanted so that they'll face the sun's rays at an angle as close to 90° as possible . . . the more directly the light strikes the collectors, the less energy will glance off and the more will be absorbed.)

I began building the sun-grabbers by nailing 2 X 4 wall studs—at 45° angles from the south edge of the floor and 24 inches on center—to the top of the 5-foot opening in the south wall of the kiln. Next, I nailed the sheets of Masonite hardboard to the bottom sides of the angled 2 X 4 studs.

The inner surfaces of my collectors were formed from a stack of 24" X 30" flat aluminum sheets that I obtained from the local newspaper printer (they're used one time, then either sold for pennies each or tossed out). I simply bent a lip on two edges of each piece of aluminum so they could be tacked between the angled 2 X 4's and supported by the hardboard sheets that were secured to the bottoms of the studs.

With the Masonite and aluminum in place, I painted the exposed side of the metal and the 2 X 4 framework flat black. Then I set the recycled storm-window glass across the 2 X 4 studs and nailed a strip of wood across the bottom of each frame to keep the glass from sliding off. Presto! Solar panels.

And they worked. . . hot air began boiling out of the top openings of the collectors soon after the glass was laid in place. Unheated air enters at the open bottoms of the collectors, is warmed as it passes over the black panels, rises to the top openings, then dumps into the drying room.

EXPERIMENT FOR IMPROVEMENT

Having come this far, I decided to experiment a bit to see if I could improve the efficiency of my home-built kiln. For starters, I placed inexpensive thermometers at the tops of two adjacent solar panels. They indicated that the temperature of the air leaving the solar collectors was about 120°F.

Since I recalled reading that a corrugated surface makes a more efficient heat collector than does a flat surface (because it has more area to absorb heat), I modified a few of the aluminum sheets by bending them back and forth over a sawhorse. With this secondgeneration aluminum in place, the temperature of the solar-heated air rose a full 10°F! Needless to say, I removed and corrugated the rest of the sheets as well.

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