Experimental Solar-Dehumidifier Kiln for Drying Lumber

The technologies of solar and dehumidification kiln-drying-two energy-efficient methods for drying lumber–were merged to take advantage of the benefits, while eliminating many of the drawbacks of the individual methods. A 1-1/2 hp dehumidifier was installed in a 500-board foot solar kiln to test the performance of the combined system. The kiln featured 122 ft2 of external solar collectors made of aluminum beverage cans, a dehumidifier operated with a high-temperature refrigerant so that the kiln could operate at temperatures to 180?F, and a small steam generator to condition the lumber at the end of drying. The kiln was tested by drying 4/4 yellow-poplar lumber. One charge was dried in each of the four seasons of the year. Drying times for the lumber from approximately 100 to 7 percent moisture content ranged from 6 days in the summer to 18 days in the winter. Drying degrade was estimated to average only $3.60 per thousand board feet. Solar-dehumidification dried wood faster with less drying degrade than solar-drying. Energy costs for the solar-dehumidifier kiln were only 82 percent of those for solar-drying.

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