Design and tests of a solar-dehumidifier kiln with heat storage and heat recovery systems

A rockbed heat storage unit, an additional solar collector, and a heatpipe heat recovery system were added to an existing experimental solar-dehumidifier kiln and tested with 4/4 yellow-poplar. This novel system kiln-dried and conditioned yellow-poplar lumber from green (92%) to 8 percent moisture content in 7 to 11 days throughout the year. These drying times are almost equal to the conventional steam-heated kiln-drying time of 6 to 10 days. Lumber quality was excellent. Only 2 out of the 603 sample boards changed in grade after drying. The lumber was lighter in color than conventional kiln-dried lumber. No collapse, surface checking, or end checking was observed in the dried lumber. Adding heat storage and heat recovery systems and a second solar collector to the solar-dehumidifier kiln increased the kiln’s energy efficiency by nearly 30 percent. A solar-dehumidifier kiln, with heat storage and heat recovery systems and an additional collector, offers an energy-efficient method of drying hardwood lumber, especially in parts of the world where sunshine is abundant and electricity is available at a reasonable cost.

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