Solar Dry Kiln for Tropical Latitudes

Developing countries that export forest products often lack the capital to build high-cost dry kilns. Many of these countries are in the tropics where solar radiation and ambient temperatures are high. The low-cost solar dry kiln described in this paper was designed and tested because solar dry kilns can be built and operated at low cost and have possible application in these countries. The design was for a 2.4-m3 capacity solar dry kiln having an insulated drying compartment attached to a horizontal external solar collector. This design allows collector sizing to match the energy demands in the dryer. The kiln was designed to be as low-cost as possible, but still be able to provide fully automatic control of scheduled drying. One dry kiln was built in Madison, Wis. in 1977 and was tested and improved during succeeding summers. Northern red oak and hard maple, 2.9 cm thick, were dried from green to 8 percent moisture content in 54 and 26 days, respectively. Kiln temperatures reached as high as 24.6?C above ambient temperatures. Vent control was adequate to provide the relative humidity control necessary for scheduled drying. Another kiln, built at a furniture factory in Sri Lanka, demonstrated that the design can perform successfully in a tropical location.

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