FPL design for lumber dry kiln using solar/wood energy in tropical latitudes

Abstract

Developing countries with a timber resource that can be manufactured into finished products either for local use or export 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/wood energy lumber dry kiln described in this report was designed and tested by the Forest Products Laboratory (FPL) for such countries where solar dry kilns can be built and operated at low cost. The FPL design is for a 6,000-fbm capacity kiln having an insulated drying compartment, an external horizontal solar collector, and a furnace room containing a wood burner. Capacities larger or smaller than 6,000 fbm are also possible. This design allows collector and wood burner sizing to match the energy demands of the dryer. The design also incorporates low-cost controls that allow unattended drying when operated as a solar-only dryer. Manual firing is necessary when the wood-burning system is supplying the energy. This kiln design is the final, commercial-size version established after years of testing several 1,000-fbm capacity prototypes. In December 1984 a kiln of this design was built in Sri Lanka at a factory that manufactures furniture and laminated beams from rubber and coconut wood.