Construction and evaluation of a timber-drying solar kiln

A solar timber kiln with the capacity to season 3•24 m3 of lumber was designed, constructed and used for seasoning commercial sawnwood. The kiln was constructed of a timber frame covered with transparent polythene sheet on the top and black leatherette on the sides. Corrugated, galvanized-iron sheet painted black and tilted at 30° to the horizontal served as a heat collector. Two fans were fitted for air circulation. The kiln attained a maximum temperature of 24° above the ambient temperature. The average efficiency of the heat collector was 38•5%. The solar kiln reduced timber drying time by 33•3–57•1% when compared with an air-drying technique. Sawnwoods (25 mm by 300 mm by 360 mm) of Mansonia altissima and Terminalia superba were dried from 46•16 to 15•02% and from 52 to 15•4% moisture content respectively in 12 days.