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Solar Drying of Microwave Preconditioned Timber
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Paper number 043100, 2004 ASAE Annual Meeting . @2004
Authors: Graham Brodie
Keywords: Solar drying, Microwave, Wood, Wood Modification
The solar energy, which reaches the earth’s surface, represents about 5000 times the present rate of power consumption by the human population. Many woodworking enthusiasts and commercial mills have adopted greenhouse style solar drying kilns because they have low running costs, low environmental impact and higher average operating temperatures than air drying systems. Wood drying rates are directly dependent on temperature, wood density and moisture permeability. Kiln can manipulate temperature, but they are powerless to manipulate wood density and moisture permeability. Application of high intensity microwaves to green wood ruptures or modifies wood cells. The net result is substantial improvement in permeability and reduction of wood density. Experimentation in a solar kiln reduced drying time for microwave treated Eucalyptus regnans samples by 33 % compared with untreated samples dried in the solar kiln at the same time. This reduction in drying time is attributable to the combination of a 9 % reduction in mean wood density, a substantial improvement in moisture permeability associated with micro-fractures created in the wood structure and a 34 % moisture loss during microwave treatment.