Innovative Wood Drying: Applying Microwave and Solar Technologies to Wood Drying

Emphasis in the hardwood industry is shifting away from structural-grade timber toward the production of high-value products. Many dense hardwoods are extremely difficult to dry without causing defects such as: splitting, warping, twisting, and collapse. Solar power is a convenient and cheap energy source that can be easily applied to timber drying. It greatly improves wood quality and reduces timber drying costs by 50% or more compared with conventional drying kilns; however solar kilns are still slow and powerless to manipulate the density and moisture permeability of wood. A thorough mathematical study of the microwave heating phenomenon demonstrates that intense microwave energy can blast tiny holes through the wood structure to create microscopic pathways through which moisture may readily move. This process reduced solar kiln wood drying times by about 33 % without causing any change in the visible quality of the dried timber. This acceleration in solar drying is attributed to a 9% reduction in wood density and a substantial increase in moisture permeability associated with the microscopic internal fractures created in the wood by the microwave treatment.