COMPUTERIZED CONTROL-SYSTEM FOR AN EXPERIMENTAL SOLAR LUMBER DRYER

The microcomputer based control system employed in an experimental highly efficient solar kiln and the advantages of using this approach in solar wood drying are discussed. The control system consisting mainly of a personal computer and a data acquisition unit, performs a number of measuring and control functions. The monitored drying variables are wood M.C., collector's temperature, kiln's temperature, and R.H. The M.C. is monitored by recording the weight of the 3.2 m3 timber stack, resting on a weighbridge. The direct and continuous monitoring of timber moisture and equilibrium moisture employed by the control system, makes it possible to run the solar drying process to a target value formed from these two measured drying variables (drying gradient). The developed control system is compared with a semiautomatic system controlling the same solar klin.