Review of solar-energy drying systems - II: an overview of solar drying technology

A comprehensive review of the various designs, details of construction and operational principles of the wide variety of practically-realised designs of solar-energy drying systems reported previously is presented. A systematic approach for the classification of solar-energy dryers has been evolved. Two generic groups of solar-energy dryers can be identified, viz passive or natural-circulation solar-energy dryers and active or forced-convection solar-energy dryers (often referred to as hybrid solar dryers). Three sub-groups of these can also be identified, viz integral-type (direct mode), distributed-type (indirect mode) and the mixed-mode type. The appropriateness of each design type for application by rural farmers in developing countries is discussed. Some very recent developments in solar drying technology are highlighted. (C) 1998 Elsevier Science Ltd. All rights reserved.