In many countries of the world, the use of solar thermal systems in the agricultural area to conservevegetables, fruits, coffee and other crops has shown to be practical, economical and the responsibleapproach environmentally. Solar heating systems to dry food and other crops can improve the quality ofthe product, while reducing wasted produce and traditional fuels—thus improving the quality of life,however the availability of good information is lacking in many of the countries where solar foodprocessing systems are most needed. Solar food dryers are available in a range of size and design and areused for drying various food products. It is found that various types of driers are available to suit the needsof farmers. Therefore, selection of dryers for a particular application is largely a decision based on what isavailable and the types of dryers currently used widely. A comprehensive review of the various designs,details of construction and operational principles of the wide variety of practically realized designs ofsolar-energy drying systems reported previously is presented. A systematic approach for theclassification of solar-energy dryers has been evolved. Two generic groups of solar-energy dryers canbe identified, viz. passive or natural-circulation solar-energy dryers and active or forced-convectionsolar-energy dryers. Some very recent developments in solar drying technology are highlighted.
Renewable and Sustainable Energy Reviews RSER 589 1–26