Multi-shelf portable solar dryer

The solar dryer reported in this paper was developed to enable farmers to add value to their produce by drying it at farm itself. It can also be used in cottage industries in remote places. The dryer has a multi-shelf design with intermediate heating, passive, integral, direct/ indirect and portable solar dryer. Intermediate heating of air in-between trays results in uniform drying in all the trays. Since the dryer at the farm is not likely to be used throughout the year, it has been made portable. A novel feature of this dryer is that the product can be dried under shade or otherwise as per requirement. The design is low cost to make it economically viable. The maximum stagnation temperature was 75 degreesC in the month of November at Ludhiana (31degreesN). During experiments on drying of fenugreck leaves the moisture evaporation on first, second and third drying day was 1.4, 0.9 and 0.4 kg/m(2) of aperture area. To overcome the problem of reduction in efficiency on second and third drying day, a semi-continuous mode of loading has been investigated, in which the efficiency remains almost the same on all drying days. The shelf life of the dried product is more than one year. (C) 2003 Elsevier Ltd. All rights reserved.