Fabrication and testing of a low cost passive solar dryer

Solar energy is a renewable and sustainable source of power for many low to high thermal applications viz. water heating, cooking, drying, power generation, cooling etc. Worldwide, the energy consumption of agriculture drying industries is considerably high but could be reduced through prudent use of solar energy, particularly in countries blessed with abundant solar energy throughout the year like India. The conventional drying process using fossil fuels has a negative impact on the environment and it is expensive too while the solar dryer is much cheaper with no harmful effects on the environment. It is estimated that removing moisture from food from 80% to 10% can prevent product wastage and growth of bacteria, yeast, mold and enzymes. Considering the importance of agriculture drying, a solar dryer was made and tested. This paper presents fabrication details and experimental study of solar dryer for its application of ginger drying. The designed system was installed and tested at the Department of Pure and Applied Physics, University of Kota. The solar dryer was a cabinet type dryer having a base of 63.5cm x 134cm. Three major sets of experiments were carried out to study the performance parameters of the system. Temperature variations at various sections in the device were measured on a number of days. In the first experiment specific amount of ginger were dried and studied. The comparative studies of open sun drying and in the solar dryer were carried out in the second experiment. The full load capacity test was done as a third set of experiments. The solar dryer, fabricated with locally available materials (plywood, G.I. sheet, polystyrene sheet) was an economically affordable system for domestic industries with the drying capacity of 5 kg of agriculture products. The thermal efficiency of a full load system was found to be 29.1%. An experimental study showed that, on the first day, 45% of moisture was removed in the dryer while only 7.06% moisture was removed in open sun drying. The maximum drying rate was recorded on the first day of full load conditions i.e.0.318 kg/h.