Development of a Passive Solar Vegetable Dryer

Abstract

Solar dryers are devices that dehydrate items with high moisture content by harnessing solar energy for its operation. The solar dryers generate heated air for removing inherent moisture in the products in contrast to open air drying, which although cheaper, exposes products to contamination from animals, insects, and dust from the environment. This study was focused on the key objective of developing a cost-effective, 4 kg capacity solar dryer that is affordable to the average Nigerian rural farmer by applying standard mechanical engineering principles and using locally available materials. The performance of the developed dryer was evaluated through practical testing, where a test sample of 0.3 kg of pepper and 0.5 kg of okra were dried using the unit and compared to open sun drying of similar quantities of the vegetables as a control experiment. The comparison aimed to assess the effectiveness of the solar dryer in terms of preservation of the aesthetic quality of the samples and drying times achieved compared to open sun drying. The results of the study showed that the solar dryer outperformed the traditional open sun drying method in both the quality of end products and the drying time. Energy consumed for drying the batch sizes using the dryer was found to be 13,110.3 kJ per kg and 8,353.8 kJ per kg for pepper and okra, respectively. The drying efficiency for these batches were determined to be about 19% and 36% for pepper and okra, respectively. The dryer attained a maximum temperature of 70 ºC.