Low cost thermal storage for solar dryers in the Himalayas

Abstract: Post-harvest losses in the himalayan regions of Nepal and Bhutan are high, and current drying methods are in need of improvement. This report improves on a previously developed solar dryer design and evaluates thermal storage solutions for the ’SolarFood: Reducing post-harvest losses through improved solar drying’ project. This report uses experimental measurements to compare different dryer configurations, as well as results from previous measurements and experiments to improve the current prototype. The report studies two different solar dryer prototypes located at Kathmandu University based on the same design. Previous hypotheses regarding leakage in the solar dryer prototype were partly solved. Incorporating a thermal storage system utilizing water as the working material can increase control over the solar dryer and increase consistency. The system presented is low-cost and performs adequately. The system is adaptable to different temperature ranges and requirements and should be applicable for use with different drying commodities. Previous studies have utilized rocks or gravel as the working material. A comparison measurement in this report shows water performs favorably toward rocks or gravel.