Performance Evaluation of an Onsite-Fabricated Solar Dryer for Drying Rhizomes in Rural Bhutan

Abstract

Post-harvest losses due to the unavailability of appropriate drying technologies poses a significant challenge to the preservation and marketability of agricultural products such as turmeric rhizomes in rural Bhutan. This study evaluates the performance of an onsite-fabricated solar dryer with testing conducted at the Khengrig Numsum Cooperative (KNC) in Zhemgang which is in rural part of Bhutan. The dryer was fabricated on-site using locally available materials to minimize cost and provide an alternative to traditional open sun drying. The dryer was tested over a one-month period by drying turmeric rhizomes. Key parameters such as solar radiation, temperature, relative humidity, drying time and moisture content were monitored throughout the process. The dryer consistently maintained internal chamber temperatures 25- 30⁰C higher than ambient conditions and reduced drying time while comparing to open sun drying. The final product achieved an average moisture content below 10% making it suitable for safe storage and market sale. The result demonstrates that the locally– fabricated solar dryer enhances drying efficiency, reduces contamination risk and improves product quality. This technology offers a viable and replicable solution for small house hold farmers and cooperatives in remote, off-grid regions of Bhutan to reduce post-harvest losses and add value to their agricultural produce.