Mitigating Post-Harvest Losses in Bhutan through Solar Food Drying: Optimization and Analysis

Abstract: Bhutan is the world’s most mountainous country which comes with some logistical difficulties. Due to slow transportation times and lackluster food preservation are the post-harvest losses high which especially affects the rural parts of Bhutan negatively. Solar Food: Reducing post-harvest losses through improved solar drying, is a project set out to design a low-cost solar powered food dryer to improve the quality of food preservation in the Himalayan region and is funded through Swedish Research Council. This project analyzes the temperature changes seen in each component of the solar dryer, such as the heat exchanger, absorber, heat storage and the drying chamber at different air flows. The collected data is utilized to calculate the different efficiencies and heat fluxes. Furthermore, the drying rate was measured for each experiment to determine which flow performs optimally for drying. Thus, getting a good transparency of the system which in turn will assist in identifying potential areas for improvement. The heat exchanger shows a decrease in performance with increasing flow, however, the heat flux between its sides remains fairly constant regardless of flow. In contrast to this shows the absorber an increase in performance with higher flows, and it plateaus after 10 l/s. The remaining energy in the heat storage at the end of each experiment peaked when the flow was 6 l/s, and 10 l/s short thereafter. The drying chamber had the highest temperatures in experiments with 10 l/s. The drying rate increased with increasing flow and showed no end to this trend. The results indicate that a larger absorber would likely be the most beneficial modification in a future design. Additionally, a larger more powerful fan would likely result in better drying rates, however this would increase the overall cost and power consumption and the availability of such equipment might be low.