Modeling and experiment of solar crop dryer for rural application

An indirect passive convectional solar dryer consisting of a solar air heater and dryer chamber is designed, manufactured and tested for its performance. It plays a major role in reducing crop wastage and opens a way to food preservation. The area of the solar collector required to dry a batch of 10 kg of tomato within two days is calculated. The performance of the collector is improved through the use corrugated absorber to create turbulence for air flow and a highly insulating material to minimize heat losses. The thermal performance of the solar dryer is tested under the local weather conditions considering the effect of wind, humidity and cloudiness. The average thermal efficiency of the solar collector is calculated to be 21.5% at air flow rate of 0.0564 kg/s. At the same air flow rate, the maximum daily drying system efficiency is calculated to be 25%. Besides the maximum temperature of the solar dryer attained at the absorber plate is 77°C at 12:00 AM when the solar radiation intensity reached 1021 W/m² during no load test. Regarding the economical feasible it is analyzed using the common economic parameters such as payback period, net present value and benefit to cost ratio analysis methods. Hence the payback period is about eight months that is someone investing in this solar dryer will return his investment with less than a year. Finally the benefit cost ratio is 11.8 since this ratio is much greater than one the solar dryer it is in the acceptable range.