Performance of a Flexible PV Film Technology as an Auxiliary Energy Source in a Solar-Electric Hybrid Greenhouse Dryer

Abstract

Solar drying is an economical way to preserve agricultural produce. The intermittent nature of solar radiation necessitates use of backup energy for improved airflow rates and to supply heat during periods of low solar radiation. This study evaluated the performance of low-cost, flexible and lightweight solar PV film developed by Power Roll Limited (UK) for food drying application. Two tests were conducted (Trial 1: with fans only on; Trial 2: with fans and electric heater on) using a forced convection solar-electric hybrid greenhouse dryer at no load (empty drying beds). Test results shows that for Trial 1 the PV was able to run throughout the day, while Trial 2 the system run for 6 hours. Further, about 95% of the PV load power was used to run the fans, with the two fans using 144.1 ± 3.0 W and the maximum fan cumulative power was 961 Wh for Trial 1. For Trial 2, the PV load (1510-1524 W) was higher than the PV charge rate (304-694 W), hence the PV power declined to 30%. Further analysis showed that dryer temperatures increased by 5.05oC at a radiation of 800 W/m2 due to the heater. The results on drying of African nightshade (Solanum scabrum) indicated this 5.05oC temperature increase realized through the backup off-grid PV system improves drying substantially. The cost benefit analysis shows that usage of the PV system led to energy saving of about US$ 1.6 from 8.5 kWh of energy used within the 6 hours of PV system deployment.