Development and testing of novel photovoltaic-thermal collector-based solar dryer for green tea drying application

Abstract

A sustainable solar based PVT tea drying system has been developed to minimize the dependency on the non-renewable commercial tea drying system. In this work, the effect of operating conditions on the performance of a photovoltaic-thermal (PVT) collector-based solar dryer is investigated under sunny and cloudy weather conditions for three different cases- Case-I (natural convection), Case-II (forced convection with an air velocity of 0.096 m/s), and Case-III (forced convection with an air velocity of 0.014 m/s). Firstly, energy performance of the PVT system has been evaluated for all the three cases under sunny and cloudy days, which show that the energy performance has been enhanced to a maximum value of 58.71% and 53.95% for sunny days and cloudy days, respectively, and these are obtained in case of case-III. Then the drying of green tea under mixed-mode drying (MMD) and indirect mode drying (IMD) are presented under sunny days for each of the three cases and compared with open sun drying (OSD) and shade drying (SD). The moisture content has been reduced from 2.95 (d.b.) to 0.14 (d.b.) in all the cases of drying modes. Further, the drying kinetics of green tea leaves is compared using existing models, and a new drying model is proposed, which is found to predict the moisture ratio better. The maximum PVT dryer efficiency, moisture effective diffusivity, and specific moisture extraction rate (SMER) are 26.37%, 4.97 × 10−9 m2/s, and 0.6125 kg/kWh, respectively, for MMD process.