An Investigation of Energy Consumption, Solar Fraction and Hybrid Photovoltaic-Thermal Solar Dryer Parameters in Drying of Chamomile Flower

In this research, drying of a medicinal plant (chamomile) in a hybrid photovoltaic-thermal solar dryer with and without heat pump was investigated. The experiments were performed at three air speeds (0.5, 1, and 1.5 m/s), three levels of air temperature (40, 50, and 60 degrees C), with and without using a heat pump. Results of analysis indicated that adding a heat pump to the photovoltaic solar dryer decreases drying time, energy consumption, and required specific energy. Solar energy fraction increased with decreasing air temperature and velocity. Analysis of the dryer-related parameters showed that the maximum and minimum thermal efficiencies were 33.8 and 16.4%, respectively, both in the no-heat-pump mode while with the heat pump, its maximum and minimum values were 38.4 and 19.7%, respectively. Moreover, the highest and lowest electrical efficiencies for the no-heat-pump mode were 13.4 and 9.1%, respectively; while using the heat pump, its maximum and minimum values were 14.1 and 10.4%, respectively. Results of analyzing the dryer's coefficient of performance for drying chamomile showed that the highest and lowest coefficients of performance were 3.41 and 1.82, respectively. Eleven mathematical models were tested, and Page's model was selected as the best for describing the drying behavior of chamomile flower.