Performance and operation mode analysis of a heat recovery and thermal storage solar-assisted heat pump drying system

A novel heat recovery and thermal storage solar-assisted heat pump drying system was set up. Moreover, the effect of different economic variables on payback period was investigated. The evaporator and condenser were integrated in the drying chamber and the water storage tank was set up in the system to recover the heat effectively and improve the utilization of solar energy. Based on a total required heat of 23.157 MJ for drying 10 kg of radish process, the theoretical analysis results illustrated that when the daily average radiation intensity was 0.480 kW/m2 the system run at solar drying (SD) mode; when the daily average radiation intensity ranged from 0.430 kW/m2 to 0.480 kW/m2 the system run at the solar-assisted heat pump drying (SAHPD) mode; when the daily average radiation intensity was less than 0.430 kW/m2, the system run at the heat pump drying (HPD) mode. The experimental results showed that the coefficient of performance of the drying system was ranged from 3.21 to 3.49 at the SAHPD mode. Furthermore, the SAHPD can save energy consumption by 40.53% in terms of heat recovery and thermal storage. The payback period for drying radish, pepper, and mushroom in the life span of the system was 6 years, 4 years, and 2 years, respectively. Therefore, it can be concluded that mushroom is the most suitable material to be dried in this system.