Comparative study on dual-source direct-expansion heat pumps based on different composite concentrating photovoltaic/fin evaporators

Abstract

Dislike the electrical performance, the heat collection capacity is always disappointing in the photovoltaic evaporators. It is always handled by adding additional finned-tube evaporators, which will increase space occupation and pipeline complexity. In this paper, a novel direct-expansion heat pump based on linear Fresnel photovoltaic/fin evaporator is designed. By integrating concentrating photovoltaic and fins into one composite photovoltaic-air evaporator, the above shortcomings can be solved and the solar & air energy can be fully utilized to maximize the output of the evaporator with a limited area. Compared with the direct-expansion heat pump with compound parabolic concentrator/fin evaporator, this system owns a higher concentration ratio, smaller photovoltaic area (making it possible to be equipped with GaAs cells), and larger finned-tube structure to enhance the heat capacity under the same receiving area. Dynamic models are established in MATLAB and comparative analysis is carried out under different wind speeds, irradiance, and ambient temperature. The influence of running time and the system performance with 40 °C water temperature (in actual application) are also discussed. The average electrical efficiency, COPPVT, and exergy efficiency of the heat pump system based on linear Fresnel photovoltaic/fin evaporator could be 28.21%, 3.55, and 27.07% under 900 W/m2, which are all higher than 16.02%, 3.15, and 20.09% in the system with compound parabolic concentrator/fin evaporator. Therefore, the newly designed system could enhance the performance of the hybrid system.