Chang Zehui, Xu Wenfu, Li Xinliang, Liu Xuedong
Aiming at the receiver overheating of the compound parabolic concentrator (CPC) for solar greenhouse heating during nonoperating periods, this study proposes a novel compound parabolic concentrator photovoltaic-thermal device, with PV modules installed inside the CPC cavity. By intercepting incident solar radiation at different incident angles, these PV modules reduce the amount of radiation concentrated on the receiver and thus mitigate the overheating risk. First, TracePro is used to simulate rays’ propagation and focusing paths of the device at different incident angles, and quantify the changing trends of its optical characteristic parameters. Based on these results, an experimental platform was established to evaluate the anti-overheating performance of the compound parabolic concentrator photovoltaic-thermal device and to compare its overheating prevention effect with that of a standard CPC. The results show that, optical parameters of the device decrease initially and rise subsequently. Compared with the standard CPC, the maximum reductions in the light acceptance rate and concentration efficiency of the device are 26.4% and 25.3%, respectively. The maximum energy flux density on the receiver surface is 9276.1 W/m2, which is 25.6% lower than that of the standard CPC. Under clear-sky conditions, the receiver fin temperature reaches a peak at noon. The maximum temperatures of fins R1 to R6 are 102.2, 92.2, 91.7, 92.7, 98.6, and 100.3 ℃, respectively. These values are 15.7, 21.1, 23.4, 13.8, 19.9, and 14.6 ℃ lower than those of the corresponding fins in the standard CPC. In addition, the maximum output power of PV module Ⅰ and PV module Ⅱ are 4.8 and 3.8 W, respectively. Economic analysis further indicates that the static investment payback period of a solar greenhouse heating system integrated with this device is approximately 2 years.
