Overall performance evaluation of a novel optical truncation method for compound parabolic concentrated photovoltaic-thermal system

Abstract

A variable geometric concentration ratio (VGCR) truncation method was proposed to enhance the performance of compound parabolic concentrated photovoltaic-thermal (CPC-PVT) system in this study. Based on a multi-physics field model of optical-thermal-electrical coupling, numerical investigations using Monte Carlo ray tracing (MCRT) and finite volume method (FVM) were conducted to analyze the effects of the variation rate of truncation ratio (k) and light incident angle (θin) on the overall performance (optical efficiency (ηop), instantaneous thermal efficiency (ηth), instantaneous electrical efficiency (ηele,total), instantaneous electrical power (P), instantaneous exergy efficiency (ηu,total) and economic performance) of CPC-PVT system. Also, the overall performance between the VGCR-CPC-PVT system and the full CPC-PVT (FCPC-PVT) system was compared. The results indicate that, when θin is smaller, there is little disparity in the overall performance between the two systems. However, as k increases, ηop, ηele,total, ηth and ηu,total of VGCR-CPC-PVT system monotonically increase, and the area of the high-temperature region on the PV panel surface decreases. When θin is larger, the VGCR-CPC-PVT system has a smaller shaded area, ηop, ηele,total, P and ηu,total are significantly improved compared with the FCPC-PVT system. Additionally, k has a significant impact on the overall performance of the system, and P, ηu,total and saved reflective surface area (S) are the criteria for selecting k. When using P and ηu,total as the selection criteria, the optimal k value is 0.04. For 0°≤θin≤38°, the average ηop, average ηele,total, average ηth, average P and average ηu,total of the VGCR-CPC-PVT system with k = 0.04 are relatively improved by 1.91 %, 4.59 %, 2.42 %, 3.12 % and 4.04 %, respectively, while the reflector area decreases by 17.5 %, compared with the FCPC-PVT system. The cost-effectiveness of concentrator increases significantly with k.