Energy and exergy analysis of a switchable solar photovoltaic/ thermal-phase change material system with thermal regulation strategies

The overheated photovoltaic (PV) panels during the late experimental period and severe temperature stratification of the phase change materials (PCMs) are critical factors influencing the photovoltaic/thermal-PCM system efficiency. In this work, an outdoor experimental switchable PV/T-PCM system coupled with copper fins and flexible thermal regulation strategies was investigated to maximize the energy conversion efficiency. The effect of different fin heights on the efficiency of the PV-PCM system without water flow was firstly investigated. Second, five cases under various thermal regulation strategies utilizing water flow were comprehensively investigated by the energy and exergy analysis. For the full-time regulation, both thermal energy and exergy efficiencies (eta th and Ex_th) increased when the water flow rate grew from 0.11 L/min (Case 2) to 2.92 L/min (Case 5). Case 5 presented the highest eta th and Ex_th of 86.49% and 2.06%, respectively, and increments of 4.40% and 4.35% in the electrical energy and exergy efficiencies, respectively, with the addition of PCMs. At the same water flow rate of 0.11 L/min, the electrical energy and exergy efficiencies in Case 6 increased by 11.46% and 11.35%, compared with Case 2, indicating that the intermittent regulation is more beneficial for improving the photoelectric efficiency of the PV/T-PCM system.