Experimental evaluation of factors affecting performance of concentrating photovoltaic/thermal system integrated with phase‐change materials(PV/T‐CPCM)

The photovoltaic/thermal(PV/T)system is a promising option for countering energy shortages.To improve the performance of PV/T systems,compound parabolic concentrators(CPCs)and phase-change materials(PCMs)were jointly applied to construct a concentrating photovoltaic/thermal system integrated with phase-change materials(PV/T-CPCM).An open-air environment is used to analyze the effects of different parameters and the intermittent operation strategy on the system performance.The results indicate that the short-circuit current and open-circuit voltage are positively correlated with the solar irradiance,but the open-circuit voltage is negatively correlated with the temperature of the PV modules.When the solar irradiance is 500 W⋅m^(−2) and the temperature of the PV modules is 27.5℃,the short-circuit current and open-circuit voltage are 1.0 A and 44.5 V,respectively.Higher solar irradiance results in higher thermal power,whereas the thermal efficiency is under lower solar irradiance(136.2-167.1 W⋅m^(−2) is twice under higher solar irradiance(272.3-455.7 W⋅m^(−2))).In addition,a higher mass flow rate corresponds to a better cooling effect and greater pump energy consumption.When the mass flow rate increases from 0.01 to 0.02 kg⋅s^(-1),the temperature difference between the inlet and outlet decreases by 1.8℃,and the primary energy-saving efficiency decreases by 0.53%.The intermittent operation of a water pump can reduce the energy consumption of the system,and the combination of liquid cooling with PCMs provides better thermal regulation and energy-saving effects under various conditions.

Thermal environment investigation of asymmetric radiation coupled with convection heating

The couple of radiation with convection heating owned advantages of less energy utilization,healthier and more comfortable indoor environment.However,local thermal discomfort was often induced by large vertical temperature difference and radiation asymmetry temperature.This work studied indoor thermal environment characteristics under different coupling ways of radiation and convection heating terminals through experiments and CFD simulation.The studied five scenarios were denoted as:(Ⅰ)lateral air supply+adjacent side wall radiation,(Ⅱ)lateral air supply+opposite side wall radiation,(Ⅲ)lateral air supply+floor radiation,(Ⅳ)lateral air supply+adjacent side wall radiation+floor radiation,and(Ⅴ)lateral air supply+opposite side wall radiation+floor radiation.The overall thermal comfort indices(including air diffusion performance index(ADPI),predicted mean vote(PMV),and predicted percent of dissatisfaction(PPD))and local thermal comfort indices under different scenarios were investigated.For Scenarios Ⅰ-Ⅲ,the local dissatisfaction rates caused by vertical air temperature difference were 0.4%,0.1%,and 0.2%,respectively,which belonged to"A”class according to the ISO-7730 Standard.While the vertical asymmetric radiation temperature of Scenario Ⅰ-Ⅱ was about 6.5℃ lower than that of Scenario Ⅲ-Ⅳ-Ⅴ.The ADPI for Scenarios Ⅲ-Ⅴ were about respectively 5.7%,16.7%,and 21.0%higher than that of Scenarios Ⅰ-Ⅱ,indicating that a large radiation area and radiation angle coefficient could reduce the discomfort caused by radiant temperature asymmetry.The coupling mode improved local discomfort by decreasing vertical temperature difference and radiation asymmetry temperature wherefore improving the PMV from-1.6 to-1.The lateral air supply coupled with asymmetric radiation heating could potentially improve the thermal comfort of occupied area,while the comprehensive effect of thermal environmental improvement,energy-saving,and cost-effectiveness needes to be further investigated.