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 ...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.展开更多
Photovoltaic(PV)walls are prone to overheating during summer,which adversely affects their thermal and electrical performance.Current solutions primarily involved ventilation and phase change energy storage,which ofte...Photovoltaic(PV)walls are prone to overheating during summer,which adversely affects their thermal and electrical performance.Current solutions primarily involved ventilation and phase change energy storage,which often proved ineffective when applied independently.This study developed a PV wall integrated with multi-channel ventilation and composite phase change materials(PV-MV-CPCM),and investigated its operational performance and strategies during summer.Experimental results indicated that increasing the ventilation wind speed by 2.0 m/s enhanced the combined thermal-electrical efficiency by 10.8%.Nonetheless,during outdoor temperature rise period,increasing the number of activated airflow layers and inlet wind speeds led to additional heat transfer to the internal surface,resulting in the wall’s internal surface temperature to rise by 0.8℃.To address this,a segmented-time ventilation control strategy was proposed based on the temperature differences across various layers.Compared to full-time ventilation,the segmented-time ventilation effectively mitigated the impact of high outdoor temperatures,reducing the wall’s internal surface peak temperature by 1.1℃,increasing the peak heat removal efficiency by 2.1%and improving the combined thermal-electrical efficiency by 3.8%.This study provided effective strategies for mitigating the overheating of PV walls during summer,thereby enhancing both thermal and electrical performance.展开更多
The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age e...The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age efficiency.Previous research mainly focused on the combination of different phase change materials,while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion cou-pled thermal storage devices.This study investigated the influence of sensible and latent heat storage materials on the thermal performance,and identified the optimal volume ratios and materials types.When the volume share of Mg-Al:PW-EG=1:1,the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%,leading to an increase of 458.5 kJ/6.6%than the sensible heat storage condition(Mg-Al:PW-EG=1:0)and 630.18 kJ/8.5%than the latent heat storage condition(Mg-Al:PW-EG=0:1).When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively,the heat storage temperature rose by 162.7°C,quantity of heat stored rose by 7535.5 kJ.While materials with large subcooling were not recommended for short-term heat storage,as approximately 25.6%(3309.3 kJ)of stored heat and 22.4%(2505.2 kJ)of exergy were wasted when the subcooling degree was 70°C.The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.展开更多
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 temper...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.展开更多
基金supported by the Hebei Province Postdoctoral Merit Funding Program(Grant No.:B2022005004)the Science and Tech-nology Nova Plan of Hebei University of Technology(Grant No.:JBKYXX2207)+2 种基金the National Natural Science Foundation of China(Grant No.:51978231)the S&T Program of Hebei(Project No.:216Z4502G)the Natural Science Foundation of Hebei Province(Grant No.:E2020202196).
文摘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.
基金supported by the Natural Science Foundation of Hebei Province(Project No.E2024202077)the National Natural Science Foundation of China(Project No.52478086)+1 种基金the Science and Technology Research Project for Colleges and Universities in Hebei Province(Project No.CXY2024026)the Natural Science Foundation of Tianjin(Project No.24JCZDJC00950).
文摘Photovoltaic(PV)walls are prone to overheating during summer,which adversely affects their thermal and electrical performance.Current solutions primarily involved ventilation and phase change energy storage,which often proved ineffective when applied independently.This study developed a PV wall integrated with multi-channel ventilation and composite phase change materials(PV-MV-CPCM),and investigated its operational performance and strategies during summer.Experimental results indicated that increasing the ventilation wind speed by 2.0 m/s enhanced the combined thermal-electrical efficiency by 10.8%.Nonetheless,during outdoor temperature rise period,increasing the number of activated airflow layers and inlet wind speeds led to additional heat transfer to the internal surface,resulting in the wall’s internal surface temperature to rise by 0.8℃.To address this,a segmented-time ventilation control strategy was proposed based on the temperature differences across various layers.Compared to full-time ventilation,the segmented-time ventilation effectively mitigated the impact of high outdoor temperatures,reducing the wall’s internal surface peak temperature by 1.1℃,increasing the peak heat removal efficiency by 2.1%and improving the combined thermal-electrical efficiency by 3.8%.This study provided effective strategies for mitigating the overheating of PV walls during summer,thereby enhancing both thermal and electrical performance.
基金supported by the Hebei Provincial Postdoctoral Sci-ence Foundation(Project No.B2022005004)the Science and Tech-nology Nova Plan of Hebei University of Technology(Project No.JBKYXX2207)+1 种基金the National Natural Science Foundation of China(Project No.51978231)the Hebei Province Funding Project for Returned Scholars,China(Project No.:C20190507).
文摘The energy storage is an effective solution for the current imbalance between energy supply and demand.In particular,the cascaded storage method can enhance the heat exchange temperature difference and heat stor-age efficiency.Previous research mainly focused on the combination of different phase change materials,while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion cou-pled thermal storage devices.This study investigated the influence of sensible and latent heat storage materials on the thermal performance,and identified the optimal volume ratios and materials types.When the volume share of Mg-Al:PW-EG=1:1,the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3%,leading to an increase of 458.5 kJ/6.6%than the sensible heat storage condition(Mg-Al:PW-EG=1:0)and 630.18 kJ/8.5%than the latent heat storage condition(Mg-Al:PW-EG=0:1).When the melting point and latent heat of phase change materials increased from 68.9∼79.1°C and 224.8 kJ/kg to 118.0°C and 344.9 kJ/kg respectively,the heat storage temperature rose by 162.7°C,quantity of heat stored rose by 7535.5 kJ.While materials with large subcooling were not recommended for short-term heat storage,as approximately 25.6%(3309.3 kJ)of stored heat and 22.4%(2505.2 kJ)of exergy were wasted when the subcooling degree was 70°C.The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.
基金This study was financially supported by the National Natural Science Foundation of China(No.51978231)the Opening Funds of State Key Laboratory of Building Safety and Built Environment and National Engineering Research Center of Building Technology(No.BSBE2019-02)+3 种基金S&T Program of Hebei(No.216Z4502G)the Natural Science Foundation of Hebei Province(No.E2020202196)the Fundamental Research Funds of Hebei University of Technology(No.JBKYTD2003)Hebei Province Funding Project for Returned Scholars,China(No.C20190507).
文摘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.
