In the absence of a simple technique to predict convection heat transfer on BIPV （building integrated photovoltaic） surfaces, a mobile probe with two thermocouples was designed. Thermal boundary layers on vertical f...In the absence of a simple technique to predict convection heat transfer on BIPV （building integrated photovoltaic） surfaces, a mobile probe with two thermocouples was designed. Thermal boundary layers on vertical flat surfaces ofa PV （photovoltaic） and a metallic plate were traversed. The plate consisted of twelve heaters where heat flux and surface temperature were controlled and measured. Uniform heat flux condition was developed on the heaters to closely simulate non-uniform temperature distribution on vertical PV modules. The two thermocouples on the probe measured local air temperature and contact temperature with the wall surface. Experimental results were presented in the forms of local Nusselt numbers versus Rayleigh numbers ＂Nu = a＇（Ra）b＇＇, and surface temperature versus dimensionless height （Ts - T∞ = c.（z/h）d）. The constant values for ＂a＂, ＂b＂, ＂c＂ and ＂d＂ were determined from the best curve-fitting to the power-law relation. The convection heat transfer predictions from the empirical correlations were found to be in consistent with those predictions made by a number of correlations published in the open literature. A simple technique is then proposed to employ two experimental data from the probe to refine empirical correlations as the operational conditions change. A flexible technique to update correlations is of prime significance requirement in thermal design and operation of BIPV modules. The work is in progress to further extend the correlation to predict the combined radiation and convection on inclined PVs and channels.展开更多
Elevated working temperatures reduce the efficiency of dye-sensitized solar cells （DSCs）, and effective temperature regulation protects them from the undesirable efficiency loss. In this work, a semi-transparent DSC...Elevated working temperatures reduce the efficiency of dye-sensitized solar cells （DSCs）, and effective temperature regulation protects them from the undesirable efficiency loss. In this work, a semi-transparent DSC module equipped with a cooling sys- tem was designed and constructed for application in buildings, the temperature and output performance of the modules with or without cooling treatment were investigated. The test results showed the cooling system could noticeably improve the power generation and reduce the module temperature. Moreover, we established a mathematical model to analyze the modules＇ ther- mal performances, and introduced the concept of cooling efficiency to evaluate the cooling effect. The model accuracy have been validated utilizing measured data, and the effects of channel depth and mass flow rate on the module temperature and cooling efficiency were further theoretically studied. The combined DSC module has been found to have a good application prospect in building integrated photovoltaic （BIPV）, and the numerical results are important in system design.展开更多
文摘In the absence of a simple technique to predict convection heat transfer on BIPV （building integrated photovoltaic） surfaces, a mobile probe with two thermocouples was designed. Thermal boundary layers on vertical flat surfaces ofa PV （photovoltaic） and a metallic plate were traversed. The plate consisted of twelve heaters where heat flux and surface temperature were controlled and measured. Uniform heat flux condition was developed on the heaters to closely simulate non-uniform temperature distribution on vertical PV modules. The two thermocouples on the probe measured local air temperature and contact temperature with the wall surface. Experimental results were presented in the forms of local Nusselt numbers versus Rayleigh numbers ＂Nu = a＇（Ra）b＇＇, and surface temperature versus dimensionless height （Ts - T∞ = c.（z/h）d）. The constant values for ＂a＂, ＂b＂, ＂c＂ and ＂d＂ were determined from the best curve-fitting to the power-law relation. The convection heat transfer predictions from the empirical correlations were found to be in consistent with those predictions made by a number of correlations published in the open literature. A simple technique is then proposed to employ two experimental data from the probe to refine empirical correlations as the operational conditions change. A flexible technique to update correlations is of prime significance requirement in thermal design and operation of BIPV modules. The work is in progress to further extend the correlation to predict the combined radiation and convection on inclined PVs and channels.
基金supported by the National Basic Research Program of China(“973”Project)(Grant No.2011CBA00700)the National Natural Science Foundation of China(Grant Nos.61204075&61404142)the Fundamental Research Funds for the Central Universities(Grant No.2016XZZX005-07)
文摘Elevated working temperatures reduce the efficiency of dye-sensitized solar cells （DSCs）, and effective temperature regulation protects them from the undesirable efficiency loss. In this work, a semi-transparent DSC module equipped with a cooling sys- tem was designed and constructed for application in buildings, the temperature and output performance of the modules with or without cooling treatment were investigated. The test results showed the cooling system could noticeably improve the power generation and reduce the module temperature. Moreover, we established a mathematical model to analyze the modules＇ ther- mal performances, and introduced the concept of cooling efficiency to evaluate the cooling effect. The model accuracy have been validated utilizing measured data, and the effects of channel depth and mass flow rate on the module temperature and cooling efficiency were further theoretically studied. The combined DSC module has been found to have a good application prospect in building integrated photovoltaic （BIPV）, and the numerical results are important in system design.
