| As reserves of fossil are limited and non-renewable,particularly the environmental pollution caused by the excessive consumption in electrical and transportation industries,the renewable and clean energy has been drawn more attention,and has been listed as a long-term energy development goal in many countries.As an important part of renewable energy,solar energy is widely used.It can be converted into electricity,a high-grade energy,by using the photovoltaic effect of photovoltaic(PV)cells.However,the photoelectric conversion efficiency of PV cells is restricted due to the accumulating heat in the battery and its high operating temperature.Hence,how to adopt effective cooling method to cool the PV cells has become a hot research area in solar applications.Due to the cooling effect involving many factors,it is difficult to control the related factors.Considering this,numerical calculation method is proposed in this paper to carried out a detailed research on the relationship between the performance of PV cells and its influence factors,and the main research contents are as follows:(1)Firstly,a three-dimensional steady-state heat transfer numerical model of PV panel was established and verified by published data.Then,the effect of the various external factors on the performance of the PV panel were studied under different cooling method based on the validated numerical model,and the results show that:Under natural cooling circumstance,the electrical efficiency of PV cells and its operating temperature vary linear with solar irradiance and ambient temperature,and the operating temperature is more affected by the ambient temperature;Under forced air and water cooling modes,the electrical efficiency of the PV panel can be improved by increasing incident solar irradiance or reducing the ambient temperature,e.g.,the average electric efficiency of the PV panel can be improved 5.6%～7.3%by forced air cooling and 9.6%～12.9%by water cooling when the incident solar irradiance were in the range of 600～800 W/m~2.In addition,the temperature difference and thermal stress between PV components can be reduced by adapting cooling measures.(2)Secondly,the different effects of channel cooling,surface cooling and circulating cooling on the performance of PV panels were studied based on simplified numerical models which were verified and passed grid independence,and the results show that:For the surface cooling,the transition state water film was inclined to low flow condition and the water film overall covering capacity was increased with the installation angle between PV panels and ground increasing;While it is opposite for the circulating water cooling mode;Under the same operating conditions for water cooling measures,the more water film covers in the front of the PV panels,the lower operating temperature was obtained which results in higher electrical efficiency.The distribution of temperature and efficiency of the battery with water channel cooling measure distribute more uniformly than surface water cooling and circulating water cooling measures,especially when the cooling water flow is low.Hence,it is better to increase the cooling water flow rate to weaken the nonuniformity distribution for the two mentioned later cooling measures.The average temperature of PV panels cooled by water channel cooling is about 6℃higher than that by surface water cooling or circulating water cooling,which results the averaged 0.35%lower in electrical efficiency under the operating conditions with 500 W/m~2solar irradiance,25℃ambient temperature and higher water flow rate.Besides,the different position of the cooling water entrance leads to different temperature among components of the PV panels.(3)Finally,the influence of solar irradiance,ambient temperature,water flow rate,and installation inclination on the operating temperature of PV panels under three different cooling measures were investigated based on orthogonal design and range analysis,and the results show that:Environmental temperature has great influence on the operating temperature of PV panels and plays a dominant role,then is the solar irradiance,and then is the cooling water flow rate and installation inclination which play an insignificant role. |
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