On Thermal Environment Within CPC Based Photovoltaic Module And Factors Affecting Its Thermal Performance

The issue of energy sustainability has long attracted the attention of all countries in the world,especially in China due to the rapid economic development,and the exploitation of new energy and environmental protection has become a new direction for a future development.From the energy point of view,the utilization of environmental-freindly solar energy presents a chance to achieve the sustainable development,especially the photovoltaic power generation technology.However,the application of PV systems for electricity generation is limited due to the high cost of electricity from phovoltaic systems.The use of cheap concentrator to reduce the use of solar cells is widely regarded to be an effective way to reduce the cost of photovoltaic power generation.In recent years,compound parabolic concentrator(CPC)based concentrating photovoltaic system(CPV,in short)has attracted much attention due to simple in the structure and no need of sun-tracking device,but the higher temperature within CPV makes the photovoltaic conversion efficiency decrease greatly,therefore,how to decrease the temperature of solar cells within CPV in simple and effective ways is a key issue to improve its photovaolatic performance.In this work,the thermal environment within CPV and factors affecting its thermal performance were analyzed and theroreically inestigated by simulations with the aim to find effective measures to improve the thermal eniroment within CPV.First,a CPC with the acceptance half-angle of θ_a=23° and geometric concentration factor of 2 is designed based on the solar geometry and time-vraiations of projected incident angle of solar rays on the cross-section of CPC-trough in a day.The CPCs is oriented in the east-west direction with the tilt-angle of the aperture being yearly adjusted two times at two tilts.Secondly,the optical performance of the CPC and solar flux distribution on base of CPCs,to which solar cells are attached,were studied by ray-tracing analysis.Finally,the heat transfer mechanism within CPV is analyzed,and thermal environment within CPC is simulated by the use of FLUENT software.Seven designs with different sizes of ventilation channel for the forced cooling of CPVs’ cavity were proposed,and the temperature drop of solar cells within CPCs for different cooling fluid velocities as compared to the CPV without using forced cooling tehcnique are similated and analyzed.The results show that,with the increases of projected incident angle of solar rays on the cross-section of CPC-trough,the temperature of the solar cell decreases,and tilt-angle of CPC’s aperture have an insiginificnat effect on the maximum temperature of solar cells;the design of ventilation channel with 20 mm in wideth is more effective for the temperature drop of solar cells;and temperature drop increases with the increase of the airflow rate.It is also found that,the design by truncating reflectors near solar cells of CPV as the ventilation channel is most effective for the cooling of solar cells with CPCs.