Design And Optimization Of Compound Parabolic Concentrator Used For Photovoltaic/thermal System

Concentrated photovoltaic(C-PV/T)technology is a representative solar energy utilization technology.It realizes the cascade utilization of energy and is easy to be combined with buildings.It has broad application prospects.The concentrator not only solves the problem of low surface irradiation intensity of photovoltaic cells,but also improves the water temperature at the outlet of the system.In this paper,a composite paraboloid structure suitable for PV/T cogeneration technology is designed.Considering its optical performance and manufacturing cost,a WD-CPC with uniform light distribution on the receiving surface and relatively low manufacturing cost is designed,and its theoretical analysis,simulation and experimental test are carried out.As follows:(1)The radiation mathematical model of the earth is established,and the radiation of sunny weather at any time is simulated.The solar radiation in Changping area of Beijing(solar altitude angle,azimuth angle,zenith angle,sunrise and sunset time)is verified by the formula.A design method for determining the concentration ratio and interception ratio after interception is studied.In addition,the formulas for calculating the parameters of CPC sizes and specifications under this design method are obtained.(2)The optimum light receiving plane and the optimum interception interval of CPC concentrator are determined.On this basis,the optimum interception ratio of CPC concentrator is determined by considering the optical performance and manufacturing cost of the concentrator.A WD-CPC with uniform light distribution on the receiving surface and relatively low manufacturing cost is designed.The simulation results show that the intercepted WD-CPC has a convergence ratio of 3,a receiving surface position of 28.0092 mm,a maximum irradiation intensity of 2616.9W/m2,a minimum irradiation intensity of 1648.0W/m2,a non-uniformity of 0.2272,a height of 333.5mm and a receiving half angle of 42.89 degrees,a WD-CPC with a convergence ratio of 4 and a receiving surface.The position is 18.0726 mm.The maximum irradiation intensity on the receiving surface is 3712.3 W/m2,the minimum irradiation intensity is 2086.3 W/m2,and the non-uniformity is 0.2804.The height of the concentrator is 543.4 mm,and the receiving half-angle is 35.35 degrees.(3)Based on the design of WD-CPC and through the sensitivity analysis function of Lighttools simulation software,the WD-CPC is further optimized,and a method of light compensation is proposed.The light compensation lens is installed in the lower part of WD-CPC,and the position of the receiving surface is moved down.The results show that for WD-CPC with a concentration ratio of 3 after interception,the light compensation lens is used.The inclination angle is 0.44 degrees and the position of the receiving surface is 29.762 mm.At this time,the maximum light intensity on the receiving surface is 2495.OW/12,the minimum light intensity is 1817.7W/m2 and the non-uniformity is 0.1570.For the WD-CPC with the intercepted concentration ratio of 4,the inclination angle of the light compensation lens is 4.10 degrees,the position of the receiving surface is 20.020 mm,and the maximum light intensity on the receiving surface is 3402.0 W/m2,the minimum intensity is 2277.2 W/m2,and the non-uniformity is 0.1980.(4)A concentrating photovoltaic photothermal(PV/T)cogeneration experimental platform was built.The performance of WD-CPC with light compensation and a concentrating ratio of 4 was tested.In the experimental performance test,on the optimal receiving plane of WD-CPC,the maximum receiving radiation is 2587.2W/m2 and the minimum receiving radiation is 1902.1W/m2.The actual non-uniformity is calculated to be 0.153.The test results are consistent with the simulation results.