Research On The Energy Conversion Characteristics Of Solar Energy Systems Based On Photovoltaic Synergy

Solar thermal utilization technology has been developed after years,but there are some technical problems to figure out for heat collector system,such as lower light-to-heat conversion efficiency and lower received solar radiation.The widespread attention was attracted to the compound parabolic concentrator(CPC)because of the advantages of high effective concentrating,simple structure and stable operation.Based on the design theory of traditional CPC,the optical properties,photovoltaic characteristics and heat collecting performance of the concentrating solar system with CPC,which matched the east-west direction of the all-glass vacuum tube and photovoltaic model,were studied by means of theoretical modeling,numerical calculation,simulation and experimental verification.The main tasks are summarized in the following:(1)The surface of compound parabolic concentrator for the collector system in the east-west direction of tubes with a spacing of 80 mm was constructed combining the principle of the edge ray of geometric optics.The physical model of the concentrating solar system with CPC was simulated and verified by optical design software,and the optical efficiency curve was obtained.The irradiance of the concentrating solar system with CPC was 2400MJ/m~2,the irradiance of the traditional concentrating solar collector system was 1735MJ/m~2 by using the way of separation theory of solar direct-scattering radiation,and the former was 38.33%higher than the latter in the theoretical solar irradiance.(2)Based on the principle of photovoltaic power generation and battery operation theory,the simplified equivalent circuit of photovoltaic power generation system,the mathematical model of power calculation of photovoltaic system and the mathematical model of battery capacity were constructed.According to the theoretical model,the output power of the photovoltaic cooperative heat collecting system was 7.04W,the battery capacity of the photovoltaic cooperative heat collecting system was 6.57Ah,and the photovoltaic synergy components were classified and selected.The simplified electrochemical reaction equations of lead-acid batteries and the important factors affecting the battery life in actual production has been analyzed.Then,the photovoltaic intelligent acquisition and control system were constructed according to the LORA wireless communication model.(3)The heat transfer model of the concentrating solar system with CPC was established by applying the basic theory of heat transfer and the principle of photothermal conversion.The thermal efficiency of the theoretical average value between the concentrating solar system with CPC and the traditional concentrating solar collector system were respectively 0.72 and 0.50 by using numerical computation methods.A comparative experimental platform of the concentrating solar collector system with CPC and the traditional concentrating solar collector system were established.The experimental result showed that the temperature rise rate of the concentrating solar system with CPC was higher than that of the traditional concentrating solar system.The maximum temperature difference between the concentrating solar system with CPC and the traditional concentrating solar collector system was 7.8?,and the improvement ratio of the collector efficiency between the concentrating solar system with CPC and the traditional concentrating solar collector system was 29.69%.The relative error between the theoretical calculated values and the experimental measurements of the concentrating solar collector system with CPC were mostly about 20%,the relative error of the traditional concentrating solar collector system were mostly within 19%.(4)The experimental comparison platform between photovoltaic cooperative heat collector system and traditional solar collector system was constructed via the combination of the concentrating solar collector system with CPC and the intelligent control system powered by photovoltaic modules,and the comparative experiments were carried out.The result showed that the temperature curve of the inlet of the photovoltaic coordinated heat collecting system was gradually increasing evenly and the fluctuation was small,the temperature change at the outlet showed a“V”curve,and the temperature of the inlet and outlet of the traditional solar collecting system was growing equably and slowly.The average temperature in the thermal insulation tank of the photovoltaic coordinated heat collecting system and the traditional solar collecting system increased by respectively 10.3?and 9.2?at the period of 12:10-13:10,the average temperature of the former increased by 7.7?,and the average temperature of the latter increased by 7.0?at the period of 13:10-14:10.