| Affected by geographical location and environmental factors,the surface of photovoltaic modules will form different degrees of ash deposition,which seriously affects the economic and safe operation of photovoltaic power stations.Cleaning photovoltaic modules can improve power generation efficiency,but also increase maintenance costs of the photovoltaic power stations.Therefore,to determine the most reasonable cleaning cycle and improve the economic benefits of power plants,it is necessary to accurately grasp the impact of ash deposition on power generation,understand the ash degree of the surface area of photovoltaic modules,analyze the reasons for the uneven distribution of ash on the surface area of photovoltaic modules,and avoid uneven ash deposition.In this paper,a clean and ash deposition photovoltaic string power generation performance comparison test bench is built in the photovoltaic power station.The distribution of surface ash of photovoltaic modules and the influence of environmental factors and ash deposition on the output performance of photovoltaic modules are studied.In the field experiment,many factors interact with each other to affect the power generation performance of photovoltaic modules,and the influence of ash deposition on the output parameters of photovoltaic modules cannot be accurately obtained.Therefore,a photoelectric test bench and an optical test bench are built in the laboratory.For the basic unit of photovoltaic modules-solar cell,the output parameters of solar cell under different irradiation intensity and ash deposition density are tested,and the spectral transmittance of ash glass is tested.In the process of field experiment,it is found that the ash distribution on the surface area of the module corresponding to a single solar cell is relatively uniform,but the ash on the surface area of the entire photovoltaic array may be uneven.Therefore,taking the photovoltaic array as the research object,the distribution law of ash deposition on the surface of the photovoltaic array and its influencing factors are studied by using the numerical simulation method.The work of this paper provides theoretical and technical support for the subsequent research on the cleaning cycle of photovoltaic power plants.A clean and ash-accumulated photovoltaic string comparison test bench was built in the photovoltaic power station,and the output parameters and environmental parameters of the two photovoltaic strings were continuously monitored.The collected data were analyzed.The results show that the correlation between dust concentration in the air and photovoltaic power generation loss is the highest,followed by temperature and humidity.It is also found that when the irradiation intensity is higher than a certain value,the power loss and current loss do not fluctuate with the change of irradiation intensity.The photoelectric and optical test benches were set up and the experiments were carried out.The corresponding relationships among the ash deposition density,the output parameters of solar cells,the actual receiving radiation intensity of solar cells,and the spectral characteristics were established.Among them,the relationship between the working current and the ash deposition density was I=I_c×exp(-0.041×c),Compared with other output parameters of photovoltaic modules,it can more accurately reflect the ash degree of the component surface area.In addition,spectral transmittance is independent of irradiation intensity.In the wavelength range of 400–950 nm,the transmittance of light at each wavelength decreases exponentially with the increase of ash deposition density,but the influence of ash deposition on the transmittance of light at different wavelengths is different.The ash deposition model of particle adhesion and stripping was established by FLUENT software,and the ash deposition model was compiled into boundary conditions by UDF.Based on this model,the surface ash process of the photovoltaic array was simulated.The results show that wind speed and dust particle size affect the surface ash content of photovoltaic modules,wind direction,and line spacing affect the surface ash distribution of photovoltaic modules,and the increase of line spacing makes the surface ash distribution of photovoltaic modules relatively uniform. |
