| In recent years,due to the large-scale exploitation and use of fossil fuels,environmental problems have become increasingly prominent.It is necessary to develop renewable energy technology and adjust the energy structure.Because of its wide distribution,clean and pollution-free,solar energy has become a leader in renewable energy.At present,the utilization of solar energy mainly includes heat utilization and photoelectric utilization.The typical utilization devices are household solar water heater and solar PV panel.As the main part of solar energy utilization,photoelectric utilization has been widely used in power generation projects in recent years.Because the efficiency of PV panel is greatly affected by the panel temperature,its performance will be restricted in practical application.PV/T system can not only generate electricity,but also take away a lot of heat from the surface of the system.Compared with PV system,PV/T system has higher utilization efficiency of solar energy,so its application is more and more widely.The performance of PV/T system is mainly related to design factors,component factors and environmental factors.After the completion of system design,design factors and component factors can not be changed,so environmental factors become the biggest constraint on system performance.Among them,the atmospheric dust in the environmental factors will greatly restrict the performance of the system.At present,there is a lack of comprehensive analysis on the dust deposition problem of the solar energy utilization system,and the dust deposition problem is often ignored in the operation and maintenance process of the solar energy utilization system.Therefore,this paper uses the constructed PV/T system as the experimental platform to conduct in-depth research on the problem of dust deposition on the surface of the system,and designs the corresponding cleaning strategy.The main contents of this paper are as follows:(1)An experimental platform and real-time data monitoring system of PV/T solar air collector are constructed,which can monitor and store the output electrical signal of PV/T system in real time.(2)This paper analyzes the source,formation and influencing factors of the dust deposition on the surface of the collector;classifies the dust deposition on the surface of the collector according to its physical properties,chemical properties and morphology;studies the influence mechanism of the dust deposition on the collector;using the cover plate sample experiment,the dust deposition density on the cover plate can reach 12.53 g/m~2 in 15consecutive days without rainfall,and the transmittance decreases by 6.16%.(3)Through the experimental study on the parameters that affect the system performance,it is found that the performance of the system increases with the increase of air mass flow;with the increase of solar radiation intensity,although the photoelectric and heat collection efficiency of the system decrease,the output power of the system increases by 45.80%;At the same time,the ambient temperature also has a great impact on the system performance,and the system performance increases with the increase of solar radiation intensity.However,when the ambient temperature exceeds 33℃,the efficiency of the photovoltaic module begins to decrease due to the influence of temperature.The results show that in the light snow weather,the experimental results show that in extreme weather such as light snow,due to the limitation of radiation intensity and ambient temperature,the operation performance of the system is low,and the average photoelectric efficiency of the whole day is 6.46%,The output power of the system is only 0.05 k W·h.The test results in different seasons show that the photoelectric efficiency and output power of the system are the lowest in winter due to the limitation of ambient temperature,and the operation performance of the system is better in other seasons.(4)The results show that the higher the dust density is,the lower the output power and photovoltaic efficiency of the system are.The maximum electric power and photoelectric efficiency are decreased by 49.17%and 48.65%,respectively,while the change of heat collection efficiency is not significant.The electric power and photoelectric efficiency of loose dust are both lower than that of bonded dust The results show that the system performance is 2.15%and 1.30%higher than that of the cohesive dust,respectively,while the heat collection efficiency of the cohesive dust is 2%higher than that of the loose dust.In the experiment of the daily variation of the dust form,it is found that the system performance decreases during the rainfall period,but it increases steadily after the rainfall.If the rainfall duration is short,the whole day performance change is not significant.(5)Taking Lanzhou as a typical example of Northwest China,through the experimental study of its dust law,it is suggested that the solar energy utilization system should be cleaned twice a month in spring and winter,and the dust should be cleaned at least once a month in spring and summer. |
