| As one of the important technical means to achieve the goal of "double carbon",solar photovoltaic(PV)power generation technology plays an increasingly significant role in the fields of energy conservation and emission reduction,and leading the transformation of the power industry.With the improvement in photoelectric conversion efficiency and the decrease in the production cost,the dust pollution on the PV module surfaces has proved to be a major factor that affects the PV power generation.Severe pollution may also damage the module surface and shorten its service life-span.The challenges such as reducing the power generation loss as well as the operation and maintenance costs caused by dust pollution,and maintaining the efficient working state of PV modules remains a research focus.Therefore,it is of great significance to investigate the deposition mechanism of dust particles to master the dust accumulation characteristics of modules,and to explore measures to improve PV power generation.To mitigate the negative impact of pollution on PV modules,this paper focused on the research of dust pollution mechanism on the PV module surfaces,dust deposition mitigation and efficiency improvement measures.A 750W PV array experimental platform was built on the roof of fan laboratory.Moreover,the deposition mechanism and conditions of dust particles on the module surfaces were explored and analyzed in depth.The effects of particle deposition on the transmittance,temperature,and output power of PV modules were discussed.Moreover,the measures to reduce dust deposition and improve power generation were investigated,which provide support for the prediction of dust deposition amount and the formulation of cleaning scheme of PV modules under natural environment.First,a series of transmittance calculation models under pollution conditions were established,and the dependent relationship between transmittance and the dust accumulation amount on the PV module surfaces was revealed.Then,the transmission attenuation of PV glass caused by dust deposition was analyzed theoretically.The rationality of the theoretical calculation models was verified by comparing them with the experimental results under the same conditions.Based on this,the variation characteristics of the PV module transmittance under a polluted condition was analyzed.The results indicated that the transmittance increases slowly with increasing particle size,but decreases slowly first with the increase in incident angle of light.When the incident angle is greater than 60°,the reduction in transmittance increases sharply.Moreover.the effect of dust deposition on the temperature and output power of PV modules was investigated experimentally.The results demonstrated that compared with the clean modules,the dust accumulation of 16.5g/m2 with serious pollution can reduce the module temperature and output power by approximately 6.3℃ and 21.36%,respectively.Second,a collision-adhesion model was established between dust particles and the PV module surfaces.Then,the mechanical behavior of particle with respect to its motion,collision and reflection processes on the module surfaces were explored.Subsequently,the particle deposition mechanisms were deeply investigated from the perspective of mechanics and energy,and the particle deposition criterion were proposed correspondingly.Moreover,the mechanical equilibrium-based particle deposition mechanism was employed to reveal the relationship between particle collision characteristics and deposition.According to the energy-based particle deposition mechanism,the natural dust deposition mathematical model of PV modules was built.The comparison between the simulation and experimental results under the same conditions verified the rationality of the mathematical model and the proposed deposition criteria.Based on this,the effects of main factors such as particle size,wind speed,wind direction,humidity,tilt angle,and atmospheric dust concentration on the dust accumulation characteristics of PV modules were numerically investigated.The results revealed that the dust concentration has the greatest impact on dust deposition,followed by particle size,and the wind direction,which has the least impact.Besides,the accumulated dust increases approximately linearly with an increase in humidity and dust concentration,while it displays a V-shaped changing pattern with increasing wind speed.Additionally,when the particle size was 30 μm,an increase in tilt angle led to a decrease in the dust deposition amount.To elaborate,the dust deposition under 7m/s can be decreased by about 47.84%when the tilt angle increases from 15°to 60°.Therefore,appropriate increment of the tilt angle is beneficial in reduction of the deposited dust.Third,a heat transfer model of polluted PV modules was constructed,and the rationality of the established model was verified by comparing the simulation results with the experimental results.Based on this,the main factors such as irradiance,ambient temperature,wind speed,wind direction,and tilt angle and their coupling effects on the PV module temperature was simulated.Then,the output power of polluted PV modules was analyzed and predicted based on the dependent relationship between the module output power and temperature.The results showed that the attenuation of PV glass transmittance caused by dust deposition is the main reason for the decrease in output power.Under the polluted state,the PV module temperature decreased slowly with the increasing wind speed and tilt angle,while increases linearly with the increase in irradiance.Nevertheless,the output power of polluted modules decreases approximately linearly with the increase in ambient temperature,while it increases slowly with increasing wind speed and tilt angle.Compared with clean modules,when the irradiance is 200W/m2 and the wind speed is 7m/s,the output power loss of polluted PV modules with a rated power of 750W is about 36.85W.Finally,based on the analysis of the working mechanism of the coating and the calculation of its surface energy,a numerical simulation of the self-cleaning superhydrophobic coating on the dust accumulation mitigation of PV modules was carried out.Then,the application effect of coating on the PV performance was explored.Moreover,the relative optimal tilt angles of PV modules in clean and polluted states were calculated and analyzed.The potential of optimizing the module titl angle in improving PV power generation under polluted conditions was discussed,and the corresponding adjustment scheme of tilt angle was formulated.Subsequently,a cleaning cycle model based on the measured data of a 20MW PV power station was established and the cleaning cycle optimization scheme of the power station was explored.Meanwhile,the economic and social application benefits of the optimization scheme were analyzed.The results suggested that the self-cleaning superhydrophobic coating can effectively reduce the dust deposition on the module surfaces compared with the uncoated modules,and the coating exhibits better dust deposition reduction at areas with small dust particle size and severe pollution.The gravity effect leads to better application effect of coating on the PV modules with larger tilt angle,and when the tilt angle increases from 15° to 60°,the coating can reduce the dust accumulation on the module surfaces by around 52.4%at the particle size of 30μm and the wind speed of 7m/s.Furthermore,compared with the power generation of the fixed PV modules with a tilt angle of 45°,the tilt angle adjustment scheme for once a month and four times a year can increase the annual power generation of the PV modules by about 5.99%and 5.39%,respectively.Additionally,based on the "minimum cost method",the recommended cleaning cycle of a 2MW PV array is 12.71d.Compared with the monthly cleaning cycle,for a 20MW PV station,the annual power generation can be increased by about 1.2771 million kW·h,which is equivalent to reducing about 1247.73t carbon emission and saving 386.32t standard coal every year,which has obvious economic and social benefits. |
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