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In recent years, PV is considered to be one of the main way to solve the current energy crisis. PV is generally built in exposed areas such as deserts and wasteland. And the efficiency of power generation of PV is easy affected by the dust accumulated on it. The research expounds the "three factors" of the effect of dust on PV, namely shielding effect, temperature effect and corrosion effect, then an efficiency evaluation method for photovoltaic cells is proposed. Finally, the field experiments show that with the increase of dust density, the short-circuit current, open-circuit voltage, and output power of the PV both decrease. The dust with a density of 10 g/m2 can reduce the maximum power of the PV by about 34%. In the initial stage of PV dust accumulation, dust has the greatest impact on its output performance. In addition, the dust density and the conversion efficiency have better nonlinear correlation. As the dust accumulation density gradually increases, the PV conversion efficiency gradually decreases. When the dust density increases to a certain extent, the PV conversion efficiency tends to be stable.

In this paper, the thermal performance of serpentine pipe flat plate collectors with different pipe diameters and pipe spacings was tested by experiments. On this basis, two phase change materials with high melting point (70 °C) and low melting point (15 °C) were laid on the upper and lower parts of the pipeline to enhance the frost resistance and high temperature resistance of the collector. The experimental results show that under strong solar radiation conditions, high-melting phase change materials can absorb a lot of heat when the water temperature of the collector is high, thereby slowing down the water temperature rise and avoiding overheating, and when the collector is cooled, phase change can be effectively utilized to slows down the rate of temperature drop of the collector, so as to achieve reasonable utilization of the overheating of the collector; in the low temperature environment, the low melting point phase change material can significantly reduce the cooling of the collector and improve the frost resistance of the collector. The placement of the two kinds of different melting point phase change materials was investigated, and the results show that the low-melting phase change material under the pipe is more conducive to the collector antifreezing. However, for the hot regions, the high-melting phase change material placed at the top of the pipe is more conducive to preventing overheating.

When the temperature of photovoltaic (PV) increases, the power generation efficiency decreases almost linearly. The temperature effect caused by high temperature has become an important factor that hinders the production of PV. In this study, the structural layout and the parameter optimization of PV cooling system are conducted. For this purpose, a thermal-electric coupled model of PV cooling system has been set up. Using the mathematical model, the effects of various parameters, such as the type of tube, tube diameter, tube spacing, water inlet temperature and flow velocity are analyzed. The results show that the average surface temperature of PV decreases with the increase of tube diameter and flow velocity and the decrease of tube spacing and water inlet temperature. Furthermore, theoretical parametric values for the optimized configuration of the PV cooling system are obtained. The experimental results show that the optimized PV cooling system can effectively reduce the surface temperature, which is about 47.0 °C lower than that of the non-cooled system. Moreover, the conversion efficiency and the exergy efficiency are exponentially related to mass flow. When the mass flow rate is 0.04 kg/s, the conversion and exergy efficiencies achieved the maximum values of 11.9% and 12.4%. When the water inlet temperature is 10 °C, the conversion and exergy efficiencies achieved the maximum values of 11.6% and 11.7%, respectively. Finally, the economic calculations were carried out in three typical cities in China. The results show that the PV cooling system can increase power generation by 7%–15%.