Shadows should be paid attention to in the design and installation of photovoltaic power plants, and more attention should be paid to later operation and maintenance. For long-term operation of photovoltaic power generation systems, dust accumulation on panels has a great impact on power generation efficiency. The dust on the surface of the panel has the functions of reflecting, scattering and absorbing solar radiation, which can reduce the transmittance of the sun, resulting in a decrease in the solar radiation received by the panel, and the output power is also reduced, and its effect is proportional to the accumulated thickness of dust. Common shadows mainly include bird droppings, dust, tree shade, buildings, fallen leaves and branches, etc. At present, there are three cleaning methods for photovoltaics: human working, water wheel cleaning and robot cleaning. 1.      Characteristics of human working Hard to manage, inefficient, and long hours. The cleaning process affects power generation. The cleaning quality is difficult to guarantee, and there are safety risks and large losses in operation. 2. Water wheel cleaning The cleaning range is limited, and it is only suitable for ground power stations with sufficient space and free entry and exit of vehicles. It won't do anything with rooftop photovoltaic panels, desert power stations, or tightly packed power stations. 3. Robot cleaning Regular cleaning, significantly increased power generation, night work, no impact on power generation, more than 50 times more efficient than human working, self-powered, self-storage, no external energy, unattended, intelligent control, no water cleaning, no waste of water resources.