In this article, you can learn everything you need to know about solar panel cleaning. What is the underlying reason why shade affects solar panel power generation? What are the precautions when cleaning solar panels? Various methods of cleaning solar panels and the pros and cons of these methods.
Why Dust and Other Shelters Affect The Solar Panels’ Power Generation
The dust on the surface of the solar panel can reflect, scatter, and absorb solar radiation, reducing the transmittance of the sun. It will reduce the solar panel’s received solar radiation, and the solar system’s output power will decrease accordingly.
1: Effecting temperature: With the dust accumulation on the solar panel’s surface, the photovoltaic module’s heat transfer resistance increases, thereby affecting the heat dissipation of the solar panel.
2: Blocking light: Dust adheres to the surface of the battery panel, which will block, absorb and reflect light. The output power of a clean panel module is at least 5% higher than that of a dusty photovoltaic module.
3: Eroding glass: Wet acidic or alkaline dust adhering to the glass cover surface of PV panels will slowly erode the glass surface.
Rainwater washes uniform dust accumulation on the surface of photovoltaic modules to the lower edge of the modules. However, due to the height limit of the module frame and rainwater tension, the resulting gray water mixture cannot be exported outside the module.
After the water evaporates to dryness, gray bands of different widths and shapes will form on the component’s lower edge. The gray band on the lower edge of the solar panel blocks the incident light, and the battery capacity in this area drop significantly or becomes a resistive element.
The current and voltage of the cell string in a solar panel, which are connected in series, will drop as a whole due to affected cells. It will turn on the internal bypass diode, significantly reducing the solar panel’s output power.
Solar Panel Cleaning Methods And Their Advantages And Disadvantages
1. Manual Cleaning
Manual cleaning is a very primitive way of cleaning solar panels, completely done by manpower. This cleaning method has low working efficiency, a long cleaning cycle, high labor cost, and potential safety hazards. In the case of being unable to work in winter in the north, large-scale photovoltaic power stations rarely use manual scrubbing.
（1）Manual Dry Cleaning
Manual dry cleaning uses a long-handled velvet mop with a special detergent. The oily electrostatic cleaner used in manual dry cleaning mainly uses the principle of electrostatic adsorption and has the effect of absorbing dust and sand.
The detergent can enhance the cleaning tool’s dust suction and decontamination ability and prevent dust and sand particles from flying during cleaning. Due to relying entirely on manpower, there are many residues on the surface of the solar panel, and the solar panel is deformed and cracked due to uneven force.
Compressed air blowing is a method of removing dust from the surface of solar panels using a special device. It is used in areas where water resources are scarce but is inefficient and can cause dust to rub against the panel at high speed, making it unsuitable for use in power stations.
（2）Manual Solar Panel Washing
Manual water washing is spraying water on the photovoltaic module’s surface to wash the photovoltaic module’s surface with the nozzle connected to the water wheel (or water pipe) to achieve the purpose of cleaning. The water flow pressure generally does not exceed 0.4MPa. Excessive water pressure will cause cracks in solar panels, resulting in large-area short circuits that will reduce power generation efficiency.
This cleaning method is superior to manual dry cleaning. The cleaning efficiency is high, but the water consumption is relatively large. In addition, after natural air-drying, water stains form on the surface of the solar panel, creating miniature shadows that block the sun’s rays and reduce power generation efficiency. The ice layer generated by high-pressure water guns in winter will seriously weaken the optical effect of the modules, especially in solar power plants in the north.
2. Semi-automatic Solar Panel Cleaning Equipment
Mainly modified by engineering vehicles, the equipment has high power and relatively high efficiency. The cleaning work has good pressure consistency on the solar panels. It will not generate unbalanced pressure on the solar panels to cause solar panel cracks.
This method is less dependent on water resources. However, the requirements for the height and width of the photovoltaic module array and the road condition between the arrays are more stringent. It cannot meet the application requirements of all large-scale photovoltaic power plants.
3. Intelligent Solar Panel Cleaning Robot
The method is to install a cleaning robot for each row of photovoltaic modules in the power station. The robot will automatically and regularly clean and unattended, saving labor costs. Photovoltaic power stations with flat terrain can be used.
The intelligent cleaning robot surpasses traditional cleaning methods as it has energy storage and is self-powered, removing the need for an external power supply and water during cleaning. It can operate at a frequency set freely and clean regularly based on environmental conditions. The cleaning force is even and won’t cause cracks in the solar panels, and it can even work at night.
Disadvantages of the intelligent photovoltaic panel cleaning robot: the robot is sometimes stuck by the uneven photovoltaic panel frame. The robot cannot return to its normal position. And it is difficult for the operation and maintenance personnel to find a place to stop the robot on site.
How to Clean Solar Panels？
Any scratches or damage to the solar panel will result in reduced energy production. An effective cleaning method must be done to avoid damaging solar panels. 15% – 25% efficiency can be lost if not cleaned properly. This means that solar panels will reduce electricity by 15%-25%, which is not good for the whole power generation system.
Note: Try not to use soapy water when cleaning components. When we wash our hands with soap, it leaves a thin film on our skin. Similarly, cleaning photovoltaic modules with soap leaves a film or residue on the surface, which promotes faster adhesion and dust accumulation, ultimately affecting the power generation of the power station. It is important to avoid using other corrosive cleaning agents.
How to Clean Different Stains?
Cleaning tools for solar panels are relatively common, such as high-pressure water guns, soft brushes, and cotton mops. These tools are inexpensive and easy to use.
If there is only a small amount of dust on the surface of the solar panel, wash it with a high-pressure water gun.
If there are granular pollutants such as sand and mud on the surface. First, use a high-pressure water gun to wash and remove the particles. Then use a soft brush to scrub to prevent particles from sticking to the electric board.
If there are viscous pollutants, such as bird droppings and oily contaminants on the surface. You must wipe the surface with a clean rag, clean it with a glass of water, and rinse it with a water gun. In the process of using the high-pressure water gun, pay attention to the pressure of the high-pressure water gun. Excessive water pressure may cause damage to the solar panel.
How Often Should Solar Panels Be Cleaned?
Centralized cleaning: Once in spring and autumn, twice a year. Clean the surface and stains that are not easy to clean in the crevices.
Special weather: Targeted solar panel cleaning is required, especially during sandstorms and heavy snowfall.
Daily cleaning: dust, bird droppings, leaves, and other shelters.
What Are The Precautions in The Process of Cleaning Solar Panels?
1. You should choose to clean the solar panels in the morning or evening. The high temperature and strong light at noon may cause electric shock injury to cleaning personnel and damage components.
2. Before cleaning, check the monitoring records for abnormal power output. If there is an abnormality, don’t clean it up immediately. It is necessary to find out the reason and use a test pen to test on the aluminum frame, bracket, and glass surface. Make sure there is no risk of electric leakage before starting cleaning.
3. Don’t step on solar panels, brackets, cable trays, and other components.
4. Don’t clean solar panels in bad weather, such as strong wind, heavy rain, and snowstorm. Also, don’t wash the solar panels with cold water in scorching weather. Washing cold water in winter is not advisable to prevent solar panels from freezing.
5. Some sharp corners are on the solar panel aluminum frame and bracket. Cleaning personnel should wear cleaning overalls and hats to avoid scratches. Items such as hooks and straps cannot be worn on the work clothes to prevent entanglement.
6.When cleaning a rooftop photovoltaic power station, staff must not stand within one meter of the roof’s edge. Don‘t throw tools and sundries off the top. After cleaning, remove all equipment and debris uniformly.
7. Using sharp and hard tools or alkaline and other corrosive cleaning agents is forbidden when cleaning. Don’t Spray water on the junction box, cable tray, combiner box, and other equipment during cleaning. Controlling the water pressure within 0.4mpa is necessary to prevent any damage to the solar panels during cleaning.
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