Why Clean Solar Panels? What Substances Are Most Harmful to Panels? What are the main safety risks of dirty substances in photovoltaic modules?
After installing a photovoltaic power station, it is inevitable to encounter situations where dust, fallen leaves, bird droppings, etc., accumulate on the surface of the components, significantly affecting the power generation of the photovoltaic power station. Therefore, regular cleaning of the solar panels of the photovoltaic power station is necessary. According to industry statistics, frequent cleaning of photovoltaic solar panels can effectively increase power generation by about 8% annually.
How do you determine the cost-effectiveness of system cleaning, and what should be considered when choosing the right partner for your photovoltaic system? So, how should photovoltaic solar panels be cleaned? How often is it appropriate to clean them? What tools are best for cleaning photovoltaic panels? This article will take you through the ins and outs of solar panel cleaning.
1. Solar Panel Cleaning Guide
Atmospheric conditions and other environmental factors continuously affect the state of photovoltaic power stations. Dirt and other types of contaminants deposited on the surface of the components can block or reduce direct sunlight, negatively impacting the system's output. Solar panel contamination appears in various ways and forms and is not always visible to the naked eye. However, even the thinnest layer of dust and dirt, such as soot and pollen, along with bird droppings and leaves, can strongly affect the performance of a photovoltaic system. Moss and lichen pose a serious risk, attacking the frame and module components, and causing permanent damage to the system. All these impurities pose a significant risk to the efficiency of the photovoltaic system.
2. Types and Causes of Photovoltaic System Contamination
(1) Types of Contamination
The most common types of contamination include:
Sand and grit contamination， Bird droppings， Oil stains
(2) Causes and Contaminating Factors
The most important risk factors for increased contamination include:
Roof or Panel Tilt: As the tilt angle of the modules decreases, the risk of dust and particles resisting on the surface increases, even during rain. Therefore, when the tilt angle is small, dirt accumulates faster on the edges and frames, posing a long-term risk of buildup on the inner surface of the modules. Increasing the width of the edges can accelerate the absorption of other dust particles.
Solar Panel Frame: As mentioned earlier, dust and particles often accumulate on the frames of photovoltaic modules. Sediments carry these dust and debris to the frame, where they settle, contributing to the formation of moss and soot. In this sense, frameless modules (e.g., thin-film) may have an advantage, although they are considered less stable.
Horizontal Installation of Solar Panels: Another method of installing solar panels is the so-called horizontal installation, where the longer side of the panel is installed facing down/up. Horizontal installation increases the surface area exposed to dust, as the longer side of the module is exposed to rainwater. In most solar panels, the distance between the frame and the solar cells on the longer side of the module is also smaller. As a result, dirt and moss accumulate faster, reducing the module's output.
Agricultural Environment: In agriculture, especially when using heavy machinery, dust and dirt are generated and transported through the air, depositing on solar panels. At the same time, livestock farms using chemicals and emitting smoke can cause large-scale and stubborn contamination of photovoltaic modules.
Industrial Environment: The negative impact of industrial environments on photovoltaic power plants is generally lower than that of agricultural environments. However, even in such cases, fine dust and soot pollution can occur, significantly reducing output in the absence of proper maintenance measures.
Arid Regions and Low Rainfall Periods: Rain and snow help remove dirt from solar panels. In areas with low rainfall or during dry periods, this automatic cleaning effect is inevitably reduced, and dirt accumulates faster on the modules. However, it is important to note that rainfall alone is not sufficient to ensure the long-term cleanliness of a photovoltaic system.
3. Levels of Contamination
In June 2018, the first study on the economic convenience of cleaning ground-mounted solar panels was conducted. In this study, five levels of contamination were identified as a benchmark for determining cleaning requirements. The five levels of contamination are defined as follows:
Level 1: Very low contamination: A very light layer of dust on the solar panel, almost invisible to the naked eye.
Level 2: Low contamination: A slight layer of dust, is clearly visible on the module.
Level 3: Moderate contamination: More stable dust deposits, traces of bird droppings, and early signs of moss and lichen on the edges of the module.
Level 4: Severe contamination: Heavy dirt, scale, bird droppings, and a high proportion of moss and lichen on the edges.
Level 5: Very severe contamination: Persistent and stubborn scale on the module, moss, and lichen spreading on the edges, (possibly) the module surface is no longer recognizable, (possibly) irreversible contamination of the module.
4. Safety Risks of Dirty Photovoltaic Systems
If individual cells of the module are soiled or covered, they may overheat. In the worst-case scenario, if the cells overheat, the module may be damaged, and combustible materials under the module may catch fire. However, in most cases of overheating, long-term damage to the module leads to performance degradation without causing a fire. If rainwater accumulates on the lower edge of the module (especially in cases of low module tilt) and remains there for a long time, moisture can enter the laminate and cause delamination issues.
5. Overview of Solar Panel Cleaning Technologies
Currently, homeowners can clean the solar panels of their household photovoltaic power stations themselves. Under normal circumstances, there is no need to spend extra money on professional maintenance teams. The tools for cleaning solar panels are also quite common, including high-pressure water guns, soft brushes, and cotton mops. These tools are low-cost and very convenient to use.
When cleaning, if there is only a small amount of dust on the surface of the solar panels, a simple rinse with a high-pressure water gun is sufficient. If there are granular pollutants such as sand or mud on the surface, you can first rinse them off with a high-pressure water gun and then use a soft brush to scrub, avoiding the particles sticking to the panels. If there are sticky pollutants like bird droppings or oily contaminants on the surface, use a clean cloth to wipe them off, accompanied by glass cleaner, and finally rinse with a water gun.
Generally, the various cleaning technologies available on the market can be divided into three macro areas: manual cleaning, machine cleaning, and robotic cleaning. Within these areas, the cleaning process also varies greatly in terms of the use of detergents, water filters, instruments, and equipment. The most common solar cleaning method is the use of resin filters, which can desalinate water to avoid residues. Some suppliers also use special cleaning methods. When using detergents, ensure they are approved by the module manufacturer and environmentally friendly.
(1) Manual Cleaning
Manual cleaning includes all cleaning techniques where cleaning is performed by human labor using specialized manual brushes. For very small systems, cleaning is usually performed according to the principles and standards of normal glass surface cleaning. For larger systems (above 7-10 kW), brushes are placed on telescopic poles, which are rotated electrically or mechanically by water pressure. Due to the higher water flow, the surface performance of high-pressure water systems is usually slightly better than that of similar brushes.
(2) Machine Cleaning
When using machines for cleaning, vehicles (such as tractors) are used to move the brush system. This significantly speeds up the cleaning process. Therefore, large-scale surfaces can be cleaned very efficiently in a short time. This type of cleaning typically requires sufficient space between rows to allow the vehicle to pass.
(3) Robotic Cleaning
This technology involves the use of specific robots. These robots are installed on the system by service providers and guided through the modules via sensor technology or remote control. Although the technology is constantly advancing, robotic cleaning of solar panels is still limited by the tilt angle or installation characteristics of the modules.
It is important to note that when using a high-pressure water gun, pay attention to the water pressure, as excessive pressure may damage the solar panels.
6. What Should Be Considered When Cleaning Solar Panels?
(1)The best time to clean is in the early morning, evening, or at night, avoiding high-temperature periods like noon to prevent damage to the solar panels.
(2)Avoid using hard or sharp objects directly on the solar panels during cleaning.
(3)Do not step on the solar panels, brackets, or other components, as this can easily damage the power station and affect its lifespan.
According to current industry maintenance experience, during seasons with more rain and snow, such as winter, cleaning once a month is generally sufficient (if there is snow accumulation, it should be cleared promptly). In other months, cleaning twice a month is appropriate. In areas with strong winds and more dust, such as the northwest, the frequency should be determined based on specific conditions.
It is important to note: Avoid using soapy water when cleaning the components. Just as a thin film remains on our hands after washing with soap, using soap to clean the components will also leave a film or residue on the surface of the photovoltaic components, which will cause dust to adhere and accumulate more quickly, affecting the power generation of the station. Additionally, other corrosive cleaning agents should not be used.
7. When Should Cleaning Be Performed?
The necessity of keeping a photovoltaic system clean is based on two fundamental factors (besides safety): effective solar output and the protection of the investment. If the performance of the photovoltaic system is significantly reduced due to contamination, cleaning is highly recommended. If contamination is found to affect the long-term preservation, safety, and operation of the system, as well as its structure, the system must be cleaned as soon as possible.
(1) When Is It Worth Cleaning Solar Panels?
Whether it is worth cleaning a photovoltaic system is ultimately an economic question. The cost of cleaning must be offset by the additional efficiency generated by the cleaning. To calculate the economic feasibility of a cleaning service, two factors must be considered: the number of kilowatt-hours the photovoltaic power plant must generate as additional output to recover the cleaning cost, and the percentage of additional output relative to the total output of the power plant.
(2) Solar Panel Cleaning Study
In 2018, the first scientific study on the cleaning of ground-mounted photovoltaic systems was conducted to understand the impact of professional cleaning on output. During the study, 17 different ground systems were partially cleaned. The output of the cleaned surfaces was then compared with the output of the uncleaned parts of the plant over six months. The main factors influencing the success of the cleaning were: the degree of module tilt, the level of contamination, and the date of the plant's grid connection.
8. Solar Panel Cleaning Requirements
Typically, the requirements for cleaning a photovoltaic system are: access to the component surface, connection to tap water, and connection to the grid. If necessary, the latter can be provided by the service company at an additional cost. On the other hand, all other necessary equipment and tools are usually provided by the service provider. Depending on the type of cleaning, there are special requirements for the accessibility of the system, which must be checked on a case-by-case basis.