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How often should solar panels be cleaned and which method is ideal?

One thing is certain: Companies also need to clean solar power systems - but how often? PV systems can only continue to work efficiently and maintain their longevity if they are clean. But when is the right time to do this? How can you tell when solar modules need cleaning and how should you clean them? We answer the most important questions and show you what costs you can expect from professional cleaning. 

Do you have to clean a solar panel system? Effects of contamination 

The short answer: Yes, solar panel systems need to be cleaned regularly. In order to convert sunlight into electricity, the solar modules need direct sunlight. But it's natural for them to get dirty over time. There are several reasons for this:   

  • Natural contaminants: dust from the air, drifting sand, leaves and seeds from surrounding trees, pollen, bird droppings, lime from rain dried by the sun   
  • Chemical deposits: industrial and car exhaust fumes, tyre abrasion, oil particles as well as particulate matter, soot from surrounding chimneys   
  • Secondary soiling: Sand and dust provide optimal living conditions for fungi, lichens and mosses, which form during prolonged soiling  

Depending on the angle of inclination of the solar panel system, rain, wind and snow remove coarse dirt. Stuck dirt such as bird droppings and industrial and car exhaust fumes often still stick to the surface. Once such dirt has accumulated on the solar panels, sunlight no longer reaches the modules and the effectiveness is reduced.  

At the same time, secondary contaminants are formed, which bind more dirt on the system, on which in turn more lichens, mosses and fungi grow. A vicious circle is created that can only be broken by effective cleaning. If the dirt settles on the edges and underneath, it also becomes increasingly difficult to remove it.  

The fact that a steep surface is not only cleaned by rain, wind and snow is also shown by St. Stephen's Cathedral in Vienna. Although the roof areas are relatively steep, moss and lichens, among other things, have accumulated here, as the news portal NÖN.at reports. The problem is that the plants store water, which freezes in winter and causes roof tiles to burst. With the help of professional cleaning, however, the roof can be freed from the dirt.

Solar panel cleaning: When is it worth it?

Whether cleaning is worthwhile depends on the losses caused by the contamination. These must be proportionate to the cost of cleaning. This can be determined using a loss calculator .  

Experience shows that losses of between 8 and 30% can be reached quickly, depending on the location. For example, we see around 12% pollution on many commercial roofs, and up to 30% in agriculture. Open spaces are more likely to have a better value of about 5-10% due to their location. 

Solar panel cleaning with PV panel cleaning robots

Hot spots caused by heavy contamination can destroy solar panels 

In the case of heavy soiling, there is also the risk of hot spots: If individual cells are completely shaded by the soiling, they no longer generate electrical voltage. As a result, they act as a barrier in the series connection of the solar panel, while the others continue to generate electricity. If the operating or reverse voltage of the shaded cell is broken, the voltage breaks off and the current flows unhindered. As a result, the solar cells can overheat to such an extent that they are destroyed.  

Cleaning solar panels - how often? The influence of location and angle of inclination

Contrary to the misconception of many, experience shows that only on a very steep slope is some of the dirt such as leaves removed. But here, too, the modules are polluted by rain, snow and wind, which transport small dust particles and the like onto the surfaces of the solar panels. Investments on commercial properties are also flatter than others and therefore tend to need to be cleaned more often. Robotic cleaning is the main tool of choice for efficient yield maximization, as the terrain and type of installation are often a difficult and unsafe environment to clean. 

In Europe, the pollution pattern and the location criteria that lead to the pollution are very different. Therefore, it is very individual how often a solar panel system needs to be cleaned. In the vicinity of industrial and agricultural enterprises, the plants tend to need to be cleaned more frequently than in urban areas, for example. This is because more exhaust gases and dust particles are deposited here. Basically, the interval can be about every six weeks up to several years.  

Solar panel system cleaning: This is how you can tell when cleaning is necessary 

Cleaning costs money and must therefore pay off compared to the loss of yield due to lower power generation and the reduction of the service life of the modules due to dirt. But it is clear that companies need to clean their solar panels at regular intervals. In principle, it should be inspected "on sight" at least once a year. If soiling such as dust layers, dirt edges, bird droppings or other deposits is clearly visible, cleaning is overdue. Normally, a plant is cleaned once a year to prevent moss from forming. 

The right time to clean solar panels

For professional cleaning companies, the question is when to achieve the best results with the least amount of effort. As a general rule, solar panels should not be cleaned at high temperatures or in frosty conditions. To achieve optimal results, one to two cleanings per year are recommended. Ideally, these take place once after the cold season or the first flowering as well as after the dry period in autumn, so that the typically low-yielding time of winter can start with optimal conditions to generate more output. In the case of stubborn dirt, periods of rain also help to soak it. If a specialist company cleans the solar panels afterwards, the stuck dirt comes off more easily. 

PV panels cleaning: These methods are the best way to do it  

Before you start cleaning, it makes sense to check the system: Are any elements broken or cables damaged? What do the surfaces of the PV modules look like? If major damage is visible, the power should be switched off and the system repaired to avoid safety risks. When it comes to the cleaning itself, cleaning agents and brushes, among other things, influence how companies best clean solar modules. 

Solar panel cleaning: The Challenge of Manual Systems in Industrial Plants 

There are several options for the cleaning itself. Manual systems often work via a rod operated from the ground or a work platform. However, this is very quickly very tedious for industrial plants and can be accompanied by high safety risks. Instead, a PV panel cleaning robot that cleans large areas efficiently and safely is a good option. 

The right cleaning agent for solar cleaning  

Harsh agents are not suitable as cleaning agents, as they attack the materials of the system and end up unfiltered in nature if they are not collected in a cumbersome way. Instead, robot-assisted cleaning is suitable, for example, which has a strong cleaning effect due to the high brush rotation. This eliminates the need for the use of chemical agents. 

Another advantage in combination with the robot is osmosis cleaning, because it keeps recontamination as low as possible. Once the surfaces have been completely cleaned by the robot and osmosis water is used, it dries off without leaving any residue. As a result, limescale deposits do not form, which accelerate re-soiling.  

Solar panels and high-pressure cleaners? Proper mechanical cleaning  

A high-pressure cleaner is not suitable for cleaning, as it exerts too much pressure on the solar panels at certain points and can therefore damage them. Instead, rotating brushes, such as those found in solar and PV panel cleaning robots, gently and effectively remove the dirt that adheres to the surfaces through chemical reactions, for example.  

Thanks to the special brush design with gentle rotation and the coordinated amount of water in a PV panel cleaning robot, companies can achieve both effective and efficient cleaning without exerting too much pressure on the solar panels at certain points and thus damaging them. This makes the robots the perfect alternative to high-pressure cleaners. The solarROBOT pro, for example, with a brush rotation of around 400 rpm and long bristles, issuitable for solar surfaces from 2000m2 , while the solarROBOT compact cleans smaller systems from 150m2.

Cleaning solar panels with robots: occupational safety and efficiency 

The robots also have the advantage that they can be controlled from a work platform. As a result, cleaners do not have to step on the sensitive solar modules and roofs, which significantly increases occupational safety. In addition, roofs are often not designed for a person to stand on them to clean the modules. The selective pressure would be too great here. 

For large roof areas with more than 150 kWp, robot-assisted systems are usually much more efficient than conventional manual systems. While the latter clean an average of between 50 and a maximum of 300 square meters per hour, depending on the brush, a robot system can do ten times as much. In addition, it achieves a consistent work result throughout the day.  

Solar panel system cleaning costs: These are the factors for the price 

The costs incurred for cleaning solar panel systems depend on the method, the size of the system and its nature. However, cleaning companies and companies can keep their costs low with the right equipment. We offer various PV panel cleaning robots that clean gently and effectively due to their high brush rotation. Whether east-west, south-facing or long contiguous surfaces – the robot can be used flexibly depending on the requirements and can also reach difficult places without any problems. In combination with a reverse osmosis system, they are an excellent way to effectively and cost-effectively clean large solar panel systems as professional cleaning systems.   

How often should solar panels be cleaned? Regularly for best efficiency and longevity of the solar panels

Regular cleaning of the solar panel system is important in order to achieve the best possible yields in the long term. At the same time, it protects the solar panels from stubborn dirt such as lichens, moss, leaves, dust particles and the like, in order to be able to use the investment of a large solar panel system as effectively as possible for as long as possible. Cleaning is best done on cooler days and times, as well as after longer periods of rain, which already soak the dirt beforehand. PV panel cleaning robots ensure thorough and gentle cleaning with a high level of occupational safety for employees. 

Would you like to learn more about our PV panel cleaning robots? Then contact us. We will be happy to advise you!


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