Solar panel cleaning - 5 tips to consider when cleaning large PV installations

Clean solar panels for the best yields - how and why to clean the solar panels: Photovoltaics continue to enjoy great popularity in Germany, especially in industry. Alongside wind power, solar energy is one of the greatest hopes of the energy transition, accounting for 23.2% of electricity generation from renewable energies. However, the great potential of the technology is also accompanied by everyday questions: How can solar panels from large systems, for example on the roof, be cleaned efficiently and safely? What photovoltaic cleaning equipment is available? We explain the dos and don'ts of automated solar panel cleaning with robots.

Solar panel cleaning from above with the PV cleaning robot solarROBOT

How often and with what should solar panels be cleaned?

In order to function optimally, it makes sense for operators of solar power systems to clean their PV modules regularly. This is because soiling such as bird droppings, grease and rust dust have a negative impact on the performance of the modules. According to the Fraunhofer Institute, soiling can significantly reduce the maximum output of a PV system. This not only reduces the yield of self-used solar energy, but also reduces the potential feed-in to the electricity grid and the corresponding remuneration. How often a system actually needs to be cleaned using conventional cleaning aids or modern PV cleaning robots depends in particular on its location and the precipitation there. Professional cleaning of solar installations is recommended at least once a year, especially in agricultural areas.

Which cleaning methods are useful for solar cleaning in industry?

Cleaning robots are an integral part of modern facility cleaning operations. The same applies to the cleaning of large PV systems. Here, the solar cleaning robots score particularly well thanks to their high efficiency and environmental compatibility - because the high rotation of the brushes ensures an optimum cleaning effect without harmful and environmentally damaging chemicals. If you also clean with osmosis water instead of conventional water, the positive effect is maximized.

5 tips - Solar panel cleaning : how to do it right

To ensure that regular cleaning of the solar panels with the PV cleaning robot is efficient and safe, there are a few important points to bear in mind:

1. safety first: Getting the solar cleaning robot safely onto the roof

Safety is the top priority when it comes to using robots to clean PV modules on the roof. Roofs in particular have individual requirements.

Protective guard fitted

As a general rule, cleaning should always be carried out by a professional using climbing aids or, ideally, ABS fall protection grids. The great advantage of solar cleaning robots - compared to manual cleaning of solar panels, e.g. with telescopic poles - is obvious: cleaning staff do not have to enter the roof at all. Once the robot has been placed on the roof and secured with ropes, it does its job safely and reliably. Experienced cleaners should always carry out a visual inspection of the parts before commissioning and switch off the solar installation for the duration of cleaning.

Good to know: The hyCLEANER solar cleaning robots are equipped with fall protection sensors . This allows the robot to recognize the end of the solar surface at an early stage and can be steered in the opposite direction for optimum cleaning of the solar panels.

Before use on the roof, a function check of the cleaning robot including edge detection, as currently only offered by hyCLEANER, is important: Watch our video here.

2. adjust the cleaning behavior of the surface and clean the solar panels correctly

Depending on how dirty an area is and how high the angle of inclination is, the cleaning behavior with the machine must be adapted. This includes roping up the robot, but it is also important to use the right driving pads. For example, it is advisable to use rubber driving pads if the area is heavily soiled with ammonia (e.g. in cowsheds).

Good to know: The hyCLEANER accessories include three different driving pads - leather, rubber or neoprene - for different applications and surface requirements. They can be easily exchanged using the Velcro fastener.

Important: Also clean the brushes of the machine and the driving pads after cleaning - this can easily be done with running water. The following applies: Never clean the machine or PV system with a high-pressure cleaner!

Photovoltaic cleaning with PV cleaning robot and work platform

3. pre-cleaning: Note the grip and angle of inclination before cleaning the solar panels

Similar to snow groomers, the solar cleaning robots are driven by two chain-driven undercarriages, which give them the necessary grip on the slippery, sometimes steep surface. Similar to the rubber compound for cars in winter and summer, the hyCLEANER cleaning robot has different types of driving pads that can be easily changed using Velcro, depending on the area of application:

  • one especially for dry cleaning, e.g. in desert regions
  • one for normal soiling (depending on the machine model with a climbing ability of up to 25°)
  • one that is specially developed for cleaning very dirty surfaces, such as cowsheds

Correct handling of the driving pads is essential to ensure the necessary grip. Pre-cleaning one or two panels before placing the robot on them is therefore always recommended (see also next point). For the best possible grip, it is also advisable to ensure that the hose is guided from above. This prevents the load from pulling downwards and making contact with the surface more difficult.

Also important: Before cleaning, the slope of the roof should be checked using a measuring device and the surface conditions correctly assessed. Depending on the model and surface condition of the area to be cleaned, the hyCLEANER cleaning robots are suitable for surfaces with slopes of up to 25° (47%).

Tip: For stubborn stains, you should soak the roof beforehand or ideally clean it after a long period of rain.

4. observe water pressure and water quantity

For maximum cleaning effect, pre-cleaning and main cleaning with water is recommended. Osmosis water is particularly suitable for both processes. The filtered water, from which salts, minerals and other impurities are removed in advance, is very gentle to clean - and yet highly effective.

To ensure gentle and successful cleaning, it is essential to use a sufficient amount of water. This is because the less water is used, the more likely it is that dirt will rub against the collector surface. This means that there is no flushing effect to loosen the dirt, meaning that the same areas have to be cleaned several times.

Solar robots work with low pressure. This means they don't need that much water pressure. Two to four bar is sufficient - this corresponds to the amount that comes out of the tap. Nevertheless, there are pressure losses associated with the hose diameter and working at height. As a rule of thumb, you lose 1 bar of water pressure for every 10 meters of height.

The diameter of the hose is just as important as the correct water pressure. It must be large enough to pump enough water into the robot. With the solarROBOT series from hyCLEANER, it is important to use supply hoses with an internal diameter of at least 10 mm.

Important: Under no circumstances should high-pressure cleaners be used for cleaning, as the high water pressure also damages the sensitive surface.

Cleaning PV modules with water: Did you know that robots use much less water than conventional high-pressure cleaners? At approx. 0.5 liters/m², that's up to 10 times less water per square meter.

5. take proper care of the battery

To ensure the longevity of the cleaning robot, you should recharge the battery from time to time, especially during the cleaning-free winter months. Similar to an e-bike, so-called "battery jogging" is important to ensure that the battery maintains its performance. What does that mean? It should be used regularly.

Robots revolutionize the professional cleaning of solar panels

The use of solar panels on roofs is not only gaining momentum in the agricultural sector. However, in order for the systems to function optimally and generate good yields, operators must maintain and clean them regularly - an attractive opportunity for professional cleaning companies and solar panel operators who take over the cleaning of their PV system themselves. Cleaning robots that clean solar panels safely and efficiently have proven themselves in use. Anyone who pays attention to the above points and pays attention to safety, cleaning basics such as water pressure, water quantity and machine care, as well as the roof condition and battery check, is ready for a lucrative solar season.

Frequently asked questions about solar panel cleaning

Cleaning solar panels with glass cleaner: does it make sense?

Chemical cleaning agents are harmful to the environment and health, cause costs and are comparable to other cleaning methods in terms of efficiency. Cleaning solar panels with glass cleaner is therefore not recommended.

Osmosis purification works at least as efficiently. Using special filter technology, a PV system can be cleaned with treated tap water. This makes it harmless to the environment and health compared to chemical agents and very cost-effective to operate.

Can you clean photovoltaics with rainwater?

Yes, rainwater can indeed be an effective and environmentally friendly way to clean solar panels during the year, especially if it falls in sufficient quantity and intensity to naturally wash away dust and other debris. In many cases, rain can reduce or delay the need for manual cleaning, especially in regions with frequent rainfall. While rainwater can be helpful for cleaning solar panels, it is important to inspect the solar panels regularly and perform a mechanical cleaning at least once a year.

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

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:   

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 NÖ 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!


Reverse osmosis cleaning in industry: how cleaning companies benefit 

The environment, the health of the cleaners and the cost of cleaning agents – the disadvantages of cleaning with chemical agents are manifold. But there is already a good alternative. This is because osmosis deep clean works exclusively with treated water thanks to a special filter technology. In combination with an effective mechanical brush, the treated water enables environmentally friendly and efficient cleaning. How exactly does reverse osmosis cleaning work and how do companies best use the method to clean PV panel modules, large glass surfaces such as glass roofs and facades?

What is reverse osmosis cleaning? 

Reverse osmosis cleaning uses treated tap water. This usually contains various minerals, lime and salts. If the normal tap water evaporates, these components remain on the surface, for example in the form of limescale stains. Even if these are only very fine residues, they form a slight bump to which soot particles and dust, for example, get caught. As a result, the cleaned surface gets dirty more quickly and has to be cleaned again after a short time. 

During reverse osmosis cleaning, the water first passes through a special reverse osmosis filter system, which cleans the water of these smallest components. As a result, there is no residue during evaporation and the surface stays clean for longer. At the same time, the cleaning power is so good that aggressive cleaning agents with silicones, synthetic abrasives or acids become superfluous.

How does osmosis work with water? 

Substances such as water molecules as well as minerals and salts generally try to distribute themselves evenly. In osmosis, two water chambers are separated from each other by a semi-permeable, i.e. semi-permeable membrane. If the concentration of molecules on the two sides differs, the matching molecules flow through this membrane. This so-called osmotic pressure persists until the concentration is balanced on both sides. 

How does a reverse osmosis system for reverse osmosis cleaning work? 

In the case of cleaning with so-called pure water (also known as osmosis water, technical water or ultrapure water), reverse osmosis is used to counteract this osmotic pressure. The goal: on the one hand, to produce water that contains as few minerals and salts as possible, while on the other hand, these substances are washed away. In order to overcome the osmotic pressure, reverse osmosis involves forcing water through this membrane at a temperature of at least 3 bar. The smaller water molecules can pass through them, while the substances undesirable for cleaning are retained by them. The higher the tap water pressure, the purer the osmosis water will be at the end. 

Did you know? Instead of flushing the wastewater down the drain, the minerals it contains make it ideal as fertilizing water for plants.

Cleaning photovoltaic systems with tap water? This water is suitable for reverse osmosis cleaning 

During reverse osmosis cleaning, normal tap water is treated. The water quality is measured in ppm and influences the settings at the plant. In Germany, the water hardness is between 70 ppm (very soft water) and about 500 ppm (very hard water). For reverse osmosis cleaning, a value of less than 30 ppm is required for facades and solar, and a value below 15 ppm for glass. 

Depending on the country, the water quality differs, so there are no universal settings for the osmosis machine to achieve these values. However, in order for the filter system to work as intended, it is necessary to use normal tap water. Well water or water from similar sources is often too polluted and quickly clogs the filter. 

Reverse Osmosis Cleaning with Reverse Osmosis vs. Osmosis with Mixed Bed Resin – Which Is Better in the Long Run? 

hyCleaner Accessories Osmobil Pro X

In addition to reverse osmosis, mixed-bed resin filters offer the possibility of producing pure water. Although these are initially cheaper to purchase, the follow-up costs are all the more expensive. While costs of €15 to €100 per 1,000 litres are incurred for mixed-bed resin filters, depending on the water hardness, the costs for cleaning with a reverse osmosis system are consistently below one euro. The cost of using a mixed-bed resin filter is therefore up to 100 times more expensive to use.

Due to the cost and practical application, a system with a mixed-bed resin filter is only suitable for small, sporadic applications for plants of up to 100 kWp with soft water, while an osmosis system works effectively and efficiently even for large orders. 

Advantages of reverse osmosis cleaning with ultrapure water 

With reverse osmosis cleaning with pure water, companies benefit from advantages in terms of the safety of the cleaners and the cleaning costs, but this process is also much more sustainable for the environment. 

Efficiency and safety in everyday work with machine cleaning 

Many surfaces are not designed for a high point load capacity. Large glass surfaces and many roofs, for example, are often not allowed to be entered for cleaning of the glass surfaces themselves or of PV panel systems for reasons of occupational safety. In such cases, a cleaning robot that is placed on the roof from a working platform and remotely controlled is suitable. This is designed for the load capacity of roofs and the like, so that cleaning can be carried out safely. A robot can also reach angled surfaces, which are becoming more common due to advances in modern architecture and the development of construction methods. 

A robot also saves the company financial resources. With the help of the perfectly matched brush and the right amount of water, it not only cleans effectively, but also more efficiently compared to manual cleaning. 

At the same time , the osmosis effect increases the cleaning power. The pure water absorbs particles better because they want to be distributed by the osmotic pressure. There are hardly any foreign particles in the water, which is why the osmotic pressure is particularly strong here compared to the dirty surface. 

Sustainable and chemical-free cleaning for health and the environment 

This also has a positive effect on the environment. Thanks to the efficient cleaning with only water, no chemicals get into nature and into the wastewater, which would otherwise have to be treated at great expense. At the same time, the intervals until the next cleaning are extended, as dirt no longer adheres to the limescale edges. This also saves resources and protects the environment.  

In combination with mechanical cleaning, this not only enables effective and efficient cleaning, but also sustainable and chemical-free cleaning. With a hand brush, it is not possible to generate enough pressure and speed in the brush rotation to remove even stubborn dirt. The cleaning robot, on the other hand, ensures an optimal cleaning result thanks to its high brush rotation and the corresponding amount of water. In combination with osmosis water, surfaces are also freed from dirt that is difficult to dissolve, while the water dries without leaving any residue and thus slows down resoiling. 

Reverse osmosis cleaning with robots in use: 3 examples 

In principle, ultrapure water can be used to clean all smooth and closed surfaces, whichcan be found on glass façades, metal façades and solar and PV panels. The following three examples show what reverse osmosis cleaning with a cleaning robot looks like in practice and how companies benefit from it. 

Robots and Ultrapure Water: Glass Cleaning of Roofs 

Glass surfaces such as glass roofs or window surfaces in large industrial halls are generally very susceptible to dirt and require a lot of maintenance, as soiling caused by the weather, exhaust fumes, weathering, plant growth, bird droppings and so on are quickly visible. At the same time, cleaning is important to prevent fatigue of the material. 

However, cleaning involves a high risk of accidents due to the height, an increased risk of slipping in dirt and moisture, and modern architecture that makes access difficult. In the case of multi-storey and spacious buildings, special building shapes or sloping glass surfaces, reverse osmosis cleaning with a telescopic rod is no longer possible. This is because many roofs are not allowed to be entered, as this can lead to serious accidents at work.  

A robot, on the other hand, is adapted to the load capacity and structure of the buildings. The workers stand in the safe basket of a work platform from which they control the robot. A hose supplies the robot with ultrapure water or tap water. Due to the cleaning properties of the pure water and the efficiency of machine cleaning, the intervals before the glass needs to be cleaned again are extended. Reverse osmosis cleaning by a robot therefore improves occupational safety and reduces the costs for materials and frequency of cleaning. 

Cleaning a photovoltaic system with tap water: Reverse osmosis cleaning by robot 

Photovoltaic systems are most efficient when they are clean, according to the Institute for Solar Research of the German Aerospace Center. But they also pollute with dust, sand, pollen, ammonia, leaves or bird droppings. As a result, they need to be cleaned regularly to prevent large yield losses. Cleaning with osmosis water and a robot is particularly suitable for photovoltaic systems, as the individual solar cells are very sensitive. Strong cleaning agents with acids or abrasives, hard brushes or high-pressure cleaners can quickly cause damage here. 

At the same time, conventional cleaning methods for large areas are very time-consuming, physically demanding and uneconomical. Floating or roof-mounted systems also pose a high safety risk for cleaning staff. A robot is therefore a good way of tackling these challenges.

Cleaning the façade: This is why osmosis water is suitable for cleaning

Facades are mainly polluted by verdigris, lichens, moss or industrial pollutants. Regular cleaning improves the external appearance and improves the longevity and value retention of the building. Depending on the material, many chemical cleaning agents are too aggressive and can damage the façade. The osmosis process cleans efficiently without chemical agents. 

In combination with a façade brush, which is attached to a work platform and controlled by it, large areas can be cleaned gently and efficiently at the same time. It is therefore also suitable for large shopping centers, furniture stores such as Ikea and other large buildings. All-in-one systems combine the use of osmosis water and cleaning robots as a professional cleaning system.

Van equipped with osmosis deep cleaning system
Van equipped with osmosis deep cleaning system

Efficient and chemical-free cleaning through reverse osmosis cleaning with robots 

The use of technical water, in combination with robot-assisted cleaning, is suitable for cleaning surfaces efficiently, effectively and sustainably. This is because the two technologies combine a wide range of advantages: Thanks to the high mechanical brush performance and the use of osmosis water, chemicals can be completely dispensed with. The robot also enables companies to achieve the highest safety standards, as employees can control it safely from the basket of a work platform. 

Would you like to learn more about the possibilities of a cleaning robot or reverse osmosis cleaning? Then contact us!