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Soiling Monitoring Systems: All you need to know

If you have a solar PV system, then you know that keeping it clean is essential for two primary reasons: to maintain its performance and to keep it looking good.

When solar panels are dirty, they lose efficiency and can even be damaged. That’s where soiling monitoring systems come in.

Soil Accumulated on Solar Panel Surface

A PV soiling monitoring system will keep track of the amount of dust, dirt, or debris that accumulates on the panels over time.

By doing this, you can be alerted when soiling is starting to have a significant impact on system performance so that you can clean the panels off and restore their efficiency as soon as possible.

In this blog post, we provide an overview of all you need to know about soiling monitoring systems.

We’ll cover aspects such as:

  • What soiling monitoring systems are?
  • How they work
  • Types available
  • How to choose the best monitoring system?  
  • Benefits of PV soiling monitoring

PV Systems Soiling Defined

The term “soiling” refers to the accumulation of snow, dirt, and dust on the surface of a PV module. Soiling can cause a number of problems for a PV system, including:

  • Reduced light absorption, which reduces energy production
  • Increased system maintenance
  • Early component failure
  • Reduced lifespan of the system

Soiling losses can be a major contributor to a PV system’s overall reduction in performance.

It’s therefore essential to understand the effects of soiling on a PV module in order to estimate the losses that may occur during the lifetime of your PV system.

The soiling of a PV system can be represented in a ratio (soiling ratio) as follows:

Soiling ratio= Actual power of the PV system under certain soiling conditions/ Expected power of the PV system when it’s free of soling.

What is a Soiling Monitoring System?

A soiling monitoring system is a device used in conjunction with solar photovoltaic (PV) systems to monitor the amount of dust, pollen, sand, and dirt accumulation on the PV modules.

The soiling monitoring system periodically samples the irradiance level of the PV array and calculates the reduction in power output caused by soiling.

The need for a soiling monitoring system arises from the fact that dirt and dust can reduce the power output of a PV system by up to 30%. In some cases, the reduction can be even more significant.

With a soiling monitoring system, loss in power output for PV systems can be reduced, boosting solar PV systems’ efficiency and ROI.

Types of Soiling Monitoring Systems for Solar PVs

The three main types of soiling monitoring systems for PV modules:

Optical soiling systems

Optical PV monitoring systems are intended to measure light loss from dust and dirt that settle on PV panels.

The optical sensor in the system measures the amount of light that passes the solar panels without being reflected back by the soiling on the PVs.

This information is used to calculate the level of dust and dirt on the panel and to create a cleaning schedule.

Automatic two PV Cell systems

These systems work by detecting the difference in power output between a clean and dirty PV cell. The difference is then used to calculate the amount of dirt on the PV cell.

This information is also used to send a signal to a robotic arm that cleans the dirty solar cell when a given amount of soling is reached.

This soiling monitoring system is perfect for rooftop projects. It eliminates the need to go near the sensor and clean it manually, which can be dangerous and time-consuming.

Traditional two PV Cell systems

Traditional soiling monitoring systems also use two PV cells.

The first PV cell is used to measure the amount of light that is being transmitted through the dirty PV panel. The second PV cell measures the amount of light that is being transmitted through the clean PV panel.

By subtracting the amount of light transmitted through the dirty PV panel from the amount of light transmitted through the clean PV panel, you can calculate the amount of dirt on the PV panel.

The difference between an automatic and a traditional two PV cell system is that the PV cell of the latter needs to be cleaned manually.

Factors that affect the Decision to Install Soiling Monitoring Systems

The decision to monitor PV soiling or not is a complex one that takes into account many factors.

Some of these factors include the location of the PV system, the age and condition of the system, and the type of dirt and dust that is present.

In general, PV systems should be monitored for soiling if any of the following conditions are present:

  • The system is located in a dusty or dirty area.
  • The system is located near a road or construction site.
  • The system is more than 5 years old.
  • The system is prone to damage by a storm or other event.

How do Soiling Monitoring Systems Work?

PV soiling monitoring systems work by detecting the level of dust and dirt accumulation on PV modules. This information is then transmitted to management software, which can provide alerts and track trends over time.

The first step in setting up a PV soiling monitoring system is to install sensors on the PV modules.

These sensors collect data and are able to detect when soiling has occurred by measuring the decrease in irradiance (the amount of light that reaches the PV cells).

When the irradiance levels drop below a certain threshold, data is recorded.

The data collected by the sensors is then sent to management software, which can provide alerts and track trends over time.

The management software can also be used to generate reports on the estimated soiling and performance of the PV modules.

The soiling monitoring units can be installed in a network to monitor the variation in soiling over across the solar PV array. This will help you to identify and address any areas that are experiencing more soiling than other areas.

A typical soiling monitoring system software will let you set alarms to show when a certain PV soiling ratio has been reached.

How to Choose the Right Soiling Monitoring System?

Here are some factors you’ll need to consider when making your PV soiling monitoring system:

Communication module

A good communication module will ensure that you are able to get real-time updates about your PV soiling conditions. It will also allow you to manage your data efficiently and make decisions quickly.

Without a good communication module, you may find yourself struggling to keep track of your PV soiling data.

Transmission loss measurement accuracy

Transmission loss measurement accuracy is critical when choosing the right soiling monitoring system for your facility.

Many factors can affect the accuracy of readings from a soiling monitoring system, including the type of sensor used, the calibration of the sensor, and the environmental conditions in which the sensor is used.

In order to ensure that you are getting accurate transmission loss measurements, it’s essential to select a soiling monitoring system that has been calibrated and tested in accordance with relevant industry standards.

Level of maintenance needed

Some PV soiling monitoring systems are very low-maintenance and can be left alone for long periods of time without requiring any attention.

Others, however, require more regular cleaning and maintenance in order to keep them functioning properly.

It’s essential to choose a system that fits your needs and is easy to maintain.

The design of the system

The last thing you want is a bulky monitoring system that takes up too much space and doesn’t look good on your roof.

Look for a system that is sleek and fits in with the rest of your roofing design.


Another thing to consider when it comes to choosing a PV soiling monitoring system is that not all systems are created equal – some are more accurate than others, and some are more expensive.

It’s crucial to find a system that offers good value for money.

Another thing to keep in mind is the cost of maintaining and operating the system. Make sure you factor this into your decision-making process.

Additional features

When choosing a PV soiling monitoring system, there are a few additional features to consider.

Temperature monitoring is one important feature to look for. The temperature of the array can affect the amount of soiling that occurs.

If the temperature is too high, then the dirt will bake on and become harder to remove. Temperature monitoring can help to adjust the cleaning schedule accordingly.

Another critical feature to consider is alarm notifications. If there is excessive soiling on your PV modules, the alarm system will engage and alert you.

How many Soiling Stations do I Need for my Solar PV Site?

There is no definitive answer to this question as it depends on a number of factors, including the size of your solar PV site, the type of dirt present, and the condition of your solar PVs.

That said, here are two general guidelines to help you determine how many soiling monitoring stations you might need:

  • For smaller solar PV sites (up to 20 MW in size), one or two soiling monitoring stations should be adequate.
  • For larger solar PV sites (over 20 MW in size), three or four soiling monitoring stations may be necessary to ensure accurate readings.

Benefits of Soiling Monitoring Systems

You know exactly where and when to clean your PV modules

Most PV module owners only clean their modules when they start to look dirty.

This generally means that the dirt and dust have built up over time to a point where they are significantly reducing the amount of light that is being absorbed.

A PV soiling monitoring system will tell you exactly when and where to clean your modules so that you can maximize their performance.

Using soiling data, you can forecast trends over time

Another benefit of using PV soiling data is that you can forecast trends over time.

For example, if you notice that the amount of soiling on your panels has increased over the past few months, you can predict that the amount of energy generated by your panels will decrease in the near future.

This information can help you create more efficient cleaning schedules for your solar panels.

It makes it possible to troubleshoot other performance losses

By diagnosing and detecting soiling issues with your PV system, you can detect when other issues are affecting its performance.

Other potential causes of loss in PV system performance that can be identified with the help of a soiling monitoring system include:

  • The PV array is installed in the wrong location.
  • The angle of the PV array is not optimal.
  • The PV array is shaded by trees or other objects.

Your solar panel investment is maximized

PV soiling monitoring systems keep your solar panels clean and optimize their performance by adjusting to the changing environment.

This results in increased energy production and a quicker return on investment for your solar panels.

You can better plan for future PV projects

There are many benefits of solar panel soiling monitoring systems. Perhaps one of the most overlooked benefits is that you can better plan for future PV projects.

By understanding how soiling occurs on your PV system and how it changes over time, you can make more informed decisions about where to install solar panels in the future. You can also use this information to optimize your existing PV system.

Final Thoughts

Soiling, or the deposition of dust, dirt, or other contaminants on a photovoltaic (PV) module, is a problem that can significantly reduce the power output of a PV system.

Soiling monitoring systems are a great way to keep track of your system’s dirt and dust levels and identify areas that need more cleaning.

With a soiling monitoring system, solar PV system owners can take proactive steps to protect their array and maintain its efficiency.

In a nutshell, you must always remember that soiling detection and cleaning are an essential part of PV system maintenance and operation.