What is photovoltaic module degradation?
PV module degradation refers to the gradual loss of the cells’ ability to convert solar energy into electrical energy. This process begins on the very first day of system operation and continues throughout the entire service life of the installation. Although most manufacturers declare a power loss of no more than 20% after 25 years, in practice the rate of degradation depends on many factors.
Several main types of degradation can be distinguished.
- The first is LID (Light Induced Degradation), which typically occurs during the first weeks of module operation.
- The second is PID (Potential Induced Degradation), associated with the occurrence of a potential difference between the cell and the module frame. This type of degradation may accelerate under conditions of high humidity and temperature.
- The third mechanism is LeTID (Light and elevated Temperature Induced Degradation), which becomes apparent over a longer period of time, mainly in monocrystalline panels.
The degradation rate may range from 0.2% to as much as 0.8% per year, and in some cases the process can proceed much faster. Factors influencing degradation intensity also include material quality, exposure to moisture, panel cooling conditions and the frequency of cleaning the active surface.
What effects does PV module degradation cause?
A decline in output power translates directly into reduced electricity yields. On an annual basis, this may mean losses of several dozen kilowatt-hours for each installed kilowatt of capacity (kWp). For large-scale commercial installations, this results in significant deviations from financial forecasts and, in some cases, may lead to exceeding permissible contractual tolerances.
Degradation also affects a reduction in the PR (Performance Ratio) indicator, which measures system performance in relation to weather conditions. A lower PR means lower system efficiency, which in turn may affect settlement conditions with the grid operator or the investor financing the project.
From an economic perspective, degradation also leads to higher maintenance costs. Older installations require more frequent inspections, replacement of individual modules or service interventions related to inverter failures. Identifying degradation symptoms too late may result in deeper losses, especially if damaged modules are not disconnected from the system in time.
How to monitor PV module degradation?
Modern PV installations are equipped with technical supervision systems that enable ongoing measurement of operating parameters. The most commonly used solution is a SCADA system, which allows remote monitoring of production and alarm data. As part of O&M (operation & maintenance) services, periodic analyses of historical data are also carried out, which may indicate a gradual decline in performance.
For more precise diagnostics, tools such as:
- current–voltage (I–V) curve analysis,
- thermographic imaging,
- electroluminescence (EL).
Each of these methods makes it possible to detect different types of damage — from microcracks and hot spots to corrosion of electrical contacts.
Regular on-site inspections carried out by O&M operators are a requirement of good technical practice, but also an important element of operational risk management. A modern approach assumes the integration of diagnostics with data analytics, allowing even minor deviations to be detected and enabling early response.
How to minimise degradation effects and limit losses?
Although PV module degradation is unavoidable, it is possible to slow it down and reduce its negative effects. Of key importance is the selection of high-quality components — both the modules themselves and mounting structures and auxiliary equipment. Investors should pay attention to quality certifications, manufacturer warranties and supplier experience in climatic conditions similar to those in Poland.
Correct installation of the system is equally important. Modules should be set at the appropriate angle and in a way that ensures free airflow, as this affects cooling. It is also essential to ensure even current loading of individual strings and to avoid partial shading, which can lead to local overheating and damage.
In modern asset management, data analytics and artificial intelligence-based solutions are playing an increasingly important role. Predictive maintenance systems, using algorithms trained on historical data, make it possible to forecast degradation in advance and take preventive action. Thanks to them, it is possible, for example, to plan the replacement of the most exposed modules before an actual failure occurs.
In the long-term maintenance of system performance, cooperation with an experienced O&M operator is of great importance. Companies specialising in the technical operation of photovoltaic farms have not only expertise, but also the necessary toolsets to carry out full diagnostics, reporting and performance optimisation. Over a multi-year perspective, such cooperation helps reduce the risk of production losses and extend the effective operating life of the system.
PV module degradation affects the efficiency and profitability of installations, which is why it should be continuously monitored and included in the system maintenance strategy. Regular measurements, the use of diagnostic tools and cooperation with a professional O&M operator help reduce performance losses and extend the service life of the installation. Implementing comprehensive service activities is today not only good technical practice, but also an economic necessity.
For photovoltaic farm owners and infrastructure operators, a good step is to start working with companies specialising in the technical operation of installations. Experts from Nomad Electric offer comprehensive audits and monitoring systems that help optimise performance and minimise the risk of losses. Contact our team to discuss opportunities to improve the operation of your PV farm.
Frequently asked questions (FAQ)
1. What does photovoltaic module degradation mean?
Degradation is a natural process involving the gradual decline in the efficiency of PV modules in converting solar radiation into electrical energy. It begins from the moment the installation is commissioned and continues throughout its entire service life, reducing energy yields over time.
2. What are the most common degradation mechanisms?
In practice, three main types of degradation occur: LID (light induced degradation), PID (potential induced degradation), and LeTID (light and elevated temperature induced degradation). Each is associated with different stages of operation and environmental conditions.
3. How does degradation affect the performance of a PV installation?
A decrease in module power directly translates into lower energy production, which in the long term affects the profitability of the investment. It may also lead to a reduced performance ratio (PR) and higher system maintenance costs.
4. How can module degradation be monitored?
Monitoring is carried out using SCADA systems, I–V curve analysis, thermographic imaging, and electroluminescence testing. Regular inspections and analysis of historical data make it possible to detect irregularities early and plan maintenance activities in advance.
5. Can the rate of degradation be limited?
Yes, by selecting high quality components, ensuring proper installation, and maintaining appropriate operating conditions. Ongoing diagnostics and preventive actions based on data analysis also play a key role.
6. What role does an O&M operator play in reducing losses?
A professional O&M operator provides comprehensive supervision of installation performance using specialized diagnostic tools and predictive solutions. This enables early problem detection, optimization of energy yields, and extension of the overall system lifetime.
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