What is PID in a solar panel?
For anyone planning to install solar panels, understanding what is PID in a solar panel is important because it can slowly reduce the amount of electricity your panels produce without causing any obvious visible damage. In this blog, Neal Solar, a reliable solar panel company in Kerala, explains what PID is, what causes it, how it affects your solar panels, and how it can be prevented and managed.
Potential-Induced Degradation (PID) is a form of performance degradation that can occur in photovoltaic (PV) modules when there is a high voltage potential difference between the solar cells and other parts of the module or system that are at ground potential. This electrical stress can cause leakage currents within the module and gradually alter the electrical characteristics of the solar cells. As a result, the module can experience a reduction in power output and, consequently, a decline in the overall energy yield of the solar system.
PID does not refer to a single failure mechanism. It can occur through different physical processes depending on the solar cell technology, module materials, encapsulation, system configuration, and environmental conditions. In crystalline-silicon PV modules, one commonly discussed mechanism involves the migration of sodium ions under an electric field, which can contribute to shunting and changes in the electrical properties of the cells. The severity of PID can also be influenced by factors such as system voltage, temperature, humidity, and the electrical position of a module within a string.
Unlike physical damage that may be immediately visible, PID can develop gradually and may initially be noticed through a decline in the electrical performance of affected modules or strings. Therefore, understanding the causes and effects of PID is important for maintaining the long-term performance and energy production of a solar PV system.
What Causes PID?
Potential-Induced Degradation occurs when electrical, material, and environmental conditions within a PV system promote leakage currents and other degradation mechanisms. The likelihood and severity of PID depend on factors such as the module’s construction, cell technology, system voltage, grounding configuration, temperature, and moisture. The major factors associated with PID include high voltage stress, ion migration, and environmental conditions.
High Voltage Stress
Solar panels in a PV system can experience a high voltage difference between the solar cells and the grounded parts of the system. Over time, this electrical stress can cause leakage currents within the module. When this continues, it can affect the electrical performance of the solar cells and gradually reduce the panel’s power output.
Ion Migration
In some crystalline-silicon solar panels, PID can involve the movement of ions, particularly sodium ions, within the module. Under an electric field, these ions can move toward the solar cells and affect their electrical properties. Depending on the module design and the type of PID, this process can contribute to power loss and reduced panel performance.
Environmental Factors
Environmental conditions can also influence the development and severity of PID. Higher temperatures and moisture can increase the conditions that contribute to leakage currents and other PID-related processes. The materials used in the module, its encapsulation, system voltage, and the panel’s position within the solar string can also affect its susceptibility to PID.
Effects of PID
Power Loss
One of the primary effects of PID is a reduction in the electrical power produced by affected PV modules. As degradation progresses, electrical characteristics such as shunt resistance and fill factor can deteriorate, resulting in lower maximum power output. In severe cases, PID can cause substantial power loss and, depending on the mechanism, potentially lead to module failure.
Lower Efficiency
When PID affects the electrical performance of a module, the module may convert less of the available solar energy into electricity. This reduction in power output effectively lowers the operating efficiency of the affected module. Because PID can develop progressively, the impact may become noticeable through a gradual decline in energy production rather than an immediately visible physical defect. I
String Impact
PID does not necessarily affect every module in a PV system equally. Its occurrence can depend on the module’s position within a string and its electrical potential relative to ground. In some configurations, modules exposed to a particular voltage polarity can experience greater degradation than others.
As a result, PID can affect the performance of individual modules and consequently reduce the output of the associated PV string. This makes system-level monitoring and appropriate testing important when investigating unexplained differences in string performance.
How to Prevent and Fix PID
Use PID-Resistant Panels
One of the most effective ways to reduce the risk of PID is to select PV modules that have been designed and tested for resistance to PID. IEC TS 62804-1:2025 provides test methods for evaluating the susceptibility of crystalline-silicon PV modules to potential-induced degradation. When selecting modules, it is important to check the manufacturer’s technical documentation and confirm that the specific module design and bill of materials correspond to the claimed PID-resistance testing.
Proper Grounding
Correct electrical system design and grounding practices are important for managing the electrical potentials that can contribute to PID. The grounding arrangement should comply with the applicable electrical standards and the requirements of the inverter and PV module manufacturers.
Grounding alone should not be treated as a universal solution for PID because susceptibility also depends on module construction, cell technology, system configuration, and environmental conditions. However, appropriate system design can help control the electrical conditions associated with PID.
Night time Reversal
Some forms of PID, particularly in crystalline-silicon modules, can be partially reversible. A PID recovery device or anti-PID system can apply a reverse voltage during nighttime to counteract the electrical stress that caused the degradation. This process is sometimes referred to as PID recovery or nighttime PID reversal.
However, recovery is not guaranteed in every case. Its effectiveness depends on the type and severity of PID and the specific module technology. Some forms of PID can partially recover through natural or electrically assisted recovery processes, while more advanced or irreversible degradation may not fully recover. Performance should therefore be measured after any recovery procedure to determine whether the intervention has restored the expected output.
Conclusion
Potential-Induced Degradation is an important PV module degradation mechanism that can reduce power output and affect the long-term energy yield of a solar installation. High voltage stress, ion migration, temperature, humidity, module materials, and system configuration can all influence the development and severity of PID. Selecting PID-resistant modules, following appropriate electrical and grounding practices, and monitoring system performance can help reduce its impact. Where suitable, nighttime PID recovery methods may also help restore some of the lost performance.
For reliable module selection, system design, installation, and long-term performance, Neal Solar, an experienced solar energy company in Kerala, can help ensure that your solar PV system is designed according to the module specifications, electrical requirements, and site conditions.
