Understanding Potential Induced Degradation in PV Modules

When exploring options for solar modules, you will probably encounter the term Potential Induced Degradation (PID) as something to watch out for. Here is a basic guide to understanding and avoiding PID in a photovoltaic module.

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What is PID?

Simply put, PID is the condition in which a solar module loses some of its capacity for electrical output due to premature degradation. In modules with PID, the electrical current begins to leak away from the internal circuit, eventually reducing the module’s power output. Modules that are susceptible to PID can negatively impact your entire PV system, causing it to underperform significantly within 2-3 years.

 

How does PID happen?

A combination of factors such as environment and grounding configuration can contribute to PID, but the primary driving factor is the PV module itself.

Each individual component of the module (solar cell, glass, frame, etc.) has its own electrical potential. Within the module, there are multiple components—each with their own level of potential. This is called potential difference, or voltage. The higher the potential difference, the more electrical current is generated between the components (sometimes called stray currents), that the module was not designed to handle. These stray currents move ions around the cell in unplanned ways, which can eventually cause the module to degrade.

electroluminescence-image-photovoltaic_thumb.jpgPhoto Source: Mit welchen Methoden lässt sich PID erkennen ?

How do I avoid PID?

The easiest way to avoid PID is to choose modules designed and tested for PID resistance.

Since a functioning solar module will naturally be exposed to the elements and will be generating voltage, the environmental factors that cause PID will be present in every scenario. Therefore, it’s important to choose a module that was intentionally constructed to avoid PID. Using materials that have a low voltage potential relative to each other, for example, can reduce the risk of a module succumbing to PID.

In this whitepaper, Advanced Energy states, “While the entire PV system interacts to cause PID, the failure mode occurs in the modules.  Fortunately PID does not occur in all modules, and tests are available to determine whether modules are susceptible or resistant to the effect. Many module manufacturers have taken steps to produce PID-resistant modules.”[1]

If a PV module is going to succumb to PID, it will happen relatively quickly. All modules lose some power output capacity over the course of a lifetime, but a good PV module should still be producing at least 80% capacity after 25 years. Modules that experience PID, on the other hand, can lose up to 80% efficiency within the first few years.

It is important to note that solar installers can design systems that can mitigate or reverse the effects of PID, if it does occur.

 

How do I know if my modules are PID-resistant?

There are ways to test modules to detect if they are susceptible to PID.

During these tests, modules are placed in an environment conducive to potential induced degradation and the conditions are accelerated. The standard PID test is 96 hours of exposure to these conditions, though some manufacturers, like Itek Energy, choose to test for 500 hours—providing our customers with that extra level of assurance that our modules not only meet, but exceed the standard for PID resistance.

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Peace of mind

Now that you understand more about what PID is and how to avoid it, you will be able to make informed choices about what type of module you want to use in your solar project. Choosing a module designed and certified as PID-free, such as Itek Energy's high-efficiency PV modules, can protect both your solar array’s performance and your peace of mind.

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[1] Advanced Energy,® Understanding Potential Induced Degradation

Kathryn Heltsley

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