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Can someone explain Potential Induced Degradation? I've been looking over the internet but a lot of the explanations go into too much detail.

  • This might be a duplicate of sustainability.stackexchange.com/q/2943/48 – EnergyNumbers Jun 2 '16 at 5:45
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    It should probably be potential-induced degradation, which would mean degradation induced by the potential difference (i.e. voltage) within the device. This is likely to be especially significant on unloaded panels, as the open circuit voltage is higher than any voltage at which power is supplied to a load. – Chris H Jun 2 '16 at 16:28
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    You should give us a link and some context if you want more detail, but the question might be a better fit at electronics.se (or even physics.se). – Chris H Jun 2 '16 at 16:29
  • Giving us a few links to the "too much detail" explanations, and telling us your understanding of what it is would let us explain it in a way that you understand better. What don't you understand? What have you looked at, and what do you think it means so far? Right now you're likely to get yest another "too much detail" explanation, or else a "way too simple" explanation. Are you asking for the physical mechanisms at play? When you say "too much detail" do you mean the formulae for ion movement in crystalline solids, or do you mean they use terms like potential and electrostatic? – Móż Jul 8 '16 at 8:12
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In very simple terms, current leaks from the solar cells to the structure of the panel. This happens when a combination of heat, water and the generated electricity cause the material the panel is made of to break down at a very low level, and start conducting electricity where we don't want them to.

It's hard to balance "how, exactly" with "not too detailed" in an answer to your question. Going beyond "very simple" above means talking about ions (atoms that have more or fewer electrons than normal), crystal structure (where those ions should be) and ion channels (where the ions move to). The explanation below is one fairly simple technical one I found online.

From Advanced Energy (pdf):

Potential Induced Degradation, as the designation implies, occurs when the module’s voltage potential and leakage current drive ion mobility within the module between the semiconductor material and other elements of the module (e.g. glass, mount and frame), as shown in Figure 1, thus causing the module’s power output capacity to degrade. The ion mobility accelerates with humidity, temperature and voltage potential. Tests have revealed the relationship of mobility to temperature and humidity: “Planar contact with the panel surface also causes a capacitive coupling to the cells, resulting in a capacitive leakage current of varying strength.” 1

The PV system and environment interact to cause PID. The conditions necessary for the occurrence of PID involve (i) environmental factors, as well as factors involving (ii) the system, (iii) the module, and (iv) the cells.2 3 “While the environment is set for each individual installation, it is possible to prevent PID by properly controlling only one of the factors

  • Very interesting - nice find. I hadn't come across this terminology before, and it's nice to see it's a recognised term and a documented phenomenon. – EnergyNumbers Jul 8 '16 at 10:16
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Technical explanations aside, here is an example from sunny Florida.

You would think that more sunlight equals more power output, but that isn't the case. It is easily possible, especially in South Florida, that the temperature of the panel can exceed the effective operating range of the solar module materials. At which point the power output drops precipitously!

It is very important to select solar modules that are designed to operate in the environment in which they will be used.

In the case of this example, a small amount of the power generated was used to pump water from a cool reservoir to run down the faces of the panels to assist in keeping them cool, thus maintaining maximum power output on especially hot days. This was very effective and resulted in a net increase in power output. The water was collected, filtered, and used again.

  • This appears to be an example of the temperature curve, not potential-induced degradation. The temperature problem is instantaneous and temporary (for the most part), while PID is permanent. – Móż Jul 8 '16 at 0:19
  • @Móż I'm no expert on this but it's been my understanding that PID gets worse with high voltage, high humidity levels and high temperatures. Why do you think the problem isn't PID here? – THelper Jul 8 '16 at 7:08
  • @THelper I'd guess that because the cooling water enabled maximum power output, there was no permanent degradation. Maybe Daniel can clarify? – EnergyNumbers Jul 8 '16 at 7:59
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    To me, the issue with the answer is that if you were extremely charitable you could consider it to imply that perhaps temperature has something to do with PID, but it doesn't explain what PID is in simple terms, which is what the question seems to be asking for. – Móż Jul 8 '16 at 8:08
  • @Móż The implication was that heat is an aspect of PID that can be controlled and the immediate indication of that thermal stress was a significant reduction in output. In the example a cooling solution was created to insure the panels would not suffer even short-term high temperatures and there should never be any permanent damage. – Daniel Jul 8 '16 at 18:12

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