The embedding material in the solar modules has a major influence on their resistance to PID. Modules equipped with POE are absolutely stable in that respect

Even though this phenomenon has been prevented by adjusting the design of conventional modules, with system voltages increasing from 1,000 to 1,500 volts, the issue of how to prevent PID is back on the engineering agenda.

Thus, a team at ZSW joined forces with business ventures Specialized Technology Resources España and CS Wismar and decided to develop a heavy-duty test that simulates decades of operation and provides more accurate information about solar modules’ resistance to PID.

The test consisted of combining the stress-inducing components of an established test known as IEC TS 62804-1 and increased the voltage by 67% to 2,500 volts. With trials running up to 1,000 hours, this test was more than 10 times longer than the standard test.

Two types of cells were tested: a resistant version and a variant that is slightly more susceptible to PID. Both cells were combined once each with the standard EVA (ethylene vinyl acetate; EVA-1) embedding material, an improved, highly resistive EVA (EVA-2), and with a polyolefin elastomer (POE).

“The results showed that PID causes the performance of modules with the EVA-1 embedding material to drop by up to around 5% after two calculated years of operation in a 1,500-volt system,” the researchers said in a media statement. “Modules equipped with EVA-2 held up even better, with the performance decreasing up to 5% only after 22 years of operation. According to the ZSW’s calculations, modules with a POE would show practically no signs of PID even after 60 years in operation.”

In the scientists’ view, long-term forecasts like the one they’ve released are important to those assessing the feasibility of solar projects for their companies, partners, borrowers, and so on.