Panasonic’s high-performance ‘HIT’ PV modules have shown no sign of being affected by potential induced degradation (PID) characteristics after testing took place at the Fraunhofer Center for Silicon-Photovoltaics (CSP).
A special PID testing regime was developed by the Fraunhofer CSP to account for Panasonic’s unique HIT solar modules. The test developed included both negative and positive voltages, whereby 5 modules were subjected to +1,000 volts for 48 hours at a temperature of 50 degrees Celsius with 50% relative humidity and 5 modules at -1,000 volts over 48 hours. According to the company, no evidence of PID was observed.
The Panasonic HIT photovoltaic modules exhibited no sign of degradation under such conditions. Of the ten modules used for the test, five were subjected to +1,000 volts, and the other five to -1,000 volts over 48 hours. The results show no evidence of PID.
Dr. Matthias Ebert, Head of the Group Module Reliability at Fraunhofer CSP, said “HIT modules differ from standard modules. The challenge for us was to develop a test method that would respect this. By testing for both positively and negatively charged voltages, we can attest to the PID resistance of HIT photovoltaic modules.”
Panasonic said that the unique HIT cells, which use thin monocrystalline n-type silicon wafers surrounded by ultra-thin amorphous silicon layers do not require insulating layers, unlike conventional crystalline silicon-based solar cells, which can collect electrical charges near an the insulating layer. It is believed the trapping effect causes PID.
“Since HIT modules have been proven to be PID resistant by one of the most authorized agencies in the field, our customers can now be fully assured that our modules deliver an excellent performance,” added Michael Seys, in charge of photovoltaic product development of Panasonic Eco Solutions Energy Management Europe.
Conventional crystalline silicon-based modules have typically have been PID tested for 5-7 days at 65 – 85 degrees Celsius and up to 85% relative humidity using the standard 1,000 volts of system voltage bias.