Potential-induced degradation (PID) particularly occurs when solar modules are operated in a damp environment with high voltage. Sodium penetrates the silicon solar cells and causes short circuits; efficiency declines, which causes performance losses and permanent output reductions. PIDcheck makes it possible to perform quality checks on modules in the field even after they have been installed, and to draw conclusions about how susceptible the modules are to the PID effect.

The previous testing procedures for determining the PID susceptibility of solar modules were complicated and expensive. The modules had to be removed from the solar parks, packed up carefully and transported to a lab for testing in permanently installed climatic chambers. PIDcheck is a portable device that allows solar modules to be checked for PID on site. At four to eight hours, using the device takes much less time than previous methods.

“The previous testing procedures in the lab, which take at least 96 hours, are very time-consuming and cause additional output reductions. Since using PIDcheck does not require the module to be taken out of the field, there are no additional performance losses. Tests can be performed within eight hours, at a module temperature of 85 °C and a cell voltage of up to 1500 V. Within this time, the modules can also be returned to their original state once the test is finished,” says Dr. Volker Naumann, a researcher at the Fraunhofer CSP. In 2012, he worked with colleagues to determine the physical principles behind potential-induced degradation. Also in a collaboration with Freiberg Instruments, the Fraunhofer CSP then developed a device that allowed testing for PID susceptibility during the production process and at the cell level (PIDcon), thus making an important contribution to improving quality control in the photovoltaic industry.

The new PIDcheck device functions through an electrical contact between the module’s surface and a conductive electrode. Depending on the module type, about half of the cells can be subject to PID exposure. In addition, PIDcheck allows a reliable performance and output forecast. Even if no PID has been found in the system so far, the installed solar module’s PID susceptibility can be determined. If PID has already occurred, the PIDcheck can be used to predict the module’s future performance.

“PIDcheck allows customers in the solar industry to perform quick quality checks; it offers many benefits not just for owners of solar power plants, but also for manufacturers, service providers, evaluators and insurance companies. The device will be available from Freiberg Instruments starting in the summer of 2018,” says Dr. Volker Naumann. 

During its presentation at the International Energy Storage and Mobile New Energy Exhibition & Conference (SNEC) in Shanghai, the development already met with an outstanding response. Dr. Volker Naumann and Dr. Christian Hagendorf, Director of the “Solar Cell Diagnostics” group at the Fraunhofer CSP, and Dr. Nadine Schüler, Development Manager at Freiberg Instruments, received the Best Poster Award for their poster on “Rapid PID Testing and Assessment of PID Stability at Installed PV Modules.” At the Intersolar Europe trade fair (June 20-22 in Munich), Freiberg Instruments will be introducing the device to potential customers from the solar industry in Hall B3, Stand 350. Volker Naumann will present the possibilities offered by the PIDcheck at the “pv magazine Quality Roundtable” on Thursday, June 21, at 11 am at the Intersolar fair