University Develops Low-cost Method to Prevent PID of Solar Panels

Gifu University has developed a method to easily prevent the “potential induced degradation (PID)” of solar panels at a low cost.

PID is a phenomenon in which the power generation capacity of crystalline silicon-based solar panels using p-type semiconductors drastically deteriorates for a short period of time. Troubles caused by PID have been reported by solar power plants both in and outside Japan.

The latest method can be applied to the PID prevention process of a solar panel production process and can be used as a PID prevention measure for solar power generation (PV) facilities that have already been built, according to the university.

PID is believed to be caused when :
(1) a high voltage is generated between solar cells and solar panel frame (cover glass) due to some cause and (2) sodium (Na) contained in the cover glass moves to the inside of cell if the voltage of the cell is minus. Temperature, humidity, voltage and other conditions are considered to have influence on the phenomenon. But the details of the movement of Na have not been found yet.

In recent years, in regard to the mechanism of the generation of PID, some people argue that the application of a high voltage to the anti-reflection coating (ARC) on the surface of cell greatly contributes to degradation. In the latest research, a glass layer made of liquid glass was inserted into a solar panel as a high-resistance layer in the aim of preventing a high voltage from being applied to ARC. The desirable composition of the glass layer is the composition of quartz, according to the university.

In a test (PID test), the university inserted the glass layer between the cover glass and sealing material (EVA) (for cells) and applied a high voltage to the solar panel for a short time to cause PID. When there was no glass layer, the power generation performance of the panel was drastically lowered. On the other hand, when a glass layer was inserted, the generation of PID was delayed. Also, when the glass layer is formed on the surface of the cover glass, it prevented PID to some extent.

The new technology to prevent PID can be introduced without drastically changing the components or structure of solar panel, the university said.

Because liquid glass is used as a material to form a high-resistance layer, components having various shapes and large-area components can be easily used. Also, the technology can be applied to existing facilities by applying liquid glass to the surfaces of solar panels.

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