Early potential induced degradation (PID) detection in the field: Cell shunt resistance characterisation at different degradation rates

Abstract

This paper examines the use of two different voltage measurement methods which could be used to detect Potential Induced Degradation (PID) in the field before any significant power loss occurs. The two methods are the open circuit voltage and the forward bias voltage measurement under light and dark conditions respectively. A theoretical analysis shows that the lower is the photocurrent or the forward bias current, the earlier PID can be detected. The experimental study of the aforementioned methods has validated the theoretical results and also revealed that the forward bias voltage method is a better and more accurate way to detect PID due to the controlled applied forward bias current. On the other hand, the measurement uncertainty of the pyranometer at low irradiance levels makes the open circuit voltage method a less promising technique for early PID detection.