Application of Infrared Thermography for Cell-Level Power Estimation of PID-s Impacted Crystalline Silicon PV Module

Abstract

The potential-induced degradation shunting (PID-s) is a severe degradation mechanism that shows a significant drop in a module power in a very short duration. Hence, timely qualitative and quantitative evaluation of PID-s is required for taking preventive measures. Current–voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V)</i> characterization and electroluminescence (EL) imaging are widely used to assess the PID-s; however, the use of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V</i> is cumbersome in the field, whereas EL cannot quantify severely affected PID-s modules since heavily shunted cells do not have active EL emission. In this article, a quantitative application of inverse infrared (IR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">INV</sub> ) imaging with biasing (performed under conditions similar to EL) is proposed for the assessment of mild to severe forms of PID-s. The relationship between cell power loss and heat dissipation with PID-s progression is studied. It was observed that PID-s follows a characteristic temperature pattern in which cell temperature is proportional to the severity of PID-s. Hence, temperature is used as a determinant of PID-s. Based on this analysis, the generalized model is developed to estimate the cell-level power loss caused by PID-s using the cell temperatures obtained from IR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">INV</sub> images. The proposed model is experimentally tested on 20 mono- and polycrystalline silicon photovoltaic modules containing mild to severe states of PID-s. Results have shown that the proposed model enables the estimation of PID-s power loss within a module with a maximum relative error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm $</tex-math></inline-formula> 5%.