Effect of Temperature and Humidity on the Degradation Rate of Multicrystalline Silicon Photovoltaic Module

Abstract

In a PV module, the relative humidity (rh) of a front encapsulant is different from that of a backside encapsulant (rh back ). In this study, the effective humidity (rh eff ) in a PV module was investigated to study the effects of moisture variation on the degradation rate (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>D</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>). rh eff represents uniform humidity in a PV module when it is exposed to certain damp heat conditions. Five types of accelerated tests were conducted to derive the relation between rh eff and rh back . rh eff showed a linear relationship with rh back at constant temperature. Two types of models, namely, Eyring and Peck models, were used for predicting the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>D</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>of PV modules, and their results were compared. The<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>D</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>of PV modules was thermally activated at 0.49 eV. Furthermore, the temperature and rh eff history of PV modules over one year were determined at two locations: Miami (FL, USA) and Phoenix (AZ, USA). The accumulated<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>D</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>values based on the temperature and rh eff of the modules were calculated by summing the hourly degradation amounts over the time history.