Evaluation of long term degradation process of monocrystalline Si photovoltaic panels

Abstract

The paper focuses on evaluation of long time degradation process of the oldest grid-on operated photovoltaic system in Czech Republic. Monocrystalline silicon cells yield to specific degradation through their life cycles. The degradation can be stratified into material degradation of the essential silicon wafer, material and mechanical degradation of other compounds of the panel and degradation of electrical substructures and components. The degradation process is affected with particular fabrification procedures and with some operating conditions. While the fabrification is out of control of the end user, the operating conditions can be partially influenced by the user. Although the weather and ambient values are the strongest acting factors, also the operating regime can significantly affect the life cycle of the panels. A photovoltaic power plant consisting from 192 monocrystalline silicon panels with installed power 20 kWp has been operated for more than 15 years. The system has own monitoring system logging particular electrical and non electrical values in 10 min interval. This data are used for basic monitoring of the system. The system is deeply inspected annually with thermovision and VA characteristic check of each panel. The main contribution of this article is evaluation of the data from 15 years of operation. Dramatic change of state was identified between 2018 and 2019. Significant amount of panels shows already visible traces of degradation such as microcracks, hotspots and connection faults.