Particular Silicon Type Photovoltaic Cells Prolonged Degradation

This paper focuses on analysis of prolonged degradation process of photovoltaic cells of different technologies based on silicon. All silicon type PV cells tend to have some specific degradation through the operational life. The degradation can originate from material issues of the essential silicon wafers, material aging or mechanical stress of other components used in the panel body and degradation of electrical substructures and elements. The degradation process can have backgrounds in particular stages during fabrication or in particular operating conditions. While the manufacturing process can not be affected by the end user, the operating conditions can be in part influenced. Environmental conditions and weather have the strongest aging effect, but also the operating regime can dramatically affect system life cycle. One of the oldest grid-on photovoltaic systems in Czech Republic is operated on the roof of the FEL builging in Pilsen. The PV plant consists from 192 monocrystalline silicon panels with installed power 20 kWp, 200 Wp tracker and experimental installation using different types of silicon panels. The plant is in operation longer than 15 years. The unit has own DAQ system for logging particular electrical and non electrical values in 10 min interval. This data can be used for basic analysis of the system conditions. Entire system is annually inspected in detail using thermovision and VA characteristic analyzer. The main contribution of this paper is analysis of the degradation process based on the data from 15 years of operation. Although the first 14 years showed only marginal degradation with minimal influence on generated power, the 2019 annual measurement detected serious change of system conditions. Significant amount of panels displays evident traces of new degradation such as microcracks, hotspots and connection faults.