Crack Statistic of Crystalline Silicon Photovoltaic Modules

Abstract

Solar cell cracks in wafer based silicon solar modules are a well-known problem. In order to identify the origin of cracks and thus lay the foundation for the inhibition of crack formation, we provide for the first time a statistic crack distribution in photovoltaic (PV) modules. We evaluate electroluminescence images of PV modules tested at the ISFH with respect to cracks. The results of the static load test and the “as delivered” PV modules are compared. Additionally we perform a simulation of the strain distribution on a glass plate subjected to a uniform mechanical load and supported at the edges, which is used as a measure for the relative mechanical load on the individual cells. The measured crack distribution correlates well with the stress distribution calculated by the simulation. “As delivered” PV modules show an average of 6% of broken cells per PV module. The analysis of the spatial distribution and orientation of micro cracks in PV modules offers valuable insight into the causes of micro cracks if the PV module is subject to a uniform mechanical load. It lays the foundation for PV module developments that reduce the risk of cracks, as well as for statistical power loss assessment.