Impact of Transportation on Silicon Wafer-Based PV Modules

Before a PV module is integrated into a PV system it has to be handled and transported. This part of a PV module’s life causes some direct returns mostly due to glass breakage. But even when the glass is not broken the mechanical loads may cause cell cracks in some cases. The cell cracks typically have a very low direct impact on the PV module performance, but may reduce the durability of the PV module power. Therefore it is imperative to test the PV module for typical load situations occurring during the transport. There is already a standard to test transport units of PV modules. However for the development of PV modules this test is quite unsuitable, because the developer does not know the loads occurring at the module and one must test a whole stack of modules which are often not accessible at the development stage. Therefore we measured the accelerations of PV module corners during transport handling and transport for well packed horizontal PV module stacks. For German country roads we found the highest random vibrations during a transport with a truck company. The reduced power spectral density (PSD) of this random vibration is quite similar to the PSD spectrum suggested for testing of PV module packages in IEC62759-1. We use this PSD to test the PV modules on a shaker being attached at the corners of the module to simulate the situation in the stack. However the suggested test in that standard produces much more cell cracks than found in the transports where the PSD was generated from. Besides the PSD spectrum we also measured shocks during the transport. An analysis of different sine shocks shows that only shocks of a specific shock length of about 40 ms and about 20 ms and maximum amplitude higher than 20 m/s can affect the PV modules. We suggest a combined application of the shocks and PSD test procedure to reproduce realistic transport conditions.