Increased PV Soiling from High Module Voltages

Abstract

Natural soiling has reduced the energy output of PV systems since the technology was first used, and viable mitigation strategies have remained elusive ever since. With the ever-increasing deployments around the world, especially in dusty environments, soiling is becoming a billion-dollar problem, worldwide. Furthermore, as plant operators continue to look for ways to increase revenue, the PV operating voltages have increased to between 1000 V and 1500 V when the sun is shining. This has resulted in some unforeseen consequences nominally combined into what is termed “Potential Induced Degradation.”1 Recent work by Jiang et. al., 2 at NREL using Atomic Force Microscopy has demonstrated that these large potentials also affect soiling by substantially increasing the attraction of dust to the surface, but also by increasing the adhesion force. Jiang et. al., have also shown that these higher soiling attraction and adhesion forces continue long into the night when the PV is no longer producing power. In this paper, we present a set of field results that demonstrate enhanced soiling rates that is due to the strong electric fields induced by these high voltage PV arrays. This includes observation of enhanced soiling rates measured in the field when a module is held at ±1000 V. This is critical information for installation operators because soiling losses may be higher on some panels than what is measured by typical soiling stations, and because the high voltages are not uniform across an array, some modules may have more soiling than others, leading to potential issues with non-uniform soiling problems at the array level. We present this set of compelling electric field induced soiling results in this paper.