Gradual Reduction of PV Generator Yield due to Pollution

Abstract

Since spring 1994 the PV-laboratory of HTA Burgdorf has operated a new test center for PV-systems with a solar generator of 60 kWp on top of the new building of the department of electrical engineering. In course of time, a development of a permanent pollution strip was observed which caused a gradual reduction of energy yield of up to 10% until the end of 1997. The most important external source of unusual pollution at this location is a main railway line (Berne-Zurich) at a distance of only about 50m. Pollution by iron dust from railway lines seems to favor development of permanent pollution strips at the edges of framed modules. As soon as pioneer plants begin to grow, this effect is enhanced, as they retain all kinds of dust arriving on the modules. Under such conditions a periodical cleaning of a PV generator seems to be necessary. To cure this problem, artifical cleaning in June 1998 became necessary. Measurements of IV-curves before and after cleaning have proved that most of the power loss is reversible.