Measuring Soiling Losses at Utility-scale PV Power Plants

Measuring Soiling Losses at Utility-scale PV Power Plants 

Michael Gostein1, J. Riley Caron2, Bodo Littmann2 1Atonometrics, 8900 Shoal Creek Blvd., Suite 116, Austin, TX 78757, USA 2First Solar, 135 Main St., Suite 600, San Francisco, CA 94105, USA  

Abstract  

The effect  of dust,  dirt, and  other contaminant accumulation on PV modules, commonly referred to as soiling, is an important environmental factor that causes reduced PV power plant energy generation. Accurate monitoring of soiling losses has become  increasingly  important,  especially  for  utility-scale  PV power plants,  and soiling  measurement systems  are now  widely deployed at First Solar power plants. In this work we show  how soiling  monitoring  data  are  indicative  of  actual  power  plant performance  and we outline  how such  data should be  collected and  analyzed.  We  study  soiling  levels  and  rates  alongside  PV plant performance in the  desert southwest  of the  United States, the Arabian Peninsula, and  Western Australia.  We demonstrate that soiling loss measurements correlate with actual power plant performance. In addition, we address measurement methodology questions,  including  measurement  precision,  site-wide  spatial non-uniformity in soiling, and the amount of rainfall required for a full recovery in soiling losses. Index  Terms —  photovoltaic  systems,  performance  analysis, solar power generation, solar energy.