Optical Characterization of PV Glass Coupons and PV Modules Related to Soiling Losses @ PARC
Mar 14 @ 6:30 pm – 8:00 pm


Greg P. Smestad, Ph.D., Sol Ideas Technology Development


One of the least understood losses in PV plants, with the highest potential for immediate positive impacts, is soiling. This talk will provide an overview on the technical and economic aspects of soiling and the observations from field data. The accumulation of dust, dirt and particles on the surface of photovoltaic modules can result in a power output drop of > 50%, although annual losses for PV in the U.S. are within the range from 2 to 5%. Where the losses are occurring within the transmitted solar spectrum can be used to inform effective mitigation (e.g., anti-soiling coatings and cleaning strategies) for a particular location, or to understand the expected losses over time. This information is critical to grid operators needing to balance energy assets and to O&M providers. The talk will also include updates on, “A unique global investigation on the spectral effects of soiling losses of PV glass substrates”, presented at the IEEE Photovoltaic Specialists Conference, PVSC-44, June 25-30, 2017 and the presentation given at the Atlas/NIST Workshop on PV Materials Durability, December 6, 2017 in Gaithersburg, Maryland.

Greg P. Smestad, Ph.D. gave a previous talk to the Santa Clara Valley Chapter of the IEEE Photovoltaic Society on January 15, 2015.



Greg P. Smestad, Ph.D. has over 25 years of experience as a scientist and engineer in the field of solar energy materials. From 1990 through 2016 he served as an Editor for the peer-reviewed Elsevier journal Solar Energy Materials and Solar Cells (He’s now an emeritus editor). He is owner and principal of Sol Ideas Technology Development, a consultancy he founded in 1996 to specialize in PV. He has frequently served as a peer reviewer for the U.S. Department of Energy on topics related to solar energy and, for one program, once performed over 200 reviews. Dr. Smestad received his Masters degree in Materials Science from Stanford University. He was then hired by Hewlett-Packard, first as a product engineer responsible for Gallium Phosphide crystal growth, and later as an LED optics design engineer. He left HP to create and manage the optics lab at the Hahn-Meitner Institute Solar Energy group in Berlin, Germany while conducting research on FeS2 solar cells. By 1992, he was part of the Solar Chemistry group of the Energy and Process Technology department at the Paul Scherrer Institute in Switzerland. Dr. Smestad received his Ph.D. in Physical Chemistry from the Swiss Federal Institute of Technology in Lausanne. He then returned to the U.S. to the Lawrence Berkeley National Laboratory to serve as an electrochemist developing electrochromic windows. He was founding faculty at the California State University, Monterey Bay and later taught at the Monterey Institute of International Studies. Through SPIE, he has also published a tutorial text on solar cells, “Optoelectronics of Solar Cells” (PM115, 2002) that approaches the topic from an optical and thermodynamic perspective. He is a co-author in High Concentrator Photovoltaics Fundamentals – Engineering and Power Plants (Springer, 2015).

Unrelated to these efforts in science, he is an 8th generation Californian (born in San José, CA) and has published the Juan Bautista de Anza National Historic Trial Guide for the U.S. National Park Service.