PV Quality Assurance and Module Durability Webinars

Dirk Goossens
KU Leuven

One of the most important properties of a sediment is its particle size distribution. Particle size is a complex parameter because the size of a particle may vary according to which definition is used. Also, many techniques exist to determine the particle size distribution of a sample. Different techniques will lead to different results. This presentation will discuss the difficulties in defining particle size and also give an overview of the current techniques used to measure the particle size distribution of a sample, and conclude by discussing a number of problems that may arise when a particle size analysis is performed.

Dirk Goossens works at the Department of Electrical Engineering and the Department of Earth and Environmental Sciences at KU Leuven (Belgium). His research focuses on wind and atmospheric dust dynamics, with applications in earth science, human health and solar energy. He has held positions at KU Leuven (Belgium), Wageningen University and Research Center (the Netherlands); the University of Paris 12 (France), the University of Paris 7 (France), and the University of Nevada Las Vegas (USA). He supervises the research activities in the Environmental Dust Wind Tunnel at KU Leuven since 1982.

Mike Bergin
Duke University

The influence of deposited particles on the transmittance of solar energy to PV panels depends on chemical and physical properties that determine light scattering and absorption properties. These factors can vary greatly depending on the sources of particulate matter, PM, responsible for deposition in a given region. In theory the decrease in transmittance to solar PV's per unit deposited mass can vary by a factor of 5-10 depending on the sources of PM, with dust being less effective than pollution particles at attenuating solar energy. Although it should be pointed out that there are few field based studies verifying this point. With this in mind I will discuss the theme of particle size related soiling loss both theoretically and based on recent field measurements we have made in India, where soiling by both dust and pollution occur. I will also touch on the need for more comprehensive predictive approaches to estimate source-specific soiling losses not only to estimate energy production, but also to develop optimal cleaning strategies.

Mike Bergin is a professor in the School of Civil and Environmental Engineering at Duke University. His general research focus is on the influence of air pollution on both climate and human health, and specifically particulate matter. He has done a wide range of studies on the emission, formation, deposition and impacts of PM and is particularly interested in how PM impacts climate. More recently, he has been studying the influence of PM on human health and is also involved in developing and deploying the next generation of air quality sensors to inform citizens on the quality of the air they breathe. He has received several awards for his work including the Presidential Early Career Award for Scientists and Engineers (PECASE), the highest award given to young scientists and engineers in the US.

Michael Gostein
Chief Technical Officer, Atonometrics, Inc., Austin, Texas

We discuss the principles and evaluation of a new all-optical soiling sensor concept developed by Atonometrics – the Mars Soiling Sensor™ – conceived as a solution for water-free, maintenance-free measurement of soiling loss. Traditional soiling sensors compare the output of a naturally soiled reference cell or module to a routinely cleaned reference, requiring water, labor, and/or automated equipment. In contrast, the Mars™ concept uses an internal microscopic imaging camera to detect the deposition of dust particles on a sensor window, coupled with image analysis that accurately determines the transmission loss due to soiling, regardless of dust type or color.

Dr. Michael Gostein is Chief Technical Officer of Atonometrics, Inc., based in Austin, Texas. Atonometrics develops test and measurement equipment for the PV industry and is a world leader in the supply of PV system soiling measurement instrumentation. Dr. Gostein has published numerous articles on test and measurement topics, including soiling measurement and PV instrumentation, and has been issued 7 patents. Prior to joining Atonometrics, he was Chief Technologist at Philips Advanced Metrology Systems, a business unit of Philips supplying optical measurement instrumentation to the semiconductor industry. Dr. Gostein received a Ph.D. in Physics from the University of Texas at Austin and a B.S. in Physics from the Massachusetts Institute of Technology.

Alan Lyons
City University of New York & ARL Designs LLC

Soiling of solar cover glass is a significant challenge that increases the LCOE of solar energy through loss of electrical output and/or increased O&M costs. Coatings can reduce adhesion of dust to glass and so reduce cleaning costs, but the use of water is required to fully restore electrical output. Since water for cleaning is expensive, especially in many arid regions, we are developing coatings that can harvest sufficient dew to self-clean the glass. The hybrid coating consists of hydrophilic regions, which promote nucleation and growth of dew droplets, surrounded by a hydrophobic coating that reduces dust adhesion and promotes dew droplet slide-off. Initial results and mechanisms will be described.

Alan Lyons received a B.Sc. (hons) degree in chemistry from Brown University and M.S. and Ph.D. degrees in polymer chemistry from Polytechnic University (now NYU-Tandon). After university, he was a Distinguished Member of Technical Staff with the research division of Bell Laboratories (formerly part of AT&T) and a founding member of Bell Labs Ireland. He joined the College of Staten Island and the Graduate Center of the City University of New York, as a Professor in the Department of Chemistry in 2008. His work is focused on developing multi-functional materials with novel wetting and catalytic properties. He has authored over 45 publications in archival journals as well as 38 issued patents. He is also a co-founder and CTO of ARL Designs LLC, a small business that develops advanced coatings for glass and metal substrates.

David Strickler
Thin Film Technology at the NSG North America Technical Center

Coated glass products for architectural applications need to maintain optical and thermal performance as well as good aesthetics for the expected 20 – 30 year lifetime of the window. Anti-reflective or anti-soiling coatings can be used on the outer surface of insulated glazing units, typically the most demanding application for coated glass in buildings. In this presentation, the EN1096-2 test methods for evaluating the durability of exposed coatings will be reviewed. In addition, the EN1096-5 test for self-cleaning coatings will be discussed.

Dr. David Strickler is the Manager of Thin Film Technology at the NSG North America Technical Center. His current responsibilities include development of new coated glass products which utilize NSG's proprietary atmospheric pressure chemical vapor deposition manufacturing process. This CVD technology is currently used to produce transparent conductive oxide coatings for thin film photovoltaic modules and heated glass doors for refrigerated display cases as well as low emissivity, solar control, anti-reflective, and anti-soiling coatings for buildings. During his 29 year career at NSG (formerly Pilkington, formerly Libbey-Owens-Ford), Dr. Strickler has also worked on projects related to electrochromic devices, sputtering technology, and novel interlayers for glass lamination. Dr. Strickler has a B.A. in Chemistry & Mathematics from Grinnell College (Grinnell, IA) and a Ph.D. in Physical Chemistry from Harvard University.

Fabian Wolfertstetter
The German Aerospace Center (DLR)

This second installment of a two-part presentation will describe the CSP soiling model developed at DLR that could be applied to PV soiling rates as well. It derives soiling rates from other weather parameter measurements like particulate concentration, wind, relative humidity and others. It is based on deposition mechanisms as used in atmospheric dust transport models such as the NMMB-MONARCH run at the Barcelona Supercomputing Center. The goal is to couple the model to dust transport models in order to produce soiling forecasts and soiling maps for solar technologies.

Fabian Wolfertstetter received his Diploma in Physics with a specialization in Biophysics from the University of Munich in 2010. He started his PhD on the topic of the effects of soiling on concentrating solar power plants at DLR's offices located in CIEMAT's Plataforma Solar de Almeria in southern Spain in 2011. After receiving his PhD from the University of Aachen in 2016, he continued working at DLR as a researcher and project manager. His main fields of research are water saving in CSP plants, especially regarding soiling and cleaning of mirrors. Other interests include ground based meteorological measurements, data management, solar resource assessment and yield analysis, optical effects of particles on solar surfaces. Fabian lives with his family in two off-grid yurts in an orange grove in Almería and runs an outdoor kindergarten with a modern educational concept.

Ben Figgis
Qatar Environment & Energy Research Institute

Measuring soiling in the field usually involves exposing collectors for days or weeks, which obscures the effects of constantly-changing weather conditions. To overcome this, an "outdoor soiling microscope" was developed which could measure deposition and removal of dust particles every few minutes. In field experiments in Qatar, this technique found that dust flux rates were dominated by wind speed, whereas relative humidity and particulate concentration had relatively less influence. The microscope could also observe condensation at fine scale, which showed that hygroscopic dust content allowed microscopic droplets to form even on hydrophobic surfaces well above the dew point.

Ben Figgis is a Research Program Manager at the Qatar Environment & Energy Research Institute, part of Hamad bin Khalifa University in Qatar. He manages the Solar Test Facility, a 35,000 m2 outdoor test site for PV and solar thermal technologies, and his research focus is on PV soiling. Ben helped establish and operate the STF from 2009 to 2014 with Chevron Qatar, and for the preceding five years was involved in setting up the Qatar Science & Technology Park. He has B.Eng and B.Sc degrees from the University of Western Australian, M.Eng from the Royal Melbourne Institute of Technology, and a PhD in mechanical engineering from the University of Strasbourg.

Fabian Wolfertstetter
The German Aerospace Center (DLR)

The efficiency of concentrating solar thermal power plants is affected 8-12 times more by same levels of soiling compared to PV panels because CSP only harvests the direct component of solar radiation. Therefore, soiling research has a long history in CSP. CSP soiling is nevertheless connected to PV soiling as its evolution over time is similar for same sites. This talk will give an overview of the CSP technology, the status and history of CSP soiling research, and a link between CSP and PV soiling rates using an optical model.

Fabian Wolfertstetter received his Diploma in Physics with a specialization in Biophysics from the University of Munich in 2010. He started his PhD on the topic of the effects of soiling on concentrating solar power plants at DLR's offices located in CIEMAT's Plataforma Solar de Almeria in southern Spain in 2011. After receiving his PhD from the University of Aachen in 2016, he continued working at DLR as a researcher and project manager. His main fields of research are water saving in CSP plants, especially regarding soiling and cleaning of mirrors. Other interests include ground based meteorological measurements, data management, solar resource assessment and yield analysis, optical effects of particles on solar surfaces. Fabian lives with his family in two off-grid yurts in an orange grove in Almería and runs an outdoor kindergarten with a modern educational concept.

Klemens Ilse
Fraunhofer Center for Silicon-Photovoltaics, Halle, Germany

For fast and reproducible testing of the anti-soiling properties of coated glasses, an advanced laboratory soiling test setup has been developed. The setup includes the control of environmental parameters such as relative humidity, temperature, wind speed, dust type and dust concentration. The applied method and apparatus are currently used as basis for the development of a VDI soiling test standard and will be presented in detail including an evaluation of important influencing factors of soiling. Furthermore, experimental results will be shown for bare glass, Anti-Reflective Coatings (ARC) and ASC using dust which settled on PV modules located in China. For the determination of soiling losses, light microscopy and light transmittance measurements are performed. Compared to reference samples, a significant reduction of accumulated dust is shown for the tested ASC, both directly after dust deposition and after a subsequent simulated natural cleaning by wind blowing..

Klemens Ilse works as a scientific researcher at the Fraunhofer Center for Silicon-Photovoltaics, Halle, Germany and at the Anhalt University of Applied Sciences. He earned Bachelor and Master Degrees of Science in Physics from Martin Luther University Halle-Wittenberg. During his studies, he specialized in photovoltaics and material characterization at the micro- and nano-scale as well as thin film deposition methods. In 2015, he started his Ph.D. with topical focus on dust deposition and soiling mechanisms on PV modules. His research interest includes adhesion mechanisms of dust particles, development of effective Anti-Soiling-Coatings as well as lab modelling of desert environments.

GovindaSamy (Mani) TamizhMani
Arizona State University (ASU)

An indoor soil deposition method has been developed to simulate natural soil deposition on glass coupons, one-cell PV modules or multi-cell PV modules. This method uses variable ambient humidity, coupon/module temperature, and dust composition within a single custom-made chamber to create a natural and uniform soil deposition layer. Anti-soiling coatings from two different manufacturers were applied on two one-cell mono-crystalline silicon modules. Three layers of Arizona road dust have been deposited on the one-cell modules with anti-soiling coatings and an uncoated one-cell reference module at varied humidity levels. The soiled modules were exposed to an open-circuit sub-sonic wind tunnel at varying speeds and the effectiveness of anti-soiling coatings have been quantified using the transmittance gain. Reflectance resulting from the anti-soiling coating has been measured and compared with the reflectance of the uncoated reference module. Reflectance measurements have also been taken to compare the behavior of Arizona road dust and soil collected from PV modules' superstrates. The soiled one-cell modules were then exposed to rain from a rain simulator. The transmittance gain due to rain exposure is quantified using rain gain and rain coefficient. These tests cumulatively may be used to help developing a test standard for evaluating the effectiveness of anti-soiling coatings.

Dr. GovindaSamy TamizhMani (Mani) is the director of Photovoltaic Reliability Laboratory (PRL) at Arizona State University. He has been working on solar photovoltaics, fuel cells and batteries over 37 years. He was the former director of ASU-PTL and president of TUV Rheinland PTL. ASU-PRL was created in late 2008 to test and predict climate-specific lifetime of PV modules through climate-specific accelerated testing, outdoor field evaluation, device testing, material testing, physical modeling and statistical modeling. He has more than 20 years of PV certification testing experience and published more than 150 papers in journals and conferences. He spearheaded the creation of "Alternative Energy Technology" program at ASU and was the recipient of "Top 5% Teaching Award in 2016-2017" from the Fulton Schools of Engineering at Arizona State University. He has been involved in the development of national and international standards over 20 years.

Thomas A. Germer
Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland

Roughness, particles, and subsurface features all contribute to diffuse light scatter from surfaces. This presentation will give an overview of the modeling capabilities that we have for estimating the contributions from these different sources. Focus will be given to a recently developed model for scattering by soiling and its validation.

Thomas A. Germer received a B.A. in physics from the University of California, Berkeley and a M.S. and a PhD. in physics from Cornell University. He came to NIST as a postdoc in 1992 and was later hired as a staff member. His research interests include light scattering from surfaces, grating scatterometry, ellipsometry, and polarimetry. He has published over 100 articles, edited a text on spectrophotometry, been granted two patents, presented short courses, and is the developer of a library of scattering software codes. He is a fellow of the SPIE. https://www.nist.gov/people/thomas-germer

Greg P. Smestad
Sol Ideas Technology Development, San José, California

This presentation reports on an international effort that studies where PV soiling losses are occurring within the transmitted solar spectrum. This can be used to inform effective mitigation (e.g., anti-soiling coatings and cleaning strategies) for a particular location. Characterization of glass coupons yielded insights about transmittance, particle distribution density and common parameters at sites world-wide. The data were fit to empirical equations related to the Ångström exponent coefficient of aerosol extinction and the IEST-STD-CC1246 cleanliness standard.

Greg P. Smestad received his Ph.D. in Physical Chemistry from the Swiss Federal Institute of Technology (EPFL) on the topic of the thermodynamic limits of quantum solar energy conversion. He received his Masters degree in Materials Science and Engineering from Stanford University, and his B.S. in Biology from the University of Santa Clara in California. He works in the area of optoelectronics and materials related to solar energy conversion and is the owner of the consulting firm, Sol Ideas Technology Development in San José, California. From 1990 to 2016, he served as Associate Editor for Solar Energy Materials and Solar Cells.

Carlos Pérez García-Pando
Barcelona Supercomputer Center (BSC)

In the last years, the development of global and regional dust forecasts has intensified because of their potential to mitigate impacts upon transportation, energy production, health and agriculture. In addition, operational weather services have started to recognize the importance of representing dust in models to reduce systematic temperature biases. In this presentation Carlos will overview the current capabilities for dust prediction and he will discuss the ongoing challenges and perspectives in the field of dust modeling.

Dr. Carlos Pérez García-Pando joined the Barcelona Supercomputer Center (BSC) in October 2016 as Head of the Atmospheric Composition Group. His research focuses on understanding the physical and chemical processes controlling atmospheric aerosols, and evaluating their effects upon climate, ocean biogeochemistry, air quality and health.Prior to joining the BSC, he held positions at the National Oceanic and Atmospheric Administration (NOAA/NCEP), the International Research Institute for Climate and Society at Columbia University (IRI), the Department of Applied Physics and Applied Mathematics at Columbia University and the NASA Goddard Institute for Space studies (NASA GISS). For more details, see https://www.bsc.es/perez-garcia-pando-carlos

Dr. Arlindo Da Silva
NASA/Goddard Space Flight Center

MERRA-2 is NASA's latest reanalysis for the satellite era (1980-present) using GEOS-5, NASA's earth system model and data assimilation system. This project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales, and includes interactive aerosols for the entire period. As a step towards an integrated Earth System Analysis (IESA), MERRA-2 includes for the first time aerosols in a reanalysis, improves the representation of stratospheric ozone, and better characterizes cryospheric processes. In this talk we will present a summary of our efforts to validate the MERRA-2 aerosols by comparison to independent in-situ measurements (PM2.5 concentrations, long term surface dust concentrations, Maritime Aerosol Network, airborne and ground based lidars, etc.).

Dr. Arlindo Da Silva is a Research Meteorologist at the Global Modeling and Assimilation Office (GMAO, formerly DAO), NASA/Goddard Space Flight Center, where he has worked since 1994. Prior to joining the GMAO, Dr. da Silva held a faculty position at the University of Wisconsin-Milwaukee from 1990-1993, and was a Visiting Scientist at Princeton University/Geophysical Fluid Dynamics Laboratory from 1989-1990. For more details, see https://science.gsfc.nasa.gov/sed/bio/arlindo.m.dasilva

Peter Tummers
DSM

With the ambition of becoming the preferred materials solution provider for high-efficiency solar PV modules, DSM has developed innovative breakthrough Anti-Soiling Coating, which boost the cost/performance ratio of solar energy systems.

Outdoor testing sites with different level of integration, testing protocols have been developed and put in place to validate and demonstrate the long-term performance of our material innovations.

Modules and PV covers glasses were exposed in a broad range of geographical locations and climatic conditions. Such testing allows for combinations of environmental stresses and pollution that are not achievable with accelerated testing in controlled environmental chambers. This approach requires setting-up of long-term testing accompanied with extensive materials characterization to understand and improve their properties.

This webinar covers key learnings from our experience with outdoor testing.

Overall, outdoor tests have proven to be challenging, but extremely valuable in generating insights for new product developments and for the validation of material performance.

Peter Tummers has been working in the fields of process analysis and applied statistics at DSM since 1987. He has been applying statistical methods mainly in the fields of analytical chemistry and statistical process control. Since 2016 he is strongly involved in the data-analysis of PV data, mainly to evaluate the outdoor performance of DSM's anti-reflective and anti-soiling coatings.

Geetanjali Patil Choori
Energy Guru

The webinar gives an overview of robotic cleaning systems around the world and it gives different parameters to consider prior to deployment of robotic cleaning and information on how to do cost benefit analysis for using robotic system, eg. SolarDuster will be explained. Also discusses same robots can be used for thermographic inspection.

Geetanjali is CEO & Co-founder of Energy Guru. To create a positive impact on society, she has invented Large Aperture Parabolic trough concentrating solar thermal boiler for factories; SunVeg, Agri Solar Dryer using concentrating solar; and SolarDuster, Robotic Waterless cleaning and inspecting system for solar modules. She started Energy Guru in USA and now has a factory in India, where innovations take their shape. Geetanjali has solid experience in executing multi-million dollar initiatives in Fortune 500 companies in USA. She has done her bachelors in Electronics Engineering, Masters in Robotics and Industrial Drives, & General Management Program from Indian School of Business.

Georg Eitelhuber
NOMADD Desert Solar Solutions PTE. LTD

Cleaning robots are now making their presence felt. But how effective are they? What risks do they pose to panel health, coatings and the LCOE of the plant over 20 years of cleaning? How could we systematically measure these things quickly and accurately? To date, no battery of tests has been developed, or even fully articulated. Yet the uptake of robots proceeds apace. This talk will identify the key metrics that define robot risk. It will then offer several innovative tests that could measure these metrics in a way that is valid, repeatable and FAST.

Georg Eitelhuber (B.Eng, MSci. RE, GradDipEd) is an innovation design expert. His industrial design experience and out-of-the-box thinking developed the patented NOMADD solar cleaning system. NOMADD stands for NO water Mechanical Automated Dusting Device. It was developed over 5 years at King Abdiullah University of Science and Technology, Saudi Arabia, where Georg resides as NOMADD's CTO. NOMADD won the 2014 MESIA Solar technology of the Year, and is being scaled to meet the cleaning needs of the exploding solar industry.

Ricard Pardell
CEO, Cleandrone, S.L.

As solar facilities become larger and larger, with projects above 100 MW becoming mainstream, asset management becomes increasingly challenging for operators. On the PV market, drones for inspection of PV farms enable operators to gather intelligence on a much faster and consistent way than previous walk through practices. Now Cleandrone is developing new systems in order to extend this functionality into new areas: solar panel and heliostat cleaning.

Ricard Pardell is an experienced technology entrepreneur and former software executive. He currently holds CEO and CTO roles in Cleandrone, leading the company's commercial and technology development. He has 30 years of experience in the IT industry, including roles as Business Unit Leader at Atos Origin and Country Manager at Aspective. Ricard holds 7 patents to his name. He was CEO and CTO of a concentrating solar PV company, Sol3g, which was sold to Abengoa (NASDAQ: ABGB) in 2010. He is Chairman of Valldoreix Greenpower, a renewable energy technology incubator. He studied economics in the University of Barcelona.