GroundWork-PVPMC-2020-06-22-Slides

© GroundWork Renewables, Inc. | All Rights Reserved In-Situ Comparison of Five Soiling Measurement Systems PVPMC June 24, 2020 Kenneth Morley, Justin Robinson Julie Chard and Josh Peterson • Accelerate solar adoption by reducing solar resource uncertainty • Solar industry leader for onsite reference measurements • Contributed to over 25GW • Early entrant working with NREL in 2008 • Outdoor R&D lab in operation since 2015 • US, Mexico, LatAM and Canada • 39 staff + 140 technicians © GroundWork Renewables, Inc. | All Rights Reserved © GroundWork Renewables, Inc. | All Rights Reserved 3 PRESENTATION OUTLINE • Introduce GroundWork Renewables (GR) R&D site • Technology and data outputs • GR soiling data processing methods • Soiling measurement system data • Next steps © GroundWork Renewables, Inc. | All Rights Reserved 4 Eclipse PVSoil RDE300 DustIQMARS TE525WS SR20 POA WS500 MEASUREMENT SITE © GroundWork Renewables, Inc. | All Rights Reserved 5 SOILING MEASUREMENT DEVICES Device Manufacturer Method Outputs Measurement Rate Data Collection Period Eclipse GroundWork Short-circuit Current (Isc) Isc, G, BOM Temp, SR, SLF Three-second May 2018 – May 2020 PVSoil GroundWork Isc Isc, G, BOM Temp, SR, SLF Three-second May 2018 – May 2020 RDE300 Atonometrics Isc & Max Power Point (MPP) Isc, Voc, G, BOM Temp, SR, SR ISC, SRPmax One-minute May 2018 – May 2020 Mars Atonometrics Optical TL, SR Daily May 2019 – May 2020 Dust IQ Kipp & Zonen Optical 2xTL, 2xSR, BOM Temp Instantaneous May 2019 – May 2020 OTHER INSTRUMENTATION Sensor Manufacturer Measurement Data Collection Period SR20 Hukseflux Plane of Array Irradiance (26.5-degree tilt) May 2018 – May 2020 WS500 Lufft Wind speed & direction, ambient temperature, relative humidity, barometric pressure May 2018 – May 2020 TE525WS Texas Instruments Rainfall May 2018 – May 2020 GROUNDWORK RESEARCH & DEVELOPMENT SITE INSTRUMENTATION © GroundWork Renewables, Inc. | All Rights Reserved 6 MODULE-BASED SYSTEMS Eclipse PVSoil RDE300 https://grndwork.com/eclipse-series-pv- soiling-measurement-system/ https://grndwork.com/rey-series- secondary-standard-ghi-sms/ http://www.atonometrics.com/products/p v-power-plant-irradiance-measurement- system/ © GroundWork Renewables, Inc. | All Rights Reserved 7 OPTICAL SOILING SYSTEMS MARS http://www.atonometrics.com/mars- optical-soiling-sensor-revolutionary-new- product/ DustIQ https://www.kippzonen.com/Product/419 /DustIQ-Soiling-Monitoring- System#.Xu_28kVKhPY © GroundWork Renewables, Inc. | All Rights Reserved 8 MEASUREMENT METHODS: PV MODULE-BASED SYSTEMS • Two modules per measurement system: Clean and Soiled • IEC 61724-1 − Method 1 = Pmax − Method 2 = Isc • Soiling ratio, SR = 𝑆𝑜𝑖𝑙𝑒𝑑 𝑀𝑜𝑑𝑢𝑙𝑒 𝑂𝑢𝑡𝑝𝑢𝑡𝐶𝑙𝑒𝑎𝑛 𝑀𝑜𝑑𝑢𝑙𝑒 𝑂𝑢𝑡𝑝𝑢𝑡 IEC 61724-1, “Photovoltaic system performance – Part 1: Monitoring,“ Edition 1.0, 2017-03 © GroundWork Renewables, Inc. | All Rights Reserved 9 MEASUREMENT METHODS: OPTICAL SYSTEMS • Measurements are based on transmission loss through a window due to the accumulation of soil • Soiling ratio, SR = (1 - Transmission Loss) • No regular cleaning • The window should be cleaned (soiling system reset) when foreign substances block transmission © GroundWork Renewables, Inc. | All Rights Reserved 10 METHODS • Matched 72-cell modules • Calibration or normalization was performed for all module-based systems • Daily maintenance − Maintain clean module − Measure and log module angular displacement N/S & E/W − Reset as necessary • All data aggregated on one logger to eliminate time offset issues © GroundWork Renewables, Inc. | All Rights Reserved 11 DATA PROCESSING • NREL Stochastic Rate and Recovery (SRR) Method* − Developed to quantify power loss due to PV degradation and soiling from PV yield data − Built into RdTools, an open source Python library for PV degradation analysis • GroundWork Data Processing Method − Rooted in the SRR method − Unique attributes of the GroundWork method:  Utilizes concurrent and co-located, ground-based irradiance measurements “Turns the dials” to optimize the SRR method for soiling measurement system outputs  Sets a moving, site-specific and time-specific GHI irradiance threshold  Factors in soiling system reset events and overlays rain and regular maintenance events using high quality maintenance logs *M. G. Deceglie, L. Micheli and M. Muller, “Quantifying Soiling Loss Directly From PV Yield,“ in IEEE Journal of Photovoltaics, vol. 8, no. 2, pp. 547-551, 2018-03 © GroundWork Renewables, Inc. | All Rights Reserved 12 GROUNDWORK DATA PROCESSING OUTPUT © GroundWork Renewables, Inc. | All Rights Reserved 13 TIME-SERIES COMPARISON: DAILY SOILING RATIO FROM ALL 5 DEVICES © GroundWork Renewables, Inc. | All Rights Reserved 14 MONTHLY SOILING LOSS: ALL 5 DEVICES © GroundWork Renewables, Inc. | All Rights Reserved 15 MONTHLY SOILING LOSS: PAIRED MODULE METHODS © GroundWork Renewables, Inc. | All Rights Reserved 16 UDAQ PARTICULATE DATA 2018 2019 © GroundWork Renewables, Inc. | All Rights Reserved 17 REAL WORLD CHALLENGES © GroundWork Renewables, Inc. | All Rights Reserved 18 SNOW TEST: PRE-CLEANING © GroundWork Renewables, Inc. | All Rights Reserved 19 SNOW TEST: POST-CLEANING © GroundWork Renewables, Inc. | All Rights Reserved 20 Snow is cleaned off of clean panel Snow melts off of soiled panel or optical measurement window EFFECTS OF SNOW ACCUMULATION AND MELTING © GroundWork Renewables, Inc. | All Rights Reserved 21 AUGUST 2019 SOILING EVENT: LINEAR REGRESSION ANALYSIS © GroundWork Renewables, Inc. | All Rights Reserved 22 AUGUST 2019 SOILING EVENT: ANALYSIS COMPARISON Eclipse RDE Isc RDE MPP PVSoil Dust IQ Mars Linear Regression Slope -2.3E-03 -2.3E-03 -2.0E-03 -1.9E-03 -1.6E-03 -1.0E-03 Median Daily Soiling Rate -2.3E-03 -2.2E03 -2.0E-03 -1.7E-03 -9.2E-04 -1.9E-03 © GroundWork Renewables, Inc. | All Rights Reserved 23 CONCLUSIONS • Variations in monthly soiling rate of module-based systems were on average 1% while optical-based soiling rates were shown to deviate by a maximum of 2% when compared to the module-based data. • The optical systems tended to underestimate the soiling at the Utah R&D site in the summer of 2019 as well as during snow events. • The Eclipse and RD300 agree the best out of the 5 soiling measurement systems. This could be due to full-size high quality modules and similar measurement methods. • The soiling tool results have a tight correlation with the linear regression calculation method. This helps to verify the accuracy of the soiling tool. • Optical soiling measurement systems have promise due to the fact there is minimal maintenance and price but the measurements aren’t quite as accurate as using the short circuit current method with full size modules. • Interannual variability is hard to measure over smaller intervals. The Utah R&D site experienced different weather and environmental conditions over two years. These include, but are not limited to, a bad fire season causing increased particulates, a snowy winter, and bird migrations causing droppings and frequent resets in the spring months. © GroundWork Renewables, Inc. | All Rights Reserved 24 WHAT’S NEXT? • Uncertainty analysis • Bifacial soiling • Improved normalization techniques and optical sensor data processing • Assess impact of light soak on normalization stability • Historical dataset coupling −Rain