Impact of Soiling on PV Module Performance for Various Climates Dr Werner Herrmann TÜV Rheinland Energie und Umwelt GmbH 51101 Cologne, Germany werner.herrmann@de.tuv.com http://www.tuv.com/solarpower
Outline Introduction PV-KLIMA test locations Experimental approach Results: Angular impact on soiling loss Soiling patterns for different climates Impact of periodical cleaning Summary 2
Photo: TÜV Rheinland Shanghai Introduction PV power loss due to soiling Dust deposition on the PV module surface is a complex phenomenon, which is mainly influenced by the environmental/weather conditions, mounting principle and glazing characteristics. Performance losses are site-specific and can strongly depend on O&M work. Climatic impacts Non-uniform soiling, glazing characteristics Installation conditions Surrounding environment 3
PV-KLIMA Project Comparative energy yield testing of PV modules Saudi Arabia Tempe Cologne Ancona Chennai Location Country Operation since Köppen-Geiger climate classification Ancona Italy 01 Nov 2013 Cfa (mediterranean) Tempe Arizona/USA 15 Dec 2013 Bwh (hot dessert) Chennai India 01 Feb 2014 Aw (tropical savanna, hot-humid/dry) Cologne Germany 01 Mar 2014 Cfb (temperate) Thuwal Saudi-Arabia 11 Mar 2015 Bwh (hot desert, sandstorm impact) 4
PV-KLIMA Test Locations Tempe / Arizona Chennai / Southeast India 2) http://www.chennai.climatemp s.com/ Location Geographical position: TUV Rheinland PTL, LLC Tempe, AZ 85282 Inclination : angle 33.5 15 Annual in-plane global solar irradiation 33.4 N / 111.9 W 358 m above sea level TUV Rheinland (India) Pvt. Ltd. Chennai 602117, India 13 N / 80 E 35 m above sea level 2360 kwh/m² 1860 kwh/m² Average annual rainfall 219 mm 1597 mm Surrounding environment industrial area, no vegetation Rural environment, Farm land 5
PV-KLIMA Test Locations Cologne / Germany Ancona / Italy Location TUV Rheinland Group 51101 Cologne, Germany Loccioni 60030 Angeli di Rosora, Italy Geographical position: 50.6 N / 7.0 E 13 N / 80 E 53 m above sea level 35 m above sea level Inclination : angle 35 35 Annual in-plane global solar irradiation 1195 kwh/m² 1556 kwh/m² Average annual rainfall 774 mm 757 mm Surrounding environment Urban environment, Flat roof of 5 storey building Hilly landscape with grassland and forest, agricultural use 6
PV-KLIMA Test Locations Thuwal / Saudi-Arabia Location Geographical position: Inclination : angle 25 Annual in-plane global solar irradiation Average annual rainfall Surrounding environment KAUST, NEO Thuwal, Saudi-Arabia 22.3 N / 39.1 O 3 m above sea level 2386 1) kwh/m² 1) Extrapolation from 204 days 70 mm University ground, coastal environment 7
Experimental Approach Measurement of soiling rate Side-by-side irradiance measurement with two mini-modules: Standard PV glazing, center cell operated in short circuit (reference cell) G EFF = I SC,MEAS /I SC,STC 1 + (T MOD 25 C) 1000 W/m² Data recording interval: 30 seconds Soiling loss = Transmission loss Lower effective irradiance reaching the cells Soiling loss factor (SLF) = Ratio of irradiances from clean and dirty cell SLF = G EFF,Dirty G EFF,Clean Clean mini-module Dirty mini-module 8
Results Angular impacts on soiling loss Dust accumulation on the glass surface changes its angular response Soiling loss depends on the angle of incidence (AoI) of direct sunlight Soiling loss due to AoI effects can be significant Tempe: -0.8% annual soiling loss is caused by angular transmission losses in the range AoI >30 W. Herrmann, M. Schweiger: Soiling and self-cleaning of PV modules under the weather conditions of two locations in Arizona and South-East India, IEEE-PVSC42, New Orleans, USA, 2015 9
Results Soiling pattern for Tempe/Arizona: Dec 2013 Sep 2015 Average daily SLF decrease in dry periods: -0.08% to -0.22% Annual soiling loss (year 1): -3.7% total loss -0.8% angular loss Annual soiling loss (year 2*): -1.4% total loss Single rainfall events Effective cleaning: SLF recovery >99% observed Significant differences in soiling patterns for 1 st and 2 nd year frequency of rainfall, dust accumulation rate 10
Results Soiling pattern for Chennai/India: Feb 2014 Sep 2015 Average daily SLF decrease in dry periods: -0.12% to -0.39% Annual soiling loss (year 1): -2.2% total loss 3-months dry season 25% soiling loss observed Recovery in rainy season: SLF >99% in first year, SLF >98% in second year Significant differences in soiling patterns for 1 st and 2 nd year 11
Results Soiling pattern for Ancona/Italy: Nov 2013 Sep 2015 Daily SLF decrease: Not applicable Annual soiling loss: 0,04% (Year 1) 0,02% (Year 2) High cleaning effectiveness due to rainfall during the whole year Comparable soiling patterns for 1 st and 2 nd year ±1% SLF variation 12
Results Soiling pattern for Cologne/Germany: Mar 2014 Sep 2015 Daily SLF decrease: Not applicable Annual soiling loss: -0,16% (Year 1) +0.17% (Year 2*) High cleaning effectiveness due to rainfall during the whole year Comparable soiling patterns for 1 st and 2 nd year ±2% SLF variation 13
Results Soiling pattern for Thuwal/Saudi-Arabia: Mar 2015 Sep 2015 PV installations in desert climate (i.e. MENA region) require periodical cleaning of PV module glass surface to optimize the energy yield Experimental approach for Thuwal test site: Periodical mechanical cleaning of the PV module surface with rotating brushes (Type NOMADD) Corresponding wet cleaning of dirty mini-module Reset SLF = 1 14
Results Soiling pattern for Thuwal/Saudi-Arabia: Mar 2015 Sep 2015 High ambient dust concentration Average daily percent decrease of SLF = -0.5% Dust storm Max. SLF change per day = -7.7% 15
Summary 1/3 Measuring results Average annual rainfall 1) Annual transmission loss due to soiling (Year 1) Average SLF decrease between rainfall events Max. daily SLF decrease Tempe / Arizona Chennai / India Ancona / Italy Cologne / Germany Thuwal / Saudi-Arabia 219 mm Year 1: -3.7% Year 2: -1.4% 2) 1597 mm Year 1: -2.1% Year 2: -7.5% 2) -0,15% per day -1.8% -0,2% per day -2.2% 757 mm negligible N/A -0.4% 774 mm negligible N/A -1.1% 70 mm N/A Periodical cleaning -0.5% per day -7.7% 1) http://de.climate-data.org 2) Measuring data of year incomplete 16
Summary 2/3 Principle effects Self-cleaning effect: Rainfall leads to nearly full recovery of PV module performance. Permanent soiling can occur if humidity condensate sticks dust to the surface or can be caused by algae growth. Soiling pattern: Great variation in daily percent decrease of soiling loss factor (SLF) makes soiling loss prediction difficult in tropical and arid climates Broader data basis required 17
Summary 3/3 Impact of soiling for various climates Hot-dry climate: Tempe: Moderate dust settlement between periodic rainfall events leads to annual performance loss <4% Thuwal: Considerable dust settlement and missing rainfall lead to substantial annual performance loss >50%, which requires periodical cleaning for economic operation of a PV power plant. Hot-humid/dry climate: Chennai: Considerable dust settlement during 3-months dry season can lead to substantial soling loss. Cleaning during dry season must be considered to improve the performance of a PV power plant. Temperate and Mediterranean climate: Ancona, Cologne: No measureable performance loss due to frequent rainfall. 18
Thank you for your attention! werner.herrmann@de.tuv.com http://www.tuv.com/solarpower Work was partially funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) under contract No. 0325517B.