Gonzalez Rodriguez, Sergio

Hanrieder, Natalie

Kuhn, Pascal Moritz

Nouri, Bijan

Wilbert, Stefan

Wolfertstetter, Fabian

Institute of Transport Research:Publications

Soiling in concentrating solar thermal power (CSP) – effects and connection to PV  German Aerospace Center (DLR), Plataforma Solar de Almería, Spain  Fabian Wolfertstetter, Stefan Wilbert, Natalie Hanrieder, Lothar Keller, Sergio Gonzalez Rodriguez, Pascal Kuhn, Bijan Nouri    fabian.wolfertstetter@dlr.de +34 950611877 > Lecture > Author  •  Document > Date DLR.de  •  Chart 1 • Short introduction to concentrating solar technology • Optical differences CSP-PV and implications for soiling • Mie based optical model • Soiling measurements • Cleaning strategies • Outlook      Outline  PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 2 Pictures: DLR, Plataforma Solar Our Partners:  DLR Energy meteorology group at CIEMAT’s Plataforma Solar de Almería, the largest CSP research facility  Research topics in CSP and PV: • Soiling  • Degradation & abrasion of solar materials • Attenuation of radiation • Circumsolar radiation • All-sky imager based nowcasting • Shadow camera based measurements  • Atmospheric measurements    http://www.dlr.de/sf/en/desktopdefault.aspx/tabid-10224/17488_read-44933/  Concentrating Solar Power PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 4 Images property of: Torresol energy, MASEN, SolarPACES  Concentrating Solar Power PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 5 Images property of: Torresol energy, MASEN, SolarPACES, [T]  • Concentration of direct sunlight with mirrors to achieve high temperatures  • Provision of electricity (turbine cycle), process heat, desalination • CSP uses only direct component of solar irradiation • Cost effective thermal storage option • Grid stabilizing effect thanks to turbine  • CSP only harvests direct component within a small acceptance angle Optics PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 6 [Wi],[W1] [K] CSP PV [B] soiling PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 7 • Short circuit current of sample cells / modules • „Cleanliness“ = ISC,soiled / ISC, clean   • Measurement:  • Reference cell ISC • 2 years of measurements at PSA  Measurement of soiling PV Ref-cells1 Ref-cells2 Images: DLR Measurement of Soiling PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 8 • Solar weighted specular reflectance ρ • Cleanliness = ρsoiled / ρclean   • TraCS: [W3] • Parallel real time measurement of 4 samples • Sun as light source • Rotation to increase measurement spot • Handheld or lab devices       [FG] • 5 years of CSP soiling data at PSA CSP Tracking Cleanliness Sensor - TraCS Ref-cells1 Ref-cells2 TraCS  Comparison of soiling PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 9  CSP soiling rate approx. 8-9 times higher than PV (0.35%/d and 0.04%/d)  Assumption: same surface densities  Optics and soiling  PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 10 CSP: Glass-silver mirror PV: Glass transparent cover • In both technologies optical losses occur due to: • Diffuse reflection • Scattering • Absorption Images: [B] CSP:  •2 passages through the soiling layer •1 passage through the (soiled) absorber tubes glass cover •Most forward scattered light is lost PV:  •1 passage through the (soiled) glass cover •Most forward scattered light is NOT lost Optical model assumptions PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 11 Assumptions:  •  Spherical particles •  Size distribution and refractive index for Saharan dust from literature [F], [Wa]  • Single interactions (no conglomeration) • Low soiling levels! (<1 g/m²)  λ=550 nm [L] Acceptance  angles for  CSP and  PV PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 12 Optical model scheme [B] PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 13 • Modelled data (black dashed) lies within the range of measured data (red and blue lines) • Tendency for underestimation in accordance with: • assumed size distribution (grav. dens.  %-covered) • assumed spherical particles (real particles = aspect ratio) • neglect of conglomeration (larger structures = diff. reflection & absorption) Optical model results [B] PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 14 enerMENA network 12 meteorological measurement stations (solar irradiance, temperature, pressure, relative humidity, wind, etc…) HVS-TSP16 from MCZ: gravimetric measurement principle Scatterometer FS11from Vaisala Grimm EDM164 Particle counter Operational since 2010 -2013 [S], https://www.dlr.de/sf/en/desktopdefault.aspx/tabid-8680/12865_read-32404/ TraCS for mirrror  soiling PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 15 • Soiling rate strongly depends on time and  location • Little CSP-specific information available in target regions for solar projects  • Efforts to estimate soiling rate from other weather parameters – next webinar!      Soiling rate: site comparison Relative frequency Soiling rate in 1/d 0 50 100 150 200 250 300 350Day of Year-0.02-0.018-0.016-0.014-0.012-0.01-0.008-0.006-0.004-0.0020Soiling RateSoiling Rate over yearAll negativ dataMoving mean window 10Moving mean window 30Moving mean window 50at PSA PSA Missour PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 16 • Microscope analysis shows different „deposition efficiencies“ for different exposure periods: 𝐸𝐸𝑑𝑑𝑑𝑑𝑑𝑑 = 𝑁𝑁𝑝𝑝,𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠(𝑑𝑑𝑝𝑝)𝐶𝐶𝑝𝑝,𝑎𝑎𝑎𝑎𝑎𝑎(𝑑𝑑𝑝𝑝) =      Particle size distributions  in air and on surface Part. Size distribution on surface Size resolved Part. concentration in amb. air From WASCOP report 3.2:  http://wascop.eu/wp-content/uploads/2018/06/WASCOP_deliverable_3.2_final_plainText.pdf = Size distribution on  mirror surface from lab  microscope Size distribution of  airborne particles  from OPC Deposition efficiency • Trade-off between cleaning cost minimization and revenue maximization • Time resolved soiling rate and irradiance information are both necessary to fully simulate effects of cleaning • Adaptation of cleaning intensity on cleanliness increases profit significantly • Better performance achieved with reinforced learning algorithm  Cleaning optimization PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 17 [W2] Number of cleaning vehicles Solar field threshold cleanliness Profit increase in %  Rel. to reference strategy Image: Abengoa Solar • Soiling is an issue in all solar technologies • CSP is more affected by soiling • Given the particle properties, the efficiency reduction can be modelled for CSP and PV • Long term measurement campaigns of soiling • Cleaning strategy optimization can increase profit of a project   Next webinar (Sept. 11):   Soiling model that derives the soiling rate from weather parameters (aerosol number size distribution, relHum, temp, wind, etc.)    Conclusion and outlook PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 18 Thank you for your attention  fabian.wolfertstetter@dlr.de PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 19 References  PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 20 • [Wi] Wilbert, S.: Determination of Circumsolar Radiation and its Effect on Concentrating Solar Power. PhD thesis, Technische Hochschule Aachen, 2014. • [W1] Wolfertstetter, F.: Effects of soiling on concentrating solar power plants. PhD thesis, Technische Hochschule (RWTH) Aachen, 2016 • [K]  Knisely, B., S. V. Janakeeraman, J. Kuitche . G. TamizhMani: Validation of Draft International Electrotechnical Commission 61853-2 Standard: Angle of Incidence Effect on Photovoltaic Modules. Arizona State University, Photovoltaic Reliability Laboratory, 2013. • [L] Laven, P.: MiePlot - A computer program for scattering of light from a sphere using Mie  theory & the Debye series. Computer Program, 2017. • [Wa] Wagner, R., T. Ajtai, K. Kandler, K. Lieke, C. Linke, T. Müller, M. Schnaiter . M. Vragel: Complex refractive indices of Saharan dust samples at visible and near UV wavelengths: a laboratory study. Atmospheric Chemistry and Physics, 12(5):2491–2512, mar 2012. • [F] Figgis, B.: PV Soiling: Qatar Perspective. DEWA Soilingworkshop 2016, 2016 • [T] THERMVOLT Systemvergleich von solarthermischen und photovoltaischen Kraftwerken für die Versorgungssicherheit Schlussbericht 01.11.2014 - 30.06.2016  • [B] Bellmann, P., Oct. 2017, „Investigation of soiling on mirror and glass samples with regard to power losses in CSP and PV technologies“, Diploma thesis, University of Dresden  • [Sc] Schüler, David, et al. "The enerMENA meteorological network–Solar radiation measurements in the MENA region." AIP Conference Proceedings. Vol. 1734. No. 1. AIP Publishing, 2016. • [W2] Wolfertstetter F, Wilbert S, Dersch J, Dieckmann S, Pitz-Paal R, Ghennioui A. Integration of Soiling-Rate Measurements and Cleaning Strategies in Yield Analysis of Parabolic Trough Plants. ASME. J. Sol. Energy Eng. 2018 • [W3] Wolfertstetter, F., Pottler, K., Alami, A., Mezrhab, A., & Pitz-Paal, R. (2012). A novel method for automatic real-time monitoring of mirror soiling rates. SolarPACES 2012. • [FG] A. Fernández-García, F. Sutter, L. Martínez-Arcos, C. Sansom, F. Wolfertstetter, C. Delord, Equipment and methods for measuring reflectance of concentrating solar reflector materials, Solar Energy Materials and Solar Cells, Volume 167, 2017 • [S] Schüler, David, et al. "The enerMENA meteorological network–Solar radiation measurements in the MENA region." AIP Conference Proceedings. Vol. 1734. No. 1. AIP Publishing, 2016. • [W4] Wolfertstetter et al, „Soiling and Condensation model applied to CSP solar field“, WASCOP project report 3.2, 2018, http://wascop.eu/wp-content/uploads/2018/06/WASCOP_deliverable_3.2_final_plainText.pdf  •      Gravimetric density vs cleanliness  measurement data PVQAT webinar > Fabian Wolfertstetter  •  Soiling of CSP and comparison to PV DLR.de  •  Chart 21 CSP soiling loss approx. 8 -14 times higher than PV, for same grav. density • Change in size distribution over time [6]: „coarse to fine“ 

Soiling in concentrating solar thermal power (CSP) – effects and connection to PV

https://elib.dlr.de/125716/1/CSPvsPV_soiling_PVQATwebinar_14_08_2018_v2.pdf

Soiling in concentrating solar thermal power (CSP) – effects and connection to PV

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