Meteorological Measurements for Solar Energy
Energy Meteorology Symposium, Wageningen, 11.5.2017 Stefan Wilbert, Fabian Wolfertstetter, Natalie Hanrieder, Bijan Nouri, Pascal Kuhn, Florian Sutter, Florian Wiesinger DLR – German Aerospace Center Institute of Solar Research Qualification Solar Energy Meteorology
• Introduction: • Solar energy options • Solar energy meteorology and its relevance for solar
power plants
• Presentation of meteorological parameters that help solar power and their measurement
Overview Meteorological measurements for solar energy
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Photovoltaic (PV) power plant options
• Different cell types • Fixed tilt, 1 or 2 axes tracker • Concentrating PV (CPV)
CPV images: Hirsch, T., N. Martin, L. Gonzalez, M. Biencinto, S. Wilbert, M. Schroedter-Homscheidt, F Chenlo, and J.F. Feldhoff. 2014. Technical report on the functional requirements for the nowcasting method. Report D2.1, FP7 project DNICast, Grant Agreement No. 608623.: DLR, CIEMAT.
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Power Tower Central Receiver
Dish Stirling
Concentrating Solar Power (CSP) technology options
Parabolic Trough & Linear Fresnel
• Electricity and/or heat
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Other solar energy technologies
• Flat plate collectors for heating and cooling • Collectors for solar water treatment • …
Images: CIEMAT, psa.es
Solar energy meteorology
Ground measurements
Prediction of plant yield
Satellite
data Modelled data
Application: • Site selection • Site specific plant layout • Optimal decisions during
plant operation
- long term yield of future plant - behavior & yield of existing plant
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Meteorological parameters relevant for solar plants Parameters - GTI (Global Tilted Irradiance)
and/or DNI (Direct normal irradiance) - Circumsolar radiation - Spectrally resolved
- Wind speed, direction and gust - Temperature, humidity, pressure - Soiling rate, dew, snow, rain - Extinction between heliostats and receiver - UV, salt concentration, abrasion Historical and live meteo data & forecasting required for bigger plants
Meteo data collection not a burden, but a chance for energy cost reduction - Low data uncertainties reduce financial risk and financing costs! - Cost reductions due to smart site specific design - Cost reductions due to optimized operation (live data, forecasting → yield ↑)
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Solar radiation measurements
Operational since 2010 -2013 Planned
Solar radiation measurements
Satellite derived data and ground measurements are required for MW+ plant projects - to reach the required accuracy for historic long term data - & for the plant operation.
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x
Direct normal irradiation per year [kWh/m²]
• Robust instrument used for solar resource assessment at remote sites
• Characterization, further improvements & calibration
Global horizontal irradiance (GHI)
Diffuse horizontal Irradiance (DHI)
DNI (Direct Normal Irradiance)
Principle of operation 1. Pyranometer measures global irradiance 2. Shadowband rotates once per minute 3. During rotation: measure the diffuse irradiance → DNI is calculated → GTI calculated
Solar radiation measurements Rotating Shadowband Irradiometers
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Instrument calibration and characterization
-Calibration is the greatest uncertainty source of common radiometers -Enhancement of calibration techniques -Evaluation of systematic errors and accuracy -Correction functions for systematic errors -Calibration of Si-sensors & RSI
Solar spectra
-Measurements with spectroradiometers -Simulations with radiative transfer codes based on measurements (aerosol properties, broadband DNI & GHI, temp., rel. hum., press., …)
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Relevant for: -efficiency -selection of PV type
Spectral effects on solar technologies and radiometers
-spectral effects on PV and Si pyranometers must be considered for yield analysis
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DNI GHI
- Measurement of aerosol properties
- e.g. NASA’s AERONET - reference for satellite based aerosol measurements
Sun photometers DLR.de • Chart 14
PSA
α
• Circumsolar radiation is forward scattered solar radiation
• Concentrating collectors use: nearly the complete disk radiation
+ a smaller fraction of the circumsolar
radiation
disk radiation
Circumsolar radiation
Relevant for: -operation and plant output -design of plants (field size) -selection of solar technology
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- SAM (Sun & Aureole Measurement), software (+ optional sun photometer) - camera based system @ 670nm - broadband radiation needed for CSP, spectral radiation for CPV
- master-system running at PSA
- 2 replicas: CNRS/Odeillo (France), Masdar Institute (United Arab Emirates)
SAM sun photometer
Measurement of circumsolar radiation – SFERA system DLR.de • Chart 16
Circumsolar Radiation Sensor using pyrheliometers
1
2
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Black Photon Instruments
Circumsolar radiation measurement with RSIs DLR.de • Chart 18
Circumsolar radiation measurement with RSIs
Shadow on pyranometer
DHI partly blocked by band
Circumsolar contribution from 1° to 3.2°
measured with an RSI
disk radiation
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- Algorithm analyses measurement during rotation - No additional hardware required
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Variability of irradiance & forecasting
Andasol parabolic trough plants
Variability of irradiance & forecasting
Forecasting and temporal and intra-plant-spatial variability are relevant for: -PV production ramp rate control -PV back up system control (diesel generator) -CSP&PV plant yield optimization (e.g. market participation) -CSP & PV plant design (storage size) -selection of solar technology depending -grid operation
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Point like
10 m
100 m
1 km
10 km
100 km
1 m
in
30 m
in
45 m
in
6 h
All sky imagers Satellite Global NWP Limited area NWP
Spat
ial r
esol
utio
n (l
og-s
cale
)
Forecast lead time (log-scale) 60 m
in
0.1
min
5 m
in
Imag
e: A
RM
INES
, SM
HI,
DLR
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Irradiance nowcasting
• Spatially resolved DNI, GTI, GHI maps with high temporal resolutions • Combination with NWP (numerical weather prediction) and satellite nowcasts
All sky imager (ASI) based irradiance nowcasting
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Example ASI image
Working principle of ASI based nowcasting systems
ASI cameras film clouds
Clouds are segmented
Clouds are geolocated
Shadow map is estimated
Sensors provide irradiance data
Irradiance map is created
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Track cloud position and extrapolate
User interface of a nowcasting system (WOBAS) DLR.de • Chart 25
Radiometer and ShadowCam-system Ground-filming cameras provide irradiance maps
6x
sunny + shaded reference image
6x
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radiometers
4 Q24 ASI (All Sky Imager) 6 M25 ShadowCams 20 Si-pyranometers Pyrheliometers + pyranometers Ceilometer
2.0km
Radiometer and ShadowCam-system
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Soiling
Soiling
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Soiling measurements for PV modules and reference cells
CSP-specific soiling measurements with TraCS or handheld reflectometers
Relevant for: -operation and plant output
-When do we have to clean? -plant design, site selection
HVS Grimm
Optical systems, e.g.:
• Scatterometer type
Gravimetrical system
• Filter in air flow
Soiling modelling based on simple measurements Dust sampling
Zagora meteo station
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Beam attenuation between heliostat and receiver
Beam attenuation in tower plants
Relevant for: -design of tower plants (field size) -selection of solar technology -operation and plant output
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Vaisala FS11 scatterometer
Optec LPV-4 transmissometer
Beam attenuation in tower plants
Before ABC
ABC improves coincidence between both sensors!
Commercially available instruments applicable for CSP if ABC correction is applied!
ABC - Absorption and Broadband Correction
After ABC
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Compare clear sky DNI measurement with modelled DNI for aerosol free atmosphere + Assumption about aerosol height profile Calculate extinction
coefficient close to ground
1km Constant aerosol extinction coefficient
Extinction modelling based on DNI measurement
Validated for PSA
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Parameters affecting durability
Radiation
Temperature
Wind
Aerosols
Sandstorms Humidity • Air humidity, dew, rain •Chemical reactions •Soiling
• Abrasion
• Salt, dust, industrial emissions • Soiling • Chemical reactions, especially on hot surfaces
• Mechanical loads • Soiling • especially UV-A, UV-B
•Chemical reactions
• Diurnal changes • frost • Mechanical stress
Relevant for: -cheaper components & longer lifetime
Parameters influencing durability
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• Durability tests of new products by outdoor exposure take too long
• Accelerated aging tests in the laboratory are used • Analysis of wind speed and flying sand concentration
analyses • Operation parameters for laboratory tests
Sandstorm chamber
Abrasion due to sandstorms
Sandstorm chamber
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Meteorological Measurements for Solar Energy Summary and conclusion Solar irradiance is the most relevant parameter, but several other parameters also have to be measured Meteo data collection & application = chance for energy cost reduction -Low data uncertainties reduce financial risk and hence financing costs -Cost reductions due to smart site specific design -Cost reductions due to optimized operation: live meteo data, nowcasting, forecasting required
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Thank you for your attention and for the invitation! Questions?
Contact:
Dr. rer. nat. Stefan Wilbert
Team Leader ‘Solar Energy Meteorology’
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
German Aerospace Center Institute of Solar Research - Qualification
Plataforma Solar de Almería, Carretera de Senés s/n, km 5, 04200 Tabernas, Spain
Tel. 0034-950277619 | Fax 0034-950260315 | [email protected]
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