Sandia/EPRI 2014 PV Systems SymposiumGround Irradiance DataJustin Robinson

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

GroundWork’s goal is to deliver revenue-gradeground irradiance data to solar power modelers

Our Solar Monitoring Station (SMS) programs include:! Program and System Design and Submittals! Equipment Supply, Fabricate and Test! SCADA Integration! Install, Commission and Validate! Operations and Maintenance! Data Quality Assurance (GroundWatch)

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

Use of Ground Irradiance Data

Gather lower uncertainty irradiance dataif.... secondary standard, site-specific and maintained

Tune satellite data for lower uncertainty resource assessment Capture micro-climates and albedo

http://kippzonen-blog.nl

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Solar Radiation Terms

GHI: Global Horizontal IrradianceDNI: Direct Normal IrradianceDHI: Diffuse Horizontal IrradianceGPOA: Global Plane of Array Irradiance

http://rredc.nrel.gov

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Component Sum Calculation

Sza: Solar Zenith AngleGHI = DNI * cos(Sza) + DHI

http://esrl.noaa.gov

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GHI

Calculated from measured DNI and DHIMeasured with PyranometerMeasured with Si-Photodiode

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GPOA

Measured with pyranometer at tilt and azimuth of arrayEstimated from DNI and DHI

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DNI

Measured with pyrheliometerCalculated by Rotating Shadowband Radiometer (RSR)

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DHI

Measured with shaded pyranometer (shadowball assembly)Measured with RSRCalculated from DNI and GHI

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SMS Considerations

Pyranometer classSensor orientation and mountingRedundant irradiance sensorsTemperature correctionInclement weatherAncillary measurementsPower budget & diagnosticsSoiling studies

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

SMS Types

Redundant GHIGHI + GPOARSR + GHISun Tracker with GHI, DNI, DHI

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Redundant GHI

Low uncertainty GHI ground data Provides for both data quality assurance and data continuityHorizontal position is easy to maintain and verify

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

GHI + GPOA

Fixed GPOA at defined angleGPOA measures albedo (ground reflection)Provides some data quality assurance and data continuityGPOA introduces tilt errorGPOA orientation is more difficult to maintain and verify

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

RSR + GHI

RSR measures DHI and GHI; Calculates DNIUnderestimation of DHI under clear sky conditionsLimited data quality assurance of dissimilar instrumentsNo data continuity of lower uncertainty GHIDHI is required by SCE; RSR is an acceptable option

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

Sun Tracker with GHI, DNI, DHI

Measures GHI, DNI, DHICalculated GHI has lowest uncertaintyExcellent data quality assurance and data continuityUpfront investment limits usage in developmentMaintenance regime is more rigorous and costly

Proprietary and ConfidentialGroundWork Renewables, Inc.

Proprietary and ConfidentialGroundWork Renewables, Inc.

Ground Metadata

Commissioning documentation and change logsSensor make, model and classDatalogger programPhoto-setSensor calibration certificatesO&M frequency and logsPeriodicity of data review

XX.XXXXXX, -XXX.XXXXXSolar Project, CA

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Ground Data Reasonableness

Characterize system uncertaintyCorrelate data with cleaning eventsCompare redundant sensors and/or component sum valuesEvaluate symmetry of irradiance curvesCompare clear sky transmittance indices (NREL SERI QC)

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Cleaning Event

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Questions