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Climatically Diverse Data Set 

for Flat-Plate PV Module 

Model Validations

Bill Marion

2013 Sandia PV Performance Modeling 

Workshop

Santa Clara, CA, May 1-2, 2013

NREL/PR-5200-58600
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Background 

• Work began in FY2011 to fulfill a FY2014 

milestone for DOE’s System Integration 

Technology Validation Project

o “Comprehensive data set, with low measurement 

uncertainty, of I-V curves and associated 

meteorological data for PV modules representing 

all flat-plate technologies and for weather 

conditions for three climatically different locations 

completed”.
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Intended Data Applications

• Validation of existing PV module models 

and/or the development of new models.

• Analysis of performance differences from 

climate.

• Data available to the public.
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Field Site Locations

• Cocoa, FL

o Florida Solar Energy Center

o Subtropical climate

o Jan 2011 – Mar 2012

• Eugene, OR

o University of Oregon

o Marine west coast climate

o Dec 2012 – Feb 2014

• Golden, CO

o NREL

o Semi-arid climate 

o Aug 2012 – Sep 2013
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PV Module Technologies Deployed

• single-crystal Si

• multi-crystal Si

• a-Si/x-Si HIT

• CdTe

• CIGS

• a-Si/a-Si and a-Si/a-Si/a-Si

• a-Si/nanocrystalline-Si tandem
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Data Measurements

• PV Module Data

o I-V curves ever 5 minutes 

o Peak-power tracking 5-minute averages

o PV module back-surface temperature

• Meteorological Data

o POA irradiance with K&Z CM22 and LI-COR

o Direct normal, diffuse and global horiz. irradiance

o Wind speed and direction; dry bulb temperature; 

relative humidity; barometric pressure; 

precipitation
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Daily Operations

• Site

o Daily maintenance, except weekends and holidays

o One of two identical PV modules cleaned for 

soiling assessment

• NREL

o Data retrieval and archiving

o Daily quality assessment of previous day’s data
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Daily Quality Assessment

• Based on ISO 17025 procedures at NREL

• Automated checks each day with email 

notification

o Irradiance and other meteorological data

o PV module temperatures

o PV performance ratios 

o I-V curves acquired meet minimum and stable 

irradiance criteria
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PV Module Characterization

• Pre- and post-deployment baseline solar 

simulator measurements at STC

• Post-deployment characterization of each PV 

module to provide performance coefficients 

and data for PV models 

o Sandia performance characterization method

o IEC 61853 performance matrix

– 23 I-V curves for a matrix of temperatures and 

irradiances ranging from 15°C to 75°C for temperatures 

and 100 W/m2 to 1100 W/m2 for irradiances
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Data Set Content and Format

• Comma Separated File (csv) for each module

• Time stamp of I-V curve

• POA irradiance

o Immediately before I-V scan, W/m2, (CMP22)

o Change during I-V scan, ±W/m2, (both CMP22 and 

LI-COR) 

• I-V curve characteristic data per ASTM 1036 data 

fitting procedures

o Isc (A), Voc (V), Pmp (W), Imp (A), Vmp (V), FF

• I-V curve data pairs, as measured
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Data Set Content and Format (continued)

• Meteorological Data

o Precip (mm) – accumulated daily total prior I-V scan

o Ambient temperature (0C) – closest 5-sec sample

o Relative humidity (%) – closest 5-sec sample

o Barometric pressure (mb) – closest 5-sec sample
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Data Set Content and Format (continued)

• Solar Data

o Direct Normal (W/m2) 

– 5-second average containing I-V scan time

– Standard deviation of 1-sec samples of 5-second average

o Global Horizontal (W/m2) 

– 5-second average containing I-V scan time

– Standard deviation of 1-sec samples of 5-second average

o Diffuse Horizontal (W/m2) 

– 5-second average containing I-V scan time

– Standard deviation of 1-sec samples of 5-second average

o Solar QA Residual (W/m2) 

– Direct Normal * cos(zenith) + Diffuse Horizontal – Global Horizontal

• Soiling Derate (example: 0.98 = 2% loss due to soiling)
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Questions, Comments, Suggestions

• PV module characterization?

• Data set content or format?

• Other?

bill.marion@nrel.gov