Characterizing solar resources and local meteorological attributes is an important first-step in the review of any solar energy project. While residential and light commercial projects may require only a cursory assessment, larger distributed generation and utility-scale projects necessitate a more rigorous evaluation. AWS Truepower’s President and CEO, Bruce Bailey and Director of Solar Services, Marie Schnitzer will cover the importance of using established resource assessment methods to lower project risk and improve project and site characterization. During the webinar they will share lessons-learned from the wind industry and provide insight on best practices in desktop studies, on-site monitoring programs, and field activities.

1. ALBANY • BARCELONA • BANGALORE September 2010
SOLAR RESOURCE ASSESSMENT: WHY IT MATTERS
SOLAR RESOURCE ASSESSMENT: WHY IT MATTERS
BRUCE BAILEY, PRESIDENT & CEO
MARIE SCHNITZER, DIRECTOR OF SOLAR SERVICES
463 NEW KARNER ROAD | ALBANY, NY 12205
awstruepower.com | info@awstruepower.com

2. Topics Addressed
• The Importance of Solar Resource Assessment
• Best Practices for On‐Site Monitoring
• Investment Grade Analysis
• Key Messages
• Questions
©2010 AWS Truepower, LLC 2

3. Importance of Solar Resource Information
Project Lifecycle Considerations:
• Early Development Phase
Early Development Phase
– Prospecting and Site Screening
– Site Comparison and Selection
Site Comparison and Selection
• Pre‐Construction and Financial
Readiness Phase
– Long‐Term Energy Assessment
– Economic Viability
• OOperational Phase
ti l Ph
– Performance Verification
– Utility Forecasting
Utility Forecasting
Characterize the Spatial and Temporal Variability of System Output
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4. The Path to an Investment Grade Analysis
• Conduct an On‐Site Measurement Campaign
• Procure High‐Quality Reference Data
• Analyze Data Sets and Predict Long‐Term Resource
• Quantify Data Uncertainties
• Conduct Energy Production Analysis
Source: photos.com
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5. ON‐SITE MONITORING PROGRAMS
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6. Solar Radiation Components
• Direct Normal Irradiance (DNI)
• Diffuse Horizontal Irradiance (DHI)
Source: nrel.gov
• Global Horizontal Irradiance (GHI)
Source: esri.com
Source: kippzonen.com
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7. Attributes of On‐Site Monitoring
• On‐site monitoring provides significant value to
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assessing a project’s potential, translating to
higher confidence in energy estimates.
– Accurate Representation of the Project Site
– Customizable for Various Technologies (e.g.,
PV or CSP) and Various Users
S ) d i
– Flexible Equipment Options and Costs
– Small Environmental Footprint
Small Environmental Footprint
– Straight‐Forward Installation & Operation
– Self‐Contained Communications and Power
Self Contained Communications and Power
Supply
©2010 AWS Truepower, LLC

8. On‐Site Monitoring Programs – Best Practices
• Measurement Plan
– Solar Instrumentation
– Meteorological: Temperature,
Wind Speed, Precipitation
– Balance of System
– Sampling/Recording Rate
– Measurement Period
• Installation and Commissioning
– Site Selection
– Audit and Sensor
Verification
– Equipment Orientation
– Communications and Data QA
– System Security
– Documentation
©2010 AWS Truepower, LLC 8

9. On‐Site Monitoring Programs – Best Practices
• Maintenance
– Regular Schedule
– Clean and Level Instrumentation
– Verify Site Security and Overall
Conditions
• Data Validation and Quality Control
– Regular System and Data Inspection
Regular System and Data Inspection
– Comparison with Reference Data
– Extreme or Suspect Values
Extreme or Suspect Values
Getting the Highest Quality Data
©2010 AWS Truepower, LLC 9

10. Campaign Data Summaries
• Site Description
• Solar Statistics
• Meteorological Statistics
• Monthly and Diurnal
Trends
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• O&M S
O&M Summary
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11. INVESTMENT GRADE ANALYSIS
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12. Developing a Long‐Term Projection
On‐Site
Modeled Data
Data
Observed
Reference
Data
Long‐Term Meteorological Characteristics
Objective Review of Resource and Energy Potential
©2010 AWS Truepower, LLC 12

13. Other Sources for Solar Resource Data
• Modeled Data
– National Solar Radiation
Database (NSRDB)
– International Databases
– Solar Maps
• Observed Reference Data
– N i
National Networks
lN k
http://eosweb.larc.nasa.gov/cgi‐bin/sse/sse.cgi?+s01#s01
– Regional and State Networks
– I t
International Sources
ti lS
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14. Modeled Solar Resource Data
• Characterizations
– Availability
– Long Periods of Record
– Consistent Methodology
• Limitations
– Spatial Resolution
– Potentially Large Biases
Potentially Large Biases
– High Data Uncertainty Source: http://www.nrel.gov/gis/solar.html
“Originally intended for use to compare various modeling scenarios –
NOT for absolute performance based on climate.”
NREL, Solar Radiation Data Sets, 2008 Solar Resource Assessment Workshop
©2010 AWS Truepower, LLC 14

15. Observed Reference Data
• The potentially higher accuracy of ground data may result in more
accurate estimates of a project’s potential, but there are very few
i f j ’ i l b h f
high quality solar measurement stations.
• Characterizations
– Complements Modeled Data Set
– P i i
Proximity to Project Site
P j Si
– Potentially Reduced Data Uncertainty
• Limitations
– Instrumentation Differences
– Varying Maintenance Practices
Varying Maintenance Practices SURFRAD Reference Station Desert Rock
SURFRAD Reference Station – Desert Rock.
http://www.srrb.noaa.gov/surfrad/
Using multiple sources of data can result in a more robust resource analysis.
Using multiple sources of data can result in a more robust resource analysis.
©2010 AWS Truepower, LLC 15

16. Considerations for Regionally Observed Data Sets
• Site Location and Exposure Reference
• Proximity to Project Site Station
• Period of Record
Site
• Data Trends
• Data Recovery Rate
D t R R t
• Site Maintenance
• Instrument Calibration
Instrument Calibration
• Correlation Between Sites
Source: photos.com
©2010 AWS Truepower, LLC 16

17. Adjusting to the Long‐Term
Short Period of Long Period of 1200
On‐site Data Reference Data 1000
Target Site GHI (W/m 2 )
800
600
Measure ‐ Correlate ‐
Measure Correlate Predict 400
200
0
0 200 400 600 800 1000 1200
Reference Site GHI (W/m 2 )
300
Reference
Wh/m 2 )
Station 250 Site
Monthly Irradiation (kW
200
150
100
50
Long‐term Resource Estimation
L t R E ti ti M
0
Jan‐02
Jan‐03
Jan‐04
Jan‐05
Jan‐06
Jan‐07
Jan‐08
Jan‐09
Jul‐02
Jul‐03
Jul‐04
Jul‐05
Jul‐06
Jul‐07
Jul‐08
Jul‐09
at the Project Site
Long‐Term Reference Data On‐Site Measured
©2010 AWS Truepower, LLC

18. Energy Production Analysis
Sun Position,
Surroundings,
Horizon, etc
H i t
Project
Location
Global/Diffuse
Global/Diffuse Component
o po e
Horizontal,
Resource
Energy Plant Selection,
Design Orientation,
Temperature,
Wind Speed
Analysis Tracking, Row
Spacing, etc
System
Losses
Soiling, Shading,
Incident Angle,
Mismatch, Wiring,
Mismatch Wiring
Availability, etc
©2010 AWS Truepower, LLC

19. Relative Uncertainties of On‐Site Monitoring
Source: lockheedmartin.com Source: austincollege.edu
Data Source Typical Annual Uncertainty
Satellite Modeled (NSRDB) ± 8‐15%
Pyranometer (GHI) ± 3‐5 %
Pyrheliometer (DNI) ± 2‐3%
Reducing the uncertainties in the solar resource
make the project more attractive to investors.
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20. Uncertainty in the Long‐Term Projections
Uncertainty Considerations
• Measurement
• Inter‐Annual Variability
• Representativeness of Monitoring Period
Representativeness of Monitoring Period
• Spatial Variability
• Transposition to Plane of Array
• Simulation and Plant Losses
Confidence in Energy Estimates
Confidence in Energy Estimates
• Probability Analysis
• P50, P75, P90, P95, P99
The uncertainty of data used in an assessment needs to be
characterized and applied to the long‐term projections
©2010 AWS Truepower, LLC

21. Key Messages
• Solar resource assessment is a sound investment
Solar resource assessment is a sound investment
• Utilize all available data sets in an resource analysis
• Consider the factors that impact the quality of the data sets
• Thorough resource assessments lead to more accurate
energy estimates
• Detailed analysis of the resource and better characterization
of the project site leads to an investment grade project
p j g p j
Image source: photos.com
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22. Resource
Assessment
Energy
Forecasting
Assessment
Supporting
the Complete
Lifecycle
Performance Project
Assessment Consulting
Independent
Independent
QUESTIONS? Engineering
&
Due Diligence
Toll Free: 1‐877‐899‐3463
Ph: 518‐213‐0044
Email: info@awstruepower.com
Web: awstruepower.com
Web: awstruepower.com
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