Nebraska Wind Resources

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Nebraska Wind Resources

• Dennis Elliott
• National Renewable Energy Laboratory
• Meeting with Nebraska Public Power District
• NREL/NWTC
• November 19, 2007

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2005 Nebraska Wind Resource Mapping Project
Collaborative effort involving

• DOE/NREL Wind Powering America program
• State of Nebraska
• NRELs wind resource group and expert consultants
• AWS Truewind

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http//www.eere.energy.gov/windandhydro/
windpoweringamerica/wind_maps.asp
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Unvalidated wind speed maps generated by model
for 70m and 100m heights
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High-Resolution Wind Mapping Approach for Nebraska

• Comprehensive modeling and validation process
  produced detailed wind resource maps with a
  spatial resolution of 200 m
• AWS Truewind used a numerical weather model with
  climatic data and wind flow model to produce the
  preliminary maps
• NREL and meteorological consultants validated
  preliminary maps of 50-m annual average wind
  resource using
• Available high-quality wind measurement data
• Experts knowledge of wind flow and wind resources
  in Nebraska
• Final wind resource maps developed based on
  revision of preliminary maps from validation
  results

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Logic of Numerical Mapping Method

• Model Design and Outputs
• MesoMap - created by AWS Truewind
• A numerical weather model (MASS) coupled to a
  wind flow model (WindMap) and global weather,
  topographical, and land cover data
• NCEP/NCAR Reanalysis (200-km grid) - most
  important global weather input for MASS
• MASS simulates weather conditions (including
  winds) over 365 random days selected from a
  15-year period
• For Nebraska, MASS runs to 2.5 km and WindMap to
  0.2 km
• Model output grids provided to NREL for review
  and validation

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Validation Process

• NREL completed a spreadsheet used in the
  validation process
• Each measurement location
• Site coordinates and elevation
• Measurement heights and period of record
• Measured speed and power
• Adjusted speed and power to map height
• Map estimates for speed and power
• Qualitative comments
• NREL AWS Truewind reviewed validation results
• AWS Truewind adjusted preliminary maps based on
  quantitative and qualitative inputs

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Nebraska Validation

• Over 50 measurement stations used for validation
• 35 Airport (6-14 m)
• 8 UWRAP (40-50 m)
• 6 RAWS (6 m)
• 1 DOE/TCS (30 m)
• 1 State (40 m)
• 3 Proprietary (24-80 m)
• Estimated accuracy of final wind maps
• Within 10 of annual speed and 20 of annual
  power at 80 of individual sites

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Annual average shear exponents can vary from 1/7
to 0.25, causing considerable uncertainty in
vertical extrapolations of wind resource
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• Even if 50-m wind resource is known, potential
  variations in shear exponents cause considerable
  uncertainty in wind resource at heights of 80-100
  m
• Measured shear exponent at Goodland is 0.235,
  with much higher wind resource at 90 m than
  estimated by 1/7 shear estimate

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• High wind shear locations can have considerably
  higher capacity factors at 80-100 m than low
  shear locations, given similar capacity factors
  at 50 m
• Goodlands capacity factor of 42.5 at 90 m is
  considerably higher than would be estimated by
  using typical shears of 1/7 to 0.2

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Quantifying Available Windy Landsand Wind
Electric Potential

• Class 3 and higher resource areas used as base
  for available windy lands
• Potentially sensitive environmental lands
  excluded
• Potentially incompatible land use excluded
• Some additional lands excluded by other factors

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Land Exclusions from Wind Potential

• Potentially sensitive environmental lands
• National Park Service, Fish and Wildlife Service,
  Wilderness, and Recreation Areas on federal land
  (predominately Forest Service and BLM lands)
• Some state and private environmental lands where
  data was available
• Half of the remaining Forest Service and
  Department of Defense lands were excluded to
  represent current dedicated use of land
• Potentially incompatible land use
• Urban areas, airports, wetlands and water bodies
• Half of non-ridge forested areas
• Other factors
• Slopes greater than 20 were excluded
• A 3 km area surrounding environmental and land
  use categories that were completely excluded
  (except water bodies) was also eliminated
• Small, isolated class 3 and greater resource
  areas were eliminated using a minimum density
  criteria

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Wind Electric Potential Estimation

• Distance from transmission lines and roads not
  included in windy land calculations
• Windy land ? electric potential
• Direct conversion from sq. km to potential
  installed capacity - 5 MW per km2 of available
  windy land

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Nebraska Wind Electric Potential (Installed
Capacity)

• Total before exclusions
  Developable
• Class 3 803 GW
  764 GW
• Class 4 162 GW
  156 GW
• Class 5 2.7 GW
  2.5 GW
• Class 6 lt0.1 GW
  lt0.1 GW
• 5 of the raw Class 3 lands excluded
• 3 of the raw Class 4 lands excluded

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Stations Selected for Analysis of Monthly and
Diurnal Characteristics
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Summary of Nebraska Wind Resources

• Good resource areas (Class 4) are located
  throughout the state
• Areas of excellent resource (Class 5) are
  dispersed over the northern half of the state.
• Winter-Spring maximum wind resource
• Prevailing wind directions are from
  west-northwest (winter) and from south (spring
  and summer)
• Tall-tower measurements (up to 80-100m) and
  remote sensing (sodar/lidar) needed to
• Estimate the wind shear at elevated heights of
  50-100m
• Characterize wind resource at hub-heights of
  advanced wind turbines