Design Environment for Offshore Wind:Examples from the Mid-Atlantic

Design Environment for Offshore Wind:Examples from the Mid-Atlantic

Revised Presentation

EBC/EEA– Offshore Wind Energy Seminar SeriesSession 3 – Deep Water: The Next Frontier

Boston, MA

31 January 2008

George HagermanVCERC Director of Research Virginia Tech Advanced Research Institute

(with contributions from Matt Unger,Virginia Tech Advanced Research Institute,and Jose Blanco, Old Dominion University Center for Coastal Physical Oceanography)

Design Environment

Covering entire scope of design environment not possible in 20 minutes!

Presentation Focus onSelected Offshore Wind Analysis Topics

Background and context• US offshore wind resource distribution by depth• Virginia’s “over the horizon” resource is not in deep water

(15 to 25 m depth contours lie ~20 to 30 km off Virginia Beach)• Virginia Coastal Energy Research Consortium feasibility-level

design study requires development of supporting wind data

Offshore resource spatial variability• Assume audience familiar with AWS Truewind mapping

(Michael Brower presentation, this seminar series, Sep 2007)• Horizontal variability: ocean-coupled sea breeze circulation• Vertical variability: wind speed profile

Hindcasts for extreme event and fatigue analyses • NOAA-NCEP Wavewatch III• Army Corps of Engineers Wave Information Studies

US Offshore Wind Energy PotentialBetween 5 and 50 Nautical Miles Offshore

With NREL assumed exclusions, total potential installed capacity is 1,057 GW. Assuming an average capacity factor of 35%, total electrical energy output would

be 3,214 TWh per year, equaling 87% of all US electrical generation in 2004.

Mid-Atlantic Offshore Wind Resource isin Shallower Depths than in Other Regions

Source: www.eere.energy.gov/windandhydro/windpoweringamerica/pdfs/workshops/2005_summit/musial.pdf

Much of the Shallow Mid-Atlantic OffshoreWind Resource is off the Virginia Coastline

Mid-Atlantic region has >70%of U.S. offshore wind energy

potential in water depths <30 m

Virginia’s Wind Energy ResourcesOffshore are Much Larger than on Land

Class 4+ areas needed for economical onshore projects are largely on

ridges in national forests and parks, and even

projects on private land seem difficult to permit

Class 5+ areas needed for economical offshore projects are in federal

waters beyond 3-n.mile limit of state jurisdiction

National Forests, Blue Ridge Parkway,

Appalachian Trail, state parklands, and

county-by-county zoning variability

Only one regulatory authority (US Minerals Management Service)

Source: http://gcep.stanford.edu/pdfs/energy_workshops_04_04/wind_bailey.pdf

Hampton Roads Area has Unique FeaturesFavorable for Offshore Wind Power Development

Minimal probability ofmajor hurricane strike

(Categories 3 through 5)

Robust coastaltransmission grid

Class 6 ( ) wind energy resourcehas been mapped within 10-15 miles(16-24 km) ofshoreline, closeto major centers of power demand 500 kV

115 kV

230 kV

Pale blue region indicates uncertain wind map accuracy

beyond 25 km offshore

Three Initial VCERC ProjectsFocus on Offshore Wind

1. Feasibility-level design and economic assessmentfor a hypothetical reference baseline offshore wind power project

2. Preliminary mapping of offshore areassuitable for offshore wind powerdevelopment, with identificationof military training areas, shipping lanes, commercial fishing grounds, and marine and avian habitats

3. Evaluation of economic development potentialof commercial offshore wind powerdevelopment and associated workforce training needs, and planning for an ocean test bed

4. Feasibility-level design and economic assessmentfor an algae-to-biodiesel cultureand processing system

Hypothetical Baseline Design Location

ODU’s Center for Coastal Physical Oceanography is compiling data on offshore wind and wave climate.

ODU’s Coastal Engineering Program is developing wind turbine tower foundation design alternatives.

ODU’s Electrical Engineering Department is developing turbine electrical interconnection design alternatives.

Wind data needed farther offshore

Based on AWS Truewindmap (transparent overlay),

Class 6 winds had been anticipated on this shoal

Class 6

Class 5

CHLV2 anemometer located 43 m above

mean sea level

Waves and solar radiationare also measured on CHLV2

Horizontal Variability: Comparing1992-2006 Measurements Across Virginia Shelf

44009 (5 m)

44014 (5 m)

CHLV2 (43.3 m)

FRF (20.4 m)

CBBT (13 m)

Station ID (anemometer height)

Wind Resource at CHLV2 only Class 4,Pulled Down by Pronounced Mid-Day Drop

CHLV2

WinterSpringSummerFallAnnual Annual average

CBBT 44014

Win

d po

wer

den

sity

(W/m

2 ) a

t 50

m e

leva

tion

Hour (GMT) Hour (GMT) Hour (GMT)

1000 to 1500 EST

Mid-Atlantic SynopticAtmospheric Circulation Climatology

Images from NOAA NCEP/NCAR Reanalysis Climatic Diagnostics Center, Earth System Research Lab (AWS Truewind presentation)

Cold season characterized by strong winds from northwest, driven by steep pressure gradient. Warm season characterized by weaker, more variable winds from south through southeast

Warm-Season Winds from South Drive Upwelling,Increasing Land-Sea Temperature Difference

SST 18-Jul-2006

Alongshorewind component

Ekman surface transport

Spring & Summer Pattern

Onshore Wind

Offshore Limit of Sea Breeze Cellis Divergent, Low Wind Zone

Extent of Onshore Sea Breeze Cell• Up to 25 km inshore• Up to 50 km offshore• 500-1,000 m vertical extent• 10-20 kt onshore wind speeds from surface up to 100 m

Inland Limit of Sea Breeze Cellis Convergent, Convective Front

13:30 EST 17:30 EST

• Detected as thin line of high reflectivity on Doppler radar• Focus of occasional severe thunderstorm development

Rutgers University Numerical Simulation Results(from 2004 M.S. thesis by Louis Bowers)

16-Apr-2004 1300 EST 16-Apr-2004 1400 EST 16-Apr-2004 1500 EST

Surface wind speed (m/s)

Current Hypothesis is that CHLV2is in Sea Breeze Offshore Divergent Wind Zone

CHLV2

WinterSpringSummerFallAnnual Annual average

CBBT 44014

Win

d po

wer

den

sity

(W/m

2 ) a

t 50

m e

leva

tion

Hour (GMT) Hour (GMT) Hour (GMT)

1000 to 1500 EST

Virginia’s best “over the horizon”offshore wind energy resources may be in deeper water after all!

Vertical Variability: EstimatingResource at Wind Turbine Hub Height

Vertical Profile Analysis ComparingCHLV2 (43.3 m) and Adjacent Buoy 44010 (5 m)

Wind speed increasing with height

Wind speed DECREASING with height

Number of daytime hours in sample

Wind speed increasing with height

Wind speed DECREASING with height

Number of nighttime hours in sample

Calibrated Power Law ExponentVaries with Season and Time of Day

α = 0.143

α = 0.311

α = 0.310

α = 0.143

α = 0.176

α = 0.193

Power Law: u2 = u1 (z2/ z1)α whereu2 is the wind speed at height z2 andu1 is the measured wind speed at the anemometer height, z1. The value ofα is often assumed to be 1/7 (= 0.143) unless data or other guidance exists, while NOAA suggests a value of 0.11 (www.ndbc.noaa.gov/adjust_wind.shtml).

Based on calibration of data subset where wind speed increases with height (from Buoy 44010 to CHLV2). We are still developing a methodology that will handle both increasing and decreasing wind speed profiles.

Effect of Power Law Coefficient onCapacity Factor of Vestas Wind Turbine Models

Vertical Wind Speed Profile UncertaintyTranslates into Significant Revenue Uncertainty

Above bar chart shows revenue uncertainty associated with ± 95% confidence interval on calibrated boundary layer profiles fitted to CHLV2 and Buoy 44010 data. LMP = Locational Marginal Price.

V90 Simulated Annual Revenue per Turbine in 2006

Navy Research on Near-Surface MarineBoundary Layer Properties may Provide Insights

USS Bennet (DD 473) makes chemical (white) andstack (black) smoke in the Solomon Islands, May 1944

Wavewatch III Offshore Wind and WaveForecast Model (hindcasts archived only since Aug 1999)

Wavewatch III hindcast accuracy is good, but less than 9 years of data are archived to date

US Army Corps of Engineers Wave Information Studies, WIS (20 years of wind and wave hindcast data)

Hourly WIS data is continuous for 1980-1999, and can be used for offshore wind resource mapping,as well as extreme event and fatigue analyses

Gaps (x) in CHLV2 wave measurements

Comparison of Measured Data andHindcast Data for 1985 Hurricane Gloria

Peak measured value = 37.1 m/s

Comparison of Measured Data andHindcast Data for 1985 Hurricane Gloria

Peak measured value = 6.2 m

References

DOE / National Renewable Energy Laboratory• AWS Truewind maps: www.awstruewind.com/maps/united-states.cfm• NREL PDFs: www.nrel.gov/wind/pubs_technologies.html#offshore

Old Dominion Univ. Center for Coastal Physical Oceanography• Home page: www.ccpo.odu.edu• Offshore wind research: http://ccpo.odu.edu/~jlblanco/windenergy

Rutgers University Sea Breeze Research• Home page: http://marine.rutgers.edu/cool/seabreeze• Influence on offshore wind resource:

http://marine.rutgers.edu/cool/weather/wind_analysis/seabreeze.pdf

Available East Coast Wind and Wave Hindcast Data• NOAA Wavewatch III: ftp://polar.ncep.noaa.gov/pub/history/waves• Army Corps of Engineers Wave Information Studies 1980-1999:

http://frf.usace.army.mil/cgi-bin/wis/atl/atl_main.html

Thank You!

Any questions?

Email: hagerman@vt.edu

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