JP Lyons - Novus Energy PartnersBob Thresher – NREL Wind Tech CenterMike Robinson – NREL Wind Tech Center Paul Veers – Sandia National Labs

IEEE PES22 July 2008

Wind Energy Technology

2 / July, 2008

Modern Wind Turbines

Gearbox Epoxy-Glass

Composite Blades

Electrical Pitch Drives

Transformer & Electrical

Doubly-FedGenerator

Main Shaft & Bearing

Power ElectronicConverter

GE 1.5sl• 1.5 MW• 77 M Rotor Diameter • 50-100 M Tower• 98% Availability• Speed 10-20 RPM• Variable Pitch

3 / July, 2008

Land Based Technology• 1.5 -3.0 MW upwind configuration• 80-100m tapered cylindrical steel towers• 3 stage gearbox• Distributed component drivetrain• Full span pitch control• 200+MW Windfarms

Performance

• 97+% Availability• 40+% CF at IEC-II 8.5 m/s• CF% +10 pts in last 5 yrs• ~65 kWhr/kg tower top mass

Vestas V100-2.75

Clipper 2.5-93

GE 2.5xl

Capacity Factor = (Annual Yield MWHrs)/(24*365*Power Rating)

4 / July, 2008

Blades

5 / July, 2008

Wind Energy Conversion

Rotor power: P = 1/2 cp ρAvw3

cp - rotor power coefficientρ - air densityA - rotor swept area

Ideal cp = 0.593 (Betz factor)where V2 = 1/3 V1 (wind velocity slows by 2/3)

Tip speed ratio: λ = vt / vw

cp = f(λ)

“Windturbines: Fundamentals, Technologies, Application and Economics”, Erich Hau, ISBN: 3540570640; (April 30, 2000)

6 / July, 2008

Wind Turbine Dynamics

“Windturbines: Fundamentals, Technologies, Application and Economics”, Erich Hau, ISBN: 3540570640; (April 30, 2000)

Periodic Forces Excite Mechanical System• dominated by blade passing frequency (BP)• 3P - wind shear, yaw error, tower shadow • 1P - rotor unbalance gravity• P - rotational frequency

Turbine Natural Frequencies• Tower bending modes • Blade flap bending mode• Blade flutter & torsional modes• Yaw system torsional mode• Drive train torsional oscillation

7 / July, 2008

Specific Yield – WTG Comparison

Specific Yield – kWHr per kg

• Key turbine design metric

• Yield driven by rotor swept area & capture efficiency

• Weight of similar technology WTGs proxy for cost

• Weight scales faster than power rating

• Need new technology to decrease pu weight and improve COE

8 / July, 2008

Wind Energy Converters

PGen

Filter

Grid

=

3~ =

3~SGPmech

Compensation

Grid

ASGPmech

PGen

DFM

=

3~ =

3~

s*PGen

PGenPmech

Filter

Grid

s*PGen

Rigid ‘Danish’ fixed speed design:Fixed speed coupling of an high slip induction generator to the grid.

Variable speed double-fed generator:4-quadrant converter feeds the rotor circuit to generate grid-synchronous voltage at the stator field.

Variable speed full converter solution:A synchronous or induction generator develops variable frequency alternating voltage which is converted via full converter into voltage/current synchronous with the grid.

Variable Speed / Variable PitchTurbines are Now the Industry Norm

9 / July, 2008

Great Progress in Last Several Years –Mimic Thermal Power Plant Performance

• Power electronics have changed wind technology from a detriment to an attribute

• ZVRT fault ride-thru to be required by FERC • Reactive power control – voltage regulation, VAR

support w/o power• Active power control - ramp rates, power curtailment,

power droop W/ frequency, virtual inertia• Forecasting can significantly improve scheduling,

penetration & integrated system performance

Grid (Friendly) IntegrationWind RIDE-THRU

0

20

40

60

80

100

120

-1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time (seconds)

Volta

ge a

t Poi

nt o

f Int

erco

nnec

tion

(Per

cent

)

200 ms

LVRT ZVRT

10% Power Increase

4% Frequency Reduction

Freq

uenc

y (H

z)

Pow

er (k

W)

Voltage at POI

Wind Plant Power Output

Wind Plant Voltage

Average Wind Speed

Colorado Green 220 kV Bus Voltage RegulationActive Power Ramp-Rate Control – ESB Ireland

Voltage Transient Ride-Thru Requirements

10 / July, 2008

Land Based Tech Improvements

Blades• Larger rotors, high eff airfoils + 10% CF• Load mitigating sweep and flap twist coupled blades• Automated carbon fiber sparcap & blade root• On site blade infusion

Power Train• Compact 1-stage integrated gearbox,

bearings, generator• Direct drive• PM generators• Full MV power conversion

Scale• 5MW machines on the Great Plains• GW scale land projects• Shipping logistics: in-situ blade & tower mfg• 90 kWhr/kg specific yield

WT Composites Sheathed Space Frame Tower

GEC Medium Speed Drivetrain Concept

Bend-Twist Coupled Blades

Controls• Multi-variable model based controls• Load mitigation & damping• Cyclic & independent blade pitch control

11 / July, 2008

Performance• Great wind 9+ m/s• Average 45+% capacity factor• 11 c/kwhr UK Thames Estuary site• SOA 5 MW viable in UK market

Offshore Wind

Offshore Technology Today• 19 Projects, 900 MW Installed, shallow water

• 3 -4 MW upwind configuration

• 5-6 MW turbines in prototype• 80 m towers• Monopile & gravity foundations < 20m• Many challenges – turbine only 1/3 project costs

40 MW Bonus Middlegrunden Farm in Copenhagen Harbor

176 MW Siemens/BonusNysted, DK

90MW VestasBarrow, UK

12 / July, 2008

Offshore Technology

Technology Needs• 5-10 MW scale turbines

• Foundation technology 40-50m• Hydrodynamic coupled design codes• 9 c/kWhr achievable in shallow water• Hurricane ride-thru

Huge renewable asset within 50 km of US coast, 40m

depths

Horns Rev 80*2 MW

Installation Jack-Up BargesShallow Depth Water Foundations

15-20m

0.5 m cushion layer

scour protection

windturbinetower

Steel latticeturbine platform

base plate

shaft

steel shaft enclosed in rebar reinforced concrete

PVC tubesfor cables

US Offshore Wind• Shallow (0-20m) limited US sites• Turbine 30% total Installation costs - staging, foundations,

grid interconnect, O&M costs dominate• Proactive environmental impact assessments & design

mitigation strategies• Support infrastructure needed – vessels, dock side sites

Range of Foundation Technologies

13 / July, 2008

Offshore Machines – Is Bigger Better?

Enercon E-112/120m, 4.5/6MW

Prokon Nord 5MW, 116m

Vestas NM110/V120m 4.2/4.5 MW

GE 3.6 MW 104/111m

Manufacturer Model Power (MW)

Rotor (m)

Nacelle Weight + Rotor

(kg)

Generator Cf (%)

Enercon E112 4.5 112 440 WF Sync 44.0Enercon E120 6 120 440 WF Sync 41.6Vestas V90 3 90 108 DFIG 43.5Vestas NM110 4.2 110 214 DFIG 44.6Vestas V120 4.5 120 214 DFIG 46.5GE 3.6s 3.6 104 280 DFIG 45.3GE 3.6sl 3.6 111 265 DFIG 47.9Siemens/Bonus 3.6 3.6 107 200 Induction 46.4Repower 5M 5 126 400 DFIG 46.3Prokon Nord Multibrid 5 116 280 PM Sync 43.4

Repower 5M 5MW, 126m

Vestas V90 3MW, 90m

Siemens Bonus 3.6 3.6MW, 107m* planned upgrades

14 / July, 2008

Large Offshore Turbines

10 MW Concept• 180 m rotor diameter• Downwind 2 blade machine• Direct drive• Flexible compliant blades• Flow control blades• High rpm/tip velocity > 100 m/s• Space frame structure• Multivariable damping controls• 40 m water depth foundation• Hurricane ride-thru capability

EU Upwind R&D Program 8-10MWClipper Britannia 7.5 MW

Industry Contemplating 7-10 MW Offshore Machines

15 / July, 2008

20% Wind Technology -What’s Needed?

• Tech investments can have huge payoff; 1 c/kWh COE worth $12B/year in 2030

• No critical barriers in materials or industrial capacity to achieve goal

• Comparable growth has been managed in other industries

• Built-in reliability

• Increased turbine size & capacity factor

• Lighter weight smarter turbines

• Offshore infrastructure & technology

• Grid integration technologies –forecasting, reserve, smarter t&d

160 MW Colorado Green Wind Plant Lamar, CO