Wind Power Part 4:Components and Maintenance

Small Wind

San Jose State UniversityFX RongèreMarch 2008

Inside a Wind turbine

GE Wind 1.5 MW

Inside a Wind turbine

Generator

Tri-phase Synchronous Generator

The central magnet rotates with the rotor shaft of the turbineA variable Magnetic Field is inducted in the stator generating an Alternative Current

When connected to the grid the generator is forced to rotate at constant speed To gain flexibility, the connection to the grid will be indirect with a double conversion AC-DC, DC-AC

-1.5

-1

-0.5

0

0.5

1

1.5

0 2 4 6

-1.5

-1

-0.5

0

0.5

1

1.5

0 2 4 6

-1.5

-1

-0.5

0

0.5

1

1.5

0 2 4 6

Generator

Tri-phase synchronous Generator Central magnet may be electromagnets fed by

the grid Central magnet may be permanent using Rare

Earth Metals*

Increasing the number of poles one can reduce the rotation speed of the generator

* In fact, the rare earth metals are not rare and new technologies are based on permanent magnets

Pole number 50 Hz 60 Hz

2 3000 3600

4 1500 18006 1000 1200

8 750 90010 600 72012 500 600

Generator Tri-phase Asynchronous Generator

The magnet of the rotor is replaced by a squirrel cage

When the cage turns faster than the magnetic field in the stator it generates a high current in it and then a magnetic field which will play the same role as the magnet

The current generated will depend of the difference of rotation between the rotor and the magnetic field in the stator: it is called the slip (typically 1%)

To gain flexibility on the rotation speed of the shaft the slip will be varied using a variation of its electrical resistance Rotor of an

asynchronous generator

Gear Box

Tip speed ratio issue for large turbines Tip speed ratio (λ) is limited

Conversion rate WMax/WWind

0

0.1

0.2

0.3

0.4

0.5

0.6

0 1 2 3 4 5 6

Blade Tip Speed

Con

vers

ion r

ate

Typically, for a 3 blade turbine is:

3<λ<5

Gearbox

Rotation speed decrease with the size of the turbine

windv

R

.

Rotation Speed per m/s of wind

Tip speed ratio: 5

0

0.1

0.2

0.3

0.4

0.5

0.6

0 10 20 30 40 50 60 70

Radius (m)

Rot

atio

n S

peed (ra

d/s

/(m

/s)) 100 kW

1,000 kW

2,500 kW 5,000 kW

500 kW

Gearbox

Torque increases a lot with power

23

0

0

3

30

3

03

32

.

...

2.

......2

1.

.

.....2

1.

W

W

vWR

R

RvR

R

v

vRW

wind

wind

wind

wind

Wind Turbine Torque

1

10

100

1,000

100 1,000 10,000

Maximal Power (kW)Tor

que/T

orque (100kW

)

Gearbox

Converts few rotation/mn in 1,500/mn The gear ratio may be 50, 100 or

more

Causes of wind turbine failuresSource: Condition Monitoring of Wind Turbines, David Infield

1.5 MW gearbox and drive train

Gearbox

Cost of repairs

Rotor19.9%

Gearbox38.0%

Generator23.1% Non-Component Assoc.

Rotor

Air Brake

Mech. Brake

Pitch Adjustment

Main Shaft / Bearing

Gearbox

Generator

Yaw System

Wind Vane / Aenemometer

Electrical Controls

Electrical System

Hydraulics

Sensors

Other

Only Failure Hours reported**

Gearbox

Multi-stage gearbox

Planetary gearbox

Low speed mainshaft

Intermediate speed stage

High speed stage

Generator

Gearbox

Multi-drive train

Multi-drive train developed by Clipper Windpower in 2002-2004 with eight generators around the main shaft.The Liberty turbine currently commercialized has four generators

Yaw Drive and Pitch Drive

The yaw drive maintains the wind turbine facing into the wind It is similar to a tracker for a solar panel

The pitch is the angle of attack of the blades in the wind flow Optimizing the pitch allows to improve

efficiency for different wind speeds

NREl wind lab: NWTC

Located in Denver (Co)

2.5 MW Dynamo-meter Structural blade testing Environment chamber at -60oF

Field testing

Offshore Wind

Technology for the Offshore oil industry

Wind resource in California

Solano415 MW

Altamont Pass586 MW

Wind resource in California

San Gorgonio619 MW

Tehachapi665 MW

Pacheco16 MW

Offshore Wind

Offshore projects up to 2004

About 460 MW Source: Offshore Wind Experiences - IEA

Offshore Wind

Projects in the USA (2007) Cape Wind (Cape Cod / Nantucket Sound) Bluewater Wind (Long Island) Nai Kun (Hecate Strait) Galveston Offshore Wind (Texas)

Cost of a wind turbine

Project cost including connection

Turbine cost

Component costs

Cost of the components of a wind turbine Costs of a Wind Turbine

Rotor Blades

25%

Pitc System

3%

Main Shaft

2%

Gearbox

15%

Brake System

1%

Transformer

4%

Nacelle

2%

Yaw Stsem

1%

Tower

31%

Generator

4%

Power Converter

6%

Main Frame

3%

Rotor Hub and

Bearings

3%

Ref: M. Gower Mat UK Energy Materials ReviewMaterial R&D Priorities for Wind Power Generation June 15, 2007

REpower MM99 wind turbine

O&M costs

O&M costs represent 10% to 12% of the cost per kWh

Price /kWh The prices in the LB database reflect the price of electricity

as sold by the project owner reduced by the receipt of any available state and federal incentives (e.g., the PTC Power Tax Credit), and by the value that might be received through the separate sale of renewable energy certificates (RECs)

Environmental Issues

Noise Visual impact Construction impact Avian impact

Source: www.omafra.gov.on.ca

350 m

250 m

Avian Impact

Source: National Wind Coordination Committee, Fact sheet Nov. 2004

Avian Impact

Source: National Wind Coordination Committee, Fact sheet Nov. 2004

Avian Impact

Source: National Wind Coordination Committee, Fact sheet Nov. 2004

Avian Impact

Main accidental death causes for birds

Source: Mick Sagrillo PUTTING WIND POWER'S EFFECT ON BIRDS IN PERSPECTIVE 2003

Death CauseMillions of death per year

in the USAUtility transmission and distribution lines 130 - 174Collisions with automobiles and trucks 60 - 80Tall building and residential house windows 100 - 1,000Lighted communication towers 40 - 50Wind Turbines* 0.093

* Number estimated using the ratio per MW provided by the NWCC multiplied by the installed wind power in the USA in 2006 (15,575 MW)

Wind Turbine(400 W-100 kW)

Guyed or Tilt-Up Tower

(60-120 ft)

Safety Switch Power

Processing Unit (Inverter)

Cumulative Production Meter

AC Load Center

Small Wind

Factors to consider

Good wind resource: Class 2 or better

Home or business located on 1 acre or more of land

Average monthly electricity bills >$100 for 10 kW system, >$50 for 5 kW system

Zoning restrictions, economic incentives

Modern Small Wind Turbines

Small turbines range from 20 W to 100 kW

Only 3-4 moving parts means very low maintenance

20- to 40-year design life Proven technology –

150,000 installed; over a billion operational hours

50 kW

400 W(Not to scale)

3 kW

10 kW10 kW

1.8 kW

Installation Cost

Estimate $2-4/installed watt for typical system

Smaller systems require smaller initial outlay, but cost more per watt

Taller towers cost more, but usually reduce the payback period

A 4-10 kW system can meet the needs of a typical home

Customers paying 12 cents/kWh or more for electricity with average wind speeds of 10 mph or more

can expect a payback period of 8-16 years

Example

Building integration

Examples of projects integrating wind power in buildings

Companies to follow www.gewindenergy.com www.clipperwind.com www.windenergy.com (Southwest Wind) www.enXco.com www.ppmenergy.com

Wind development worldwide

Major Wind Development countries

Rank Nation 2005 2006 20071 Germany 18,415 20,622 22,2472 United States 9,149 11,603 16,8183 Spain 10,028 11,615 15,1454 India 4,430 6,270 7,8505 China 1,260 2,604 6,0506 Denmark (& Faeroe Islands) 3,136 3,140 3,1297 Italy 1,718 2,123 2,7268 France 757 1,567 2,4549 United Kingdom 1,332 1,963 2,38910 Portugal 1,022 1,716 2,150

Installed windpower capacity (MW)[28][29][30]