wind power part 4: components and maintenance small wind san jose state university fx rongère march...
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Wind Power Part 4:Components and Maintenance
Small Wind
San Jose State UniversityFX RongèreMarch 2008
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
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0 2 4 6
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-1
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-1
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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
Projects in the USA (2007) Cape Wind (Cape Cod / Nantucket Sound) Bluewater Wind (Long Island) Nai Kun (Hecate Strait) Galveston Offshore Wind (Texas)
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
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
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
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]