October 30, 2007 © SKF Group Slide 1

Why is there no ideal bearing concept

EWEC 2012

Presented by Reiner Wagner,

Application Engineering Manager Renewable Energy, Germany

2012-04-17

October 30, 2007 © SKF Group Slide 3

Increased turbine Size

PowerRotor_DmHub Height

2010

Increasing turbine size Higher profitability

10 MW150 m160 m

October 30, 2007 © SKF Group Slide 4

Wind turbine concepts

- Horizontal drivetrain - 3 Rotor blades- pitch and speed controlled

October 30, 2007 © SKF Group Slide 5

Main driver for Competitiveness

Competitiveness Wind Energy

Investment cost ReliabilityAvailability

Operation cost

Maintenance andRepair concept

High degree of integrationLighter

Lower investment cost Higher repair costLower availability

Low degree of integrationHeavier

Higher investment costLower repair costHigher availability

October 30, 2007 © SKF Group Slide 6

Basic turbine drive train concepts today

Wind Turbine

Turbines with gearbox

Hybrid turbines

Gearless turbines

Low degree of integration• gearbox can be replaced without dismantling the rotor • high speed shaft could be exchanged on top the tower • generator bearings can be replaced in the nacelle• most of the components have few and strict defined functions

High degree of integration• very few mechanical parts can be replaced in the nacelle • bearing replacement requires an exchange of the complete nacelle• a lot of components have to be multifunctional

October 30, 2007 © SKF Group Slide 7

Gearless and Hybrid1

October 30, 2007 © SKF Group Slide 8

Gearless designs

Requires a tight runout limit

Go for a bearing system which is able to live with small clearance or preload

Cross locatedTRB

Double row TRB combined with CRB

October 30, 2007 © SKF Group Slide 9

Hybrid designs

Requires a very small bearing distance and main bearing should be integrated into the design

NautilusTM bearing

NautilusTM bearingBearing distance = row distance

October 30, 2007 © SKF Group Slide 10

2Designs with gearbox(a flashback of drive train development)

October 30, 2007 © SKF Group Slide 11

The early years (mid 80´s to mid 90´s)

Challenges: Pioneer period Very few experienceNo resources No established structuresbut enthusiastic pioneers

Design features: Simple concepts Rotor directly applied to the gearbox Input shaftNo rotor bearingsFew moving partsOverdesigned ?

Rotorhub direct mounted on input shaft

To generator

October 30, 2007 © SKF Group Slide 12

Turbine size are growing through the 90ties

Challenges: Still Pioneer periodBusiness model ?Few resources Turbine growthIncreased gear ratio

Design features: Drive train became more complex since weight was increasingHigher rotor weight and planetary stages in gearboxes required main shaft and main bearing

Still some turbines without main shaft and main bearing but they die out cause of continuous turbine growth

October 30, 2007 © SKF Group Slide 13

The MW class (1.5MW)

Challenges: Wind turbine industry got recognizedRapid company growth Market pressure increaseFeed in tariff decreasingPressure on turbine prices

Design features: Almost all turbines are designed with 3 point suspensionReduced to one rotor bearing Gearbox torque arms to support rotor loadRotor has to be removed beforegearbox disassembly

October 30, 2007 © SKF Group Slide 14

The Multi Megawatt class (5MW offshore)

Challenges: Reliability and availability became extremely important

Design features: Main shaft are equipped with SRB and CARBTM

Gearbox can be exchanged without taking down the rotorNo internal forces by using the CARBTM concept. No rotor loads on the gearbox torque support

October 30, 2007 © SKF Group Slide 15

The multi MW class (stiff design)

Challenges: Reduced drive train dynamic

Design features: Main shaft are equipped with DRTRB and CRB bearing Preloaded bearings

October 30, 2007 © SKF Group Slide 16

The multi Megawatt Class (high integration)

Challenges: Light weight designReduced drive train dynamic

Design features: Main shaft are equipped with NautilusTM (DRTRB) bearing Light weight rotor shaftPreloaded bearings

October 30, 2007 © SKF Group Slide 17

Drive train development

Rotor carried byGearbox input shaft

till 1996Up to 300 kW

2 point suspension

3 point suspension

Seperate rotor shaft Carried by 2 bearings

2006 – 20092.5 – 5 MW

2000 - 20061 MW – 2.5 MW

1996 - 2000300 – 1000 kW

today5 MW and bigger

Nautilus concept

High degreeOf integration

Low degree Of integration

NautilusTM

DRTRB / CRB

SRB / CARB

October 30, 2007 © SKF Group Slide 18

Future main shaft bearing concepts

As long as there are: - different drive train concepts - different maintenance and repair concepts - different sites (onshore and offshore) - etc

There will be space for different rotor bearing concepts

Thank you

Nautilus extendedrange

Cross locatedTRB