October 30, 2007 © SKF Group Slide 0

Why is there no ideal bearing concept EWEC 2012 Presented by Reiner Wagner, Application Engineering Manager Renewable Energy, Germany

October 30, 2007 © SKF Group Slide 2 Increased turbine Size Power Rotor_Dm Hub Height 2010 Increasing turbine size Higher profitability 10 MW 150 m 160 m

October 30, 2007 © SKF Group Slide 3 Wind turbine concepts - Horizontal drivetrain - 3 Rotor blades - pitch and speed controlled

October 30, 2007 © SKF Group Slide 4 Main driver for Competitiveness Competitiveness Wind Energy Investment cost Reliability Availability Operation cost Maintenance and Repair concept High degree of integration Lighter Lower investment cost Higher repair cost Lower availability Low degree of integration Heavier Higher investment cost Lower repair cost Higher availability

October 30, 2007 © SKF Group Slide 5 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 6 Gearless and Hybrid 1

October 30, 2007 © SKF Group Slide 7 Gearless designs Requires a tight runout limit Go for a bearing system which is able to live with small clearance or preload Cross located TRB Double row TRB combined with CRB

October 30, 2007 © SKF Group Slide 8 Hybrid designs Requires a very small bearing distance and main bearing should be integrated into the design Nautilus TM bearing Bearing distance = row distance

October 30, 2007 © SKF Group Slide 9 2 Designs with gearbox (a flashback of drive train development)

October 30, 2007 © SKF Group Slide 10 The early years (mid 80´s to mid 90´s) Challenges: Pioneer period Very few experience No resources No established structures but enthusiastic pioneers Design features: Simple concepts Rotor directly applied to the gearbox Input shaft No rotor bearings Few moving parts Overdesigned ? Rotorhub direct mounted on input shaft To generator

October 30, 2007 © SKF Group Slide 11 Turbine size are growing through the 90ties Challenges: Still Pioneer period Business model ? Few resources Turbine growth Increased gear ratio Design features: Drive train became more complex since weight was increasing Higher 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 12 The MW class (1.5MW) Challenges: Wind turbine industry got recognized Rapid company growth Market pressure increase Feed in tariff decreasing Pressure on turbine prices Design features: Almost all turbines are designed with 3 point suspension Reduced to one rotor bearing Gearbox torque arms to support rotor load Rotor has to be removed before gearbox disassembly

October 30, 2007 © SKF Group Slide 13 The Multi Megawatt class (5MW offshore) Challenges: Reliability and availability became extremely important Design features: Main shaft are equipped with SRB and CARB TM Gearbox can be exchanged without taking down the rotor No internal forces by using the CARB TM concept. No rotor loads on the gearbox torque support

October 30, 2007 © SKF Group Slide 14 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 15 The multi Megawatt Class (high integration) Challenges: Light weight design Reduced drive train dynamic Design features: Main shaft are equipped with Nautilus TM (DRTRB) bearing Light weight rotor shaft Preloaded bearings

October 30, 2007 © SKF Group Slide 16 Drive train development Rotor carried by Gearbox input shaft till 1996 Up to 300 kW 2 point suspension 3 point suspension Seperate rotor shaft Carried by 2 bearings 2006 – – 5 MW MW – 2.5 MW – 1000 kW today 5 MW and bigger Nautilus concept High degree Of integration Low degree Of integration Nautilus TM DRTRB / CRB SRB / CARB

October 30, 2007 © SKF Group Slide 17 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 extended range Cross located TRB