With or without gearbox? Drive train development for wind turbines
Technologie-Workshop “Windenergie – Quo Vadis?”
Andreas Urban / Business Engineer SKF Österreich AG
2010-12-02
(from a supplier perspective)
October 30, 2007 © SKF Group Slide 3
Wind energy is a fast growing market
Within the next 10 years 6 times
the capacity
Offshore is coming
Strong growth in Asia (China)
October 30, 2007 © SKF Group Slide 5
Basic drive train concepts: integration degree
Gearless Turbines (Direct Drive)
Turbines with gearbox Hybrid Turbines
Generator speeds [rpm] 1200 – 1800 150 - 400 12-30
Degree of integration
October 30, 2007 © SKF Group Slide 6
Geared vs. Gearless
Will this picture change in the coming years?
If so, what are the drivers?
85% geared 15% gearless
October 30, 2007 © SKF Group Slide 7
Main issues and trends
• In many new developments for Multi-Megawatt turbines geared versions are slowly loosing ground in favor of hybrid and direct drive ones – but why?
• Reliability is more and more becoming a major issue – less components less risk of failures?
• Emerging offshore taking off – increased need of high reliability • Reduce O&M cost, low maintenance efforts, lower lifetime cost/kWh electricity • Requirements for increased service life • Expanding turbine warranty periods • Easy maintainability and replaceability • Optimize turbine efficiency • Drive train integrations • Reduce nacelle weight (compact designs) • Reduce turbine cost • Supply chain and logistics constraints • Shift in new turbines designs in favor of stiff
rotor bearing arrangements
October 30, 2007 © SKF Group Slide 9
Key challenges on main shafts
Main shaft challenges: • Ambient conditions, understanding of loads induced • Design philosophy (rigid/flexible) • Serviceability • Space limitations • Integration vs. disintegration • Weight • Structural deformations • Cost vs. Quality • Design for reliability
In particular for bearings: • Bearing selection for stiffness resp. flexibility • High load, high torque and low speed application • Permanently changing loads and torque • Extreme loads • Lubrication regime and contamination
October 30, 2007 © SKF Group Slide 10
Basic drive train concepts: integration degree
Degree of integration
2-point suspension 3-point suspension
Moment bearing (no shaft)
2 separate housings
1 joint housing
1 bearing in gearbox separate Integrated
in gearbox
Moment bearing (no shaft)
Full integration
2-point suspension
Moment bearing
Common hub + axis No axis
Turbines with gearbox Hybrid Turbine
Direct Drive
Nautilus DRTRB+CRB TRB+TRB
Nautilus SRB+CARB
DRTRB+CRB
SRB Nautilus Nautilus (TRB+TRB) (SRB+SRB)
October 30, 2007 © SKF Group Slide 11
Key challenges in wind gearboxes
Wind gearbox challenges: • Ambient conditions, understanding of loads induced • Serviceability • Space limitations • Weight • Vibration characteristics and levels • Cost vs. Features vs. Quality vs. Availability • Design for reliability
In particular for bearings: • Extremely high torque at very low speed • Low load and high speed applications • Low speed and torque (idling) • Permanently changing loads and torque • Extreme loads, brake loads & negative torque • Oil cleanliness, lubrication regime and contamination
October 30, 2007 © SKF Group Slide 12
Key challenges in wind gearboxes
BUT: Bearings are often not the root cause of failures!
Bearings fail mainly
in the planetary stage
on high speed shafts
October 30, 2007 © SKF Group Slide 13
Key challenges in wind generators
Wind generator challenges: • Ambient conditions, understanding of loads
induced • Serviceability • Space limitations, compactness • Weight • Vibration characteristics and levels • Cost vs. Quality vs. Availability • Design for reliability and robustness • Noise levels • Efficiency
In particular for bearings: • Lubrication regime – wear and starvation problems • Vibration and shock loads • Contamination • Electrical erosion • Quiet running (noise and vibration levels) • Temperatures
October 30, 2007 © SKF Group Slide 15
Design considerations - weight
Source EER (Emerging Energy Research)
gearless hybrid
October 30, 2007 © SKF Group Slide 16
Design considerations
Criteria Geared Gearless Remarks
CAPEX o o To be proven
OPEX o + If reliability really higher for gearless
Reliability o + Less components – less failures Really true?
Supply chain - Logistics
+ o Rare earth?
Serviceability o o To be proven
Efficiency o + No gearbox friction losses avoided
Weight + o Refer to previous slide
CAPEX … Capital expenditure
OPEX … Operational expenditure
October 30, 2007 © SKF Group Slide 17
How will the future WTG look like?
Race on reliability?
New concepts?
Innovation vs. evolution?
October 30, 2007 © SKF Group Slide 18
Pitch bearings
Yaw bearing
Mainshaft housings and locknuts
Condition Monitoring WindCon/WebCon
Couplings
Automatic distributed lubrication system
Monitoring and diagnostics services
Mechanical repairs & refurbishment
Sealing solutions
Bolt tensioning tools
Tower alignment services
Engineering Consultancy Services
Plain bearings
Maintenance tools and grease
SKF contribution to wind turbine technology
Gearbox bearings TRB/CRB/SRB/CARB/DRTRB
Generator bearings DGBB/Insocoat/Hybrid
Mainshaft bearing(s) SRB/CARB/TRB/CRB//Nautilus