Current and FutureWind Turbine Design Trends

Matthew Huaiquan Zhang

Content

• Current WTG Design Concepts

• Trends Shaping the Industry

• Possible Future Designs

Current WTG Design Concepts

Current WTG Design Concepts

Gear

SCIG

Soft-starter

Capacitor

Grid

Type AFixed speed (one or two)

• Simple and low cost• Robust and low maintenance• Compact size and light weight

• Low energy conversion• No control of active and reactive

power • Large power fluctuations• High mechanical stress• No LVRT ability

Drawbacks:

Current WTG Design Concepts

Gear

WRIG

Capacitor

Soft-starter

Variable resistance

Grid

Type BLimited variable speed

• 10% ~16% speed range• Simple and low cost• Improved energy conversion

• Limited speed range• Poor control of active and

reactive power• External resistance loss• No LVRT

Drawbacks:

Current WTG Design Concepts

Grid

DFIG

Gear

Reduced-capacity power converter

Type CReduced-capacity var. speed

• ±30% speed range• Rotor generates power (25~ 30% )• High power conversion (MPPT)• Active and react. power control• Low converter loss/cost• LVRT ability (additional equip.)

• Gearbox faults, especially for larger turbines

• Increased gearbox loads from grid transients

• Power quality can be improved

Drawbacks:

most popular

Current WTG Design Concepts

GridGear

PMSG/WRSG/SCIG/WRIG

Full-capacitypower converter

Type DFull capacity variable speed

• With or without gearbox• lower O&M costs (direct drive)• Maximum efficiency (low wind)• Better reactive power control• Strong grid support• LVRT ability (no add. equip.)• lower grid connection costs

• High converter cost/loss• Demagnetization (PMSG)• Heavy• More expensive ??

Drawbacks:

new star

Current WTG Design ConceptsType A Type B Type C Type D

Vestas:V27, V34, V47

Suzlon:S88-2.1MWS82-1.5MW

Vestas:V90-2.0MWV80-2.0MW

Gamesa:2.0MW platform

GE:1.5MW series

Sinovel

Repower…

Vestas:V112-3.0MW

GE Wind:GE110-2.75MW

Gamesa:G128-4.5MW

Siemens:SWT3.6-107

GoldWind

Enercon

Trends Shaping the Industry

Trends Shaping the Industry

Source: IEA 2013

The Larger the Better

• 20MW found feasible (UpWind, 2011).• Onshore transport and assembly constraints

Weight reduction!!

Trends Shaping the IndustryOptimising Power-to-Swept Area Ratio:Larger swept area with higher reach provides greater energy capture, improving performance and reducing the cost of wind energy (LCOE).

• More flexible and aerodynamic blades• Better pitch and drive chain control• Stronger blade bearing and pitch systems • Novel hub design & rotor architectures• Smart, stronger, lighter materials• Reduce tower-head-mass ratio• Deploy condition-monitoring systems

Trends Shaping the IndustryFriendly Grid IntegrationIncreasing wind penetration above 20% results in increasing amounts of wind dumping. Also, more wind power is connected to weak grid.

• Active and reactive power control• LVRT ability• Voltage support during grid faults• Better power quality

– Harmonics filtering– Voltage fluctuations, flickers and step-changes

• Predictable power production

Full Capacity Type D

Trends Shaping the IndustryDiverse Operation Conditions:In order to develop wind energy in areas which do not meet the standard IEC categories.

• Cold and icy climate– Materials for cold climate– De-icing ability

• Tropical cyclone– Extreme load survival

• High altitude• Aerodynamic design for low air density• Electrical insulation• Specific Cooling system

Trends Shaping the IndustryGoing OffshoreThe United Kingdom is set to install 18 GW capacity off the UK coasts by 2020. The conservative government has halted onshore wind subsidy scheme (RO and possibly CfD?)• More reliable machines

– Direct Drive: no gearbox failures– PMSG/SCIG: no rotor coil, no slip rings

• Larger size– 10 MW ~ 20 MW– Lower BOP cost

• Large-scale, long-distance transmission– New grid code

Possible Future Designs

Possible Future DesignsTransverse Flux PMSGThe flux lines lie in the perpendicular or, in other words, transversal plane to the direction of movement and that of current flow.

• High torque density, more compact size• Allows current and magnetic loading to

be set almost independently, resulting in a more favourable construction

Still to improve:• High flux leakage

Possible Future DesignsHigh-Voltage GeneratorWTG are commonly operated at 690 V with a good selection of standardised equipment.

• Reduced current and thereby reduced loss;

• Reduced generator size;• Higher efficiency, especially at

higher loads;• Possible direct grid connection;• Potential alternative for large

WTGs exceeding 3MW.

• High costs of high-voltage power electrics and auxiliaries;

• High safety requirements;

Drawbacks:

• Tjæreborg 2MW – 10kV• Growian 3MW – 6.3kV• Vestas V90-3.0MW - 1000V• Multibrid 5MW – 3300V• Zephros Z72-2.0MW – 4000V

Pioneers:

Possible Future DesignsSuperconductor GeneratorLarge wind turbine gearbox problems call for gearless multi-pole generators which are very heavy. It is crucial to reduce the weight for future 10-20MW wind turbines.

• 50~60% reduction in weight and generator size;

• High efficiency;• Reduced running costs;

• Cooling facilities still requires intensive research

Main Difficulty:

Possible Future Designs‘Flying Machine’Rotors on the kite act like propellers on a helicopter to launch it from the ground station. Once flying, air moving across the rotors forces them to rotate, driving a generator to produce electricity.

• Reach more powerful winds at higher altitudes, generating 50% more energy

• Eliminate 90% of the materials, low cost

http://www.google.com/makani

Possible Future DesignsBladeless/VortexIt works by taking advantage of a phenomenon called Kármán vortex street, which is a "repeating pattern of swirling vortices."

• No gears or bearings, reduces manufacturing and maintenance drastically;

• No lubrication needed, noiseless, thus more environmental-friendly;

• More efficient;

http://www.vortexbladeless.com/

Summary

• Full capacity generators are quickly becoming the industry mainstream;

• Direct-drive, full-capacity PMSGs are likely to dominate offshore market;

• Weight-reducing technologies are very attractive;• Radical new concepts are very interesting;

Thank you!