14. gearless wind turbine technology - mr varhala rao k

99thth Green Power 2010: CIIGreen Power 2010: CII14&15 July 201014&15 July 2010

Chennai Trade Centre, Chennai Chennai Trade Centre, Chennai

Gearless Wind Turbine Technology:Gearless Wind Turbine Technology:StateState--ofof--thethe--ArtArt

ReGen Powertech Pvt Ltd, Chennai

ReGen Powertech Pvt Ltd, Chennai, India

New Technology Trends : Wind Turbine DesignNew Technology Trends : Wind Turbine Design

v For the past Quarter century, conventional Wind Turbine Design used a step-up Gear Box to increase the slow rotational speed of a Wind Turbine Rotor to high speed at which conventional Generator spins.

This standard industry approach has started changing for the past few years with New Technology Trends and Advances such as Gearless Wind Turbine Designs and Perman ent

Magnet Generators (PMG).

This is the start of the next revolutionary cycle of the Wind

Turbine Industry.

2 / 3 3



v As Wind Turbines have grown in size over the past decade,

Gear Box b reak downs head the list of failure, with the biggest economic consequences for Plant Owners.

v The main driving force behind the trend to do away with Gear Boxes is fear of Gear Boxes failure.

v Market d emand is for a simple Drive Train with fewer

components.

3 / 3 3ReGen Powertech Pvt Ltd, Chennai, India


v Not many IEC Class II Wind Resource areas are available in

the country now . All the remaining Wind Energy Potential is from IEC Class III and IV Wind Resource areas. That means energy Production is to be maximised by New Technology Wind Turbines and by reducing downtime of the machine with

equipment failures and improving the availability of the machine.

v No Gear Box is the most reliable Wind Turbine Configuration.

4 / 3 3


Outline of the PresentationOutline of the Presentation

1. Requirements for Wind Turbines for Low-wind Regimes2. Generator Systems for Wind Turbines

• Doubly-Fed Inductions Generators• Direct-Drive Synchronous Generators

3. Gearless Wind Technology – State-of-the-Art

4. Advanced Gearless Technology• Design Characteristics• Winding Specification and Manufacturing

5. Efficiency Comparison in Relation to Geared Systems

6. Conclusions

5 / 3 3ReGen Powertech Pvt Ltd, Chennai, India

Wind Becoming Cost CompetitiveWind Becoming Cost Competitive

Source:

Shell Global Scenarios

Cost trend of wind-generated electricity at sites > 8.5 m/sav. wind speed:

How about low-wind regimes with < 8.5 m/s???

ReGen approach: Maximising the energy productionReducing the total cost with focus on O&M

6 / 3 3


Low Wind Speed Turbines Low Wind Speed Turbines –– Basic RequirementsBasic Requirements

Special features of low wind speed turbines:1. Reduced capital investment through mass and load minimisation:

- Minimized extreme loads in load case “50-year storm”.- Reduced extreme loads in operating gust load cases.- Minimum fatigue loads by intelligent controller design.

How to capture low-wi nd si tes for wind energy?Low-wind regimes need low wind speed turbines for achieving competitive cost of energy (COE)!

7 / 3 3

2. Reduced O&M cost through design simplicity and redundancy:- No gearbox through direct drive generators.- Minimum number of proven components.- Redundant design of auxiliary systems and sensors.

3. Increased energy capture, especially at partial load:- Highly efficient components (blades, generator, converter).- Larger rotor on same turbine platform (low specific power W/m2)- Taller towers, especially in very low-wind regimes.


Low Wind SpeedLow Wind Speed Turbines Turbines ––Reduced O&M CostReduced O&M Cost

Reduced O&M cost through design simplicity and redundancy

No gearbox through direct drive generators:- No gearbox failures.- No oil cooling / monitoring systems.

No generator excitation through permanent magnets:- Very s imple and reliable generator rotor.- No rotor pole winding issues.

No generator cooling system:- Very s imple passive generator air-cooling.

No separate generator bearings:- Turbine bearings also perform as generator bearings.

No couplings, no mechanical brake:- Generator rotor directly flanged to turbine rotor.- Pure aerodynamic braking by full-span blade pitch.

8 / 3 3

Nacelle -Conventional Nacelle-Vensys Tower Head


Low W ind Speed Turbines Low W ind Speed Turbines –– Increased Energ y C aptureIncreased Energ y C apture

Increased energy capture, especially at partial load

Taller towers, especially in low-wind regimes:- Up to 0.5% more energy y ield per meter hub height: 100 m vs. 65 m means up to 18% higher output!

Low specific turbine power < 400 W/m2:- Large and effic ient rotor blades for given turbine platform.

Wide-range variable-speed plus low cut-in rotor speed:- Highest rotor effic iency under partial load.- Moderate fatigue loads under full load.

Highly efficient generator, especially under partial load:- No excitation losses through permanent magnets.- No gearbox losses through direct drive.- Simple and effic ient frequency converter using latest technology of low-loss IGBTs.

9 / 3 3

ReGenWEC at NSL-BhimasamudraWind Farm


M echan ical P ower Sou rce

Variab le SpeedIn put

Tran sm is si on

M achin eT ype

Rotor

Sta tor

Frequ encyCon vert er

Out put

D irect G earbox

I ndu ct ion M achinesL ow- Speed Synch ro nous

+ Un convent iona l Concep ts

Con ventio nal

S ynchron ous

E xciterWind ing

P erman entM a gnets

3- Ph as eWind ing

3-P ha seWi ndin g

3 -P has e

Wind ing

3 -P has e

Wind ing

Fu ll-S ize

2Q or 4Q

F ull -Size

2Q or 4Q

Fu ll- Size

4Qu adrant

30 % P N4 Quad rant

El ect r ical P ower Network

Fixed Volta ge + F req uency

Squ irrel

Cage

3-P has eWi ndin g

Power Conversion of VariablePower Conversion of Variable--Speed SystemsSpeed Systems

10 / 33


VariableVariable--Speed Speed –– The 2 Competing SystemsThe 2 Competing SystemsGeared drive with doubly-fed induction generator

• Component sourcing from different suppliers

• Small dimensions and masses (easier manufacturing an transport)

• Smaller power converter rating (but almost identical converter cost)

Advantages compared to gearless systems:

11 / 33ReGen Powertech Pvt Ltd, Chennai, India

VariableVariable--Speed Speed –– The 2 Competing SystemsThe 2 Competing Systems

• Fewer components, higher reliability• No gearbox (less losses, failures,

maintenance, noise)• Higher partial load efficiency (3 – 5%

higher energy production for permanent-magnet excitation)

• No generator slip rings and brushes (lower maintenance cost)

• Low voltage, low speed, reliable generator rotor (especially true for permanent-magnet excitation)

• Grid-code requirements easily achieved by simple power converters

Direct-drive synchronous generator – Advantages:

converter

12 /3 3


Pros & Cons of VariablePros & Cons of Variable--Speed SystemsSpeed SystemsDou bly -f ed inducti on ge nerat or wi th gear bo x

Direct -dr iv e generat or wit h dir ect -c urrent exci tat io n

Direct -dr iv e generat or wit h permanent-magnet exc ita ti on

Main cur ren t su pplie rs Vesta s, GE, Gam esa, Norde x, RE power,

etc.

Enercon, M Torres, La gerwe y, e tc.

VENSYS, Rege nPowert ec h, G ol dwi nd ,

etc.

Avera ge d rive trai n efficie ncy 89 % 90 % 93 %

Towe r t op mass 100 % 130 % 100 %

Man ufac turi ng c ost 100 % ~ 1 10 % ~ 1 00 %

Reliability – – + ++

Power qualit y – ++ ++

Comp one nt s ou rcing + – –

13 / 33

Direct drive with permanent magnets offers the highest potentialsGeneral industry trend: automation, railways, marine propulsion, etc.


Ener

gy p

rodu

ct /

kJ/

m3

Year of d eve lo pme nt

General Drive Syst em Trends:Increasing number of variable-speed vs. fixed speed applications (system advantages)

Rising energy cost → efficiency becoming more important

Low noise requirements

Increasing number of high-torque drives with permanent magnets (omission of gearbox)

General Drive System Trends General Drive System Trends –– Permanent MagnetsPermanent Magnets

Paper producti on Ship propu lsi onCranes / Lo gis tic s Railw ay a p plic ati o ns

14 / 33


Permanent Magnet GeneratorsPermanent Magnet Generators

v Use of a PMG in a Direct Drive Turbine can reduce overall mass of Drive Train to that of a Gear Box-plus-Generator in a conventional Wind Turbine of equal size

v PMG provides an overall increase in efficiency since it produces more power at part load operation than achieved by a Conventional Generator, which reaches peak efficiency at full

load. High efficiency at part load increases the output of WindTurbines, which only operate in full load operation during periods when the wind is blowing hard enough for the machine

to be operating at full load capacity.


Gearless Technology Gearless Technology –– Passive Generator CoolingPassive Generator Cooling

Passive cooling system• Totally enclosed generator, stack cooling with backside cooling fins

• No ambient air gets contact with winding

• Perfectly cooled magnets, high flux, no de magnetisation

• Outstanding cooling performance: max. temperature rise 70 °K !!!

1External rotor withpermanent magnets

1

Internal stator2

Cooling duct3

23

16 / 33


Gearless Technology Gearless Technology –– Generator Cooling Generator Cooling PerformancePerformanceMeasured generator temperature rise (Regen Powertech w ind turbines)

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

0 4 0 0 8 0 0 1 2 0 0 16 0 0

P_ m i ttel in kW

delta

_T in

K

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

0 2 4 6 8 1 0 1 2 14 1 6

v _W i n d in m / s

delta

_T in

K

40°C + 70°C = 110°C: Temperature stress less than Class B (130°C)


The VENSYS 70 / 77 Generator:

Rated output: 1.5 MWStator voltage: 690 VRated speed: 19.0 or 17.3 rpmInternal statorExternal rotorInsulation class: Class FDimensions: D < 5 m, L < 1.5 mGenerator mass: 45 tons

Gearless Technology Gearless Technology –– The GeneratorThe Generator

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Generator Stator at ReGen’s Tada Manufactur ingFacility


Advanced winding designForm-wound windings with rectangular conductors

High copper filling of the slots → lower losses

Low dielectric stress between single conductors!

Low-tech impregnation process sufficient

Gearless Technology Gearless Technology –– Generator WindingGenerator Winding

19 /3 3ReGen Powertech Pvt Ltd, Chennai, India

Suitable Variable-speed Technology:

• Passive diode rectifier: high effic iency, low EMI.

• Very low harmonics to the grid.

• Automatic adjustment to 50 Hz or 60 Hz.

• Measured and certified low-voltage ride through operation.

• Full reactive power control.• High reliability: air cooling with only 1 fan, robust converter control.

• Good serviceability : modular design with fast IGBT exchange.

“Simple converter” of highly integrated IGBT modules• Integrated current sensor • Integrated temperature sensor• Integrated heat sink• Integrated driving circuit & protection

Gearless Technology Gearless Technology ––Frequency ConverterFrequency Converter

20 / 33


Air intake

Cool & clean

Cooling airexhaust Effective tower base cooling:

Tower internal air < 10°K above ambient

Gearless Technology Gearless Technology –– Optimised Tower Base Optimised Tower Base CoolingCooling

1. Fre que ncy c onv ert er

(IGBT he at si nks)2. Filter ch okes

3. Tra nsfo rm er

4. Air exh aust5. Towe r in ter nal air

1

2

2

3

5

4

Source: VENSYS Energy AG


Rated total efficiency over 94%

Up to 5% higher efficiency than conventional drive train!

3 – 5% higher energy production!

Efficiency measured directly: • = 1 – Pout / Pin

Gene rat or only

Fre que ncy

conve rte r

Tot al dri ve

Typic al ge ne rat or

+ ge ar box (calc. )

PM DirectPM Direct--Drive Efficien cy Drive Efficien cy –– Load Test of 1.2 MW Load Test of 1.2 MW SystemSystem

Source: VENSYS Energy AG

22 / 33


PM DirectPM Direct--Drive Efficiency Drive Efficiency –– Measured Power Measured Power CurveCurve

Source: VENSYS Energy AGWindtest Report WT6547/08

23 / 33

Power Pe rformance M easurement Report


PM DirectPM Direct--Drive Efficiency Drive Efficiency –– Measured Power Measured Power CurvesCurves

Considerably better cPcurve, especially at low output

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PM DirectPM Direct--Drive Efficiency Drive Efficiency –– Energy ProductionEnergy Production

Considerably better energy production, especially at low wind sites!!

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Ener

gy p

rodu

ctio

n /

GW

h

Calculated Ener gy Pr oduction Based on Measured Power Curves

0.00 0

1.00 0

2.00 0

3.00 0

4.00 0

5.00 0

6.00 0

7.00 0

4.0 5.0 6.0 7.0 8.0Average w ind s pe ed / m/ s

VENSYS 7777

Conventional 1.5 MW

+ 9.4 %+ 109 MWh

+ 6.8 %+ 152 MWh

+ 5.6 %+ 197 MWh

+ 4.9 %+ 230 MWh

+ 4.3 %+ 248 MWh

ReGen Powertech Pvt Ltd, Chennai, India26 / 33

Turbine Requirements for Low-wind Regimes:• Highly effic ient transmission system (gearbox, generator and converter), partial load

effic iency of special importance for low-wind regimes• Highly effic ient rotor blades, variable-speed plus low cut-in rotor speed

• Low specific power < 400 W/m2: larger rotor for given turbine platform

ConclusionsConclusions

Wind Generator Systems:• Direct-drive systems with permanent magnets offer distinct advantages and will become increasingly competitive (general industry trend)• Direct-drive systems with permanent magnets offer energy yield advantages between 3% and 10%: the lower the wind speed, the larger the benefit

Future Perspectives:• Optimised permanent-magnet generators for gearless wind turbines will appear on the market offering further cost advantages over geared turbines

• Optimised turbines for low-wind regimes will open up new markets worldwide


AdvantagesAdvantages of ReGen/VensysReGen/Vensys V77 WEC comparedWEC compared to thethe otherother conventionalconventionalWECsWECs -SummarySummary

Ø Direct Dr ive Design

Ø Permanent Magnet Excitation

ØPassive A ir Cooling System

Ø Safety System

Ø Power Electronics

M ove to Topic-Performance of ReGen WE Cs-few details


1. Direct1. DirectDriveDriveDesignDesign

The WEC functions without Gear Box, interm ediate Shaft and Couplings

Advantages:

i. Less wear and tear, smooth oper ation is achieved.

ii. Breakdown time due to the failures of the above com ponents is elim inated.

iii. The intens ive maint enance required for the above components is elim inated.

iv. The Part-load efficiency of the Generator increases.

Click


2. PermanentPermanent MagnetMagnet ExcitationExcitationThe excitation required for the Generator is produc ed by very high qual ity permanent magnets(Nd Fe B) m ounted on the Rotor yoke and they ar e corrosion pr otected.

Advantages :

i. No need to generate Direct Current for excit ation, so energy is saved.

ii. There will be no power cons umed, even when the Wind is v ery low.

iii. The Slip-ring assem bly to transmit the current to generat or rotor is not required.

iv. Associated circ uitry and equipm ent/com ponents requir ed for exc itation are el iminated.

v. Stable and sufficient gener ator excitation can be achieved for the entire life span of the turbine. Click


3. PassivePassive AirAir CoolingCooling SystemSystemThe cool a ir flow which drives the rotor is gu ided dir ectly over the war m generator parts by special ly formed Ducts.

Advantages:

i. This ensures h igh ly efficient and fa il-safe oper ation.

ii. No additional fans or contro l units ar e required.

iii. The degree of cooling corresponds directly to the power output. Henc e, constant gener ator temperature is maint ained a ll the times.

Click


4. SafetySafety SystemSystemThe triply redundant blade pitc h system contro ls the power output and, if necess ary, slows or stops the rotation of the turb ine by turning the rotor b lades out of the wind. Toothed belts ar e used to trans mit the power from the motor for pitching the b lades. Maintenance-free double lay er capacitors( Ultra Caps), whos e capacity is not affected by temper ature, are us ed for backup ener gy storage. They supply the power necess ary for control ling the p itch of the blades (e.g) in cas e of a grid fai lur e.

Advantages: i. The rotor brakes, whic h are susc eptible to heavy wear, are not needed.

ii. The forces involv ed ar e distributed over many teeth, which minimiz es wear and virtually elim inates the risk of failure.

iii. Long l ife can be achieved by toothed belts.

iv. The use of toothed belts and Ultra Caps ens ures the m aintenance-free, fail-safe oper ation of the pitch system. Click


5. PowerPower ElectronicsElectronicsThe air-c ooled frequency conv erter designed es pec ial ly feeds the entir e power output of the generator into the public Grid. Sem i-Conductor d iodes ar e used to rectify the current on the gener ator side of the conv erter system. The activ e IGBT-modules on the gr id-s ide comply with a ll r equirem ents with r egar d to the supply of curr ent to the grid. The entire c onv erter system is of modular design. A further feature is the met hod of gr ounding the system.

Advantages:

i. The decoupl ing of generat or and grid with the he lp of the frequency converter m akes var iab le speed oper ation of the generator possible.

ii. This feature which leads to a higher power out put when oper ating under partia l load and a smoot her power output at full load.

iii. A maximum of grid stab ility is a lways guaranteed.iv. It requires very little in the way of maintenance.v. Grounding system ens ures low EMI-loads, whic h sign ificantly incr eas es

the oper ation reliab ility of the sensors and controllers.Click


Start of next revolutionary Cycle …

NSL-Bhimasamudra Wind Farm

ThankThank YouYou

14. gearless wind turbine technology - mr varhala rao k

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