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Digital Displacement®

wind-turbine transmission

14th European Conference“Latest Technologies on Renewable Energy … ”

Heriot Watt University21st February 2011

Jamie Taylor

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”Doing more with less”

• Wind-turbine transmissions

• Artemis Intelligent Power

• Digital Displacement® (DD)

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“25 GW of additional UK offshore wind energy generation capacity by 2020”

1: Moray Firth

2: Firth of Forth

3: Dogger Bank

4: Hornsea

5: East Anglia

6: Southern Array

7: West Isle of Wight8: Atlantic Array

9: Irish Sea

The Crown Estate Round 3

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Wind-turbine transmission options

Mechanical gearbox

Direct drive

Hydrostatic transmission

Inverter

Generator

Pump Motor

Generator

Gearbox

Induction generator

Inverter

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Gearbox transmission – 5MW

Gearbox

Doubly-fed induction generator

Hub

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Direct-drive wind-turbine

7.5 MW turbine expected soon but no offshore models.

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DD pump

DD motors

Synchronousgenerators

Digital Displacement®

wind-turbine transmission

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Digital Displacement®comparison matrix

Digital Displacement comparison matrix – 1.5 MW

Digital Displacement transmission

Gearbox + doubly-fed induction generator

Direct drive

Mass of transmission ~ 7.5 tonnes ~ 14 tonnes > 30 tonnes

Fault ride-through Several seconds buffering, depending on accumulator size.

150 ms with power electronics.

150 ms with power electronics.

Cost

Potentially low: due to low

weight and elimination of power electronics and transformer.

Medium: requires more

steel, power electronics and step-up transformer.

High: requires very large

amounts of steel and copper.

Reliability & Serviceability

Multiple parallel stress paths, low inertia, inherent over-torque protection. Modular

construction for in-situ component replacement.

3-5 highly-stressed sliding-contact lines, high referred generator inertia seen by

wind rotor, no over-torque protection.

Large diameter heavy generator has high inertia.

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DD wind-turbine transmission - schematicVariable-displacement

hydraulic pumpHydraulic

accumulatorVariable-displacement

hydraulic motorSynchronous generator

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“To commercialise Digital Displacement®technology

and other innovations in fluid power by licensing to industrial partners.”

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DD Origins: Salter’s Duck

Slow ring–cam pump& fast axial motors

University of

Edinburgh 1970’s

“The intelligent control of large forces is not a bad description of the requirements of renewable energy”.

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mechanical commutation ( 1980s )

electronic commutation

( 1990 )

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• Fluid flow from each cylinder of a radial piston machine is controlled by a fast solenoid poppet valve

• The valve is kept open by a permanent magnet latch

• When the valve remains open, fluid flows alternately into and out of the tank surrounding the pump

• That cylinder is disabled, does no work, is at tank pressure, and consumes very little idle power

Digital Displacement - idling

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• The low pressure valve (LPV) can be shut within a few milliseconds by sending a pulseof current to a coil

• When the valve is shut at bottom dead centre, that cylinder is enabled, and does one pumping stroke

• After the pumping stroke, the valve reopens, the cylinder intakes from the tank and remains idle until the coil is pulsed again

Digital Displacement - pumping

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Required flow (command)

En

ablin

g f

ract

ion

0 18 litre/min

0%

25%

50%

75%

100%

...000000000000...

...111111111111...

...101010101010...

...100010001000...

1

1

1

1

1

1

0

0

0

0

0

0...111011101110...

VIDEO

VIDEO

Variable displacement - pumping

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Laboratory prototype of DD wind-transmission

generator drive motor1500/1800 rpm4-bank 24-cylinders 960 cc/rev 800 kW

Ring-cam pump20 rpm2-bank 68-cylinders180 litre/rev 1.8 MW

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816 pump strokes/revolution

34 cylinders 24 cam-lobes

Ring-cam pump

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High-speed generator drive motor

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Artemis Digital Displacement®

wind-transmission Predicted efficiency compared with gearbox transmission

(Ref: DD wind transmission.xls)

50%

60%

70%

80%

90%

100%

0 5 10 15 20 25Wind speed - m/s

Efficiency

DD transmission + synchronous generator

gearbox + DFIG + converter

At low wind-speeds, the higher DD efficiencies are due to being able to operate at aerodynamically-optimum rotor-speeds and to reduce pressure proportionally to power.

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Artemis Intelligent Power Ltd.

www.artemisip.com

3 Edgefield Industrial EstateLoanheadMidlothian, EH20 9TBScotland, UK

���� +44 131 440 6260Fax +44 131 516 8151