Digital Displacement wind-turbine transmission

Transcription

1 Digital Displacement wind-turbine transmission 14 th European Conference Latest Technologies on Renewable Energy Heriot Watt University 21 st February 2011 Jamie Taylor 1

2 Doing more with less Wind-turbine transmissions Artemis Intelligent Power Digital Displacement (DD) 2

3 The Crown Estate Round 3 1: Moray Firth 25 GW of additional UK offshore wind energy generation capacity by : Firth of Forth 3: Dogger Bank 4: Hornsea 5: East Anglia 9: Irish Sea 8: Atlantic Array 6: Southern Array 7: West Isle of Wight 3

4 Wind-turbine transmission options Mechanical gearbox Gearbox Induction generator Inverter Direct drive Generator Inverter Hydrostatic transmission Pump Motor Generator 4

5 Gearbox transmission 5MW Hub Gearbox Doubly-fed induction generator 5

6 Direct-drive wind-turbine 7.5 MW turbine expected soon but no offshore models. 6

7 DD pump Digital Displacement wind-turbine transmission DD motors Synchronous generators 7

8 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 overtorque protection. Modular construction for in-situ component replacement. 3-5 highly-stressed slidingcontact lines, high referred generator inertia seen by wind rotor, no over-torque protection. Large diameter heavy generator has high inertia. 8

9 DD wind-turbine transmission - schematic Variable-displacement hydraulic pump Hydraulic accumulator Variable-displacement hydraulic motor Synchronous generator 9

10 To commercialise Digital Displacement technology and other innovations in fluid power by licensing to industrial partners. 10

11 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. 11

12 mechanical commutation ( 1980s ) electronic commutation ( 1990 ) 12

13 Digital Displacement - idling 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 13

14 Digital Displacement - pumping The low pressure valve (LPV) can be shut within a few milliseconds by sending a pulse of 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 14

15 Variable displacement - pumping Enabling fraction 100% 75% 50% 25% 0% VIDEO VIDEO Required flow (command) 18 litre/min 15

16 Laboratory prototype of DD wind-transmission Ring-cam pump 20 rpm 2-bank 68-cylinders 180 litre/rev 1.8 MW generator drive motor 1500/1800 rpm 4-bank 24-cylinders 960 cc/rev 800 kw 16

17 Ring-cam pump 816 pump strokes/revolution 24 cam-lobes 34 cylinders 17

18 High-speed generator drive motor 18

19 Artemis Digital Displacement wind-transmission Predicted efficiency compared with gearbox transmission 100% Efficiency 90% 80% DD transmission + synchronous generator 70% gearbox + DFIG + converter 60% 50% 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 Wind speed - m/s (Ref: DD wind transmission.xls) 19

20 Artemis Intelligent Power Ltd. 3 Edgefield Industrial Estate Loanhead Midlothian, EH20 9TB Scotland, UK Fax