Pulsed Power Load Support - Hebner-Gattozzi - May 2010


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Pulsed Power Load Support - Hebner-Gattozzi - May 2010

  1. 1. Pulsed Power Loads Support and Efficiency Improvementon Navy Ships<br />R. E. Hebner, J. D. Herbst, A. L. Gattozzi<br />Center for Electromechanics<br />University of Texas, Austin<br />May 20, 2010<br />
  2. 2. Statement of the Problem<br />Increasing demand for reliable electric power<br />Projected expansion of pulsed loads<br />Rising fuel costs<br />Technical Solutions<br /><ul><li>Advanced power generation
  3. 3. Energy storage technologies</li></li></ul><li>Study for the DDG51 Destroyer<br />High speed generators at 15,000 RPM 3 MW can be coupled directly to the gas turbine<br />Elimination of gear box<br />New class of power electronics allows decoupling of the 60 Hz distribution frequency from the generated frequency<br />Turbine speed can be adjusted to maximize SFC<br />Energy storage provides additional benefits<br />(details later) <br />
  4. 4. Notional 3 MW Power Module<br />
  5. 5. Benefits of Storage<br />Support of intermittent duty high power loads<br />Load leveling (more efficient turbine operation)<br />Power quality and stability improvement<br />Stiffer power bus<br />Single turbine at near full load instead of two turbines at fractional loads<br />Higher efficiency & expanded engine operational hours <br />Reduction of turbine thermal cycling<br />Maintenance reduction and operational life extension<br />
  6. 6. Storage Technologies Considered<br />Capacitors<br />Low energy density – not considered further<br />Batteries<br />Li-ion technology<br />Flywheels<br />Batteries and flywheels competitive evaluation on several points follows<br />
  7. 7. 1. Technology Readiness Level (TRL)<br />Li-ion batteries:<br />Preferred technology for low power electronics<br />Some developments in the kWh and kW (electric vehicles)<br />No MW level application identified low TRL<br />Flywheels:<br />UPS system up to 1 MW in commercial use<br />20 MW system being planned<br />
  8. 8. 2. Scaling<br />Li-ion batteries:<br />3 MW 10 minute power delivery is difficult<br />Practical packaging of large scale array is challenging<br />Lacking direct examples at these power levels, projections were made from installations with other battery chemistries<br />
  9. 9. S&C PureWave UPS System2.5 MVA, 60 s, Lead-Acid <br />Li-ion equivalent at 2.5 MW, 10 minutes = <br />121 m3<br />
  10. 10. Alaska Golden Valley Cooperative Project27 MW, 15 min, NiCd<br />Li-ion equivalent at 2.5 MW, 10 minutes = <br />116 m3<br />
  11. 11. 3. Performance Degradation<br />Li-ion batteries:<br />Capacity fade (temperature and depth of discharge cycles)<br />Energy capacity typically based on 1 hour discharge (1C rate)<br />In our case 10 min discharge = 6C rate <br />Higher internal resistance than other chemistries (higher heating)<br />
  12. 12. 4. Life<br />Li-ion batteries:<br />Short useful life relative to ship’s service life<br />May need to replace 3-4 times over 35 years<br />Support of pulsed loads and load leveling function will require frequent cycles<br />Asymmetrical charge / discharge rate<br />Flywheels:<br />Independent energy stored and power delivery<br />NASA study found no significant degradation after 110,000 deep discharge cycles<br />Can be designed for 35 years life<br />
  13. 13. 5. Reliability<br />Li-ion batteries:<br />Low voltage of 3.6 V/cell 188 cells needed for 680 Vdc bus to generate 450 V 60 Hz<br />Many strings in parallel to supply needed current<br />Several thousand cells needed on board<br />Failure of single cell impairs the whole system<br />Flywheels:<br />Based on standard rotating machine technology<br />
  14. 14. 6. Safety<br />Li-ion batteries:<br />Demonstrated catastrophic failure mode<br />Very sensitive to charging voltage (4% maximum overcharge limit)<br />New non-flammable electrolytes reduce energy and power by ~30%<br />Complex cell monitoring system (eliminates failed cell from array)<br />Based on all the issues above, flywheels are preferred technology<br />
  15. 15. Flywheel Storage<br />Upgrade main generator:<br />Package the system in the current volume of the AG9140 <br />Remove low speed generator and gearbox<br />Use high speed generator and power electronics<br />Integrate independent flywheel storage modules into existing power system:<br />Flywheel + motor/generator + power electronics + auxiliaries<br />
  16. 16. Stand-alone Flywheel Storage System(8 needed for 10 min. discharge)<br />
  17. 17. Table 1. Physical Characteristics for 2.5 MW, 10-minute UPS Energy Storage System<br />
  18. 18. Table 2. Electrical Characteristics for 2.5 MW, 10-minute UPS Energy Storage System<br />
  19. 19. Simulation Study of Common DC Bus Topology<br />
  20. 20. Simulation Studies: UPS Function<br />
  21. 21. Response of AC Grid to Loss of Gas Turbine Generator Set at t = 0.75 s<br />Flywheel Discharge and Recharge Cycles (Discharge (0-7 s) and Recharge (7-10 s))<br />
  22. 22. DDG51 Fuel Saving Estimate<br />Baseline parameters taken from BAA07-029: 4,000 hours of operation per year with a ship service power of 2525 kW (electrical) and a fuel cost of $100 per barrel<br />Turbine specific fuel consumption for the AE1107 engine provided by Rolls-Royce<br />Baseline fuel consumption using current DDG51 CONOPS with two AG9140RF units providing the required 2525 kW<br />Projected resulting fuel savings are $1.25 million per ship per year <br />