Flywheel Energy Storage

Transcription

1 Flywheel Energy Storage An Alternative to Batteries for UPS Systems Daryl R. Brown Pacific Northwest National Laboratory GLOBALCON 2004 March 25, 2004

2 Outline Project Background Technology Description Technology Application Specific Products Case Study Summary and Conclusions 2

3 Project Background Fort McPherson, Georgia Application Federal Energy Management Program/New Technology Demonstration Program Federal Technology Alerts Project Scope 3

4 So What s a Flywheel? A form of mechanical or kinetic energy storage Energy is stored by causing a device to spin on its axis Energy storage is proportional to flywheel mass and the square of rotational speed. Conceptually simple: key is integration with electrical system 4

5 Motor-Generator with Flywheel Motor Flywheel Generator 5

6 Motor-Generator with Flywheel and Power Electronics AC DC DC AC VSD Motor Flywheel Generator Rectifier & Inverter 6

7 UPS System With Battery and/or Flywheel 7

8 Potential Applications Almost anywhere batteries are currently used in UPS systems Substitute for batteries Supplement to batteries With or without backup generation Key time-oriented characteristics Batteries 15 minute backup Flywheels 15 second backup Generators 10 seconds to full power 8

9 Battery/Flywheel Comparison (1) Backup power period much longer for batteries Standby power consumption less for batteries Initial cost generally less for batteries Life-cycle cost generally less for flywheels Design life much longer for flywheels 9

10 Battery/Flywheel Comparison (2) Operating temperature range wider for flywheels Frequent cycling much easier for flywheels Flywheel reliability better than single battery string Flywheels more compact than batteries Flywheels avoid chemical release issues Flywheel maintenance less frequent/complicated 10

11 Flywheel Design Variations Rotational speed Rotor material Type of bearings Use of vacuum enclosure 11

12 Active Power Flywheel 12

13 Designed Power Solutions Flywheel 13

14 Piller Flywheel 14

15 Urenco Power Technologies Flywheel 15

16 Installation Requirements Hardware for attaching to concrete slab Cabling for connection to DC bus of UPS system DC disconnect switch AC connection for auxiliary equipment Must match DC bus voltage Wise to consult UPS manufacturer to ensure electrical compatibility 16

17 Maintenance Requirements Generally less frequent and less expensive than for batteries Changing cabinet air filters Check/change vacuum pump oil Replacement of mechanical bearings Replacement of vacuum pump 17

18 Case Study Bldg. 200, Ft. McPherson, Georgia FORSCOM HQ Houses critical command, control, and communications equipment Requires reliable power supply on 24/7 basis 18

19 Previous UPS System kva units operating in parallel 4 wet cell battery strings, one for each 500 kva UPS unit, occupying 2400 SF room adjacent to UPS room Diesel-fired generators 19

20 UPS System Condition Diesel generators could reliably start within 10 seconds One battery string had failed, reducing system capability and creating a hazardous environment Other battery strings unreliable Annual battery maintenance approximately $30,000 20

21 Current Design Requirements Peak power demands reduced since building first constructed Two 500 kva units operating in parallel now required. One 500 kva unit could meet critical power demand, but two needed to meet system reliability requirement 21

22 Why Did They Get the Flywheels? Wet cell battery same initial cost, but shorter life and more maintenance VRLA battery half the initial cost, but much shorter life and more maintenance Could reclaim 2400 SF room for other uses Diesel generators could start reliably and quickly, so longer backup period of batteries of little value Eliminated battery environmental and safety issues 22

23 Flywheel Cabinet 23

24 Flywheel Cabinet Internals 24

25 Two 250 kva Flywheels per Cabinet 25

26 Summary and Conclusion DC flywheel energy storage systems can be used as a substitute or supplement for batteries in UPS systems. Batteries offer a significantly longer storage period, but this may not matter depending on application. Batteries will usually have a lower first cost, but flywheels offer longer life, reduced maintenance, smaller footprint, and better reliability. DC flywheel energy storage will usually have a lower life-cycle cost compared to batteries. 26

27 Additional Battery/Flywheel Comparative Data in Paper/FTA Purchase costs Installation costs Routine maintenance costs Periodic maintenance costs Footprint Standby power consumption Example life-cycle cost comparison Additional specific application summaries 27

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29 How do I get a copy? Download PDF from FEMP website: < Get a hard copy: < Get on FEMP NTDP distribution list: < 29