ORNL/TM-2010/280 An Assessment of Flywheel High Power Energy Storage Technology for Hybrid Vehicles December 2011 DOCUMENT AVAILABILITY Reports produced after January 1, 1996, are generally available free via the U.S. Department of Energy (DOE) Information Bridge. Web site http://www.osti.gov/bridge Reports produced before January 1, 1996, may be purchased by members of the public from the following source. National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone 703-605-6000 (1-800-553-6847) TDD 703-487-4639 Fax 703-605-6900 E-mail [email protected] Web site http://www.ntis.gov/support/ordernowabout.htm Reports are available to DOE employees, DOE contractors, Energy Technology Data Exchange (ETDE) representatives, and International Nuclear Information System (INIS) representatives from the following source. Office of Scientific and Technical Information P.O. 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The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. ORNL/TM-2010/280 Materials Science and Technology Division An Assessment of Flywheel High Power Energy Storage Technology for Hybrid Vehicles James G. R. Hansen David U. O’Kain * * David U. O’Kain is retired from ORNL and is participating in this assessment as a consultant to ORNL December 2011 Prepared for Vehicle Technologies Program, Office of Energy Efficiency and Renewable Energy, Department of Energy Prepared by OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37831-6285 managed by UT-BATTELLE, LLC for the U.S. DEPARTMENT OF ENERGY under contract DE-AC05-00OR22725 This page intentionally left blank. ii TABLE OF CONTENTS LIST OF TABLES .....................................................................................................................v LIST OF FIGURES ................................................................................................................ vii LIST OF ABBREVIATIONS AND ACRONYMS ................................................................ ix 1. EXECUTIVE SUMMARY ..................................................................................................1 2. INTRODUCTION ................................................................................................................4 3. BACKGROUND ..................................................................................................................5 3.1 Flywheel High Power Energy Storage for Hybrid Vehicles .......................................... 5 3.2 Hybrid Electric Versus All-Mechanical Flywheel System Implementation .................. 6 3.3 Energy Stored and Delivered ......................................................................................... 7 3.4 Flywheel Stresses and Materials .................................................................................... 9 4. STATE OF THE ART IN FLYWHEEL HIGH POWER ENERGY STORAGE ..............13 4.1 Maturity of Flywheel Systems ..................................................................................... 19 4.2 Flywheel System Performance Parameters .................................................................. 22 4.3 Flywheel Systems Compared to Batteries and Ultracapacitors ................................... 27 5. FLYWHEEL SAFETY AND CONTAINMENT ...............................................................32 5.1 Composite Rotors Have Different Failure Characteristics ........................................... 32 5.2 Design Approaches To Reduce Flywheel Risk ............................................................ 33 5.3 Flywheel Standard for Safe and Reliable Operation for Space Applications .............. 36 6. CONCLUSIONS.................................................................................................................37 7. RECOMMENDATIONS ....................................................................................................38 8. REFERENCES ...................................................................................................................39 APPENDIX A – SUMMARY INFORMATION PROVIDED BY DEVELOPERS OF FLYWHEEL ENERGY STORAGE SYSTEMS ................................................................. A-1 APPENDIX B – FIA ENVIRONMENTALLY SUSTAINABLE MOTOR SPORT POLICY .................................................................................................................................B-1 APPENDIX C – HOOP STRESS IN A THIN ROTATING RING ......................................C-1 APPENDIX D - THICK RIGHT CIRCULAR CYLINDER RIMS AND ROTORS WITH VARIABLE THICKNESS ................................................................................................... D-1 APPENDIX E - EVALUATION OF THE ENERGY STORAGE REQUIREMENT FOR A LIGHT DUTY VEHICLE ................................................................................................. E-1 iii This page intentionally left blank. iv LIST OF TABLES Table 2-1. Flywheel requirements ............................................................................................ 4 Table 3-1. Max specific energies for thin ring flywheels made of different materials ........... 10 Table 4-1. Nominal weight and specific power for non-energy storage components of Toyota hybrid electric vehicles ........................................................................................................... 13 Table 4-2. Respondent organizations ..................................................................................... 14 Table 4-3. Level of maturity of flywheel systems ................................................................. 15 Table 4-4. Performance summary of flywheels for hybrid vehicle applications ................... 17 Table 4-5. Flywheels compared with USABC Power Assist HEV Battery Goals ................. 30 Table 4-6. Flywheels compared with USABC Plug-in HEV Battery Goals .......................... 30 Table 4-7. Flywheels compared with USABC Goals for Advanced Batteries for EVs ......... 31 Table 4-8. Flywheels compared with FreedomCar ultracapacitor end-of-life requirements .. 31 v This page intentionally left blank. vi LIST OF FIGURES Figure 3-1. Comparison of typical hybrid electric and mechanical energy storage and power delivery systems ........................................................................................................................ 7 Figure 3-2. Delivered energy versus speed ratio ...................................................................... 8 Figure 3-3. Idealized flywheel – rotating thin ring with wall thickness t ................................. 9 Figure 3-4. Flywheel rim specific energy vs radius ratio and velocity ................................... 11 Figure 3-5. Flywheel rim energy density vs radius ratio and velocity .................................... 12 Figure 4-1. Peak power versus delivered energy .................................................................... 24 Figure 4-2. Specific power versus specific energy ................................................................. 25 Figure 4-3. Power density versus energy density ................................................................... 26 vii This page intentionally left blank. viii LIST OF ABBREVIATIONS AND ACRONYMS AC Alternating Current AFRL Air Force Research Laboratory AIAA American Institute of Aeronautics and Astronautics ANSI American National Standards Institute BEV Battery Electric Vehicle CCM Centre for Concepts in Mechatronics CFT Clutched Flywheel Transmission CRADA Cooperative Research and Development Agreement CVT Continuously Variable Transmission DARPA Defense Advanced Research Projects Agency DC Direct Current DOE U.S. Department of Energy DOT U.S. Department of Transportation EV Electric Vehicle FHSPV Flywheel Hybrid System for Premium Vehicles FIA Fédération Internationale de l'Automobile FMECA Failure Mode Effects and Criticality Analysis HEV Hybrid Electric Vehicle ICE Internal Combustion Engine IGBT Insulated Gate Bipolar Transistor ISS International Space Station g Acceleration of gravity, 9.81 m/s2 J Joules KERS Kinetic Energy Recovery System LLNL Lawrence Livermore National Laboratory kW Kilowatts kWh Kilowatt-hours LEESS Lower Energy-Energy Storage System MLC Magnetically Loaded Composite MTBF Mean Time Between Failures NEV Neighborhood Electric Vehicle OEM Original Equipment Manufacturer ORNL Oak Ridge National Laboratory PAHEV Power Assist Hybrid Electric Vehicle PHEV Plug-In Hybrid Electric Vehicle PM Permanent Magnet PNGV Partnership for a New Generation of Vehicles RPM (rpm) Revolutions per Minute SPU Surge Power Unit UPS Uninterruptible Power Supply USABC United States