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Electro-Mechanical Batteries - Future Scoping and Applications

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Electro-Mechanical Batteries - Future Scoping and Applications ELECTRO-MECHANICAL BATTERIES - FUTURE SCOPING AND APPLICATIONS MINI PROJECT 2015 EPSRC Centre for Doctoral Training in Energy Storage and its Applications MINI PROJECT 2015 Mini Project 2015 DATE AUTHOR 16 April 2015 Thomas Bryden Thomas Bryden PhD Research Student Centre for Doctoral Training in Energy Storage and its Applications Faculty of Engineering and the Environment University of Southampton Highfield Campus Southampton SO17 1BJ UK Email: [email protected] Page 1 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications MINI PROJECT 2015 1 Contents Mini Project 2015 ________________________________________________________________________________________ 1 2 Executive Summary _________________________________________________________________________________ 4 3 Introduction _________________________________________________________________________________________ 5 4 Component Details __________________________________________________________________________________ 6 4.1 Rotor _______________________________________________________________________________________________________ 7 4.1.1 Strength _________________________________________________________________________________________________ 7 4.1.2 Vibration ________________________________________________________________________________________________ 9 4.2 Bearing design ____________________________________________________________________________________________ 9 4.3 Enclosure design _________________________________________________________________________________________ 11 4.4 Motor/generator design _________________________________________________________________________________ 13 5 Commercial Applications _________________________________________________________________________ 15 5.1 Transport applications __________________________________________________________________________________ 16 5.1.1 Purely mechanical systems ___________________________________________________________________________ 16 5.1.2 GKN Hybrid Power ____________________________________________________________________________________ 17 5.2 Grid connected applications ____________________________________________________________________________ 17 5.2.1 Uninterruptable Power Supply ______________________________________________________________________ 18 5.2.1.1 Active Power ____________________________________________________________________________________ 18 5.2.2 National grid frequency regulation __________________________________________________________________ 19 5.2.2.1 Beacon Power ___________________________________________________________________________________ 20 5.2.2.2 Temporal Power _________________________________________________________________________________ 21 5.2.3 Isolated grid renewable penetration and frequency regulation ___________________________________ 21 5.2.3.1 ABB_______________________________________________________________________________________________ 21 5.2.4 Fusion research _______________________________________________________________________________________ 23 6 Current Research __________________________________________________________________________________ 24 6.1 Current research projects _______________________________________________________________________________ 24 6.1.1 NASA research_________________________________________________________________________________________ 24 6.1.2 Boeing research _______________________________________________________________________________________ 25 6.2 Individual component research _________________________________________________________________________ 26 Page 2 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications MINI PROJECT 2015 6.2.1 Rotor ___________________________________________________________________________________________________ 26 6.2.2 Bearings _______________________________________________________________________________________________ 27 6.2.3 Enclosure ______________________________________________________________________________________________ 27 6.2.4 Motor/generator ______________________________________________________________________________________ 28 7 Design Study _______________________________________________________________________________________ 29 7.1 Tesla Model S car _________________________________________________________________________________________ 29 7.2 Boeing 702HP satellite platform ________________________________________________________________________ 30 7.3 JR EAST Series 400 electric train _______________________________________________________________________ 31 8 Conclusions ________________________________________________________________________________________ 32 9 References _________________________________________________________________________________________ 33 Appendix A ______________________________________________________________________________________________ 38 Appendix B ______________________________________________________________________________________________ 39 Appendix C ______________________________________________________________________________________________ 40 Appendix D ______________________________________________________________________________________________ 47 Appendix E ______________________________________________________________________________________________ 49 Appendix F ______________________________________________________________________________________________ 51 Page 3 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications EXECUTIVE SUMMARY 2 Executive Summary A detailed review of Electro-Mechanical Batteries (EMBs) is conducted. Future improvements that have the potential to overcome some of the EMB negative characteristics, namely low specific energy, high self discharge rates and high capital costs, are examined. The specific energy of an EMB is limited by the maximum tensile strength of the material chosen and so will increase as new stronger, lighter materials are discovered. The self discharge rate of an EMB is currently limited by the bearings and so may be decreased as superconducting bearings are used, Boeing is currently working on an EMB that will lose only 0.9% of its stored energy per hour. The high capital cost is mainly due to the use of expensive materials and the precision manufacturing techniques required. Initially all the components of an EMB are described and the specification limits determined, seen in Table 1. Table 1 - EMB specification limits SPECIFICATION COMPONENT LIMITS a Mass: ͙ = ͅ (Section 4.1.1) Specific Energy Rotor material ( ` Volume: ͙1 = ͅ (Section 4.1.1) Specific Power Motor/generator Power rating of motor/generator and control system Active magnetic bearing losses: Ohmic, Eddy current losses, Bearing hysteresis, power for power controller Efficiency Enclosure Proportional to Pressure^3 and Rotational Velocity^2 AC Permanent magnet motor/generator losses: Ohmic, Eddy Motor/generator current losses, hysteresis, power for power controller Current commercial applications are then reviewed. Commercially, EMBs are available for transport applications and grid connected applications. Grid connected applications include Uninterruptable Power Supply (UPS), National grid frequency regulation, Isolated grid renewable penetration and frequency regulation and Fusion research. A table, Table 3, is created comparing the specific energy of a selection of commercially available EMBs. Current EMB research is then described, including projects at NASA and Boeing as well as detailing research on each of the EMB individual components. The Boeing research project is particularly interesting as superconducting bearings are being used to achieve low self discharge rates. The author also suggests a method using magnetic coupling to enable multiple EMBs to be powered from one motor/generator. Finally a brief design study is conducted to determine the sizes of EMBs required for various applications. It is stated that an EMB currently could not be used to power a car. For a satellite application it is found that current commercially available EMBs are too heavy however if an EMB was designed specifically for the satellite it may be feasible. For a train application it is determined that EMBs could be used to reuse some of the energy currently lost during braking. Page 4 Thomas Bryden: Mini Project 2015 - Electro-mechanical Batteries - Future Scoping and Applications INTRODUCTION 3 Introduction Flywheels have been used to store energy for thousands of years, the earliest known example is the potter’s wheel 1. A flywheel works by storing energy in a rotating mass. Nowadays, flywheels can be attached to a motor/generator to create an EMB for energy storage, technical details of which are discussed in Section 4. Energy storage is required on a range of scales from small scale storage for handheld devices to large scale storage for national grids. EMBs are currently suitable for transport applications where they are used in regenerative braking systems 2 where their high cycle life makes them very competetive. EMBs are also currently used for frequency regulation on large 3 and small grids 4 where their fast response time enables them to keep the grid frequency within tight tolerance bounds. EMBs are also currently able to provide a few seconds of uninterruptable power supply, which can be used at data centres 5 or on small renewable grids with backup
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