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Capacitive Electric Load Leveling Systems
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  1. Capacitive Electric Load Leveling Systems Conceptual Design Review November 9, 2004 Erin Davis Fred Jessup Benton O’Neil

  2. Presentation Outline • Customer Needs • Key Research Issues • Design Methods and Alternatives • Deliverables • Team Productivity

  3. Customer Needs • Reduce vehicle weight • Improve fuel efficiency • Achieve system payback period of one year • Demonstrate feasibility for tractor-trailers

  4. Key Research IssuesDetermined by Testing • Battery • Starting requires high-power density storage • Peak current ~600A • Large, heavy battery • Alternator • Supplies current regardless of engine load • Reduces engine efficiency during heavy loading • If controlled, could improve engine efficiency

  5. Possible Problems to be Addressed In Design • Battery Problem • High power requires heavy lead acid batteries • Non ideal charging and discharging • Alternator Problem • Supplies current regardless of engine mechanical load • Both Battery and Alternator Problem

  6. Design #1 – Addresses Battery • Converter controls discharging and charging of battery • Capacitor bank assists in starting engine and supplies some peak current due to low ESR • Battery current is normalized through control of DC/DC converter

  7. Scope Definition - Addressing Batteries • Pros • Ultracapacitors are ideal for supplying high current • Feasible as bolt-on system – no internal vehicle signals needed • Significant decrease in weight with reduced battery size • Improved battery charging algorithm • Increased battery life • Cons • No direct fuel efficiency improvement • Ideal charging algorithm is difficult to determine • Bi-directional DC/DC converters

  8. Design #2 – Addresses Alternator • Capacitor bank provides peak power through control of DC/DC converter • Battery starts engine with assistance of capacitors • Engine load due to alternator is normalized by switching algorithm

  9. Scope Definition – Addressing Alternator • Pros • Direct improvement in fuel efficiency • Reduction in battery power and size • Cons • Complex control system • Not feasible for bolt on system • Need for engine load monitoring • No guarantee of battery life improvement • High power DC/DC converter required

  10. Design #3 – Addresses Both • Combination of Design #1 and Design #2 • Battery current normalized by DC/DC converter • Engine load due to alternator normalized by switching algorithm

  11. Scope Definition - Addressing Both • Pros • Increase in battery life • Increase in fuel efficiency • Cons • Complex control • Large and complex system

  12. Initial Designs Decision Matrix

  13. Decision Matrix Results • Focus on Design #1 • Issues still needing to be address • Ideal charging algorithm • Specific DC/DC converter selection • Bi-directional versus unidirectional DC/DC converters • Buck, Boost, Buck-Boost • Capacitor bank sizing • Battery sizing • Physical • Power

  14. Design Focus ConclusionBattery: starting engine, weight issues • Basic Operation • Caps start engine • Small battery charges caps though converter • Alternator charges battery

  15. Modeling • Present system • Battery starting a 3.0L Lincoln LS engine • Discharging Capacitors • Starting engine • Charging Capacitors • Battery charging the capacitors through different converter topologies

  16. Modeling Objectives • Test different scenarios quickly, easily and safely • Compare design alternatives • Capacitors • Size, capacitance, and weight • Maximum and minimum voltage, charging time, and usable energy • Peak current magnitude, engine speed, motor torque • Converters • Control methods • Topologies • Verify the design prior to implementation

  17. Simulink Output

  18. Capacitor Selection • Using MathCAD • Parameters obtained from MAXWELL • Prices for set energy needed to start engine

  19. Converter Decision Matrix

  20. Preliminary Cost Analysis

  21. Remaining Design Choices • Battery • AH rating necessary to supply loads during engine off • Acceptable weight of battery • Control • Analog vs digital • Finalized converter topology

  22. Key Deliverables • As of Now • Stock System Models • Preliminary Cost Analysis • As of December 15, 2004 • Design Description Report • Detailed Parts List

  23. Foreseen Challenges • Design • DC/DC Converter • Control System Development • Installation • Engine Heat Signature • Packaging • Wiring, connections • Vibration • EMI Shielding

  24. Team Productivity • CELLS Team Webpage • Project Status Reports • Weekly meeting agendas / minutes • Extracurricular Activities

  25. Questions?