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 Issues Determined 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 Weighting FactorDesign #1Design #2Design #3 Benefit to Battery Benefit to Alternator Time to Complete Cost Weight Size Efficiency Total

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 Conclusion Battery: 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 Weighting FactorBuckBoostBuck-Boost Energy Storage Control Complexity Low Voltage Charging Total

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 WebpageTeam Webpage Project Status Reports Weekly meeting agendas / minutes Extracurricular Activities

25 Questions?