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

Capacitive Electric Load Leveling Systems

Conceptual Design ReviewNovember 9, 2004

Erin Davis

Fred Jessup

Benton O’Neil

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Presentation Outline

• Customer Needs

• Key Research Issues

• Design Methods and Alternatives

• Deliverables

• Team Productivity

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Customer Needs

• Reduce vehicle weight

• Improve fuel efficiency

• Achieve system payback period of one year

• Demonstrate feasibility for tractor-trailers

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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

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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

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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

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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

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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

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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

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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

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Scope Definition - Addressing Both

• Pros– Increase in battery life– Increase in fuel efficiency

• Cons– Complex control– Large and complex system

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Initial Designs Decision Matrix

  Weighting Factor Design #1 Design #2 Design #3

Benefit to Battery

0.15 1 3 2

Benefit to Alternator

0.05 3 1 2

Time to Complete

0.20 1 2 3

Cost 0.20 1 2 3

Weight 0.20 1 2 3

Size 0.10 1 2 3

Efficiency 0.10 1 2 3

Total 1.00 1.10 2.10 2.80

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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

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Design Focus ConclusionBattery: starting engine, weight issues

• Basic Operation– Caps start engine– Small battery charges caps though converter– Alternator charges battery

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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

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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

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Simulink Output

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Capacitor Selection

• Using MathCAD– Parameters obtained from MAXWELL– Prices for set energy needed to start engine

Capacitor Pricing

Price_0350 216dollars Total_Weight_0350 1.19lb Charge_Time_0350 13.125s

Price_0013 175dollars Total_Weight_0013 3.351lb Charge_Time_0013 14.464s

Price_0008 444dollars Total_Weight_0008 6.173lb Charge_Time_0008 16.5s

Price_0010 606dollars Total_Weight_0010 8.102lb Charge_Time_0010 17.333s

Price_2500 300dollars Total_Weight_2500 11.188lb Charge_Time_2500 16.667s

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Converter Decision Matrix

Weighting Factor Buck Boost Buck-Boost

Energy Storage 0.40 3 1 2

Control Complexity

0.20 2 1 3

Low Voltage Charging

0.40 1 3 1

Total 1.00 2.00 1.80 1.80

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Preliminary Cost Analysis

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Remaining Design Choices

• Battery– AH rating necessary to supply loads during

engine off– Acceptable weight of battery

• Control– Analog vs digital

• Finalized converter topology

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Key Deliverables

• As of Now– Stock System Models– Preliminary Cost Analysis

• As of December 15, 2004– Design Description Report– Detailed Parts List

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Foreseen Challenges

• Design– DC/DC Converter– Control System Development

• Installation– Engine Heat Signature– Packaging

• Wiring, connections

– Vibration– EMI Shielding

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Team Productivity

• CELLS Team Webpage

• Project Status Reports

• Weekly meeting agendas / minutes

• Extracurricular Activities

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Questions?