Conceptual Design Review by hilen

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

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 Issues
Determined by Testing
• Battery
Starting Engine - Battery and Alternator Current
500 Starting Engine

– Starting requires highpower density storage
• Peak current ~600A • Large, heavy battery

400

300 Battery (A) Alternator (A) 200 Alternator Charging Battery 100 Turning Key "OFF"

Current (A)

• Alternator
– Supplies current regardless of engine load
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Turning Key "ON" 0 0 1 2 3 4 5 6 7 8 9

-100 Time (s)

• 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 1 Design #2 3 Design #3 2

Benefit to Battery
Benefit to Alternator Time to Complete Cost Weight

0.15

0.05

3

1

2

0.20 0.20 0.20

1 1 1

2 2 2

3 3 3

Size
Efficiency Total

0.10
0.10 1.00

1
1 1.10

2
2 2.10

3
3 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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Battery: starting engine, weight issues

Design Focus Conclusion

• 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_0 350 216dollars Price_0 013 175dollars Price_0 008 444dollars Price_0 010 606dollars Price_2 500 300dollars To tal_Weight _0350 1.19lb To tal_Weight _0013 3.351lb To tal_Weight _0008 6.173lb To tal_Weight _0010 8.102lb To tal_Weight _2500 11.188 lb Charge_Time_0 350 13.125  s Charge_Time_0 013 14.464  s Charge_Time_0 008 16.5s  Charge_Time_0 010 17.333  s Charge_Time_2 500 16.667  s

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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?

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