Capacitive Electric Load Leveling Systems

Report
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
2
Customer Needs
•
•
•
•
Reduce vehicle weight
Improve fuel efficiency
Achieve system payback period of one year
Demonstrate feasibility for tractor-trailers
3
Key Research Issues
Determined by Testing
• Battery
Starting Engine - Battery and Alternator Current
– Starting requires highpower density storage
500
Starting Engine
• Peak current ~600A
• Large, heavy battery
400
Current (A)
300
• Alternator
Battery (A)
Alternator (A)
– Supplies current regardless
of engine load
200
Alternator Charging Battery
Turning Key "OFF"
100
Turning Key "ON"
0
0
1
2
3
4
5
-100
Time (s)
6
7
8
9
10
• Reduces engine efficiency
during heavy loading
• If controlled, could improve
engine efficiency
4
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
5
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
6
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
7
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
8
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
9
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
10
Scope Definition - Addressing Both
• Pros
– Increase in battery life
– Increase in fuel efficiency
• Cons
– Complex control
– Large and complex system
11
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
12
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
13
Design Focus Conclusion
Battery: starting engine, weight issues
• Basic Operation
– Caps start engine
– Small battery charges caps though converter
– Alternator charges battery
14
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
15
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
16
Simulink Output
17
Capacitor Selection
• Using MathCAD
– Parameters obtained from MAXWELL
– Prices for set energy needed to start engine
Capacitor Pricing
P rice_ 03 5 0 2 16d ol lars
Tot al_ Weig ht _0 350 1 .19l b
Ch arg e_Ti me_0 35 0 1 3.1 25s
P rice_ 00 1 3 1 75d ol lars
Tot al_ Weig ht _0 013 3 .35 1l b
Ch arg e_Ti me_0 01 3 1 4.4 64s
P rice_ 00 0 8 4 44d ol lars
Tot al_ Weig ht _0 008 6 .17 3l b
Ch arg e_Ti me_0 00 8 1 6.5s
P rice_ 00 1 0 6 06d ol lars
Tot al_ Weig ht _0 010 8 .10 2l b
Ch arg e_Ti me_0 01 0 1 7.3 33s
P rice_ 25 0 0 3 00d ol lars
Tot al_ Weig ht _2 500 1 1.1 88l b
Ch arg e_Ti me_2 50 0 1 6.6 67s
18
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
19
Preliminary Cost Analysis
20
Remaining Design Choices
• Battery
– AH rating necessary to supply loads
during engine off
– Acceptable weight of battery
• Control
– Analog vs digital
• Finalized converter topology
21
Key Deliverables
• As of Now
– Stock System Models
– Preliminary Cost Analysis
• As of December 15, 2004
– Design Description Report
– Detailed Parts List
22
Foreseen Challenges
• Design
– DC/DC Converter
– Control System Development
• Installation
– Engine Heat Signature
– Packaging
• Wiring, connections
– Vibration
– EMI Shielding
23
Team Productivity
•
•
•
•
CELLS Team Webpage
Project Status Reports
Weekly meeting agendas / minutes
Extracurricular Activities
24
Questions?
25

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