Download P12441: Thermoelectric Power Pack

P12441: Thermoelectric Power
Pack
Andrew Phillips
Colin McCune
Lauren Cummings
Xiaolong Zhang
Customer Needs
Needs Importance
Description
Comments/Status
Component cost
1
3
Cheap cost of system
2
1
5 year life span (3x use per day)
3
2
No user interaction for system protection
Should be handled by system
4
3
User-friendly operation
Minimal user interaction
5
2
Operational in harsh environments
Exposure to moisture/salinity
6
1
Ability to charge auxiliary device
7
3
Plan to apply to team 12442’s stove
8
2
Fan runs at start-up
9
3
Safe to operate
10
1
System must be transportable
11
3
Thermoelectric use
12
1
Package shall be 3’’ x 3’’ x 1.5’’ and 3 lbs
13
3
Rugged design
Multiple start/restart cycles
Survive crush test and drop test
Importance Scale: 1 - Low, 2 - Moderate, 3 - High
Engineering Specifications
Spec
Description
Importance Units Marginal Target
Comments/Status
1
Component Cost
3
$
10
10
2
Product Life Span
2
Years
1
5
3
Battery Lifespan
1
Years
1
5
4
Aux charging
2
Wh
1
7
Being able to charge ~2 cell
phones per use.
5
Fan Battery size
3
Wh
1
2.5
Energy required for 5 product startups
6
Weight
1
lb
0.5
3
Include battery packs
7
Volume
1
in
.5x.5x.5
3x3x1.5
Include battery packs
8
User actions during
operational cycle
1
#
2
0
Assume 2 hr/use and 3 uses/day
Importance Scale: 1 - Low, 2 - Moderate, 3 - High
Engineering Specs
Customer Needs
Cheap Cost of System
Component Cost
5 Year Lifespan
No Interaction for System
Protection
Product Lifespan
User Friendly Operation
Battery Lifespan
Aux Charging
Fan Battery Size
Endure Harsh Environments
Charge Auxiliary Device
Apply to P12442’s Stove
Fan Runs at Start-up
Weight
Safe to Operate
Volume
User Interaction During
Cycle
Transportable
Thermoelectric Use
Size Req. (3x3x1.5), Under
3lbs
Rugged Design
Control Power
to System
Monitor TE
Output
MPPT
Monitor Open
Circuit Voltage
Functional
Decomposition
Of TEG Power
Control Voltage
Run Fan
Control Fan State
Control Voltage
Manage TE
Power
Charge Fan
Storage
Limit Current
Control Current
Monitor
Storage Level
Turn Off Current
Control Voltage
Limit Current
Run Aux
Control Current
Monitor Device
Storage Level
Turn Off Current
Control Voltage
Charge Aux
Storage
Limit Current
Control Current
Monitor
Storage Level
Turn Off Current
Function Decomposition Enclose System
Under a
certain size
House system
Under a
certain weight
Protect from
environment
Enclose
System
Protect
system
Protect from
dropping
Protect from
crushing
Connect to fan
Provide
connections
Connect to TE
Connect to
AUX
Block Diagram
Comparison of Old and New Systems
P11461
P12441
• Purely analog system,
“dumb”.
• Power intensive system
• Did not understand how the
TEG operated until late in
the project.
• Utilize microcontrollers to
make “smart” system.
• Utilize MPPT technology to
guarantee maximum power
is delivered to system.
• Utilizing knowledge from
previous project.
Moving Power Point Tracking (MPPT)
Equations of Operation
Power Generated:
𝑊 = 𝛼 𝑇ℎ − 𝑇𝑐 𝐼 − 𝑅𝑒 𝐼2
𝑑𝑊
= 𝛼 𝑇ℎ − 𝑇𝑐 − 2𝑅𝑒 𝐼𝑚𝑎𝑥 = 0
𝑑𝐼
Maximum Current:
𝛼(𝑇ℎ − 𝑇𝑐 )
𝐼𝑚𝑎𝑥 =
2𝑅𝑒
Voltage Created:
𝑊
𝑉=
= 𝛼 𝑇ℎ − 𝑇𝑐 − 𝑅𝑒 𝐼
𝐼
Moving Power Point Tracking (MPPT)
Equations of Operation
Perturb and Observe (P&O)
Samples the output voltage, then calculates the derivative of the IV curve.
Very effective, easy to implement, but can oscillate under rapidly changing conditions.
Incremental Conductance (INC)
Very similar to the P&O method, but this measures the incremental conductance of
the PSU to calculate the derivative of the IV curve.
More Accurate than P&O, but can still oscillate and is more difficult to implement.
Constant Voltage Method
Estimates the maximum power point voltage to the OC voltage at 76%.
76% is normally a good estimate, but can easily vary.
Very easy to implement.
wastes energy taking measurements and the peak might not be at 76%.
Power from TEG with a 75 Degree
Temperature Difference
5.0%
4.5
1.6
4.5%
4
4.0%
3.5
Power (W)
3.5%
1.2
Voltage (V)
1.4
Efficiency
1.8
3.0%
y = -2.5626x + 4.0509
R² = 1
3
2.5
1.0
2.5%
Power
2
0.8
2.0%
Module
Q
1.5%
Efficien
cy
0.6
0.4
1.5
1
1.0%
0.5
0.2
0.5%
0.0
0.0%
0
0
0.5
1
0
0.2
0.4
0.6
1.5
Current (A)
Current (A)
0.8
1
1.2
1.4
Power from TEG with a 175 Degree
Temperature Difference
4.0
5.0%
7
4.5%
3.5
6
4.0%
2.5
3.0%
2.0
Efficiency
Power (W)
3.5%
Voltage (V)
3.0
5
y = -2.7341x + 6.4522
R² = 1
4
2.5%
3
2.0%
1.5
1.5%
2
1.0
1.0%
1
0.5
0.5%
0
0.0
0.0%
0
0.5
1
1.5
2
0
0.5
1
2.5
Current (A)
Current (A)
1.5
2
2.5
Power from TEG with a 225 Degree
Temperature Difference
6.0
5.0%
8
4.5%
7
5.0
4.0%
3.0%
3.0
2.5%
2.0%
Efficiency
Power (W)
3.5%
4.0
Voltage (V)
6
y = -2.7934x + 7.5668
R² = 1
5
4
3
2.0
1.5%
2
1.0%
1.0
1
0.5%
0
0.0
0.0%
0
0.5
1
1.5
2
0
0.5
1
2.5
Current (A)
Current (A)
1.5
2
2.5
Power Management
• Using the MPPT, maximum power can be
harvested from the TEG. When maintaining a
200 degree temperature difference across the
TEG, 4V at 1.25 A can be obtained.
• This voltage can then be boosted to a voltage
that can be used by the fan and auxiliary
output.
• The boost converters must be designed to
allow for a range of input voltages.
Boost Converters
• When the switch is closed
current in passed through
the inductor. The
capacitor supplies the
output voltage to the
load.
• When the switch is
opened the inductor
maintains that current
and the current loop
passes through the diode
charging the capacitor
and powering the load
Boost Converter Operations
Output Voltage In CCM
𝑉𝑠
𝑉𝑂 =
1−𝐷
• This equation is for a purely resistive load, this
equation will need to be modified as to
accurately model the behavior of the boost
converter with an RL load.
• This can be done in the ORCAD suite.
Top 10 Risks (Part 1)
ID Risk Item
1
Exceeding
target cost
per unit
Effect
Cause
Likelihood Severity Importance Action to Minimize Risk
- Component
cost
- Other features of the end
- Manufacturing 3
product may be not included
cost
- Unit will not have full
Device
functionality
2 requires too
- Unstable behavior when
much power
operated
- Poor design
and component 2
selection
3
3
9
- Minimize the amount of
components
- Increase the functionality of All Team
existing components(ex: have
more tasks run within the uC)
6
- Design to be as power
efficient as possible
- Utilize MPPT functions
- Using the uC as much as
possible
All Team
All Team
All Team
- Component
failure
System
- The stove will take longer to
- Bug in the code
cannot power heat up
3
in the uC
2
fan during
- Take longer for the TEG to
- Improper
"warm up" provide full power
design/part
selection
1
2
- Design the unit to operate
on battery power
- Ensure the uC operates
correctly
Going over
- Difficult to be able to fund
4 development
further development
budget
3
3
- Track spending
- Ordering correct parts
- Proper testing
- Poor planning
1
Owner
Importance Scale: 1 - Low, 2 - Moderate, 3 - High
Top 10 Risks (Part 2)
ID Risk Item
Effect
- Sell less units
Complexity - Improper use
5
of operation - Reduce system
lifetime
Decreased
6
Reliability
End of
7 lifetime
disposal
Power
8 storage
capacity
9 ESD
Cause
Likelihood Severity Importance Action to Minimize Risk
- Poor Design
1
- Fewer sales
- Poor part selection
- Unit will get
- Poor fabrication
damaged more often - Poor design
- Pollution
- System startup
failure
- Cannot charge
devices without a
fire
- Electronics failure
- More replacement
parts will be
necessary
3
3
- Minimize user interaction
- Make simple to operate
- Design the unit to be as robust
as possible
- Choose high-lifetime
components
- Use ROHS parts; use less
batteries/heavy metal
components
- Increase total lifetime of the
unit
Owner
All
Team
All
Team
1
3
3
- Battery chemicals Heavy metals with the 3
PCB
1
3
- Poor system design
- Poor system storage 1
capacity
2
2
- Use high-capacity storage to
meet customer specs
Battery
Team
6
- Follow ESD prevention
measures
- Ensure proper grounding
All
Team
6
- Strict scheduling milestones
- Effective and reachable
deadlines
- Component delivery time
- Ordering parts early enough
All
Team
- Poor grounding
- Poor ESD prevention 2
in the labs
- Poor planning,
- Less time for de- Complex system
Prototype
bugging
- Poor testing
10 construction
- Failure to deliver on procedures
time
time
- Unforeseen
circumstances
2
3
3
All
Team
MSD I
10 Weeks
Week One
Week Two
Week Three
Project Assignment
TEG Unit Testing
Functional Decomposition
Customer/Engineering Needs
Project Risks
Winter Break, Three Weeks
uC Development
MPPT Selection/Coding
Charging Circuit/Converter Investigation
Week Four
Team Re-Group, Report Vacation Results
Week Five
System Design Presentation
Week Six
Week Seven
Week Eight
Week Nine
Week Ten
Software Team
Further uC Work
Interface with HW
Develop MPPT Code
Hardware Team
Charging Circuit Design
Interfaces to the uC, Fan,
and User Interaction
MSD II
10 Weeks
Week One
Week Two
Week Three
Week Four
Week Five
Week Six
Week Seven
Week Eight
Week Nine
Week Ten
Software Team
Hardware Team
Preliminary
Demonstration of working
MPPT Code
Stable DC-DC Voltage
Conversion Circuitry
Software Team
Optimized MPPT Code
Successful Interface with
HW Team
Software Team
Full Functionality with
HW Team, Further
Optimized Code
Hardware Team
Successful Battery
Charging and Fan Control,
Interface with uC Team,
PCB Layout
Hardware Team
Full Functionality with uC
Team, PCB
Fabrication/Construction
Successful Final Demonstration/Project Delivery