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Stove
TEG
DC-DC
Converter
Battery
DC – DC Converter For a Thermoelectric Generator
Ciaran Feeney
4th Electronic Engineering Student
FYP Progress Presentation
Supervisor: Dr. Maeve Duffy
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Presentation Overview

Project overview

Progress to date

Future work and timeline

Questions
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Project Overview

Researchers in Trinity College Dublin are developing a
energy harvesting system for use in developing countries.

Generate electricity using a Thermoelectric Generator(TEG)
from excess heat produced during the cooking process.

Store energy generated in a battery

Use stored power in low power applications

This project focuses on providing an impedance match
between the source and load using a DC-DC Converter and
Microcontroller
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System Block Diagram
Stove
TEG
DC – DC
Converter
Microcontroller
Battery
Pack
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Progress To Date

Thermoelectric generator operation understood

Battery charge and discharge profile established

DC-DC converter Topology determined

Basic analysis of 1st SEPIC DC-DC converter circuit complete

Suitable Microcontroller found

Website online and blog regularly updated
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Thermoelectric Generator
Single Thermoelectric Couple
Full Thermoelectric Generator
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Thermoelectric Generator
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Thermoelectric Generator
Equivalent TEG Circuit Model
Battery Charge and Discharge
Profiles
Voltage increase with constant current 2A
3.7
3.6
3.5
3.4
Voltge across BAttery
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3.3
3.2
3.1
3
Vbatt
2.9
2.8
2.7
2.6
2.5
2.4
0
10
20
30
40
TIme(mins)
50
60
70
80
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Battery Charge and Discharge
Profiles
Discharge Through 3.3ohm Load
Approx Vload = 2.5
Approx Iload = .8
3.4
3.3
3.2
Voltage
3.1
3
2.9
Vbatt
2.8
2.7
2.6
2.5
2.4
0
20
40
60
80
100
Time (mins)
120
140
160
180
200
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DC-DC Converter

Require DC-DC converter that can provide an output voltage
above and below input voltage

Variation of Buck Boost topology decided upon

SEPIC DC-DC Converter

Non-inverting output

Isolation between output and input terminals due to coupling
capacitor
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DC-DC Converter
SEPIC Topology
SEPIC Converter 1st Prototype
Chosen Components
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DC-DC Converter
Input Voltage 4V
Matched Voltage 2V
Output Voltage .846V
Duty Cycle 41.8%
Efficiency 71.4%
Resistive Load
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DC-DC Converter
Efficiency
90
88
86
84
82
80
78
Effiiciency %
76
74
72
70
68
"Efficiency"
66
64
62
60
58
56
54
52
50
0
2
4
6
Input Voltage
8
10
12
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DC-DC Converter

Redesigned SEPIC Converter

Switching frequency is now 80kHz

Reduces size of components

Reduces cost

Diode Replaced by MOSFET

Circuit Components
Inductor Coupled
MOSFET
MOSFET
Coupling Capacitor
Input Capacitor
Output Capacitor
16uH 10A Wureth .0027ohm
NXP MOSFET Power 30V 98A N-CH MOSFETs
NXP MOSFET Power 30V 98A N-CH MOSFETs
Aluminum Organic Polymer Capacitors 16V 100uF 7Mohms
Aluminum Organic Polymer Capacitors 16V 100uF 7Mohms
Aluminum Organic Polymer Capacitors 16V 100uF 7Mohms
€5.83
€0.82
€0.82
€0.561
€0.561
€0.561
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DC-DC Converter

New Design Replacing diode with MOSFET

Design includes Equivalent Series Resistances for
components
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Microcontroller


Required characteristics

PWM (Pulse Width Modulation)

Analog Input pins
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Low power consumption

Low cost

Easily programmable
Chosen Controller – Arduino Uno

Fulfills all of the above criteria

Cost €24.31
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Abundance of information available online
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Future Work

MPPT

Initial Investigation shows that load current should be maximized
as the battery can be viewed as a purely voltage source.

Preliminary investigation into current sensors reveals that a hall
effect sensor should be used instead of a current sense resistor.

Sensor to be placed in series with battery

A hall effect sensor has been singled out for further investigation
The Allegro Microsystems Current Sensor
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Rated for 5A

Low series resistance 1.2mΩ

Cost low €6.54
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185mV per Amp
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Future Work


Charge Algorithm
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Constant current to 3.6V
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Constant voltage of 3.6V until charge cut off current is reached or
30 minutes has elapsed
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Voltage to be monitored across battery
Yet to be decided whether a constant voltage will be applied

Researchers in Trinity College Dublin to decide this
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Future Work

Implementation of Circuit with

Thermoelectric Generator

Microcontroller implementing MPPT

Simulated cooking profile/Actual cooking duration
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Battery

Efficiency analysis over cooking profile

Identify were improvements can be made
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Timeline
Efficiency Analysis
MPPT & Charge
1st Draft of Mock Algorithm
Circuit Analysed
and Deficiencies
located. Circuit
Optimised to
minimise
deficiencies.
16th of January
2011
Final Circuit and Testing
MPPT & Charge
Algorithm
Bench Demonstration
decided upon
Finished circuit
and completed. completed
Final Thesis
th
incorporating MPPT Week of the 14
of March 2011
and charge
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14 of February algorithm. Circuitry
1st of April 2011
2011
tested over full
charge and
discharge cycle
with TEG and
battery.
7th of March 2011
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Questions