+ DC – DC Converter For a Thermoelectric Generator Ciaran Feeney 4 th Electronic Engineering Student FYP Progress Presentation Supervisor: Dr. Maeve Duffy StoveTEG DC-DC Converter Battery

+ Presentation Overview Project overview Progress to date Future work and timeline Questions

+ 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

+ System Block Diagram TEG Stove DC – DC Converter Battery Pack Microcontroller

+ Progress To Date Thermoelectric generator operation understood Battery charge and discharge profile established DC-DC converter Topology determined Basic analysis of 1 st SEPIC DC-DC converter circuit complete Suitable Microcontroller found Website online and blog regularly updated

+ Thermoelectric Generator Single Thermoelectric CoupleFull Thermoelectric Generator

+ Thermoelectric Generator

+ Equivalent TEG Circuit Model

+ Battery Charge and Discharge Profiles

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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

+ DC-DC Converter SEPIC Topology SEPIC Converter 1 st Prototype Chosen Components

+ DC-DC Converter Input Voltage 4V Matched Voltage 2V Output Voltage.846V Duty Cycle 41.8% Efficiency 71.4% Resistive Load

+ DC-DC Converter

+ Redesigned SEPIC Converter Switching frequency is now 80kHz Reduces size of components Reduces cost Diode Replaced by MOSFET Circuit Components Inductor Coupled16uH 10A Wureth.0027ohm€5.83 MOSFETNXP MOSFET Power 30V 98A N-CH MOSFETs€0.82 MOSFETNXP MOSFET Power 30V 98A N-CH MOSFETs€0.82 Coupling CapacitorAluminum Organic Polymer Capacitors 16V 100uF 7Mohms€0.561 Input CapacitorAluminum Organic Polymer Capacitors 16V 100uF 7Mohms€0.561 Output CapacitorAluminum Organic Polymer Capacitors 16V 100uF 7Mohms€0.561

+ DC-DC Converter New Design Replacing diode with MOSFET Design includes Equivalent Series Resistances for components

+ Microcontroller Required characteristics PWM (Pulse Width Modulation) Analog Input pins Low power consumption Low cost Easily programmable Chosen Controller – Arduino Uno Fulfills all of the above criteria Cost €24.31 Abundance of information available online

+ 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 Rated for 5A Low series resistance 1.2m Ω Cost low € mV per Amp

+ Future Work Charge Algorithm Constant current to 3.6V Constant voltage of 3.6V until charge cut off current is reached or 30 minutes has elapsed 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

+ Future Work Implementation of Circuit with Thermoelectric Generator Microcontroller implementing MPPT Simulated cooking profile/Actual cooking duration Battery Efficiency analysis over cooking profile Identify were improvements can be made

+ Timeline Efficiency Analysis 1 st Draft of Mock Circuit Analysed and Deficiencies located. Circuit Optimised to minimise deficiencies. 16 th of January 2011 MPPT & Charge Algorithm MPPT & Charge Algorithm decided upon and completed. 14 th of February 2011 Final Circuit and Testing Finished circuit completed incorporating MPPT and charge algorithm. Circuitry tested over full charge and discharge cycle with TEG and battery. 7 th of March 2011 Bench Demonstration Final Thesis Week of the 14 th of March st of April 2011

+ Questions