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Final Year Project Project Progress Presentation Title: Energy Conversion for low voltage values. Supervisor: Dr.Maeve Duffy Supervisor: Dr.Maeve Duffy

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  • Final Year ProjectProject Progress

    Presentation

    Title: Energy Conversion for low voltage values.

    Supervisor: Dr.Maeve DuffySupervisor: Dr.Maeve Duffy

  • Aim of Project

    The aim of this project is to develop circuits to

    demonstrate the performance of bio fuel cells

    which are being developed by the Energy which are being developed by the Energy

    research centre in NUI Galway.

    The ideal end goal would be where a microbial

    fuel cell arrangement has the ability to charge

    a mobile phone battery.

  • Outline of Presentation

    This presentation will deal with the following topics:

    1. Overview of Project

    2. Progress to date2. Progress to date

    3. Project Plan

    4. Time Management

    5. Questions

  • 1) Overview of project:

  • 2) Progress To Date:

    Thvenin equivalent circuit

    LED Demonstration

    Low power devices identified

    Demonstration of fuel cell powering low Demonstration of fuel cell powering low

    power devices

    Research of charging algorithms

  • Thvenin Equivalent circuit:Power Density curve:

    0.4

    0.5

    0.6

    Power density (mW/m2)

    800

    1000

    1200

    Voltage (V)

    0

    0.1

    0.2

    0.3

    0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

    Current density (mA/cm2)

    Power density (mW/m

    0

    200

    400

    600

    Voltage (V)

  • Blue line represents the power density Vs current density.

    White line represents Voltage Vs current density .

    Area across which power density is measured is 5.4cm^2.

    1cm^2 = 0.0001m^2

    The point at which we have maximum power output is the

    second from right so we take this point.

    When worked out the following outputs result:

    Power ~ 0.486 milli-WattsPower ~ 0.486 milli-Watts

    Voltage ~ 0.42 volts

    Current ~ 1.215 milli-Amps

    Internal Resistance of Fuel Cell ~ 345 ohms

  • Thvenin Equivalent circuit:

  • LED Demonstration:

    On testing the LEDs found in the electronics labs it was found

    that the lowest power LED needed a minimum of 3.8 milli-

    Amps and a minimum of 1.83 volts to light.

    This meant the voltage & current output from the fuel cell

    needed to be stepped up.

    There is three solutions to this problem:There is three solutions to this problem:

    1) Cascade a number of fuel cells in parallel, this way increasing

    the current output and then use a DC-DC boost converter to

    step up the voltage.

    2) Use an RC circuit to boost the current using a mosfet to sfor

    switching and then use a DC-DC boost converter to step the

    voltage up.

    3) Order a low power LED (1 milli-Amp LED can be obtained)

  • Low power devices identified:

    Voltage needed:

    1.5 Volts DC

    Power needed:

    0.0001 Watts

    Current needed:

    66.66 micro-

    Amps

    Voltage needed:

    5 volts DC

    Power needed:

    0.9 Watts

    Current needed:

    0.18 Amps

    Voltage needed: ~5

    volts DC

    Power needed:

    unknown

    Current needed:

    unknown

  • Demonstration of fuel cell powering low power

    devices:

    To demonstrate these devices a DC-DC boost converter needed

    to be designed.

    This caused problems as most common DC-DC boost converters

    use either diodes or BJTs which have a diode between the

    base and emitter. The BJT is used due to its fast switching base and emitter. The BJT is used due to its fast switching

    speeds. The diodes cause a minimum of 0.3 voltage drop. As

    the output voltage from the fuel cell is so low already we can

    not afford to use BJTs.

  • Demonstration of fuel cell powering low power

    devices:

    Using a boost converter obtained from Texas instruments called

    the TPS61200 I am currently trying to boost the output

    voltage of the fuel cell enough to allow me to power one of

    the low power devices mentioned above.

    This converter gets around the problem of using BJTs by using This converter gets around the problem of using BJTs by using

    MOSFETs instead.

    The TPS61200 can needs 0.8 volts to startup, after which it can

    operate at a voltage as low as 0.3 volts.

    As the TPS61200 was to small to fit on a board I needed to order

    the evaluation module.

  • Demonstration of fuel cell powering low power

    devices:

  • Demonstration of fuel cell powering low power

    devices:

  • Demonstration of fuel cell powering low power

    devices:

  • Demonstration of fuel cell powering low power

    devices:

    From using the formula to work out the minimum inductance

    needed (Vin = L * DI/DT) ,I found that the minimum

    inductance required was 2.1333 micro-Henrys.

    So the 2.2 micro-Henry should be satisfactory to induct the

    input current from the fuel cell.input current from the fuel cell.

  • Research of battery chemistries, charging

    algorithms:

    Example of type of voltage and current used to charge a phone:

    My phone (Sony Ericsson) is a lithium-polymer battery which

    supplies 3.6 volts to the phone. And has 780 milli-Amp hours.

    The charger for the phone supplies 5 volts and a current of

    1Amp. This is probably implementing a charging algorithm 1Amp. This is probably implementing a charging algorithm

    known as constant charge where a constant charge is applied

    to the battery.

    The type of charging algorithm I will most likely have to

    implement is trickle charging as it charges the battery with a

    small current over a long period of time.

  • 3) Project Plan:

    As identifying a suitable DC-DC boost converter has slowed me

    down I have revised my project plan as follows:

    January 22nd: Configure the DC-DC boost converter to power a

    low power device.

    February 5th: More research on battery chargers. Design battery February 5th: More research on battery chargers. Design battery

    charger needed to charge a typical phone battery.

    February 19th: Either configure TPS61200 to output voltage

    needed to power battery charger circuitry or identify a DC-DC

    boost converter which can.

    March 3rd: Identify a suitable microprocessor to read in voltage

    across the battery and adjust the battery charger output

    accordingly and Design a suitable Trickle Charge algorithm.

  • March 6th: Test the circuitry with different loads attached.

    March 8th: Test the complete circuitry with a rechargeable

    battery and determine overall efficiency.

    March 16th: Draft Final Report.

    March 24th: Submission of Final Report.

    March 29th: Oral and practical presentation.

  • 4) Time Management:

    I feel that in the first semester time management also had a role

    in slowing my progress on the project so this semester I aim to

    improve on this.

    This is a quiet tight schedule but I believe if I dedicate Tuesday

    evenings and Fridays to practical work in the Laboratory as evenings and Fridays to practical work in the Laboratory as

    well as any other free time and Saturdays to research I will be

    able to get it done.

  • 5) Questions!!