# project progress presentation.ppt - nui galway compsoccompsoc.nuigalway.ie/~rambo/fyp/project...

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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:

• Thévenin 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

Thévenin 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

Thévenin Equivalent circuit:

LED Demonstration:

On testing the LED’s 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 BJT’s 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 BJT’s.

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 BJT’s by using This converter gets around the problem of using BJT’s by using

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-Henry’s.

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!!