Assign 1

Review of Assignment 1

Design of Electronic Systems

ELEE1129

MSc Electronics & Communications Engineering

1

MSc Electrical & Electronic Engineering

MSc Electrical Power Engineering

ASSIGNMENT 1

ENERGY SOLUTIONS FOR

UNINTERRUPTIBLE POWER SUPPLIES

22

The assignment is to evaluate the use of

Super Capacitors as the energy source

in Uninterruptible Power Supplies

Assignment 1: Aim

• To investigate an ‘real-life applications’

requiring continuous operation that demand

an ‘Uninterruptible Power Supply’ (UPS)

• To investigate experimentally Supercapacitors

3

• To investigate experimentally Supercapacitors

and a simple flywheel for energy storage

• To critically evaluate the Super Capacitor

against alternatives to provide the energy

storage requirement in a typical UPS

3

Tasks

• Task 1:

– Investigation of UPSIdentify common energy storage solutions for typical

applications requiring UPS

– Identify at least 2 UPS applications (where Super Capacitors may be a

viable solution)

– Determine the Energy requirements for one of these applications

4

– Determine the Energy requirements for one of these applications

• Task 2: WS1 Super Capacitor Lab

• Task 3: WS 2 Flywheel Lab

4

Task 4: Technology Study:

Evaluation Super Capacitors for UPS (Formal Report)

• Propose Energy storage solutions based upon

a Super Capacitor and other ‘conventional’

approach for the typical UPS requirement of

Task 1.

5

Task 1.

• Critically evaluate the SuperCapacitor as the

Energy Storage device in this application.

• Include your laboratory results from Task 2

and 3 in your evaluations

5

Report Structure• Title page

• Contents page

• Introduction

• Problem analysis

• Problem Solution

• Problem Implementation

6

• Problem Implementation

• Results

• Discussion of results

• Conclusion

• Future Work (if any)

• References

• Appendices (if any)

Title Page

• Your title page should show the following:-

• Document title• Design of Electronic Systems

• Assignment 2

• Energy Storage Solutions for ‘XXX’ (your UPS Application)

7

• Energy Storage Solutions for ‘XXX’ (your UPS Application)

• Your name and Student ID

• The date

• The place and program

Problem analysis (15%)

Research and investigate applications that require a UPS. Choose such a typical application for your design study and in this section define the energy requirement. This can be ‘hypothetical’ – made-up but realistic.

8

realistic.

• What is the primary power source?

• How long will the primary source be unavailable?

• Produce an Outline Specification for the energyrequirements (voltage, current, time, etc.)

• Any other factors?(temperature, environmental)

Problem Solution (5%)

• Propose potential solutions to power the application – to meet the requirement

• Consider use of SuperCapacitor – identify suitable component

• Ideally at least 2 other sources of stored energy

9

• Ideally at least 2 other sources of stored energy

• Make suitable calculations (estimations) to show how each source might meet the requirement

Problem Implementation (10%)

• Outline here how the lab experiments will

provide useful data to underpin your

estimates

– Outline Super Cap (5%)

10

– Outline Super Cap (5%)

– Flywheel (5%)

Results (20%)

• Experimental Results

• SuperCapacitor Lab (10%)

– Measured Capacitance, Internal resistance against datasheet

11

datasheet

• Flywheel Lab (10%)

– Stored energy, efficiency

Conclusions/

Discussion of Results (40%)• Review your estimates in light of the

experimental data– Do they support your estimates?

– Did the experiments highlight any practical limitations in either methods

12

limitations in either methods

• Draw appropriate Conclusions from your work:– Advantages / Disadvantages of Super Capacitors

with particular reference to your application

Introduction and Conclusion

(10%)These are read together FIRST! They should tell me what the report is about.

Introduction – what is contained in the report. What the objectives of the work were. It may include a reference if significant – i.e. preceding published work.

13

Conclusions – did you achieve the objectives? Did it work! In this instance could be useful to include significant summary results –i.e. What the energy requirement was and what energy was developed experimentally. (shouldn’t contain a reference)

n.b. 1 page each, be concise - no ‘waffle’, no ‘personal’ experience!

Some thoughts (1)

• Consider that this report will be used as the

technical basis for a product development.

– Have you made a good case?

– Will your boss recommend this for PV funding

14

– Will your boss recommend this for PV funding

– Will you have a job next year?

14

Some thoughts (2)

• Your assignment is not a lab report on Super

Capacitors. It is a study into their use in a UPS

application – you choose. This should be

reflected in the Title, Introduction, Conclusion

15

reflected in the Title, Introduction, Conclusion

and then the main body...

• Is the English good? (get someone else to read

through it – preferably different nationality to

yourself)

15

Assignment 1 marking Scheme

Marks will be apportioned:

• UPS Application 20% Analysis 15%/Discussion 5%

• Super Capacitor 25% Solution/Implemt/results/Discussion

• Flywheel 25% Solution/Implemt/results/Discussion

• Critical Evaluation 20% Discussion

16

• Critical Evaluation 20% Discussion

• General Format 10%

16

Typical Student Report

17

Typical Student Report

17

Introduction

Talked about UPS in general, possibly Super Capacitor

some going into great detail – more than one page!

1818

Problem Analysis

UPS Applications• Handheld Megaphone

• Flash lamp

• Electric Vehicle

• Laptop / Mobile Charger

• Digital Camera

• Computer Backup

• IT (data centre)

• Alarm Clock

• MP3 Player

19

• Digital Camera

• Hospital Equipment

• Emergency Light

• Aquarium (Pump, filter)

• Wireless Computer

Mouse

19

• Radio Tuner

• TV

Problem Analysis

UPS Applications• Handheld Megaphone

• Flash lamp

• Electric Vehicle

• Laptop / Mobile Charger

• Digital Camera

• Computer Backup

• IT (data centre)

• Alarm Clock

• MP3 Player

20

• Digital Camera

• Hospital Equipment

• Emergency Light

• Aquarium (Pump, filter)

• Wireless Computer

Mouse

20

• Radio Tuner

• TV

These are PORTABLE

applications for

Supercapacitors –

NOT UPS

Problem Analysis

Energy Calculation

Typically defined Voltage and Power. Some defined

Time say,

Voltage = 12V, Time = 12hours, Power = 20W ½ CV2 is TOTAL

energy stored in

2121

Energy = 20W x 12 h = 240 Wh

Then calculated Capacitance required from

½ CV2 = 240 Wh,

If V=12 V then C = (2 x 240) / 144 = 3.33F

energy stored in

capacitor in

Joules

- needed to

define minimum

working voltage

- Needed to

convert Wh to J

Problem Solution

This section should propose the Super Capacitor, flywheel and

other potential energy storage technologies.

Could include calculations.

Could include background on Super Capacitor.

2222

Could include background on Super Capacitor.

Fuel Cells are not a solution

Problem Implementation

This section should introduce the experiments (why do them)

and outline the experimental procedure – refer to Fig 1

Vin

Vmot

or

Ext Imoto

Few gave figures a

caption, less a Figure

2323

F - Vout

Ext

Int

Speed

Imoto

r

Most students put nothing here, just went straight into results!

At best showed a picture of the Flywheel / Supercap circuit

Figure 1: Schematic of Flywheel jig

caption, less a Figure

number. Virtually no-

one referred to the

figures in the text!

ResultsTime Volts Current

0 0.00 0.50

30 0.45 0.46

60 0.80 0.42

90 1.08 0.40

120 1.29 0.37

150 1.46 0.36

180 1.59 0.35

210 1.69 0.34

240 1.77 0.33

270 1.83 0.32

Charging

Little reference to what

result is from.

Worksheet asked for

plot of data – no need

to incorporate table of

2424

270 1.83 0.32

300 1.88 0.32

330 1.92 0.31

360 1.95 0.31

390 1.97 0.31

420 1.99 0.31

450 2.00 0.30

480 2.01 0.30

510 2.02 0.30

540 2.03 0.30

570 2.03 0.30

600 2.04 0.30

630 2.04 0.30

660 2.04 0.30

690 2.04 0.30

to incorporate table of

data!

Results

Charging

1.50

2.00

2.50

No Axis Labels /Units

Both curves black –

probably colour in

2525

0.00

0.50

1.00

0 200 400 600 800

probably colour in

WORD but printed

B/W

No Key

ResultsTime Volts Current

0 2.05 0.3

30 1.77 0.26

60 1.53 0.22

90 1.32 0.19

120 1.14 0.16

150 0.98 0.14

180 0.85 0.12

210 0.73 0.1

240 0.63 0.09

270 0.55 0.08

300 0.47 0.06

Discharging

Many people used too

high a range on

Ammeter – lost

resolution

2626

300 0.47 0.06

330 0.41 0.05

360 0.35 0.05

390 0.30 0.04

420 0.26 0.03

450 0.23 0.03

480 0.19 0.02

510 0.17 0.02

540 0.15 0.02

570 0.13 0.01

600 0.11 0.01

630 0.09 0.01

660 0.08 0.01

690 0.07 0.01

ResultsDischarging

‘Ripple’ caused by

poor resolution in

measurement1.2

1.4

1.6

1.8

2.0

2727

0.0

0.2

0.4

0.6

0.8

1.0

0 200 400 600 800

V I Hz V

V mA power F Vfout K.E

0 0 0 0 0 0

0.25 85 0.02125 7.1 0.36 0.02107

0.41 115 0.04715 14.3 0.74 0.085472

0.62 150 0.093 20.1 1.15 0.168867

0.79 172 0.13588 31.17 1.38 0.406094

0.98 206 0.20188 33.44 1.7 0.467397

ResultsFlywheel Often there was little note that the results now

related to the flywheel experiment

28

0.98 206 0.20188 33.44 1.7 0.467397

1.21 255 0.30855 41.65 2.09 0.725075

1.4 315 0.441 50.11 2.41 1.049547

1.57 343 0.53851 53.1 2.6 1.178534

1.88 432 0.81216 64.1 3.13 1.717391

2.05 486 0.9963 70.4 3.44 2.071565

2.3 566 1.3018 79.36 3.87 2.632428

2.51 625 1.56875 86.2 4.22 3.105759

2.71 692 1.87532 92.5 4.51 3.576322

2.9 753 2.1837 98.05 4.79 4.018356

3.1 805 2.4955 104.2 5.12 4.538252

3.3 870 2.871 111.1 5.38 5.159187

3.5 930 3.255 116.3 5.38 5.653437

3.71 1013 3.75823 121.9 5.38 6.210986

3.73 1016 3.78968 125 5.38 6.530902

28

Again Table not needed

if these results are to be

plotted in a graph

4

5

6

80

100

120

140

V F

ou

r

Fre

qu

en

cy H

z

Results

29

0

1

2

3

0

20

40

60

0 0.5 1 1.5 2 2.5 3 3.5 4

V F

ou

r

Fre

qu

en

cy H

z

V motor

29

Vfout saturated at

higher speeds, but no

comment in text /

analysis

4

5

6

7

Kin

eti

c E

ne

rgy

Results

What does this curve

say?

The K.E. Is stored

energy whilst the

30

0

1

2

3

0 0.5 1 1.5 2 2.5 3 3.5 4

Kin

eti

c E

ne

rgy

Power W

30

energy whilst the

Power is the rate of

energy being lost.

No real relation – no

point to graph?

Results

1.5

2.0

Mo

tor

Vo

lts

(V)

Slow-down characteristic

Usually a screen dump often with two

traces (Vfout and VM)

Curves not distinguished

V/Div and Time/Div not clearly labelled

3131

0.0

0.5

1.0

0 5 10 15 20 25 30 35

Mo

tor

Vo

lts

(V)

Time Seconds

V/Div and Time/Div not clearly labelled

Discussion of Results

Usually very little post-processing. Mostly vague statements like

‘Flywheel are not suitable because it decays too quickly’ or

‘Super capacitor is suitable because it can charge quickly and

discharge slowly’ (actually a rubbish statement as the

charge/discharge rate depends on the resistance in the circuit!)

3232

Compare to theory – most students ignored this from the

worksheet – main reason to do lab experiment to confirm Super

Capacitor behaves like an ordinary capacitor

Few students attempted to consider analysing the Flywheel –

usually by saying energy stored = ½ Iω2 = Energy required. This

is a reasonable initial estimate of it’s potential – but no

consideration to the Flywheel loses

Conclusions

Good that most students kept this to one page but usually very

vague again.

Many students listed disadvantages / advantages from the

literature, etc. – the ‘conclusion’ is to present conclusions from

the work within the report – NOT somebody else’s findings!

3333

the work within the report – NOT somebody else’s findings!

Tutor Suggested Report

34

Tutor Suggested Report

34

Introduction

This Report is about...

Use of Supercapacitors to provide a UPS solution for

Display / Memory function in a PC.

3535

Display / Memory function in a PC.

Problem Analysis :UPS Application

Tutor Suggestion

Want to save information on PC screen –

1. Power data save circuit – 5V, 20mA, 5s,

(Use Flywheel) – define min voltage 4V

3636

Energy = 5V x 20 mA x 5s = 0.5J

2. Maintain Memory Circuit – 5V, 100µA, 1week

(Use SuperCapacitor) define min voltage 3V

Energy = 5V x 100µA x 7x24x60x60 = 302J

Problem Implementation

To evaluate the technology some simple experiments were

conducted on a commercially available Super Capacitor and

a Flywheel test jig using a CDROM.

Details can be found in the Appendix A (Super Capacitor)

and B Flywheel)

3737

and B Flywheel)

No need to describe experiment just add a copy of the

Worksheets in the Appendices

However list the tests to be made...

Problem Implementation

Tests to be made:

Test 1: Charging Characteristics of the Super Capacitor

Test 2: Discharging Characteristics of the Super Capacitor

3838

Test 3: Calibration measurements of the Flywheel (Current,

Speed, Vfout as a function of Vmotor)

Test 4: Slow-down characteristic of the Flywheel (Vmotor

with

(a) no load (b) 500 Ohm (c) other

Problem Solution

The following energy storage technologies are outlined with

regard to the UPS requirement

Super Capacitor,

Flywheel

3939

Flywheel

Rechargeable Batteries (propose type – NiCd)

Results

1.50

2.00

2.50

Vo

lta

ge

/ C

urr

en

tTest 1: Charging Characteristics of the Super Capacitor

4040

0.00

0.50

1.00

1.50

0 200 400 600 800

Time Seconds

Vo

lta

ge

/ C

urr

en

t

Volts

Current mA

Can clearly relate what these results these are – Test 1!

Also measure resistances:

Measure value of 6.8Ω = 7.1Ω

Measure value of 10Ω = 9.8Ω

Results

Test 2: Discharging Characteristics of the Super Capacitor

1.50

2.00

2.50V

olt

ag

e /

Cu

rre

nt

4141

0.00

0.50

1.00

1.50

0 200 400 600 800

Vo

lta

ge

/ C

urr

en

t

Time s

Volts

Current A

Results

Test 3: Calibration measurements of the Flywheel

(a) Current as a function of Vmotor)

800

1000

1200

Cu

rre

nt

mA

4242

0

200

400

600

800

0 1 2 3 4

Cu

rre

nt

mA

Motor Voltage

4

5

6

100

120

140

Results

Test 3: Calibration measurements of the Flywheel

(b) Speed and Vfout as a function of Vmotor)

43

0

1

2

3

4

0

20

40

60

80

0 1 2 3 4

V F

ou

r

Fre

qu

en

cy H

z

V motor 43

Results

Test 4: Slow-down characteristic of the Flywheel (Vmotor)

(a) No Load

1.5

2.0

Mo

tor

Vo

lts

(V)

4444

0.0

0.5

1.0

0 10 20 30 40

Mo

tor

Vo

lts

(V)

Time Seconds

Discussion of ResultsUse this section for post-processing of results and applying

to the UPS application

Compare Theory to Experiment for Super Capacitor

Energy Calculations for UPS

4545

Analyse Energy stored in Flywheel and losses.

Analyse if it can it be used for UPS.

Discussion of ResultsSuper Capacitor

Comparison of Super Capacitor to Theory

Plot discharge curve against theoretical curve (assume C=30F)

showing good agreement

1.2

1.4

4646

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800

Vo

lt

TIme S

measured

Theory

Discussion of ResultsSuper Capacitor

15

20

25

30

0.8

1

1.2

1.4

measured

TheoryVolts

Calculate

Energy

Released

dtEE ∫∆=

26J

4747

0

5

10

15

0

0.2

0.4

0.6

0 100 200 300 400 500 600 700 800

Theory

Esum

Time

Released

through

numerical

integration

(J)

tR

VE ∆

∆=∆

2

JVC

E 262

3.1*30

2

22

===

Discussion of ResultsSuper Capacitor

Initial drop in discharge voltage

can be used to calculate Internal

Resistance.

Vr = 0.2 V,

4848

Vr = 0.2 V,

Initial current 0.3A

Rint = 0.2/0.3 = 0.07Ω

Accuracy poor as small value.

Could also consider the two time

constants for charge / discharge

– here Rint and C unknown, but

two equations so can solve

Discussion of ResultsSuper Capacitor

UPS Applications (could be presented in Analysis / solution section)

Capacitance required:

Vmax = 5 V..................... I max = 100µA

Vmin = 3V ......................Imin = 166µA (assuming constant Power)

4949

Vmin = 3V ......................Imin = 166µA (assuming constant Power)

I avg = 133µA

C = 133 x10-6 x (7x24x60x60)/(5-3) = 42F

Cap working Voltage = 2.3V, so need 5/2.3 = 3 in series

Solution 12 capacitors = 4 x (3 x 30F in series ) in parallel = 40F

V

TIC

∆

∆×=

Discussion of ResultsFlywheel - Losses

2.5

3.0

3.5

4.0

4.5

5.0

600

800

1000

1200

Resistance

Current mA mA

R

505050

0.0

0.5

1.0

1.5

2.0

2.5

0

200

400

600

0 0.5 1 1.5 2 2.5 3 3.5 4

Resistance

Current mA

Motor Voltage

R

Steady State Drive condition gives energy lost by friction

Find Equivalent internal resistance (approx. 4 Ohm) = Vmotor/Imotor

Discussion of ResultsFlywheel – Discharge losses

3

4

5Motor Volts (V) / Energy (J)

V

4.5J

515151

0

1

2

0 5 10 15 20 25 30 35

Motor Volts (V) / Energy (J)

Time Seconds

V

E

Calculate Electrical loss, assuming 4Ω load and numerically

integrate

Time constant ~ 30/5 =6 seconds

Discussion of Results

Flywheel – Stored Energy

HzF

VVfout

cmrgmmr

I

125

:6

)6,14(2

2

=

=

===

5252

From Numerical Integration of Electrical Losses – 4.5J

JI

EK

F

HzF

5.62

..

7852

125

2

==

==

=

ω

πω

Discussion of Results

Flywheel – Equivalent Circuit

Equivalent circuit for Flywheel – Capacitor

with internal shunt resistor to represent

losses. Capacitance determined from stored

K.E.

JCV 5.61 2

=

5353

C ~ 3.3F, R~4 gives a time constant of 12s.

Measured time constant around 6s. – more

detailed analysis of speed/losses needed.

Fx

C

JCV

3.32

5.62

5.62

2==

=

Discussion of Results

Flywheel – Application

For application want to use Flywheel to

power Data Save circuit.

5V, 20 mA ~ RL = 5/0.02 = 250 Ω

Assume constant power

5454

Assume constant power

At 4V, I = 25 mA , RL = 4/0.025 = 160 Ω

Assume RL = 160 Ω, then time constant still of order 6s.

After 5s flywheel voltage will have dropped to 1V.

Possibly can use with a DC/DC voltage converter to give

4V from a minimum of 1V, ignoring conversion losses.

Conclusions

This report has investigated a Super Capacitor and a

CDROM Flywheel as potential solutions for UPS

applications.

It has been demonstrated that the Super Capacitor behaves

5555

It has been demonstrated that the Super Capacitor behaves

just like a conventional capacitor and can clearly meet the

memory UPS requirement.

The Flywheel was shown to exhibit characteristics of a

conventional capacitor but suffers from high internal losses.

However it may be possible to recover some energy for

very short, low power UPS requirements.