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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
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!
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.