Post on 04-Jun-2018
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Pico Power Generation for
the Developing World(Summary Lecture)
Loren Wyard-Scott 1 *
&
Dr. James Andrew Smith 2*1Dept. of Electrical& Computer Engineering
University of Alberta
Edmonton, Alberta, Canada
2Dept. of Electrical& Computer EngineeringRyerson University
Toronto, Ontario, Canada
* Member, IEEE
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Outline
The Projects Objectives
Improving the Design Process
Using Technology Closer to its Potential Super Capacitor Discharging and
Charging
Knowing the Measurement Tools Conclusion
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The Project:
Scenario & Goals
Scenario A remote village of 500
people No night-time electricity Have small low-power
lamps Objective
Build a small power source
30 minute lamp operation Preferably human-powered Night-time discharging
Bas-Ravine, Haiti
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The Projects Objectives
Were these goals simple to meet?
Is your project a Success? A Failure?
Do you have enough information to answer these questions? You
are on the path to a solution, but there is still a lot of work to do!
Many of you may have found that the objectives areunder-specified.What process did you go through to better specify your project?
Designing and evaluating often requires groups to workin the grey.
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Improving the Design Process
Did you get lost on the way to finding asolutionin the grey?
Finding a good solution to any real-world
problem requires:1. Understanding the problemfrom many
perspectives! (e.g. users, manufacturers)
2. Understanding what technology is available(always changing!): Product Knowledge
3. Understanding the principals of operation ofthe technologies used.
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Improving the Design Process
Finding your way through any of these three
items can be challenging. It gets simpler with
experience(like this project)!
Tools and protocols that can help:1. Correlation matrices: Understanding Design Trade-offs
2. State Diagrams
3. Block Diagrams
4. Multi-discipline Design Teams
5. Critical Design Review
6. Putting the Project Through its Paces: Testing
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Design: Correlation Matrices
Real design problems always have trade-
offs. Cheap, fast, good: pick two.
To help understand the tradeoffs and how
they will affect the outcome is important.
A tool that helps understand the tradeoffs
is a Correlation Matrix.
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Design: Correlation Matrices
More Storage
Capacity
User
ConvenienceLow Cost
More StorageCapacity +++(highly positive) --(quite negative)
User Convenience N/A
Low Cost
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Design: Characterizing System
States
A state diagram can help characterize the system!
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Design: Block Diagram
Block diagrams are a great way to
communicate your ideas to fellow designers.
They provide a simple view of what could be a
complicated system.
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Design: Multi-Discipline Design Teams
Almost every real-world project involves morethan one field of technology.
Teams that have a wider set of experiences andknowledge to draw from are typically more
successful. Commonly required skill sets:
electrical
mechanical
manufacturing industrial design
technical writing
financial
resource management
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Design: Critical Design Review
In practice it is not always possible to develop ateam that has all skill sets covered.
A Critical Design Review(CDR) is a standard
stage of project design that can help offset thislack.
Once a (usually paper-based) design iscomplete, the design is reviewed by people from
all walks of life, including experts. The feedback is used to improve the design, or,
in some cases, terminates it: go or no go.
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Design: Testing
Testing a new product is a complicatedprocess.
There are discipline- and technology-
specific courses and books dedicated totesting.
Companies that do nothing but this aspect
of project development exist. Ensure that the end-user has a chance
to use a product candidate!
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Using Technology Closer to its
Potential
Understanding the options that are at yourdisposal when designing is important:Product Knowledge gained from reading
trade publications, journals, etc. Your education provides you with the tools
to understand how particular technologyworks.
Device datasheets are key tounderstanding the capabilities of a device.
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Technology: Options
On-going developments in science, engineeringand manufacturing are leading to amazingadvances in energy generation, storage anddistribution.
Keeping an eye on new developments is critical!
For instance, new storage technologies canallow power generated during the daytime to be
stored more effectively for night-time use! Batteries are not the only way to store electricity Capacitors and fuel cells are becoming alternatives
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Technology: Options
Source: http://en.wikipedia.org/wiki/Supercapacitor, accessed 29 March 2008.
http://en.wikipedia.org/wiki/Supercapacitorhttp://en.wikipedia.org/wiki/Supercapacitor8/13/2019 RWEP Final5 48 SummaryLecture PicoPower v3
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Technology: Options
Source: http://en.wikipedia.org/wiki/Supercapacitor, accessed 29 March 2008.
Capacitor Technology
http://en.wikipedia.org/wiki/Supercapacitorhttp://en.wikipedia.org/wiki/Supercapacitor8/13/2019 RWEP Final5 48 SummaryLecture PicoPower v3
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Technology: Options
Adding key components canboost your devicesperformance substantially! Capacitor filters on rectifiers
make the voltage more usable
Component optimization canmake a design even moreeffective Tuning the capacitor value
allows optimal performance forcertain generator input speeds
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Technology: Options
Hopefully this has demonstrated to you
that
Understanding what devices are available;
and
Understanding how these devices operate
both come into play during design.
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Super Capacitor Discharging and
Charging
You may have noted a few things whiletesting your design:
the LED remains on for longer than you
expected; there is no (easily) definable time that the
LED turns offit slowly fades; and
it takes less time to charge the super
capacitor than to discharge it.All of these observations have a common
component: time.
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Super Capacitor Discharging and
Charging
Capacitors do not provide a constant voltage until there
is no energy left.
The decay in the voltage is actually exponential and is
given by:
finishfinishstart)( VeVVtVt
c
where Vstartis the voltage at t=0, Vfinishis the final
(steady-state) voltage, and is known as the timeconstantof the circuit. (You will see a lot more about
time constants in every field of engineering.)
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Super Capacitor Discharging and
Charging
For a circuit with a resistor and a capacitor,
RC
The next slide shows a plot of Vc(t) with Vstart= 5V, and
Vfinish
=2.0V for two different time constants.
Why is Vfinishset to 2.0V? (What is the forward voltage
drop of an LED?)
Can you explain why charging of the capacitor is
quicker than discharging?
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Super Capacitor Charging and
Discharging
1
1.5
2
2.5
3
3.5
4
4.5
5
Time
Vc(t)
Smaller Time Constant
Larger Time Constant
Note that real capacitors have a resistance, potentially increasing the time
constant!
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Knowing the Measurement Tools
It is always important to understand the
capabilities and limitations of the test equipment
and measurement processes.
Understanding these bounds while constantly
asking is what we are observing consistent with
what we know? is important to any scientific
process.
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Conclusion
Conventional, limited, sources of energyare being taxed more heavily as the worldpopulation increases.
As a result, environmentally- and energy-conscious designs are now of paramountimportance.
The system you developed here hastaught you how some of the emergingtechnologies operate.
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Conclusion
You have learned a lot about the design
process, and have hopefully enjoyed yourselves
while doing so.
Successful completion of the project itself, PicoPower Generation for the Developing World,will
see underprivileged peoples provided with a
safe power generation and storage system that
can be used to expand their opportunities byimproving productivity and literacy.
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For more information
Light Up The World (LUTW)
http://www.lutw.org/
Bicycle Dynamo Rectifiers & Filters http://pilom.com/BicycleElectronics/DynamoCircuits.htm
Super Capacitors
http://en.wikipedia.org/wiki/Supercapacitor
Micro Hydro Installations
http://www.green-trust.org/hydro.htm