Summary Lecture - IEEE Real World Engineering Projects

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Transcript Summary Lecture - IEEE Real World Engineering Projects

Pico Power Generation for
the Developing World
(Summary Lecture)
Loren Wyard-Scott 1 *
Dr. James Andrew Smith 2 *
Dept. of Electrical & Computer Engineering
University of Alberta
Edmonton, Alberta, Canada
Dept. of Electrical & Computer Engineering
Ryerson University
Toronto, Ontario, Canada
Member, IEEE
The Project’s Objectives
Improving the Design Process
Using Technology Closer to its Potential
Super Capacitor Discharging and
• Knowing the Measurement Tools
• Conclusion
The Project:
Scenario & Goals
• Scenario
– A remote village of 500
– No night-time electricity
– Have small low-power
• Objective
– Build a small power source
– 30 minute lamp operation
– Preferably human-powered
– Night-time discharging
Bas-Ravine, Haiti
The Project’s 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 are
–What process did you go through to better specify your project?
• Designing and evaluating often requires groups to work
in “the grey”.
Improving the Design Process
Did you get lost on the way to finding a
solution – in “the grey”?
Finding a good solution to any real-world
problem requires:
1. Understanding the problem – from many
perspectives! (e.g. users, manufacturers)
2. Understanding what technology is available
(always changing!): “Product Knowledge”
3. Understanding the principals of operation of
the technologies used.
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:
Correlation matrices: Understanding Design Trade-offs
State Diagrams
Block Diagrams
Multi-discipline Design Teams
Critical Design Review
Putting the Project Through its Paces: Testing
Design: Correlation Matrices
• Real design problems always have tradeoffs. “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”.
Design: Correlation Matrices
More Storage
More Storage
User Convenience
Low Cost
Low Cost
(highly positive)
(quite negative)
Design: Characterizing System
A state diagram can help characterize the system!
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.
Design: Multi-Discipline Design Teams
• Almost every real-world project involves more
than one field of technology.
• Teams that have a wider set of experiences and
knowledge to draw from are typically more
• Commonly required skill sets:
industrial design
technical writing
resource management
Design: Critical Design Review
• In practice it is not always possible to develop a
team that has all skill sets covered.
• A Critical Design Review (CDR) is a standard
stage of project design that can help offset this
• Once a (usually paper-based) design is
complete, 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”.
Design: Testing
• Testing a new product is a complicated
• There are discipline- and technologyspecific courses and books dedicated to
• Companies that do nothing but this aspect
of project development exist.
• Ensure that the end-user has a chance
to use a product candidate!
Using Technology Closer to its
• Understanding the options that are at your
disposal when designing is important:
“Product Knowledge” gained from reading
trade publications, journals, etc.
• Your education provides you with the tools
to understand how particular technology
• Device datasheets are key to
understanding the capabilities of a device.
Technology: Options
• On-going developments in science, engineering
and manufacturing are leading to amazing
advances in energy generation, storage and
• Keeping an eye on new developments is critical!
• For instance, new storage technologies can
allow 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
Technology: Options
Source:, accessed 29 March 2008.
Technology: Options
Capacitor Technology
Source:, accessed 29 March 2008.
Technology: Options
• Adding key components can
boost your device’s
performance substantially!
– Capacitor filters on rectifiers
make the voltage more usable
• Component optimization can
make a design even more
– Tuning the capacitor value
allows optimal performance for
certain generator input speeds
Technology: Options
• Hopefully this has demonstrated to you
–Understanding what devices are available;
–Understanding how these devices operate
both come into play during design.
Super Capacitor Discharging and
You may have noted a few things while
testing your design:
– the LED remains on for longer than you
– there is no (easily) definable time that the
LED turns off – it 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.
Super Capacitor Discharging and
• 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:
Vc (t )  Vstart  Vfinish e
 Vfinish
where Vstart is the voltage at t=0, Vfinish is the final
(steady-state) voltage, and  is known as the time
constant of the circuit. (You will see a lot more about
time constants in every field of engineering.)
Super Capacitor Discharging and
• 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 Vfinish set to 2.0V? (What is the forward voltage
drop of an LED?)
• Can you explain why charging of the capacitor is
quicker than discharging?
Super Capacitor Charging and
Larger Time Constant
Smaller Time Constant
Note that real capacitors have a resistance, potentially increasing the time
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
• Conventional, limited, sources of energy
are being taxed more heavily as the world
population increases.
• As a result, environmentally- and energyconscious designs are now of paramount
• The system you developed here has
taught you how some of the emerging
technologies operate.
• You have learned a lot about the design
process, and have hopefully enjoyed yourselves
while doing so.
• Successful completion of the project itself, Pico
Power 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 by
improving productivity and literacy.
For more information
• Light Up The World (LUTW)
• Bicycle Dynamo Rectifiers & Filters
• Super Capacitors
• Micro Hydro Installations