1. Pico Power Generation for the Developing World (Summary Lecture)
Loren Wyard-Scott 1 *
&
Dr. James Andrew Smith 2 *
1 Dept. of Electrical & Computer Engineering
University of Alberta
Edmonton, Alberta, Canada
2 Dept. of Electrical & Computer Engineering
Ryerson University
Toronto, Ontario, Canada
* Member, IEEE
A background lecture (20-30 PowerPoint slides) that motivates and introduces the problem and provides the necessary technical background (for presentation to the students). The impact of the problem’s solution on society must be demonstrated and illustrated in the context of a real-world, contemporary application.

2. Outline The Project’s Objectives Improving the Design Process
Using Technology Closer to its Potential
Super Capacitor Discharging and Charging
Knowing the Measurement Tools
Conclusion

3. The Project: Scenario & Goals
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
A remote mountain village has limited access to electrical power and, as a result, the village homes are lit with candles and kerosene lamps after dark. Narrow mountain paths limit access to neighboring villages and limits the supply of diesel for the village generators. Your task is to develop a small and sustainable source of electricity for the village using solar and/or mechanical techniques. The goal is to create a power source (centralized or distributed) that can provide 1 Watt-hour of energy for night-time use.
Photo: (Bas-Ravine, Haiti)
Bas-Ravine, Haiti

4. 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 under-specified.
What process did you go through to better specify your project?
Designing and evaluating often requires groups to work in “the grey”.

5. 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:
Understanding the problem – from many perspectives! (e.g. users, manufacturers)
Understanding what technology is available (always changing!): “Product Knowledge”
Understanding the principals of operation of the technologies used.

6. 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

7. 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”.

8. Design: Correlation Matrices
More Storage Capacity
User Convenience
Low Cost
+++
(highly positive) --
(quite negative)
N/A

9. Design: Characterizing System States
A state diagram can help characterize the system!

10. 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.

11. 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 successful.
Commonly required skill sets:
electrical
mechanical
manufacturing
industrial design
technical writing
financial
resource management

12. 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 lack.
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”.

13. Design: Testing Testing a new product is a complicated process.
There are discipline- and technology- specific courses and books dedicated to testing.
Companies that do nothing but this aspect of project development exist.
Ensure that the end-user has a chance to use a product candidate!

14. Using Technology Closer to its Potential
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 works.
Device datasheets are key to understanding the capabilities of a device.

15. Technology: Options
On-going developments in science, engineering and manufacturing are leading to amazing advances in energy generation, storage and distribution.
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

16. Technology: Options
Source: accessed 29 March 2008.

17. Technology: Options Capacitor Technology
Source: accessed 29 March 2008.

18. 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 effective
Tuning the capacitor value allows optimal performance for certain generator input speeds

19. 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.

20. Super Capacitor Discharging and Charging
You may have noted a few things while testing your design:
the LED remains on for longer than you expected;
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.

21. 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:
where Vstart is the voltage at t=0, Vfinish is the final (steady-state) voltage, and t is known as the time constant of the circuit. (You will see a lot more about time constants in every field of engineering.)

22. Super Capacitor Discharging and Charging
For a circuit with a resistor and a capacitor,
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?

23. Super Capacitor Charging and Discharging
Note that real capacitors have a resistance, potentially increasing the time constant!

24. 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.

25. Conclusion
Conventional, limited, sources of energy are being taxed more heavily as the world population increases.
As a result, environmentally- and energy-conscious designs are now of paramount importance.
The system you developed here has taught you how some of the emerging technologies operate.

26. Conclusion
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.

27. For more information Light Up The World (LUTW)
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Super Capacitors
Micro Hydro Installations