rwep final5 48 summarylecture picopower v3

8/13/2019 RWEP Final5 48 SummaryLecture PicoPower v3

1/27

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


2/27

Outline

The Projects Objectives

Improving the Design Process

Using Technology Closer to its Potential Super Capacitor Discharging and

Charging

Knowing the Measurement Tools Conclusion


3/27

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


4/27

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.


5/27


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.


6/27


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


7/27

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.


8/27

Design: Correlation Matrices

More Storage

Capacity

User

ConvenienceLow Cost

More StorageCapacity +++(highly positive) --(quite negative)

User Convenience N/A

Low Cost


9/27

Design: Characterizing System

States

A state diagram can help characterize the system!


10/27

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.


11/27

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


12/27

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.


13/27

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!


14/27

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.


15/27

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


16/27

Technology: Options

Source: http://en.wikipedia.org/wiki/Supercapacitor, accessed 29 March 2008.
http://en.wikipedia.org/wiki/Supercapacitorhttp://en.wikipedia.org/wiki/Supercapacitor


17/27

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/Supercapacitor


18/27

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


19/27

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.


20/27

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.


21/27


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.)


22/27


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?


23/27

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!


24/27

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.


25/27

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.


26/27

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.


27/27

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

rwep final5 48 summarylecture picopower v3

Documents