Pico Power Generation for the Developing World 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

Why Small Electrical Generation Systems? Economics –More affordable in isolated or low-income locations Reliability –Sustainable maintenance with local resources Productivity –Longer work days –Indoor working conditions Literacy –Schoolwork is possible even in the evening

Power Generation & Usage in the Developed World Minority of world population Use a majority of energy resources Electrical Lighting is abundant & taken for granted Earth at night. Where are the developed nations? Pollution problems caused by power generation

Trivia! Energy use in a typical American Home [1] [1] Energy Kid’s Page, U.S. Department of Energy, accessed 01 Dec [2] Beursten, Bruce E., Theodore L. Brown & Eugene Le May Jr. Chemistry: The Central Science. Engelwood Cliffs, NJ: Prentice Hall, Total energy consumed in America in 1995: 9.2 × J [2]

More Trivia There are 34.2 MJ/L of automotive gasoline [1]. Keep this in mind as you tackle this project! [1]Nommensen, Arthur. List of common conversion factors (Engineering conversion factors). IOR Energy.List of common conversion factors (Engineering conversion factors)

Power Generation & Usage in the Developing World Majority of the world’s population 2 billion people without modern lighting or power Current Solutions –Nothing –Kerosene –Diesel Dangers –Fires –Carbon Monoxide –Sulfur Dioxide Voting by candlelight in Haiti

Challenges Faced in the Developing World Limited electricity supply –Often no electrical grid –Only micro energy sources (diesel, solar, hydro) Difficult operating conditions –Temperature ranges –High humidity –Dust and dirt Limited replacement parts –Limited distribution infrastructure –Sustainability: require local businesses

Power Generation Examples Bicycle Dynamo –3 Watts Wind Turbine (typical): –1 Mega Watt –300,000 Bike Dynamos! Hydro Plant (La Grande-1, Canada): –1400 Mega Watts Coal Plant (typical): –500 Mega Watts Nuclear Plant (Pickering, Canada): –4100 Mega Watts 1 Mega Watt: power for 1000 North American houses

Your mission: Pico Power! We would like you to design and construct a system that will provide a small amount of light for a short duration. The “light” will be a Light Emitting Diode (LED) with a current-limiting resistor, and the duration is to be a minimum of 10 minutes. Moreover, during the 10 minutes, the user needs to concentrate on reading, and so the energy to power the light needs to be generated before-hand and stored!

Engineering Development Process 1.Identification of problem –What function is missing? –Talk to the clients/users! 2.Identification of affordable technology –What actuators and sensors? At what cost? 3.Determine level of functional replacement –What is possible? –Keep it simple & effective! 4.Risk evaluation –Never underestimate what can go wrong! 5.Prototype device, test & start again (Steps 1 -5) 6.Test on larger population set 7.International certification 8.Manufacture & distribute device Start End Manufacture Prototype Test  

Rapid Prototyping “Express - Test - Cycle” approach to design –Identify a need & design objectives –Brainstorm for solutions –Express an idea in a physical device –Test the device –Discover problems that you weren’t aware of –Repeat until you’ve met the design objectives Rapid prototyping systems –Combine modular, off-the-shelf components –Great for quick mock-ups & functional testing –Examples Breadboards Vector board Speed Wire Breadboard system

Outline of Technical Topics Knowledge about key topics will help you succeed: The basics: –Electricity –Ohm’s Law –Power and Energy –Capacitors –Diodes (including LEDs) Applied electrical engineering: –AC and DC Generation –Rectifying –Filtering –Regulating –Life of a Power Source

Electricity Background Voltage [Volts]: –A “force” that tries to move electrons –Provided by devices such as batteries Current [Amperes, Amps]: –This is the “flow” of electrons –Carried by wires Resistance [Ohms]: –Resist the flow of electrons –Intentionally provided by resistors. –Unintentionally provided by almost all real-world components

Ohm’s Law Relates the main electrical measures I = V / R –Battery has constant voltage [ V ] –Current [ I ] varies with resistance [ R ] –Larger resistance means smaller current

Power and Energy Energy is measured in Joules Power, measured in Watts, is Energy per unit time: Electrically, the power being used in a circuit with fixed voltage and current is: Example: if a 12V battery provides 1 Amp of current to power the stereo in your car, it is providing 12W of power. If the stereo is on for 1 hour, the battery provides 12W(60 minutes)(60 seconds/minute) = 43,200 Joules.

Batteries as an Energy Source Batteries are made of individual cells Series cells: more voltage Parallel cells: same voltage, longer life Single CellSeries CellsSeries & Parallel Cells

Resistances in Series & Parallel Resistances in series add up. Resistances in parallel: Series Resistance Parallel Resistance

Voltage Drops Batteries increase circuit voltage Resistors & other devices “drop” voltage –Sum of “drops” equals battery voltage Imagine walking on a mountain. –Battery raises you to the top –Resistors, etc. drop you down.

Capacitors Temporarily store electrical charge Can rapidly discharge current when needed Positive sign means it is polarized & must be connected right. Where do you find them? –In circuit boards near components that need steady current –In camera flashes Capacitive filtering

Capacitors in Series & Parallel Capacitances in parallel add Capacitances in series

Capacitors: Energy Storage Like batteries, capacitors store energy. An ideal capacitor with a constant voltage can store: Capacitance is measured in Farads. Be aware that capacitors have a maximum rated voltage. Exceeding this voltage can put the capacitor (or you) in danger. Warning: large capacitors can store a lot of energy. Always handle carefully!

Diodes Semiconductor devices Current flows in one direction only The diode’s PN junction controls current flow Anode & Cathode on either side of the junction If the Anode has a more positive voltage than the Cathode, it is “forward biased” –Lets current through Otherwise it is “reverse biased” –Will not let current through AnodeCathode

Diodes: The Corner Model A “model” is a simplified imaginary version of the actual device Apply a low voltage –It stays off –No electrons go through –Current is zero Apply a high voltage –It turns on! –Electrons pass through –Current is allowed Voltage drop across diode is constant: V d

Light Emitting Diode (LED) Operates like a regular diode The lens lets photons out –Converts electrons to photons Higher current –Brighter light!

LED Operation To control brightness, change the current by changing the resistance in the circuit V d depends on the LED 1V to 3V If the battery is low, the LED will not turn on Too much current will burn the LED out!

AC vs. DC Systems Alternating Current (AC) systems are those that have time-varying (usually sinusoidal) voltage current waveforms Direct Current (DC) systems have constant voltage and current

AC Generators Loads run at the same frequency as generators Requires rectifiers & filters for DC loads Very good for long distance power transmission Bicycle Dynamos are AC generators

DC Motors as Generators DC motors can be driven like generators Brushes tend to wear out Output is constant so rectifiers are not needed Not efficient for long distance transmission (at lower voltages)

Rectifying I The process of converting an AC waveform into another waveform that has a DC component Recall that diodes operate as “one-way valves” A “half-wave” rectifier is shown here:

Rectifying II An improvement is a “full-wave” or “bridge” rectifier Positive voltage: one diode pair on Negative voltage: other diode pair on

Filtering I If periodic / alternating voltages need to be smoothed, capacitors can be used as filters –Capacitors store electrical charge, like a bucket stores water –Electrons are brought to the capacitor by input current, like drops of water into a bucket –When needed, capacitor outputs current like the water bucket’s output valve

Filtering II The size of the capacitor, C, determines how constant the output voltage is!

Regulating Regulating is the process of controlling the system to get the output we want Generator output can be regulated by 1.Changing the mechanical input speed 2.Circuitry on the electrical output 7805 Regulator (5 V, Amp output) Place between filtered rectifier and load Pin 1: input ( VDC) Pin 2: Ground Pin 3: output (5 VDC) Add 0.33 uF filter caps Pin 1 and Pin 2; Pin 3 and Pin

Life of a Power Source Battery life –Inversely proportional to current Low current operation –Higher resistance –Lower current –Weaker light & longer life High current operation –Lower resistance –Higher current –Brighter light & shorter life This applies to any device that stores electrical energy, including capacitors!

Final 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 –10 minute (min) lamp operation –Preferably human-powered –Night-time discharging Keep in mind: –Target group for the final design –What socio-economic factors affect engineering projects? –Where will the device be used? –How will the target group use the device? Bas-Ravine, Haiti

Packaging for the Real World KISS: “Keep it Simple, Stupid!” –Simpler designs have less flaws –Murphy’s Law: “If it can go wrong, it probably will.” Intuitive usage –Nobody reads the manuals –Must be easy to recharge & operate! Rugged design –Can you drop it without breaking it? Design for the local environmental conditions –Dust, sand, snow, humidity, etc.

For more information Micro Hydro Installations – Light Up The World (LUTW) – Bicycle Dynamo Rectifiers & Filters –