* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Solid State Lighting for the Developing World
Survey
Document related concepts
Nanofluidic circuitry wikipedia , lookup
Nanogenerator wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Schmitt trigger wikipedia , lookup
Operational amplifier wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Voltage regulator wikipedia , lookup
Current source wikipedia , lookup
Power MOSFET wikipedia , lookup
Power electronics wikipedia , lookup
Current mirror wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Surge protector wikipedia , lookup
Transcript
Pico Power Generation for the Developing World Loren Wyard-Scott 1 * & Dr. James Andrew Smith 2 * 1Dept. of Electrical & Computer Engineering University of Alberta Edmonton, Alberta, Canada 2Dept. 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 • Pollution problems caused by power generation Earth at night. Where are the developed nations? Trivia! Energy use in a typical American Home [1] Total energy consumed in America in 1995: 9.2 × 1019 J [2] [1] Energy Kid’s Page, U.S. Department of Energy, http://www.eia.doe.gov/kids/energyfacts/saving/efficiency/savingenergy.html, accessed 01 Dec 2008. [2] Beursten, Bruce E., Theodore L. Brown & Eugene Le May Jr. Chemistry: The Central Science. Engelwood Cliffs, NJ: Prentice Hall, 1997. 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. 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 – – 2. What is possible? Keep it simple & effective! Risk evaluation – 5. 6. 7. 8. Prototype What actuators and sensors? At what cost? Determine level of functional replacement – – 4. What function is missing? Talk to the clients/users! Identification of affordable technology – 3. Start Never underestimate what can go wrong! Prototype device, test & start again (Steps 1 -5) Test on larger population set International certification Manufacture & distribute device Test Manufacture End 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: P E t P IV 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 Cell Series Cells Series & Parallel Cells Resistances in Series & Parallel • Resistances in series add up. Req R1 R 2 • Resistances in parallel: Req Series Resistance 1 1 1 R1 R 2 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 Ceq C 1C 2 • Capacitances in series Ceq 1 1 1 C1 C 2 Capacitors: Energy Storage • Like batteries, capacitors store energy. • An ideal capacitor with a constant voltage can store: 1 2 E CV 2 • 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 Anode • 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 Cathode 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: Vd Light Emitting Diode (LED) • 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 • Vd 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, 0.5 - 1.0 Amp output) • • • • • Place between filtered rectifier and load Pin 1: input (7 - 30 VDC) Pin 2: Ground Pin 3: output (5 VDC) Add 0.33 uF filter caps • 7805 Pin 1 and Pin 2; Pin 3 and Pin 2 1 2 3 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: – – – – Bas-Ravine, Haiti 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? 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 – http://www.green-trust.org/hydro.htm • Light Up The World (LUTW) – http://www.lutw.org/ • Bicycle Dynamo Rectifiers & Filters – http://pilom.com/BicycleElectronics/DynamoCircuits.htm