Presentation 3.50 MB, 125 downloads

Transcript Presentation 3.50 MB, 125 downloads

Electronics

Sources of Electrical Energy

Presentation Overview

 Terms and Definitions  Major Sources of Electricity and Basic Action  Energy Sources and Devices that Transform Them into Electricity Energy  Where Electricity Comes From  Overview and Details of Electricity Generation as a Power Source Copyright © Texas Education Agency, 2013. All rights reserved.

Terms and Definitions

Battery cell- device that transforms chemical energy into electrical energy Electrolyte- conducting liquid in battery in which ions move Energy- capacity to do work Generator- device that transforms mechanical energy into electrical energy Alternator- generator that produces alternating current Photoelectric effect- a method of transforming light energy into electrical energy Copyright © Texas Education Agency, 2013. All rights reserved.

Terms and Definitions

Thermocouple- device that transforms heat energy into electrical energy Piezoelectric effect- a way of transforming pressure into electrical energy Magnet- material with property of attracting iron and producing a magnetic field external to itself Infrastructure- the basic physical systems of a business or nation (i.e., transportation, communication, sewage, water, and electric systems) Static electricity- stationary charges of electricity Copyright © Texas Education Agency, 2013. All rights reserved.

Why do we use a lot of electricity?

Because electricity is useful in three ways: 1.

There are a lot of ways to create electricity Electricity is very efficient to transmit over short or long distances Electricity can be converted into a lot of other forms of energy But what is electricity?

• Electricity comes from charge.

Electrical Charge

 Charge is a function of individual particles, electrons, and protons.

 Conductors have a lot of free electrons, but they naturally move randomly and stay dispersed (electrons repel each other).

 It takes energy to separate and then concentrate charges.

 Electrons must be separated from an atom then forced to group together.

Charge Buildup

 Voltage is a potential energy created by the separation and buildup of charge.

  Electrical energy Related to the external forces that can be measured due to a buildup of charge  Following is a summary of the different processes used to separate and build up charges.

 Each process is usually described as an energy conversion process.

Summary of Electrical Energy Conversion Processes

Each of the following methods are different ways to separate charge:  Thermal energy into electrical energy  Light energy into electrical energy  Chemical energy into electrical energy  Mechanical energy into electrical energy Which of the following process fits into which category?

Major Sources of Electricity and Basic Actions

Chemical source- opposite charges produced on two different kinds of cell plates Magnetic source- moving parts with magnet, which generates electricity Pressure source- physical distortion of small crystal Heat source- two dissimilar metals joined together when heated produces electricity Light source- electrons emitted when light strikes surface; photoelectric effect Friction source- Rubbing two objects together Copyright © Texas Education Agency, 2013. All rights reserved.

Chemical Source and Devices

Magnetic Source and Devices

Pressure Source and Devices

Heat Source and Devices

Light Source and Devices

Friction Source and Devices

Energy Use

 All of these methods are used to create electrical energy, but most do not have the capacity to create very much of the electricity we use.

 For example, the total number of batteries made each year is in the tens of billions, which represents thousands of mega watt-hours of energy.

Where Does Electricity Come From?

 We turn on a light switch and get electricity.

 We take this for granted, but the abundant and affordable availability of electricity is directly related to our quality of life.

 About 40 percent of our total energy use comes from electricity.

 Where does the electrical energy we use in the United States come from?

A Multi-Step Process

 The process has many parts and steps.

 The two major pieces are the distribution process and the generation process.

   We are more aware of the distribution system because we see it.

We see the distribution system because that is how we get power to our homes and businesses.

The electricity generating plants are typically large, but they are not usually located near homes or population centers.

Electrical Infrastructure

 The system built to provide electricity to homes and businesses is an example of infrastructure.

 We see part of that infrastructure with telephone poles (called a utility pole) and overhead power wires.

 Other parts of the infrastructure include power stations, substations, and transformers.

 We don’t often see the power stations.

Electricity Delivery

It Starts With Heat

 By far, the most common energy source for electricity comes from burning fossil fuels.   About 68 percent of our electricity Another 20 percent comes from nuclear  The following chart details U.S. energy use and sources.

 We need to understand more about the most important method for generating electricity.

Electricity Generation

 Renewable energy sources get a lot of attention but still provide only a small fraction of the energy we use.

 The most important renewable energy source is hydroelectric, which uses water pressure behind dams to turn large turbines.

  We get about 7 percent of our electricity this way.

Other renewables account for a little more than 3 percent of our electricity generation.

Overview of the Most Common Electricity Generating Process

Fuel creates heat Heat boils water Water becomes steam Steam drives a turbine The turbine spins a generator The generator produces electricity The electricity is delivered to homes and businesses Copyright © Texas Education Agency, 2013. All rights reserved.

Nuclear Power Plant

Fuel Creates Heat

 This process is called combustion.

 Also called burning  A chemical reaction between fuel and oxygen  Fuel is usually a carbon based organic molecule (a hydrocarbon)  An exothermic reaction  Heat and light are released.

 Other byproducts can include CO 2 , water, nitrogen dioxide, carbon monoxide, and ash.

Nuclear Power

 The fuel source is the element uranium.

 The uranium fuel generates heat through a process called fission.

    The nucleus of the atom splits into smaller pieces.

It requires the absorption of a neutron to start the process.

Several neutrons are also released, which can continue the fission process in a chain reaction.

Nothing is burned or exploded.

Heat Boils Water

 The chemical or nuclear reaction creates heat, which is thermal energy.

 This thermal energy is stored as superheated steam by boiling water.

 Steam can hold a lot of energy.

 Steam heat and pressure drive a turbine, which converts the thermal energy to mechanical energy.

Steam Engine

 Converts heat into mechanical work  About 90 percent of all electricity is generated using steam as the working fluid.

 The device that uses the steam is called a steam turbine.

Steam

 The gaseous phase of water  Steam at a temperature above the vaporization point (100 °C) is called superheated steam.

 Superheated steam has tremendous internal energy due to pressure and temperature.

 That energy can be released, yet stays above the condensation temperature of water.

 Energy is released as kinetic energy against turbine blades through mechanical expansion.

Steam Drives a Turbine

 Steam is directed by nozzles against propeller like blades to drive the turbine.

 Steam comes out of the nozzle at high velocity and high pressure.

 Some of the velocity and pressure of the steam is converted into kinetic energy of the turbine rotor.

 This process allows the turbine to convert heat energy into rotary mechanical energy.

Turbine Pressure Stages

 Not all of the steam energy is used up in one stage; there is enough steam energy to drive multiple turbine stages.

  There are many blades and nozzles and many stages in a turbine. Pressure and temperature get lower and lower as the steam moves through each stage.

 Each stage is designed for maximum efficiency at the lower pressures and temperatures for each successive stage.

Electricity Generation

More Steam Details

 A steam engine is an example of an external combustion engine.

 The steam engine was the driving force behind the Industrial Revolution.

 The thermodynamic process used is called the Rankine Cycle.

 At the end of the cycle, steam is condensed back to water (in a condenser) and returned to the boiler.

Electromagnetic Induction

 Finally, the mechanical energy of the turbine drives an electrical generator.

 The generator converts mechanical energy into electrical energy.

 This uses a process called electromagnetic induction.

 Electromagnetic induction requires a conductor to be exposed to a changing magnetic field.

Generator Action

 A conductor sees a changing magnetic field in a generator as it rotates through the field.

 This is called relative motion.

 The conductor is forced to rotate because of the turbine, which drives the generator.

 Another way to get a changing magnetic field is to have alternating current through a stationary conductor.

 This is called transformer action.

Electrical Work

 As the conductor moves through the magnetic field, a voltage is induced in it.

 If the conductor completes an electric circuit with a load, current is produced.

 This current and voltage performs electrical work, which is the useful output of a generator.

 The conductor, usually a wire, takes work to drive the generator from the turbine.

The Load on a Generator

 The current that flows through the conductor also creates a magnetic field.

 This second magnetic field is a function of the current drawn by the load, and it opposes the original magnetic field in the generator.

  The two magnetic fields interact.

This interaction is called motor action.

 This motor action is the mechanical load on a generator.

Work In Equals Work Out

 The more current, the larger the magnetic field around the conductor.

   This increases the amount of interaction between the two magnetic fields.

An increase in motor action This increases the load or drag on the generator, forcing the turbine to work harder to overcome this load.

 More electrical work out of a generator requires more mechanical work in.

More Induction Facts

 Both Michael Faraday and Joseph Henry discovered inductance separately.

 They were each rewarded by naming electrical terms after them.

  The Farad is the unit of capacitance.

The Henry is the unit of inductance.

 The principles of magnetic induction were described mathematically by James Clerk Maxwell.

Coal-fired Power Plant

Typical Diagram of a Coal-fired Thermal Power Station

1. Cooling tower 8. Surface condenser 10. Steam control valve 19. Superheater 2. Cooling water pump 11. High pressure steam turbine 20. Forced draught (draft) fan 3. Transmission line ( 3 phase ) 4. Step-up transformer ( 3-phase ) 12. 13. Deaerator Feedwater heater 5. Electrical generator ( 3 phase ) 6. Low pressure steam turbine 7. Condensate pump 14. Coal conveyor 15. Coal hopper 16. Coal pulverizer 21. Reheater 22. 23. 24. 25. Combustion Economiser Air preheater Precipitator air intake 17. Boiler steam drum 26. Induced draught (draft) fan 9. Intermediate pressure steam turbine 18. Bottom ash hopper 27. Flue gas stack Copyright © Texas Education Agency, 2013. All rights reserved.

Fossil Fuel Energy

Current and Future Production

What does the Historical Oil Production Chart Mean?

 Onshore oil production has dropped dramatically since the 1980s.

 This has lead to the perception that the oil and gas industry is in decline.

 Perception: A poor career choice  However, offshore oil production is significant and has been stable for 40 years.

Oil Production

 However, note the sharp upward trend starting in the late 2000s.

 This is a result of improved oil production from sources that were unproductive.

 This improved production is a direct result of technology.  Fracking in shale and tight formations  Note the projected oil production for the future on the next chart.

Government Projections

 Note that the petroleum energy supply is projected to be stable for the next 30 years.

 Stable jobs, careers, and income  Also note the rising natural gas production estimates on the next slide.

 This energy source means natural gas will be replacing coal for electrical generation.

 Natural gas is cleaner than coal.

Presentation Review

 Terms and Definitions  Major Sources of Electricity and Basic Action  Energy Sources and Devices that Transform Thermal Energy into Electricity Energy Copyright © Texas Education Agency, 2013. All rights reserved.

Presentation 3.50 MB, 125 downloads

Transcript Presentation 3.50 MB, 125 downloads

Electronics

Sources of Electrical Energy

Presentation Overview

Terms and Definitions

Terms and Definitions

Why do we use a lot of electricity?

Electrical Charge

Charge Buildup

Summary of Electrical Energy Conversion Processes

Major Sources of Electricity and Basic Actions

Chemical Source and Devices

Magnetic Source and Devices

Pressure Source and Devices

Heat Source and Devices

Light Source and Devices

Friction Source and Devices

Energy Use

Where Does Electricity Come From?

A Multi-Step Process

Electrical Infrastructure

Electricity Delivery

It Starts With Heat

Electricity Generation

Overview of the Most Common Electricity Generating Process

Nuclear Power Plant

Fuel Creates Heat

Nuclear Power

Heat Boils Water

Steam Engine

Steam

Steam Drives a Turbine

Turbine Pressure Stages

Electricity Generation

More Steam Details

Electromagnetic Induction

Generator Action

Electrical Work

The Load on a Generator

Work In Equals Work Out

More Induction Facts

Coal-fired Power Plant

Typical Diagram of a Coal-fired Thermal Power Station

Fossil Fuel Energy

Current and Future Production

What does the Historical Oil Production Chart Mean?

Oil Production

Government Projections

Presentation Review

Directory