4.1 Electrical Energy Sources and Alternatives. 1. Using Heat to Generate Electricity 65% of all electric power is generated by burning fossil fuels such.

4.1 Electrical Energy Sources and Alternatives

1. Using Heat to Generate Electricity

65% of all electric power is generated by burning fossil fuels such as coal, oil, or natural gas. Most of the fossil fuel used in power plants is coal.

In coal-fire generating plants, the coal is first crushed into a fine powder. It is then blown into a combustion chamber and burned. The heat from the burning coal boils water and superheats the resulting steam to a high temperature and pressure. This high pressure steam drives a large turbine.

The turbine is long shaft with many fan blades. Steam striking the blades turns the turbine. The turbine shaft rotates large electromagnetic coils in the generator to produce electricity. Oil or natural gas can be burned in the combustion chamber instead of coal.

2. Nuclear fission is the splitting of the atoms of a heavy element such as uranium. The nuclear fission takes place in a nuclear reactor. The splitting of the atoms releases an enormous amount of energy. This release of energy is used to produce high-pressure steam that drives the turbine.

3. Geothermal energy is energy that is derived from the internal heat of the Earth. Hot water and steam naturally come to the Earth’s surface after being heated by hot rock within the Earth’s crust. The steam can be channeled through pipes and used to drive turbines.

4. Biomass is biodegradable waste such as agricultural waste or composting , or garbage that can be used as an energy source for steam-driven generators.

5. Cogeneration is the use of waste energy from another process, such as heating or generating electricity. The process of manufacturing glass uses very high temperature furnaces. The waste heat from the manufacturing process can be used to produce steam to drive a turbine to generate electricity.

6. Using Water Power to Generate Electricity

• About 20% of the world’s electricity is generated by hydro-electric power plants. These plants capture the energy of falling water. Most hydro-electric power plants use a dam built across a river to store water in a reservoir. Water is directed through a channel called a penstock to a large paddle-covered turbine. The rushing water rotates the turbine which is connected to a generator in the same way as a steam-driven turbine.

Alternative Energy Sources

7. Moving water from ocean tides can also power turbines that run generators.

8. Wind energy can be harnessed to turn a shaft. A number of wind-powered generators can be connected together in wind farms to produce large amounts of electrical energy.

9. Solar cells use the photovoltaic effect to produce electricity. Today’s silicon-based solar cells are much more efficient than the first solar cells. Eg. calculators, switches for automatic street lights and burglar alarms

10. Fuel cells generate electricity directly from a chemical reaction with a fuel such as hydrogen. The hydrogen comes from sources such as gasoline or alcohol.

Renewable and Nonrenewable Energy

• Nonrenewable resources cannot be replaced as they are used up. Alberta’s fossil fuel resources (coal, oil, and natural gas) are nonrenewable resources.

• Renewable resources can be renewed or replenished naturally in relatively short periods of time. Wind energy, solar energy, geothermal energy and biomass are renewable resources. Trees are a renewable resource if they are managed carefully.

4.2 Electricity and the Environment

• Every method of generating electricity affects the environment. Some methods create undesirable by-products that can have negative effects on human health and the environment.

Air Pollution

• The burning of fossil fuels results in the release into the atmosphere of many problem-causing substances.

• Fly ash is airborne ash that is produced from burning coal. Fly ash contains small amounts of mercury which is a poisonous metal that can damage the nervous system.

• Some of the most harmful molecules that are released from burning coal are sulfur dioxide (SO2(g)), nitrogen oxides (NOx(g)), and carbon dioxide (CO2(g)).

Other Environmental Effects

• Strip-mining techniques are used when deposits of coal are near the surface. Plants, animals, soil, and rocks are cleared away above the coal deposits so the coal can be mined. The land can be reclaimed by replacing the soil and plants; however the original natural environment is usually not fully restored.

• Oil and gas wells can release poisonous gases into the environment. Concentrations of chemicals around wells are monitored for safety.

• Steam turbines often release large amounts of warm water into nearby lakes and rivers. Increases in water temperature can alter freshwater ecology and can sometimes kill fish.

• Nuclear power plants, hydro-electric power plants, wind farms, the process of making solar cells, geothermal plants, and generators that uses tidal or wave energy all can have negative effects on the environment. However, the green sources of energy – especially wind, tide, and geothermal – harm the environment much less than fossil fuels do.

Conserving Energy and Nonrenewable Resources

• The main benefit of conserving energy and nonrenewable resources is less pollution. Also, temporary shortages of resources can cause hardship and price jumps. When fuel prices skyrocket, poorer countries cannot afford the energy they need.

A Sustainable Future

• Sustainability means using resources at a rate that can be maintained indefinitely. Without sustainable energy use, future generations may not be able to support themselves. Decisions made with sustainability in mind can involve compromise – taking the bus may not be as convenient as driving your car, however, this will conserve fuel.

4.3 Electrical Technology and Society

Benefits of Electrical Technologies

• Electrical technologies have improved our standard of living. Most improvements or inventions have come as a result of a desire to improve speed, efficiency or convenience. This has resulted in freeing up people's time to do other things.

Drawbacks of Electrical Technologies

• More technology means more resources are needed to manufacture and operate them, making sustainability more difficult to achieve. As technology advances, obsolete devices become waste, adding to our problems of waste disposal. Some technologies are too expensive for some countries to adopt, leading to isolation and exclusion.

Computers and Information

• Computers have revolutionized the way we accomplish many tasks, including writing, calculations and communications. Computers use binary numbers (0s and 1s) to store and transmit data which has led to the digital technology era.

Electricity and Computers

• Electrical current is used in one way or another in storing or transmitting information. Lasers, photodetectors, and electrical pulses all enable electronic devices to complete the tasks they are made to do.

• A computer hard drive uses electrical pulses to record and transmit information, by using an aluminum or glass disk, with a thin layer of magnetic material that spins at up to 300km/h. The electrical pulses are sent to an arm with read and write heads, which are magnetic coils that magnetize spots on the spinning disk.

• Reading - magnetic spots induce current in the electromagnetic coil, reproducing 0's and 1's in the original signal and are sent to the computer's processor.

• Writing - electrical signals are responded to from the computer's processor.

Electrical Transmission of Information

• Electrical signals are sent from computer to computer throughout the world, making the storage and transmission of information compact, easy and relatively cheap. Concerns with this ease are access, privacy and safety.

• Misleading or false information is also a problem and the ‘information explosion’ has created other storage, handling and access problems. Search engines help locate some of the information you may be looking for, but they cannot access everything.