Generation of Electrical Energy

Generators

• Power stations use various types of generators to produce electricity.
• Among these are
• thermal generators
•  hydroelectric generators
• diesel generators
• gas turbine  generators
• nuclear generators

Thermal generators

• Fuels such as coal and petroleum are burned in a boiler to produce steam.
• The steam produced,under high pressure, rotates the turbines at high speed.
• These turbines are connected to a large generator which produces electricity.
• The steam is then cooled until it condenses in a condenser and is channelled back to the boiler to repeat the process.
• The change of energy is as follows:
• Chemical energy from the fuel is converted to heat energy during burning.
• Heat energy is converted to kinetic energy as the steam turns the turbines and generator.
• Kinetic energy is converted to electrical energy as the generator produces electricity.

Hydroelectric generators

• Hydroelectric generators use water to produce electricity.
• Dams are built to hold water at a high altitude.
• When water from this dam is released in a tunnel, the water will cause the turbine which is connected to a generator in the tunnel to spin, generating electricity.
• The change of energy is as follows:
• Stored energy from the water is converted to mechanical energy as the water flows through the tunnel.
• Mechanical energy from the flowing water is converted to kinetic energy as the water turns the turbines.

Gas turbine generators

• Air is sucked in, filtered and compressed in a compressor.
• The compressed air is then mixed with natural gas.
• The mixture of compressed air and natural gas is ignited by a spark plug in a combustion chamber.
• The burnt mixture produces hot gas that expands with great force.
• This high-pressure, high-velocity gas from the combustion chamber turns the turbines and generator.
• The change of energy is as follows:
• Chemical energy from natural gas is converted to heat energy as the gas is burnt.
• Heat energy is converted to mechanical energy as hot gas from the burning mixture expands.
• Mechanical energy is then converted to kinetic energy as the gas turns the turbines.
• Kinetic energy from the turbines is converted to electrical energy as the generator produces electricity.

Diesel generators

• This generator works the same way as a diesel engine that uses diesel as fuel.
• Burning the diesel in an engine would produce a great thrust.
• This thrust would move the piston and turn the axle to rotate the generator.
• The change of energy is as follows:
• Chemical energy from the diesel is converted to heat energy as it is burnt after mixing with air.
• Heat energy is converted to mechanical energy as hot gas from the burning mixture expands and creates a thrust in the engine.
• Mechanical energy is then converted to kinetic energy as the gas turns the turbines.
• Kinetic energy from the turbines is converted to electrical energy as the generator produces electricity.

Nuclear generators

• A nuclear power station produces nuclear energy in a reactor.
• Heavy nucleus of an atom such as uranium and plutonium are split into fragments, releasing enormous amounts of energy.
• Energy from the nuclear fission reaction changes water to steam.
• The steam under high pressure turns the turbines, which in turn rotates the generator to produce electricity.
• The change of energy is as follows:
• Nuclear energy in the atoms is converted to heat energy when the atoms split.
• Heat energy is converted to kinetic energy as the steam turns the turbines.
• Mechanical energy is converted to electrical energy as the dynamo connected to the turbines produces electricity.

Alternative Sources of Energy

• Solar energy
• Energy from the Sun can be converted to electricity by solar cells (or photovoltaic cells)
• Some drawbacks of using solar energy include the high cost of infrastructure, the unavailability of solar energy at night and during seasonal periods such as winter.
• Wind
• Wind power is a more realistic and economically viable form of energy.
• Low operating costs and efficient generation of energy means that more countries are developing wind generators.
• Geothermal
• Geothermal energy comes from the structure of the Earth and its interior heat source and circulation.
• (b) There is a continual flow of heat energy towards the surface of the Earth through volcanoes and hot springs.
• Biomass
• Wood and animal waste can be burnt to produce energy.
• The decomposition of dead organisms produces fuels such as alcohol, methane and biogas (mixture of methane and carbon dioxide).