P3.2 How can electricity be generated?
Electricity is a SECONDARY ENERGY SOURCE because we use primary sources to produce it – these primary sources can be non-renewable or renewable.
Electricity is convenient because:
- It is transmitted easily over distance, through electricity cables
- It can be used in many ways, for example electric lamps, heaters, motors etc.
Mains electricity is produced by GENERATORS. Generators are the devices that transfer kinetic energy into electrical energy.
Most of the electricity we use is generated by using primary energy sources to heat water in power station
Generators can be turned DIRECTLY, for example by:
- Wind turbines
- Hydroelectric turbines
- Wave and tidal turbines
When electricity is generated using these sources, there are two steps:
- The turbine turns a generator
- Electricity is produced
Generators can be turned INDERECTLY, for example by:
- Fossil fuels
- Nuclear fuels
The heat from the fuel boils water to make steam, which expands and pushes against the blades of a turbine. The spinning turbine then turns the generator.
Generators work using a process called ELECTROMAGNETIC INDUCTION.
Generators produce voltage by spinning a coil of wire inside a magnetic field or by spinning a magnet inside a coil of wire. The bigger the current supplied by a generator, the more primary fuel it uses every second.
In a NUCLEAR power station, the energy is released due to changes in the nucleus of radioactive substances. Nuclear power stations do not produce carbon dioxide, but they do produce RADIOACTIVE WASTE.
Nuclear waste emits ionising radiation, and this can cause a number of health-related issues:
- Irradiation means exposure to radiation. This can happen naturally through background radiation from sources such as the Earth or space. It could also happen by exposure during medical treatments such as X-rays. In such cases the cells may become damaged, but the person does not become radioactive. Increased exposure may eventually lead to cancer and death
- Contamination involves a radioactive material being placed inside a person. This can be far more damaging than irradiation, yet it is often used in medical treatments where the risk is considered worth the benefit, such as tumour suppression.
The electricity produced in the generators is sent to a transformer and then to the NATIONAL GRIDS at high voltages. However energy is lost to the environment at each stage. The voltage is then reduced to a safer level of 230V, after which we can access it in our homes.
Due to the inefficiency of the electrical energy transfer through cables, the National Grid uses extremely high voltages through its network of pylons. Over half a million volts is often used, meaning a low current is needed and less energy is lost due to heat.