Turning a generator produces electricity. To turn the generators we connect them to turbines. We use different energy resources to turn the turbines. Wind and water flow can turn turbines directly. Steam is often used, produced by heating water. The heating is done by burning fuels, or using other heat sources. The video below shows how a coal fired power station works. In a modern gas-fired power station the hot exhaust gases from the burners are used to turn the turbines and then to heat water to steam which turns the turbines.
The Main Fuels
Electricity can be generated in large power stations from:
- Fossil fuels (coal, natural gas and oil) which were formed hundreds of million years ago and will eventually run out. All the fossil fuels produce carbon dioxide when burned. The extra carbon dioxide from burning fossil fuels is a cause of global warming which causes climate change.
- In a nuclear reaction a large amount of energy is released from small amounts of uranium and plutonium. One advantage is that no carbon dioxide is formed.
- Biofuels (wood, suger and manure) are materials from recently living plants and animals. Carbon dioxide is removed from the atmosphere when plants grow and then released when fuels are burned or fermented. As long as more plants are grown there is no net change, biofuels are carbon neutral.
When we decide which fuels to use in power stations we have to take lots of factors into account:
- Transport costs and the cost of the fuel.
- The availability of the fuel – will it run out or will it be difficult to get?
- The start-up time – how long it will take to commission (plan and build)?
- The cost of building the power station.
- How much it will cost to decommission (take apart at the end of its life) and to dispose of waste materials.
- Maintenance costs and availability of cooling water.
- Pollution and waste, for example whether carbon dioxide is emitted.
- The risk of accidents.
A voltage is induced across a coil of wire by moving a magnet into or out of a coil. Moving the coil instead of the magnet would have the same effect.
This effect is used in dynamos and generators.
There are three ways to increase the voltage:
- Use stronger magnets.
- Use more turns of wire in the coil.
- Move the magnet (or the coil) faster.
This process is called electromagnetic induction.
A generator in a power station uses an electromagnet to produce a magnetic field. The electromagnet rotates inside coils of wire so that the coils are in a changing magnetic field and a voltage is induced.
The video below explains electromagnetic induction.