Power from COAL
What is coal?
360 million years ago Queensland was a very different place to what it is today. If you were to travel back in time you would see vast areas of dense plant life. Large freshwater lakes and swamps covered a large part of the state.
As the plants died they partially decayed to peat, a brown spongy material. Over time this peat was covered in sediment washed down by floods or rivers. In a process that took millions of years this plant material was crushed and heated, producing coal.
Australia has an abundant supply of coal (in fact it should last about 700 years based on the present rate of use).
Coal use in Queensland
Queensland has enormous reserves of high quality coal deposits, particularly in central Queensland. Most of the electricity generated in Queensland comes from coal-fired power stations. In these power stations the energy in the coal is transformed into electrical energy. This happens in various stages:
- coal is burnt to heat water
- the water boils and turns to steam
- the steam turns a turbine
- the turbine turns a generator and electricity is produced.
The computerised control systems at Stanwell Power Station are among the most technologically advanced in the world. In fact, the station is so highly automated that it is possible for one operator to use video screens to monitor all parts of the plant.
Image of Stanwell Power Station supplied courtesy of the Stanwell corporation.
Electricity from coal
The process of producing electricity from coal involves several steps that changes the energy stored in coal to electrical energy.
The principle behind the coal-fired power station is very simple.
Coal is burnt to heat water until the water turns to steam. The steam is forced under great pressure through a turbine. The turbine turns a generator, which produces the electricity. The turbine in the power station is turning the generator at 3000 revolutions per minute (rpm). This produces an alternating current with a frequency 50 Hertz. (Hertz is the unit for frequency. 50 Hertz means the electricity changes direction 50 times per second.)
A "step-up" transformer increases the output of the generator to a much larger voltage.
The large voltage is necessary in order to "push" the electricity over the long distances it has to travel. The Stanwell Power Station generates 20,000 volts of electricity, which is "stepped-up" to 275,000 volts. Find out how to calculate the energy from steam.
Benefits and Disadvantages
Benefits of a coal-fired power station
- Australia has a good supply of coal
- Coal is a relatively cheap source of energy
- Electricity supply is reliable
- Infrastructure, such as rail lines and ports, is in place to deliver coal efficiently
- Coal is not a renewable resource
- During the production of electricity carbon dioxide is released contributing to greenhouse gases
- When it is burned, some other gases are released that pollute the atmosphere
- Coal mining changes the environment where it is mined
- Rehabilitation is a costly necessity
Coal-fired power stations provide relatively low-cost electricity to business and industry. This is an important comparative advantage when dealing in international markets. By lowering the cost of production of our goods and services they become more competitive and therefore a valuable source of import dollars. This can only lead to a better economy and consequently a higher standard of living.
However, the community is exhibiting very real concerns about the environment. This is reflected in the level of environmental regulation and has encouraged energy producers to become environmentally conscious. As a result there have been attempts to reduce greenhouse gas emissions through the implementation of ecologically friendly practices and policies.
