The coal used in power stations is a fossil fuel formed over millions of years from the remains of decaying plants, which became peat and was then fossilised.
In MegaWatt, coal is a low cost and high capacity technology, but an option with a high environmental impact.
The largest source of electricity production in the world is coal! In 2018 it made up a massive 38% of the total supply, more than other fossil fuels like gas and a far larger percentage than options like nuclear or renewables. This share is projected to fall as other options meet more of the increasing demand for electricity. In a coal-fired power station, the chemical energy of the coal is released as heat when it is burned. This heat is used to change liquid water to steam, which is then passed through a steam turbine to extract some of the heat energy and convert it to kinetic energy. The kinetic energy in the spinning turbine is transferred to a generator, where the conversion to electrical energy takes place. Coal is cheap, with abundant supplies of fuel and the ability to construct power plants quickly close to where the demand is. A trade-off with the use of coal is that is has large carbon emissions, and contributes to poor air quality due to other products of burning the fuel.
Now for some stats from the UK grid in 2019.
Coal provided 2.1% of UK generation, a record low not seen since before the industrial revolution. This is down from 4% of generation in the previous year, and 18% in 2013.
The UK announced plans to phase out coal by 2025, and in 2020 this was brought forward to 2024. These decisions are all part of a wider strategy for reaching net zero carbon emissions by 2050.
There are currently 4 active coal power stations, and plans are in place to convert two of these to gas using the existing infrastructure.
Carbon capture and storage technology is being explored as an option for capturing emissions from power plants. In the UK, this is being applied to biomass plants, however the technology will be applicable to coal plants too.
Mining coal near the surface can be difficult, and requires lots of explosives! Check out the video below to see how this happens.
Whilst coal evokes images of being dirty and polluting, it proves its usefulness in periods of electricity shortfall. As recently as November 2020, 3 coal plants were fired up to supply 6% of the UK's electricity due to a period of low wind.
If you want to learn more, here are some examples of coal plants around the world.
Drax, Yorkshire. The Drax plant formerly had 6 units which burned coal, however 4 of these have since been converted to biomass plants. The remaining 2 units are capable of providing 6% of the UK's electricity.
Bełchatów, Poland. Currently, up to 80% of Poland's electricity is coal-powered. 20% of this power is produced by Bełchatów power station, which has an installed capacity of over 5,000 MW.
All of the numbers we used for the UK statistics can be found in the Digest of United Kingdom Energy Statistics 2020 which is from the Department for Business, Energy & Industrial Strategy (the people in government who look after our energy policy). The 2019 UK grid capacity is based on the total for fossil fuel conventional steam capacity. Other statistics are from the International Energy Agency overview of electricity.