Wiktor Wise
Coal-fired power plants are thermal power stations that burn coal to generate electricity. They are the most common method of electricity generation worldwide, accounting for about a third of the world's electricity. In this process, coal is pulverized and burned in a boiler to produce high-pressure steam. This steam is then directed towards a turbine, where it spins a generator to create electricity. The steam is then cooled, condensed back into water, and returned to the boiler to restart the process.
| Characteristics | Values |
|---|---|
| How coal creates electricity | Coal is burned in a boiler to produce steam, which then flows into a turbine, spinning a generator to create electricity. |
| How coal turbines work | The force of the steam on the blades of the turbine spins a rotor shaft, which is connected to a generator. The generator then converts the mechanical (kinetic) energy of the rotor to electrical energy. |
| Types of turbines | Steam turbines, combustion (gas) turbines, hydroelectric turbines, and wind turbines. |
| Global use | Coal-fired power stations generate about a third of the world's electricity, with China accounting for over half of this. |
| Environmental impact | Coal-fired power stations are the largest single contributor to climate change, releasing 12 billion tonnes of carbon dioxide annually. They also cause many illnesses and early deaths, mainly from air pollution. |
| Phase-out | The UN Secretary General has called for OECD nations to phase out coal-fired generation by 2030 and the rest of the world by 2040. Britain plans to phase out coal by October 2024. |
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What You'll Learn
How coal is converted into electricity
Coal is a fossil fuel that has been used to generate electricity since the Industrial Revolution. It is delivered by truck, rail, barge, ship, or coal slurry pipeline to coal-fired power stations, which burn coal to generate electricity. There are about 2,500 coal-fired power stations worldwide, each capable of generating a gigawatt of electricity. They produce about a third of the world's electricity.
Coal-fired plants produce electricity by burning coal in a boiler to produce steam. The steam, under high pressure, flows into a turbine, which spins a generator to create electricity. The steam is then cooled, condensed back into water, and returned to the boiler to start the process over. The Kingston Fossil Plant in Tennessee, for example, burns coal to heat its boilers to about 1,000 degrees Fahrenheit to create high-pressure steam. The steam is piped to the turbines at pressures of more than 1,800 pounds per square inch. The turbines are connected to the generators and spin them at 3,600 revolutions per minute to make alternating current (AC) electricity at 20,000 volts. River water is pumped through tubes in a condenser to cool and condense the steam coming out of the turbines.
The coal is usually pulverized and then burned in a pulverized coal-fired boiler. The heat from the burning pulverized coal converts boiler water to steam, which is then used to spin the turbines that turn the generators. Thus, the chemical energy stored in coal is converted successively into thermal energy, mechanical energy, and, finally, electrical energy.
While coal remains the leading source of electricity production globally, it has fallen out of favour in some regions due to its environmental and health impacts. Coal-fired power stations are the largest single contributor to climate change, releasing approximately 12 billion tonnes of carbon dioxide annually. The UN Secretary General has called for OECD nations to phase out coal-fired generation by 2030 and the rest of the world by 2040.
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The burning of coal to produce steam
Coal is a fossil fuel that is delivered to power stations by highway truck, rail, barge, collier ship, or coal slurry pipeline. It is then pulverized and burned in a boiler, converting boiler water to steam. The steam is piped to the turbines at pressures of over 1,800 pounds per square inch. The turbines are connected to the generators and spin them at 3,600 revolutions per minute to make alternating current (AC) electricity at 20,000 volts.
Steam is used in coal-fired power stations instead of direct combustion because coal contains impurities that would result in a buildup of carbon deposits on the turbine blades over time. This would throw off the balance of the blades and affect gas flow. In addition, coal does not generate enough thrust from combustion to power the turbine.
The steam used to power the turbines is then cooled and condensed back into water, which is returned to the boiler to start the process over. This process of burning coal to produce steam allows coal-fired power stations to convert the chemical energy stored in coal into thermal energy, mechanical energy, and finally, electrical energy.
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Steam spinning the turbine
Steam plays a crucial role in spinning the turbine within a coal-fired power plant. The coal, often pulverized, is burned in a boiler to produce high-pressure steam. This steam is generated by heating boiler water to extremely high temperatures, often exceeding 1,000 degrees Fahrenheit. The resulting steam is then directed towards the turbine at high pressures, typically exceeding 1,800 pounds per square inch.
The high-pressure steam is channelled with tremendous force onto the blades of the turbine rotor shaft. This force causes the rotor shaft to spin at incredible speeds, typically reaching 3,600 revolutions per minute in a coal-fired power plant. The spinning rotor shaft is connected to a generator, which lies at the heart of converting mechanical energy into electrical energy.
The rotor shaft's rotational energy is transferred to the generator, which then converts this mechanical (kinetic) energy into electrical energy through the principles of electromagnetic induction. This process of spinning the turbine and generating electricity is dependent on the pressure and force of the steam. The steam's pressure and force are influenced by the temperature and volume of the steam generated in the boiler.
It is worth noting that coal-fired power plants are not the only ones that utilize steam turbines. Steam turbines are also employed in solar thermal, geothermal, and nuclear power plants. Additionally, steam turbines are the most common type of turbine used for electricity generation, accounting for about 42% of U.S. electricity generation in 2022.
The use of steam in coal-fired power plants offers advantages such as higher pressure and efficiency compared to direct combustion. However, it is important to address the environmental impact of coal-fired power plants, which are significant contributors to air pollution and climate change.
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The role of coal-fired power stations
A coal-fired power station is a thermal power station that burns coal to generate electricity. There are about 2,500 coal-fired power stations worldwide, each capable of generating a gigawatt of electricity. Together, they produce about a third of the world's electricity.
Coal is delivered to the power station by highway truck, rail, barge, collier ship, or coal slurry pipeline. Generating stations are sometimes built next to a mine, especially when mining low-value coal such as lignite, which is not worth transporting long distances. In such cases, the coal may be delivered by conveyor belt or massive diesel-electric-drive trucks. A large plant under full load requires at least one unit train's worth of coal every day.
At the power station, the coal is pulverized and burned in a boiler to produce high-pressure steam. The steam is then directed at tremendous pressure into a turbine, which spins a generator to create electricity. The steam is then cooled, condensed back into water, and returned to the boiler to start the process over.
Coal-fired power stations are the largest single contributor to climate change, releasing approximately 12 billion tonnes of carbon dioxide annually. They also cause many illnesses and early deaths, mainly from air pollution. As a result, the UN Secretary General has called for OECD nations to phase out coal-fired generation by 2030 and the rest of the world by 2040.
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The phasing out of coal
Coal-fired plants produce electricity by burning coal in a boiler to produce steam. The steam, under high pressure, flows into a turbine, which spins a generator to create electricity. However, coal is the most carbon-intensive fossil fuel and is responsible for over 30% of the global average temperature increase above pre-industrial levels. As a result, there is a global push to phase out coal.
Many countries have already transitioned away from coal, with Ontario being the first jurisdiction in North America to eliminate coal in electricity generation in 2014. In 2016, the Government of Canada announced plans to phase out coal-fired electricity generation by 2030. Alberta followed suit in 2024, phasing out its last coal power plant. Germany, which is due to shut down its last coal-fired power station between 2035 and 2038, has the largest transition announced so far. The United Kingdom has also set a target to fully phase out coal by 2024, and the United States cut its coal power use in half between 2014 and 2022.
While the priority is to phase out the oldest and least efficient plants, more than USD 1 trillion of capital has yet to be recovered in younger plants in the existing coal fleet, mostly in Asia, which accounts for two-thirds of global capacity. A rapid phase-out risks creating stranded assets, and managing the move away from coal is not simple, especially when it proceeds at the speed required. However, the establishment of special purpose entities might be necessary to pool various funding sources and manage disbursements on the ground. There is also an important role for blended finance, along with carbon pricing, in accelerating the closure of coal power plants and increasing investment in clean energy.
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Frequently asked questions
Coal-fired power plants burn coal to produce steam. The steam, under high pressure, is then used to spin a turbine, which in turn rotates a generator to create electricity.
Using combustion to turn the turbines would likely result in a buildup of carbon deposits on the turbine blades over time. Steam is faster than combustible energy and direct combustion supply will harm the turbine.
Coal is delivered to power plants by highway truck, rail, barge, collier ship, or coal slurry pipeline. Generating stations located near a coal mine may receive coal by conveyor belt or massive diesel-electric-drive trucks.
The coal is pulverized and then burned in a boiler. The heat from the burning coal converts the water in the boiler into steam.
Coal power plants are the largest single contributor to climate change, releasing approximately 12 billion tonnes of carbon dioxide annually. They also cause many illnesses and early deaths, mainly from air pollution.
