Molly Ayala
Coal-fired power plants burn coal to generate steam, which then turns turbines to generate electricity. This process, known as the Rankine cycle, involves pulverizing coal into a fine powder and burning it in a boiler to produce heat. The heat converts boiler water into steam, which spins a turbine connected to a generator, producing electricity. Coal-fired power plants provide about a third of the world's electricity, with countries like China, India, and South Africa heavily relying on coal for their energy needs. However, coal combustion releases harmful pollutants and greenhouse gases, contributing to air pollution and climate change. As a result, many countries are transitioning away from coal towards more sustainable energy sources.
| Characteristics | Values |
|---|---|
| How coal is converted to electricity | Coal is burned to heat water, creating steam. The steam then spins a turbine to produce electricity. |
| Coal-fired power plants | There are about 2,500 coal-fired power plants worldwide, capable of generating a gigawatt each. |
| Environmental impact | Coal plants produce large quantities of different pollutants, reducing air quality and contributing to climate change. |
| Health impact | Coal-burning power plants are responsible for thousands of deaths each year due to emissions of particulates and microscopic air pollutants. |
| Global usage | Coal provides access to electricity for those who previously didn't have it, increasing quality of life and reducing poverty. China accounts for over half of global coal-fired electricity generation. |
| Decarbonisation | Britain aims to phase out coal usage by 2024 through the introduction of new innovations and technologies. |
| Coal consumption | In 2022, about 513 million short tons of coal were consumed in the United States, equal to about 9.8% of total U.S. energy consumption. |
| Conversion to other forms | Coal can be converted into synthetic natural gas (syngas) and has been converted to liquids in South Africa for decades. |
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What You'll Learn
How coal is delivered to plants
Coal is a fossil fuel that has been used to generate electricity since Thomas Edison's Holborn Viaduct coal plant started generating electricity for public use in 1882. The burning of coal releases thermal energy, which is then used to produce electricity. However, coal usage is being phased out in many countries due to its environmental impact and contribution to climate change.
Now, onto the main question: how is coal delivered to these plants?
Firstly, it is important to note that some coal plants are mine-mouth, meaning they are located at the coal mine, so the coal does not need to be transported over long distances. For these plants, the process of delivering coal is relatively straightforward.
However, for plants that are not mine-mouth, coal is typically transported by train. The amount of coal required by these plants is staggering; a 1000 MWe coal plant uses 9000 tonnes of coal per day, which is equivalent to the capacity of a train with 90 cars, each carrying 100 tonnes of coal. To supply this amount of coal for a full year, 365 trains would be needed, and if each train were 3 km long, the combined length of these trains would be approximately 1100 km.
Once the coal arrives at the plant, it needs to be unloaded from the train. Traditional methods involve using cranes to lift the coal from the train cars. However, newer plants have adopted a more efficient method where the floor underneath the train tracks drops away, allowing the coal to be quickly unloaded into underground containment, even while the train is still moving.
After unloading, the coal is pulverized into a fine powder by a large grinder. This step maximizes the burning efficiency of the coal, ensuring nearly complete combustion to maximize heat output and minimize pollutants. The pulverized coal is then fed into a boiler, where it is burned to heat water and produce steam. This steam is directed through pipes to a turbine, causing it to rotate at high speeds and spin a generator, thus producing electricity.
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The process of burning coal
Coal-fired power plants require an enormous amount of coal. For example, a 1000 MWe coal plant uses 9000 tons of coal per day, equivalent to a whole trainload. The amount of coal used in a year would require 365 trains, and if each is 3km long, a single train carrying all of this coal would be about 1100km long.
Burning coal releases stored solar energy as thermal energy, but it also produces carbon dioxide and methane, which are harmful greenhouse gases. Coal-fired power plants have many associated environmental impacts on the local ecosystem, and they produce large quantities of different pollutants, which reduce air quality and contribute to climate change.
In recent years, coal consumption has declined in many countries, primarily due to the decline of coal use in the electric power sector. Britain, for example, plans to phase out coal in its power mix by October 2024, in favor of new innovations and technologies that will allow the country to operate with zero carbon.
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How coal generates electricity
The primary use of coal in the United States is to generate electricity. Coal is a fossil fuel that has generated electricity in Great Britain since the industrial revolution. In 2022, coal accounted for about 19.5% of U.S. electricity generation. Similarly, coal provides about 40% of the world's electricity. Countries like South Africa, China, and India use coal for 94%, 70-75%, and 70-75% of their electricity needs, respectively.
The process of converting coal to electricity involves multiple steps. First, coal is milled into a fine powder, which increases its surface area and allows it to burn more quickly and efficiently. This powdered coal is then blown into the combustion chamber of a boiler, where it is burned at high temperatures. The combustion of coal releases thermal energy in the form of heat. This heat is transferred to pipes containing water, which boils to become steam. The steam generated is under tremendous pressure and is directed into a turbine containing thousands of propeller-like blades. As the steam enters the turbine, it pushes the blades, causing the turbine shaft to rotate at high speed.
The turbine is connected to a generator, which consists of carefully wound wire coils and magnets. The rapid rotation of the wire coils within the strong magnetic field produces electricity through a process known as electromagnetic induction. This electricity is then transformed into higher voltages for efficient transmission via power line grids. Once the electricity nears its point of consumption, such as homes, the voltage is reduced to safer levels suitable for domestic use.
After passing through the turbine, the steam is cooled and condensed back into water. This water is then returned to the boiler to restart the process, ensuring that the same water is used repeatedly in the thermal cycle. While burning coal is a relatively efficient way to generate electricity, it produces harmful emissions, including carbon dioxide and methane, contributing to climate change and reduced air quality. As a result, there is a growing trend towards decarbonizing electricity and phasing out coal usage in favor of cleaner energy sources.
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Coal-fired power plants and their environmental impact
Coal-fired power plants burn coal to produce steam, which then turns turbines to generate electricity. In 2022, coal accounted for about 19.5% of U.S. electricity generation. However, coal-fired power plants have a significant environmental impact.
The process of burning coal releases a variety of airborne toxins and pollutants, including mercury, lead, sulfur dioxide, nitrogen oxides, particulates, and various other heavy metals. These emissions have been linked to asthma, cancer, heart and lung ailments, neurological problems, and even premature death. Additionally, the ash produced by coal-fired power plants, which amounts to more than 100 million tons per year, can contaminate waterways and drinking water supplies if not properly disposed of.
Coal mining, an essential step in the process, also has environmental repercussions. Surface mining, for example, involves removing the soil and rock above coal deposits, altering the landscape and potentially harming aquatic life downstream with pollutants. Mountaintop removal and valley fill mining have significantly impacted the Appalachian Mountains, with similar consequences.
To mitigate these issues, various measures have been implemented. U.S. air pollution laws mandate the use of pollution-control devices to capture fly ash emissions. The Clean Air Act and The Clean Water Act aim to reduce pollutants released into the air and water. Additionally, power plants employ flue gas desulfurization equipment ("scrubbers") to remove sulfur and other impurities from smoke before it exits the smokestacks.
While these efforts have helped, the transition away from coal towards cleaner energy sources is essential to avoiding the worst impacts of coal on the environment and public health.
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The future of coal-fired power stations
Coal-fired power stations burn coal to generate electricity. The chemical energy stored in coal is converted into thermal energy, then mechanical energy, and finally electrical energy. This process involves pulverizing the coal and burning it in a boiler to heat water, creating steam that spins turbines to generate electricity.
Coal-fired power stations have been a significant source of electricity globally, contributing about a third of the world's electricity. However, they are also major contributors to air pollution and climate change, releasing approximately 12 billion tonnes of carbon dioxide annually. As a result, there has been a growing trend towards phasing out coal-fired power stations and transitioning to renewable energy sources.
In recent years, several countries and regions have made significant strides in moving away from coal-fired power generation. For example, Portugal closed its last remaining coal plant in 2021, becoming the fourth country in the European Union to do so. Germany has also accelerated its timeline for phasing out coal, with the western state of North Rhine-Westphalia set to decommission its coal plants by 2030. Additionally, the UK's last coal-fired power plant is expected to cease operations by the end of 2024.
However, the future of coal-fired power stations is not uniform across the globe. While advanced economies have generally seen a decline in coal demand, emerging economies like India, Indonesia, and Vietnam are witnessing increasing demand due to rising electricity needs coupled with economic and population growth. China, the world's largest consumer of coal, continues to add new coal-fired power plants, although its consumption is expected to level off due to the expanding renewables sector.
To align with net-zero emission targets, carbon capture, utilisation, and storage (CCUS) technologies are being implemented in some coal-fired power plants. As of June 2023, only four commercial coal-fired power plants worldwide have adopted CCUS, with the Taizhou project in China being the most recent addition. While coal-fired power generation still plays a significant role in meeting global energy demands, the transition towards renewable and sustainable energy sources is gaining momentum.
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Frequently asked questions
Coal is burned to heat water, creating steam. This steam then spins a turbine to produce electricity.
Coal-fired power plants or coal power plants are also known as coal-fired power stations.
Burning coal produces carbon dioxide and methane, which are harmful greenhouse gases. Coal-fired power plants also produce large quantities of pollutants, which reduce air quality and contribute to climate change.
