Rajan Wilcox
Fossil fuels, such as coal, oil, and natural gas, have been the predominant sources of electricity generation globally. Power plants burn these fuels to heat water and produce steam, which drives a turbine connected to an electric generator, thus converting mechanical energy into electricity. However, with growing concerns over climate change and environmental degradation, the transition towards cleaner, renewable energy sources is becoming increasingly crucial. While fossil fuels accounted for over a third of global electricity production in 2020, there has been a notable shift towards renewables in recent years, with countries like Sweden, Norway, and France obtaining over 90% of their electricity from nuclear or renewable sources.
| Characteristics | Values |
|---|---|
| Most common fossil fuels used | Coal, natural gas, oil, fuel oil |
| Electricity generation process | Fossil fuels are burned to heat water and produce steam, which drives a turbine connected to an electric generator, converting mechanical energy into electricity |
| Environmental impact | Fossil fuels are major contributors to greenhouse gas emissions, air pollution, and other environmental issues |
| Global electricity production | Coal is the largest source of electricity production globally, followed by gas |
| Country-level variation | The primary source of electricity varies by country and region due to factors like resource availability, energy policies, and infrastructure development |
| Transition to renewables | There is a growing shift towards renewable energy sources such as wind, solar, hydropower, and nuclear to reduce carbon emissions and minimize environmental impact |
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What You'll Learn
Burning fossil fuels to heat water and produce steam
Fossil fuels such as coal, oil, and natural gas are burned to produce electricity. Fossil fuel power plants burn these fuels to create heat, which is used to generate steam to drive turbines that generate electricity. This process is known as thermal generation.
Steam turbines are used to generate most of the world's electricity. In 2022, they accounted for about 42% of electricity generation in the US. Fossil fuel plants require large quantities of coal, oil, or gas, and these fuels need to be transported over long distances, which can result in supply issues and unstable costs.
The burning of fossil fuels releases carbon dioxide and other greenhouse gases, contributing to climate change and air pollution. It also emits pollutants such as NOx, SOx, CO, PM, organic gases, and polycyclic aromatic hydrocarbons. Organizations like the IEA are concerned about the environmental impact of burning fossil fuels.
However, fossil fuels have been essential in powering the Industrial Revolution and improving the quality of life worldwide. Many developing countries still rely on them for energy production, and they are relatively easy to use and cheap, making them a significant source of electricity globally.
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Steam turns turbines to generate electricity
Steam turbines are a vital component of power plants that burn fossil fuels to generate electricity. Steam is channelled through the turbine, turning the blades and generating electricity. The modern steam turbine was invented in 1884 by Charles Parsons, whose first model generated 7.5 kilowatts (10.1 hp) of electricity.
The steam turbine is a type of heat engine that derives its thermodynamic efficiency from the use of multiple stages in the expansion of steam, resulting in a process similar to ideal reversible expansion. The rotary motion generated by the turbine can be coupled to a generator to produce electricity. Turbines are made in a variety of sizes, with the smallest being <0.75 kW (<1 hp) units used for mechanical drives, and the largest being 1,500 MW (2,000,000 hp) turbines used for electricity generation.
The operation of a steam turbine is based on the principle of extracting thermal energy from pressurised steam and transforming it into mechanical work. The turbine's spinning blades turn as hot, gaseous steam flows past them, with the steam expanding and cooling, giving off its energy. This process is similar to that of a steam engine, where steam expands and cools as it flows past the blades, releasing its energy.
The steam turbine's ability to generate rotary motion makes it particularly well-suited for driving electrical generators. In 1996, about 90% of all electricity generation in the United States was through the use of steam turbines. More recently, in 2022, about 42% of all electricity generation in the United States was attributed to steam turbines.
There are different types of steam turbines, including impulse turbines and reaction turbines. Impulse turbines, such as Curtis turbines, have blades that move solely due to the impact of steam, resulting in a steam velocity drop but minimal pressure drop. On the other hand, reaction turbines, like the one invented by Parsons, have curved blades that turn when steam hits them, causing a pressure drop and an increase in steam velocity.
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Coal is the most widely used fossil fuel
Fossil fuels are formed from the remains of ancient organisms. Coal, a black or brownish-black sedimentary rock, is a fossil fuel that can be burned to generate electricity. Coal is the most widely used fossil fuel, supplying just over a third of global electricity generation. It is the largest source of energy for generating electricity in the world and the most abundant fossil fuel in the United States.
Coal is composed mostly of carbon and hydrocarbons, which contain energy that can be released through combustion (burning). The combustion of coal releases gases and particulates that are harmful to the environment. Carbon dioxide is the primary emission, and it is a greenhouse gas that contributes to climate change. Coal is also the single largest source of sulfur dioxide (SO2) emissions and the second-largest source of nitrogen oxides (NOx), which are harmful to human health and the environment.
Coal is classified into five categories based on its stage of formation: peat, lignite, sub-bituminous, bituminous, and anthracite. Younger coals, such as lignite and sub-bituminous coals, are easier to burn because they contain a higher amount of volatile compounds. Older coals, on the other hand, are more difficult to burn as they are made almost entirely of solid carbon. Anthracite was preferred in the past over bituminous coal because it burns cleaner, produces less smoke and ash, and is more efficient in terms of heat production.
The use of coal varies across different regions. In China, coal consumption is expected to level off due to the increasing adoption of renewable energy sources and strong growth in electricity demand. In contrast, emerging economies such as India, Indonesia, and Vietnam are experiencing rising demand for coal due to their growing energy needs and economic and population growth. In the United States, bituminous coal accounts for almost half of the coal used for energy production, primarily sourced from Kentucky, Pennsylvania, and West Virginia.
While there is a growing movement to phase out coal and transition to cleaner energy sources, coal continues to play a significant role in electricity generation worldwide. However, to reduce the environmental impact of coal and achieve net-zero emissions targets, governments and industries need to develop and implement less polluting technologies, such as carbon capture, utilisation, and storage (CCUS).
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Fossil fuels are major contributors to greenhouse gas emissions
Fossil fuels are the dominant cause of global warming. They are formed from the decomposition of carbon-based organisms that died millions of years ago, creating carbon-rich deposits that are extracted and burned for energy. Fossil fuels include coal, oil, and natural gas.
In the United States, about 74% of human-caused greenhouse gas emissions come from burning fossil fuels for energy. The largest source of greenhouse gas emissions in the US is burning fossil fuels for electricity, heat, and transportation. In 2022, 60% of electricity in the US came from burning fossil fuels, with coal and natural gas being the most commonly used. Coal is the most widely used fossil fuel for electricity generation globally.
Coal combustion is the largest single source of sulfur dioxide emissions and the second-largest source of nitrogen oxides, which together form fine particulate matter. Pollutants emitted from coal combustion include greenhouse gases (mainly CO2), particulate matter (including ash and unburned carbon), nitrogen oxides, and sulfur oxides. Other emissions from coal power stations include carbon monoxide, unburned hydrocarbon compounds, some carcinogens, and trace metals such as lead and mercury.
Oil releases a significant amount of carbon when burned, contributing approximately a third of the world's total carbon emissions. Oil spills have also had a devastating impact on ocean ecosystems. Natural gas is often promoted as a cleaner energy source than coal and oil, but it is still a fossil fuel and accounts for about a fifth of the world's total carbon emissions.
To generate electricity, power plants burn fossil fuels using steam boilers, combustion turbines, or both. Steam boilers burn fuel to heat water and produce steam, which is then channelled through a turbine to generate electricity. Combustion turbines burn fuels to create exhaust gases, which spin a turbine to generate electricity.
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Fossil fuel-fired power plants are a leading source of air pollution
Fossil fuels are a combination of organic compounds and inorganic, mineral matter. Coal, for instance, is a fossilized plant material preserved by burial in sediments and transformed by geological forces into a carbon-rich rock. The burning of fossil fuels at power plants releases harmful emissions, including sulfur dioxide (SO2), nitrogen oxides (NOX), particulate matter (PM), carbon dioxide (CO2), mercury (Hg), and other pollutants. These emissions have detrimental effects on both human health and the environment.
SO2, primarily produced by coal-fired power plants, contributes to acid rain and fine particle (PM2.5) pollution. Elevated levels of ground-level ozone and fine particles can aggravate heart and lung diseases, leading to serious health issues such as heart attacks, asthma attacks, strokes, and increased susceptibility to respiratory infections. Power plants are also the largest source of airborne mercury emissions, which affect the nervous system and brain functions, particularly in children.
In addition to the direct health impacts, fossil fuel-fired power plants contribute to climate change through their CO2 emissions. This, in turn, affects ecosystems by influencing plant growth, animal behaviour, and the interaction of organisms with their physical environment. The emissions from coal combustion also include nitrogen oxides, which contribute to nutrient enrichment in aquatic and terrestrial ecosystems. This increased nitrogen pollution reduces plant biodiversity and alters the growth and survival of various organisms, potentially leading to changes in the biological community.
The impact of power plant emissions extends beyond the immediate vicinity of the plants. Air pollution can travel long distances, affecting communities located miles away. Low-income communities and communities of colour in the US experience disproportionately high exposure to particulate air pollution, particularly from coal-fired power plants. This disparity in exposure to air pollution is also evident among Hispanic and Black children, who face significantly higher levels of potential exposure compared to their White counterparts.
While interventions and initiatives, such as fuel-economy standards and regional emission limits, have been implemented to address air pollution and CO2 emissions, fossil fuel-fired power plants remain a leading source of air pollution with significant health and environmental consequences.
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Frequently asked questions
Fossil fuels are fuels made from the remains of dead plants and animals that existed millions of years ago. Examples include coal, natural gas, and oil.
Fossil fuels are burned to create heat, which powers a steam turbine. This turbine rotates and generates electricity.
Coal is the largest source of electricity from fossil fuels, followed by gas.
Fossil fuels are major contributors to greenhouse gas emissions, air pollution, and other environmental issues.
