Process of generating electrical power

Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery (transmission, distribution, etc.) to end users or its storage (using, for example, the pumped-storage method).

Usable electricity is not freely available in nature, so it must be "produced" (that is, transforming other forms of energy to electricity). Production is carried out in power stations (also called "power plants"). Electricity is most often generated at a power plant by electromechanical generators, primarily driven by heat engines fueled by combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. Other energy sources include solar photovoltaics and geothermal power. There are also exotic and speculative methods to recover energy, such as proposed fusion reactor designs which aim to directly extract energy from intense magnetic fields generated by fast-moving charged particles generated by the fusion reaction (see magnetohydrodynamics).

Phasing out coal-fired power stations and eventually gas-fired power stations,[1] or, if practical, capturing their greenhouse gas emissions, is an important part of the energy transformation required to limit climate change. Vastly more solar power[2] and wind power[3] is forecast to be required, with electricity demand increasing strongly[4] with further electrification of transport, homes and industry.[5] However, in 2023, it was reported that the global electricity supply was approaching peak CO2 emissions thanks to the growth of solar and wind power.[6]

History

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[7] with 62% of total renewable power generation added in 2020 having lower costs than the cheapest new fossil fuel option.[8]

Past costs of producing renewable energy have declined significantly,with 62% of total renewable power generation added in 2020 having lower costs than the cheapest new fossil fuel option.

[9][10]
(LCOE) is a measure of the average net present cost of electricity generation for a generating plant over its lifetime.

Levelized cost: With increasingly widespread implementation of renewable energy sources, costs for renewables have declined, most notably for energy generated by solar panels. Levelized cost of energy (LCOE) is a measure of the average net present cost of electricity generation for a generating plant over its lifetime.

Dynamos and engine installed at Edison General Electric Company, New York 1895

The fundamental principles of electricity generation were discovered in the 1820s and early 1830s by British scientist Michael Faraday. His method, still used today, is for electricity to be generated by the movement of a loop of wire, or Faraday disc, between the poles of a magnet. Central power stations became economically practical with the development of alternating current (AC) power transmission, using power transformers to transmit power at high voltage and with low loss.

Commercial electricity production started with the coupling of the dynamo to the hydraulic turbine. The mechanical production of electric power began the Second Industrial Revolution and made possible several inventions using electricity, with the major contributors being Thomas Alva Edison and Nikola Tesla. Previously the only way to produce electricity was by chemical reactions or using battery cells, and the only practical use of electricity was for the telegraph.

Electricity generation at central power stations started in 1882, when a steam engine driving a dynamo at Pearl Street Station produced a DC current that powered public lighting on Pearl Street, New York. The new technology was quickly adopted by many cities around the world, which adapted their gas-fueled street lights to electric power. Soon after electric lights would be used in public buildings, in businesses, and to power public transport, such as trams and trains.

The first power plants used water power or coal.[11] Today a variety of energy sources are used, such as coal, nuclear, natural gas, hydroelectric, wind, and oil, as well as solar energy, tidal power, and geothermal sources.

In the 1880s the popularity of electricity grew massively with the introduction of the Incandescent light bulb. Although there are 22 recognised inventors of the light bulb prior to Joseph Swan and Thomas Edison, Edison and Swan's invention became by far the most successful and popular of all. During the early years of the 19th century, massive jumps in electrical sciences were made. And by the later 19th century the advancement of electrical technology and engineering led to electricity being part of everyday life. With the introduction of many electrical inventions and their implementation into everyday life, the demand for electricity within homes grew dramatically. With this increase in demand, the potential for profit was seen by many entrepreneurs who began investing into electrical systems to eventually create the first electricity public utilities. This process in history is often described as electrification.[12]

The earliest distribution of electricity came from companies operating independently of one another. A consumer would purchase electricity from a producer, and the producer would distribute it through their own power grid. As technology improved so did the productivity and efficiency of its generation. Inventions such as the steam turbine had a massive impact on the efficiency of electrical generation but also the economics of generation as well. This conversion of heat energy into mechanical work was similar to that of steam engines, however at a significantly larger scale and far more productively. The improvements of these large-scale generation plants were critical to the process of centralised generation as they would become vital to the entire power system that we now use today.

Throughout the middle of the 20th century many utilities began merging their distribution networks due to economic and efficiency benefits. Along with the invention of long-distance power transmission, the coordination of power plants began to form. This system was then secured by regional system operators to ensure stability and reliability. The electrification of homes began in Northern Europe and in the Northern America in the 1920s in large cities and urban areas. It was not until the 1930s that rural areas saw the large-scale establishment of electrification.[13]

Methods of generation

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2019 world electricity generation by source (total generation was 27 petawatt-hours)[14][15]

 

 Coal (37%)

 

 Natural gas (24%)

 

 Hydro (16%)

 

 Nuclear (10%)

 

 Wind (5%)

 

 Solar (3%)

 

 Other (5%)

Several fundamental methods exist to convert other forms of energy into electrical energy. Utility-scale generation is achieved by rotating electric generators or by photovoltaic systems. A small proportion of electric power distributed by utilities is provided by batteries. Other forms of electricity generation used in niche applications include the triboelectric effect, the piezoelectric effect, the thermoelectric effect, and betavoltaics.

Generators

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Wind turbines usually provide electrical generation in conjunction with other methods of producing power.

Electric generators transform kinetic energy into electricity. This is the most used form for generating electricity and is based on Faraday's law. It can be seen experimentally by rotating a magnet within closed loops of conducting material (e.g. copper wire). Almost all commercial electrical generation is done using electromagnetic induction, in which mechanical energy forces a generator to rotate.

Electrochemistry

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Large dams, such as Hoover Dam in the United States, can provide large amounts of hydroelectric power. It has an installed capacity of 2.07 GW.

Electrochemistry is the direct transformation of chemical energy into electricity, as in a battery. Electrochemical electricity generation is important in portable and mobile applications. Currently, most electrochemical power comes from batteries.[16] Primary cells, such as the common zinc–carbon batteries, act as power sources directly, but secondary cells (i.e. rechargeable batteries) are used for storage systems rather than primary generation systems. Open electrochemical systems, known as fuel cells, can be used to extract power either from natural fuels or from synthesized fuels. Osmotic power is a possibility at places where salt and fresh water merge.

Photovoltaic effect

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The photovoltaic effect is the transformation of light into electrical energy, as in solar cells. Photovoltaic panels convert sunlight directly to DC electricity. Power inverters can then convert that to AC electricity if needed. Although sunlight is free and abundant, solar power electricity is still usually more expensive to produce than large-scale mechanically generated power due to the cost of the panels.[citation needed] Low-efficiency silicon solar cells have been decreasing in cost and multijunction cells with close to 30% conversion efficiency are now commercially available. Over 40% efficiency has been demonstrated in experimental systems.[17] Until recently, photovoltaics were most commonly used in remote sites where there is no access to a commercial power grid, or as a supplemental electricity source for individual homes and businesses. Recent advances in manufacturing efficiency and photovoltaic technology, combined with subsidies driven by environmental concerns, have dramatically accelerated the deployment of solar panels. Installed capacity is growing by around 20% per year[2] led by increases in Germany, Japan, United States, China, and India.

Economics

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The selection of electricity production modes and their economic viability varies in accordance with demand and region. The economics vary considerably around the world, resulting in widespread residential selling prices. Hydroelectric plants, nuclear power plants, thermal power plants and renewable sources have their own pros and cons, and selection is based upon the local power requirement and the fluctuations in demand. All power grids have varying loads on them but the daily minimum[citation needed] is the base load, often supplied by plants which run continuously. Nuclear, coal, oil, gas and some hydro plants can supply base load. If well construction costs for natural gas are below $10 per MWh, generating electricity from natural gas is cheaper than generating power by burning coal.[18]

Nuclear power plants can produce a huge amount of power from a single unit. However, nuclear disasters have raised concerns over the safety of nuclear power, and the capital cost of nuclear plants is very high. Hydroelectric power plants are located in areas where the potential energy from falling water can be harnessed for moving turbines and the generation of power. It may not be an economically viable single source of production where the ability to store the flow of water is limited and the load varies too much during the annual production cycle.

Generating equipment

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A large generator with the rotor removed

Electric generators were known in simple forms from the discovery of electromagnetic induction in the 1830s. In general, some form of prime mover such as an engine or the turbines described above, drives a rotating magnetic field past stationary coils of wire thereby turning mechanical energy into electricity.[19] The only commercial scale electricity production that does not employ a generator is solar PV.

Turbines

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Large dams such as Three Gorges Dam in China can provide large amounts of hydroelectric power; it has a 22.5 GW capability.

Almost all commercial electrical power on Earth is generated with a turbine, driven by wind, water, steam or burning gas. The turbine drives a generator, thus transforming its mechanical energy into electrical energy by electromagnetic induction. There are many different methods of developing mechanical energy, including heat engines, hydro, wind and tidal power. Most electric generation is driven by heat engines. The combustion of fossil fuels supplies most of the energy to these engines, with a significant fraction from nuclear fission and some from renewable sources. The modern steam turbine (invented by Sir Charles Parsons in 1884) currently generates about 80% of the electric power in the world using a variety of heat sources. Turbine types include:

Turbines can also use other heat-transfer liquids than steam. Supercritical carbon dioxide based cycles can provide higher conversion efficiency due to faster heat exchange, higher energy density and simpler power cycle infrastructure. Supercritical carbon dioxide blends, that are currently in development, can further increase efficiency by optimizing its critical pressure and temperature points.

Although turbines are most common in commercial power generation, smaller generators can be powered by gasoline or diesel engines. These may used for backup generation or as a prime source of power within isolated villages.

Production

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Total worldwide gross production of electricity in 2016 was 25 082 TWh. Sources of electricity were coal and peat 38.3%, natural gas 23.1%, hydroelectric 16.6%, nuclear power 10.4%, oil 3.7%, solar/wind/geothermal/tidal/other 5.6%, biomass and waste 2.3%.[21]

In 2021, Wind and solar generated electricity reached 10% of globally produced electricity. Clean sources (Solar and wind and other) generated 38% of the world's electricity.[22]

Energy flow of power plant

Historical results of production of electricity

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[23]

Production by country

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The United States has long been the largest producer and consumer of electricity, with a global share in 2005 of at least 25%, followed by China, Japan, Russia, and India. In 2011, China overtook the United States to become the largest producer of electricity.

Environmental concerns

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Variations between countries generating electrical power affect concerns about the environment. In France only 10% of electricity is generated from fossil fuels, the US is higher at 70% and China is at 80%.[24] The cleanliness of electricity depends on its source. Methane leaks (from natural gas to fuel gas-fired power plants)[25] and carbon dioxide emissions from fossil fuel-based electricity generation account for a significant portion of world greenhouse gas emissions.[26] In the United States, fossil fuel combustion for electric power generation is responsible for 65% of all emissions of sulfur dioxide, the main component of acid rain.[27] Electricity generation is the fourth highest combined source of NOx, carbon monoxide, and particulate matter in the US.[28]

According to the International Energy Agency (IEA), low-carbon electricity generation needs to account for 85% of global electrical output by 2040 in order to ward off the worst effects of climate change.[29] Like other organizations including the Energy Impact Center (EIC)[30] and the United Nations Economic Commission for Europe (UNECE),[31] the IEA has called for the expansion of nuclear and renewable energy to meet that objective.[32] Some, like EIC founder Bret Kugelmass, believe that nuclear power is the primary method for decarbonizing electricity generation because it can also power direct air capture that removes existing carbon emissions from the atmosphere.[33] Nuclear power plants can also create district heating and desalination projects, limiting carbon emissions and the need for expanded electrical output.[34]

A fundamental issue regarding centralised generation and the current electrical generation methods in use today is the significant negative environmental effects that many of the generation processes have. Processes such as coal and gas not only release carbon dioxide as they combust, but their extraction from the ground also impacts the environment. Open pit coal mines use large areas of land to extract coal and limit the potential for productive land use after the excavation. Natural gas extraction releases large amounts of methane into the atmosphere when extracted from the ground greatly increase global greenhouse gases. Although nuclear power plants do not release carbon dioxide through electricity generation, there are risks associated with nuclear waste and safety concerns associated with the use of nuclear sources.

Per unit of electricity generated coal and gas-fired power life-cycle greenhouse gas emissions are almost always at least ten times that of other generation methods.[35]

Centralised and distributed generation

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Centralised generation is electricity generation by large-scale centralised facilities, sent through transmission lines to consumers. These facilities are usually located far away from consumers and distribute the electricity through high voltage transmission lines to a substation, where it is then distributed to consumers; the basic concept being that multi-megawatt or gigawatt scale large stations create electricity for a large number of people. The vast majority of electricity used is created from centralised generation. Most centralised power generation comes from large power plants run by fossil fuels such as coal or natural gas, though nuclear or large hydroelectricity plants are also commonly used.[36] Centralised generation is fundamentally the opposite of distributed generation. Distributed generation is the small-scale generation of electricity to smaller groups of consumers. This can also include independently producing electricity by either solar or wind power. In recent years distributed generation as has seen a spark in popularity due to its propensity to use renewable energy generation methods such as rooftop solar.[37]

Technologies

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Centralised energy sources are large power plants that produce huge amounts of electricity to a large number of consumers. Most power plants used in centralised generation are thermal power plants meaning that they use a fuel to heat steam to produce a pressurised gas which in turn spins a turbine and generates electricity. This is the traditional way of producing energy. This process relies on several forms of technology to produce widespread electricity, these being natural coal, gas and nuclear forms of thermal generation. More recently solar and wind have become large scale.

Solar

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Wind

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Coal

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Natural gas

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Natural gas is ignited to create pressurised gas which is used to spin turbines to generate electricity. Natural gas plants use a gas turbine where natural gas is added along with oxygen which in turn combusts and expands through the turbine to force a generator to spin.

Natural gas power plants are more efficient than coal power generation, they however contribute to climate change but not as highly as coal generation. Not only do they produce carbon dioxide from the ignition of natural gas, but also the extraction of gas when mined releases a significant amount of methane into the atmosphere.[65]

Nuclear

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Nuclear power plants create electricity through steam turbines where the heat input is from the process of nuclear fission. Currently, nuclear power produces 11% of all electricity in the world. Most nuclear reactors use uranium as a source of fuel. In a process called nuclear fission, energy, in the form of heat, is released when nuclear atoms are split. Electricity is created through the use of a nuclear reactor where heat produced by nuclear fission is used to produce steam which in turn spins turbines and powers the generators. Although there are several types of nuclear reactors, all fundamentally use this process.[66]

Normal emissions due to nuclear power plants are primarily waste heat and radioactive spent fuel. In a reactor accident, significant amounts of radioisotopes can be released to the environment, posing a long term hazard to life. This hazard has been a continuing concern of environmentalists. Accidents such as the Three Mile Island accident, Chernobyl disaster and the Fukushima nuclear disaster illustrate this problem. [67]

Electricity generation capacity by country

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The table lists 45 countries with their total electricity capacities. The data is from 2022. According to the Energy Information Administration, the total global electricity capacity in 2022 was nearly 8.9 terawatt (TW), more than four times the total global electricity capacity in 1981. The global average per-capita electricity capacity was about 1,120 watts in 2022, nearly two and a half times the global average per-capita electricity capacity in 1981. Iceland has the highest installed capacity per capita in the world, at about 8,990 watts. All developed countries have an average per-capita electricity capacity above the global average per-capita electricity capacity, with the United Kingdom having the lowest average per-capita electricity capacity of all other developed countries.

See also

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References

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Where does our electricity come from?

Electricity is essential for modern life, yet almost one billion people live without access to it. Challenges such as climate change, pollution and environmental destruction require that we change the way we generate electricity.

Over the past century, the main energy sources used for generating electricity have been fossil fuels, hydroelectricity and, since the 1950s, nuclear energy. Despite the strong growth of renewables over the last few decades, fossil-based fuels remain dominant worldwide. Their use for electricity generation continues to increase in both absolute and relative terms: in 2017, fossil fuels generated 64.5% of worldwide electricity, compared with 61.9% in 1990. 

Access to reliable electricity is vital for human wellbeing. Currently one in seven people in the world has no access to electricity. As such, electricity demand will continue to rise. At the same time, greenhouse gas emissions must decrease drastically if we are to mitigate climate change, and we must switch to cleaner sources of energy to reduce air pollution. This will likely require large increases of all low-carbon energy sources, of which nuclear is an important part. 

In order to achieve a sustainable world, all sectors of the economy will need to be decarbonised, including transport, heat and industry. Electricity provides the means to utilise low-carbon energy sources, and so widespread electrification is seen as a key tool for decarbonising sectors traditionally powered by fossil fuels. As the end uses for electricity grow, and as the benefits of electricity are extended to all people, demand will grow significantly. 

Coal, gas and oil

Fossil fuel power plants burn coal or oil to create heat which is in turn used to generate steam to drive turbines which generate electricity. In gas plants hot gases drive a turbine to generate electricity, whereas a combined cycle gas turbine (CCGT) plant also uses a steam generator to increase the amount of electricity produced. In 2017, fossil fuels generated 64.5% of electricity worldwide.

These plants generate electricity reliably over long periods of time, and are generally cheap to build. However, burning carbon-based fuels produces large amounts of carbon dioxide, which drives climate change. These plants also produce other pollutants, such as oxides of sulphur and nitrogen, which cause acid rain. 

The Cottam power station in the UK, which uses both coal and gas for electricity generation (Image: EDF Energy)

The burning of fossil fuels for energy causes considerable numbers of deaths due to air pollution. For instance, it is estimated that in China alone 670,000 people die prematurely - every year due to the use of coal. 

Fossil fuel plants require very large quantities of coal, oil or gas. In many cases these fuels need to be transported over long distances, which can result in potential supply issues. The price of the fuels has historically been volatile, and can rise sharply at times of shortages or geopolitical instability, which can result in unstable generation costs and higher consumer prices. 

Hydroelectric power

Most large hydroelectric power plants generate electricity by storing water in vast reservoirs behind dams. Water from the reservoirs flows through turbines to generate electricity. Hydroelectric dams can generate large amounts of low-carbon electricity, but the number of sites suitable for new, large-scale dams is limited. Hydroelectric power can also be produced by run-of-river plants but most of the rivers that are suitable for this have already been developed. 

The Three Gorges Dam in China is the world’s largest hydroelectric dam and the world’s largest power station (Image: Le Grand Portage, CC BY-SA 2.0)

In 2017, hydropower accounted for 16% of worldwide electricity generation.

The flooding of reservoirs behind dams and slowing the flow of the river system below the dam can also have a serious impact on the environment and local populations. For instance, during the construction of the world’s largest hydroelectric dam – the Three Gorges Dam in China – some 1.3 million people were displaced. 
In terms of the number of deaths from accidents, hydroelectric power is the most deadly energy source. The accident with the highest death toll was the collapse in 1975 of the Banqiao Dam in China’s Henan province, which resulted in 171,000 direct and indirect fatalities according to official estimates.

Nuclear power

Nuclear power reactors use the heat produced from splitting atoms to generate steam to drive a turbine. No greenhouse gases are produced in the fission process, and only very small amounts are produced across the whole nuclear life- cycle. Nuclear power is an environmentally-friendly form of electricity generation, and does not contribute to air pollution. In 2018, nuclear power generated 10.5% of the world’s electricity.

The Paluel Nuclear Power Plant in the north of France, one of the world’s largest nuclear power plants (Image: Areva)

Nuclear power plants, like fossil-fuelled power plants, are very reliable, and can run for many months without interruption, providing large amounts of clean electricity, regardless of the time of day, the weather or the season. Most nuclear power plants can operate for at least 60 years, and this contributes to making nuclear electricity the most affordable when comparing to other electricity generators.

Nuclear fuel can be used in a reactor for several years, thanks to the immense amount of energy contained in uranium. The power from one kilogram of uranium is about the same as 1 tonne of coal. 

As a result, a correspondingly small amount of waste is generated. On average, a reactor supplying a person’s electricity needs for a year creates about 500 grams of waste – it would fit inside a soda can. Just 5 grams of this amount is used nuclear fuel  – the equivalent of a sheet of paper. There are several management strategies available for the used fuel, such as direct disposal or recycling in reactors to generate more low-carbon electricity.

Wind and solar

Renewables, such as wind, solar and small-scale hydro, produce electricity with low amounts of greenhouse gas emissions across their entire life-cycle. In 2017, wind and solar generated 4.4% and 1.3%, respectively, of the world’s electricity. They do not produce electricity predictably or consistently due to their inherent reliance on the weather. Electricity generation from wind turbines varies with the wind speed, and if the wind is too weak or too strong no electricity is produced at all. The output of solar panels is reliant on the strength of the sunshine, which depends on a number of different factors, such as the time of day and the amount of cloud cover (as well as the amount of dust on the panels). 

Another problem is that there might not be enough space or public willingness to accommodate the vast number of turbines or panels required to produce enough electricity. This is due to the fact that energy from the wind or the sun is diffuse, meaning that very significant amounts of land are required in order to generate a significant quantity of electricity.

Because electricity cannot be easily stored, renewables have to be backed up by other forms of electricity generation. The largest batteries cannot operate for days, let alone the weeks that would be required to back up renewables in order to ensure the supply of round-the-clock electricity. In order to ensure a steady supply of electricity, gas plants are increasingly providing backup services to renewables electricity. Natural gas plants emit large amounts of carbon dioxide during operation, and significant amounts of methane are often released during the extraction and transport of gas, both of which contribute to climate change. 

Biomass 

A biomass plant operates in a very similar way to gas- and coal-fired power plants.  Instead of burning gas or coal, the plant is fuelled by different forms of biomass (such as purpose-grown trees, wood chips, domestic waste, or ‘biogas’). In 2017, biomass generated 2.3% of the world’s electricity.

The Drax power station in the UK has partially replaced coal with imported biomass as fuel for electricity generation (Image: Andrew Whale, CC BY-SA 2.0) 

Biomass production can require a lot of energy, both in terms of production of biomass itself and in terms of transport. Due to this, the energy required can be greater than the energy value in the final fuel, and the greenhouse gas emissions can be as high, or even greater, than those from equivalent fossil fuels. Additionally, it can take more than 100 years for the emitted carbon dioxide to be absorbed, which leads to a short-term emissions increase. 

Other environmental impacts related to land use and ecological sustainability can be considerable. Additionally, as with coal, the use of biomass can contribute to air pollution, and thus has negative health impacts for populations local to biomass plants.  

What will power our electric future?

Electricity is growing in importance. If we are to address climate change and reduce air pollution, we will need to increase the use of all low-carbon energy sources, of which nuclear is an important part.

To meet the growing demand for sustainable energy, World Nuclear Association has introduced the Harmony programme, which sets a target for nuclear power to provide at least 25% of electricity before 2050. This would mean that nuclear generation would have to triple globally by then. In order to drastically reduce the levels of fossil fuels, nuclear and renewables need to work together to secure a reliable, affordable and clean future energy supply.

The World Nuclear Association’s Silent Giant white paper provides further information on the need for nuclear in a clean energy system.