Sustainable Energy
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Energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...
is
sustainable Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...
if it "meets the needs of the present without compromising the ability of
future generations Future generations are Cohort (statistics), cohorts of hypothetical people not yet born. Future generations are contrasted with current and past generations and evoked in order to encourage thinking about intergenerational equity. The Moral agenc ...
to meet their own needs." Definitions of sustainable energy usually look at its effects on the environment, the economy, and society. These impacts range from
greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...
and
air pollution Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...
to
energy poverty In developing countries and some areas of more developed countries, energy poverty is lack of access to modern energy services in the home. In 2022, 759 million people lacked access to consistent electricity and 2.6 billion people used dangerous a ...
and
toxic waste Toxic waste is any unwanted material in all forms that can cause harm (e.g. by being inhaled, swallowed, or absorbed through the skin). Mostly generated by industry, consumer products like televisions, computers, and phones contain toxic chemi ...
.
Renewable energy Renewable energy (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...
sources such as
wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...
,
hydro Hydro (from ) may refer to: Energy technologies * Water-derived power or energy: ** Hydropower, derived from water ** Hydroelectricity, in electrical form * "Hydro", AC mains electricity in parts of Canada * Micro hydro, a type of hydroelect ...
,
solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...
, and
geothermal energy Geothermal energy is thermal energy extracted from the crust (geology), crust. It combines energy from the formation of the planet and from radioactive decay. Geothermal energy has been exploited as a source of heat and/or electric power for m ...
can cause environmental damage but are generally far more sustainable than fossil fuel sources. The role of
non-renewable energy A non-renewable resource (also called a finite resource) is a natural resource that cannot be readily replaced by natural means at a pace quick enough to keep up with consumption. An example is carbon-based fossil fuels. The original organic ma ...
sources in sustainable energy is controversial.
Nuclear power Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by ...
does not produce carbon pollution or air pollution, but has drawbacks that include
radioactive waste Radioactive waste is a type of hazardous waste that contains radioactive material. It is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, nuclear decommissioning, rare-earth mining, and nuclear ...
, the risk of
nuclear proliferation Nuclear proliferation is the spread of nuclear weapons to additional countries, particularly those not recognized as List of states with nuclear weapons, nuclear-weapon states by the Treaty on the Non-Proliferation of Nuclear Weapons, commonl ...
, and the risk of accidents. Switching from
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...
to
natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...
has environmental benefits, including a lower climate impact, but may lead to a delay in switching to more sustainable options.
Carbon capture and storage Carbon capture and storage (CCS) is a process by which carbon dioxide (CO2) from industrial installations is separated before it is released into the atmosphere, then transported to a long-term storage location.IPCC, 2021Annex VII: Glossary at ...
can be built into power plants to remove their
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
() emissions, but this technology is expensive and has rarely been implemented.
Fossil fuel A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geolog ...
s provide 85% of the world's energy consumption, and the energy system is responsible for 76% of global greenhouse gas emissions. Around 790 million people in
developing countries A developing country is a sovereign state with a less-developed Secondary sector of the economy, industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. ...
lack
access to electricity Access may refer to: Companies and organizations * ACCESS (Australia), an Australian youth network * Access (credit card), a former credit card in the United Kingdom * Access Co., a Japanese software company * Access International Advisors, a hed ...
, and 2.6 billion rely on polluting fuels such as wood or
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ca ...
to cook. Cooking with biomass plus fossil fuel pollution causes an estimated 7 million deaths each year. Limiting global warming to will require transforming energy production, distribution, storage, and consumption. Universal access to clean electricity can have major benefits to the
climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...
, human health, and the economies of
developing countries A developing country is a sovereign state with a less-developed Secondary sector of the economy, industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. ...
.
Climate change mitigation Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include energy conservation, conserving energy and Fossil fuel phase-out, repl ...
pathways have been proposed to limit global warming to . These include phasing out coal-fired power plants, conserving energy, producing more electricity from clean sources such as
wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...
and
solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...
, and switching from fossil fuels to electricity for transport and heating buildings. Power output from some renewable energy sources varies depending on when the wind blows and the sun shines. Switching to renewable energy can therefore require
electrical grid An electrical grid (or electricity network) is an interconnected network for electricity delivery from producers to consumers. Electrical grids consist of power stations, electrical substations to step voltage up or down, electric power tran ...
upgrades, such as the addition of
energy storage Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an Accumulator (energy), accumulator or Batte ...
. Some processes that are difficult to electrify can use
hydrogen fuel The hydrogen economy is an umbrella term for the roles hydrogen can play alongside low-carbon electricity to reduce emissions of greenhouse gases. The aim is to reduce emissions where cheaper and more energy-efficient clean solutions are not avail ...
produced from low-emission energy sources. In the
International Energy Agency The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organization, established in 1974, that provides policy recommendations, analysis and data on the global energy sector. The 31 member countries and 13 associatio ...
's proposal for achieving net zero emissions by 2050, about 35% of the reduction in emissions depends on technologies that are still in development as of 2023. Wind and solar market share grew to 8.5% of worldwide electricity in 2019, and costs continue to fall. The
Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World Met ...
(IPCC) estimates that 2.5% of world
gross domestic product Gross domestic product (GDP) is a monetary measure of the total market value of all the final goods and services produced and rendered in a specific time period by a country or countries. GDP is often used to measure the economic performanc ...
(GDP) would need to be invested in the energy system each year between 2016 and 2035 to limit global warming to . Governments can fund the research, development, and demonstration of new clean energy technologies. They can also build
infrastructure Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and pri ...
for electrification and sustainable transport. Finally, governments can encourage clean energy deployment with policies such as
carbon pricing Carbon pricing (or pricing) is a method for governments to Climate change mitigation, mitigate climate change, in which a monetary cost is applied to greenhouse gas emissions. This is done to encourage polluters to reduce fossil fuel combustion, ...
,
renewable portfolio standard A renewable portfolio standard (RPS) is a regulation that requires the increased production of energy from renewable energy sources, such as wind, solar, biomass, and geothermal. Other common names for the same concept include Renewable Electric ...
s, and phase-outs of
fossil fuel subsidies Fossil fuel subsidies are energy subsidies on fossil fuels. Under a narrow definition, fossil fuel subsidies totalled around $1.5 trillion in 2022. Under more expansive definition, they totalled around $7 trillion. They may be tax breaks on c ...
. These policies may also increase
energy security Energy security is the association between national security and the availability of natural resources for energy consumption (as opposed to household energy insecurity). Access to cheaper energy has become essential to the functioning of modern ...
.


Definitions and background


Definitions

The United Nations
Brundtland Commission The Brundtland Commission, formerly the World Commission on Environment and Development, was a sub-organization of the United Nations (UN) that aimed to unite countries in pursuit of sustainable development. It was founded in 1983 when Javier Pér ...
described the concept of
sustainable development Sustainable development is an approach to growth and Human development (economics), human development that aims to meet the needs of the present without compromising the ability of future generations to meet their own needs.United Nations General ...
, for which energy is a key component, in its 1987 report ''
Our Common Future __NOTOC__ ''Our Common Future'', also known as the Brundtland Report, was published in October 1987 by the United Nations through the Oxford University Press. This publication was in recognition of Gro Harlem Brundtland, former Norwegian Prime Mi ...
''. It defined sustainable development as meeting "the needs of the present without compromising the ability of future generations to meet their own needs". This description of sustainable development has since been referenced in many definitions and explanations of sustainable energy. There is no universally accepted interpretation of how the concept of
sustainability Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...
applies to energy on a global scale. Working definitions of sustainable energy encompass multiple dimensions of sustainability such as environmental, economic, and social dimensions. Historically, the concept of sustainable energy development has focused on emissions and on
energy security Energy security is the association between national security and the availability of natural resources for energy consumption (as opposed to household energy insecurity). Access to cheaper energy has become essential to the functioning of modern ...
. Since the early 1990s, the concept has broadened to encompass wider social and economic issues. The environmental dimension of sustainability includes
greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...
, impacts on
biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...
and ecosystems, hazardous waste and toxic emissions, water consumption, and depletion of non-renewable resources. Energy sources with low environmental impact are sometimes called ''green energy'' or ''clean energy''. The economic dimension of sustainability covers economic development, efficient use of energy, and energy security to ensure that each country has constant access to sufficient energy. Social issues include access to affordable and reliable energy for all people,
workers' rights Labor rights or workers' rights are both legal rights and human rights relating to labor relations between workers and employers. These rights are codified in national and international labor and employment law. In general, ...
, and
land rights Land law is the form of law that deals with the rights to use, alienate, or exclude others from land. In many jurisdictions, these kinds of property are referred to as real estate or real property, as distinct from personal property. Land use ...
.


Environmental impacts

The current energy system contributes to many environmental problems, including
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
, air pollution,
biodiversity loss Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in Biodiversity, b ...
, the release of toxins into the environment, and water scarcity. As of 2019, 85% of the world's energy needs are met by burning fossil fuels. Energy production and consumption are responsible for 76% of annual human-caused greenhouse gas emissions as of 2018. The 2015 international
Paris Agreement The Paris Agreement (also called the Paris Accords or Paris Climate Accords) is an international treaty on climate change that was signed in 2016. The treaty covers climate change mitigation, adaptation, and finance. The Paris Agreement was ...
on climate change aims to limit global warming to well below and preferably to 1.5 °C (2.7 °F); achieving this goal will require that emissions be reduced as soon as possible and reach net-zero by mid-century. The burning of fossil fuels and
biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...
is a major source of air pollution, which causes an estimated 7 million deaths each year, with the greatest attributable disease burden seen in low and middle-income countries. Fossil-fuel burning in power plants, vehicles, and factories is the main source of emissions that combine with oxygen in the atmosphere to cause
acid rain Acid rain is rain or any other form of Precipitation (meteorology), precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists b ...
. Air pollution is the second-leading cause of death from non-infectious disease. An estimated 99% of the world's population lives with levels of air pollution that exceed the
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
recommended limits. Cooking with polluting fuels such as wood, animal dung, coal, or
kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...
is responsible for nearly all indoor air pollution, which causes an estimated 1.6 to 3.8 million deaths annually, and also contributes significantly to outdoor air pollution. Health effects are concentrated among women, who are likely to be responsible for cooking, and young children. Environmental impacts extend beyond the by-products of combustion.
Oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...
s at sea harm marine life and may cause fires which release toxic emissions. Around 10% of global water use goes to energy production, mainly for cooling in thermal energy plants. In dry regions, this contributes to
water scarcity Water scarcity (closely related to water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity. One is ''physical.'' The other is ''economic water scarcity''. Physic ...
. Bioenergy production, coal mining and processing, and oil extraction also require large amounts of water. Excessive harvesting of wood and other combustible material for burning can cause serious local environmental damage, including
desertification Desertification is a type of gradual land degradation of Soil fertility, fertile land into arid desert due to a combination of natural processes and human activities. The immediate cause of desertification is the loss of most vegetation. This i ...
.


Sustainable development goals

Meeting existing and future energy demands in a sustainable way is a critical challenge for the global goal of limiting climate change while maintaining economic growth and enabling living standards to rise. Reliable and affordable energy, particularly electricity, is essential for health care, education, and economic development. As of 2020, 790 million people in developing countries do not have access to electricity, and around 2.6 billion rely on burning polluting fuels for cooking. Improving energy access in the
least-developed countries The least developed countries (LDCs) are developing countries listed by the United Nations that exhibit the lowest indicators of socioeconomic development. The concept of LDCs originated in the late 1960s and the first group of LDCs was listed by ...
and making energy cleaner are key to achieving most of the United Nations 2030
Sustainable Development Goals The ''2030 Agenda for Sustainable Development'', adopted by all United Nations (UN) members in 2015, created 17 world Sustainable Development Goals (SDGs). The aim of these global goals is "peace and prosperity for people and the planet" – wh ...
, which cover issues ranging from
climate action Climate action (or climate change action) refers to a range of activities, mechanisms, policy instruments, and so forth that aim at reducing the severity of human-induced climate change and its impacts. "More climate action" is a central demand o ...
to
gender equality Gender equality, also known as sexual equality, gender egalitarianism, or equality of the sexes, is the state of equal ease of access to resources and opportunities regardless of gender, including economic participation and decision-making, an ...
.
Sustainable Development Goal 7 Sustainable Development Goal 7 (SDG 7 or Global Goal 7) is one of 17 Sustainable Development Goals established by the United Nations General Assembly in 2015. It aims to "Ensure access to affordable, reliable, sustainable and modern energy for a ...
calls for "access to affordable, reliable, sustainable and modern energy for all", including universal
access to electricity Access may refer to: Companies and organizations * ACCESS (Australia), an Australian youth network * Access (credit card), a former credit card in the United Kingdom * Access Co., a Japanese software company * Access International Advisors, a hed ...
and to clean cooking facilities by 2030.


Energy conservation

Energy efficiency—using less energy to deliver the same goods or services, or delivering comparable services with less goods—is a cornerstone of many sustainable energy strategies. The
International Energy Agency The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organization, established in 1974, that provides policy recommendations, analysis and data on the global energy sector. The 31 member countries and 13 associatio ...
(IEA) has estimated that increasing energy efficiency could achieve 40% of greenhouse gas emission reductions needed to fulfil the Paris Agreement's goals. Energy can be conserved by increasing the technical efficiency of appliances, vehicles, industrial processes, and buildings. Another approach is to use fewer materials whose production requires a lot of energy, for example through better building design and recycling. Behavioural changes such as using
videoconferencing Videotelephony (also known as videoconferencing or video calling) is the use of audio signal, audio and video for simultaneous two-way communication. Today, videotelephony is widespread. There are many terms to refer to videotelephony. ''Vide ...
rather than business flights, or making urban trips by cycling, walking or public transport rather than by car, are another way to conserve energy. Government policies to improve efficiency can include
building codes A building code (also building control or building regulations) is a set of rules that specify the standards for construction objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permissi ...
, performance standards,
carbon pricing Carbon pricing (or pricing) is a method for governments to Climate change mitigation, mitigate climate change, in which a monetary cost is applied to greenhouse gas emissions. This is done to encourage polluters to reduce fossil fuel combustion, ...
, and the development of energy-efficient infrastructure to encourage changes in transport modes. The
energy intensity Energy intensity is a Measurement, measure of the efficient energy use, energy inefficiency of an Economic system, economy. It is calculated as units of energy per unit of GDP (Gross Domestic Product) or some other measure of economic output. Hi ...
of the global economy (the amount of energy consumed per unit of
gross domestic product Gross domestic product (GDP) is a monetary measure of the total market value of all the final goods and services produced and rendered in a specific time period by a country or countries. GDP is often used to measure the economic performanc ...
(GDP)) is a rough indicator of the energy efficiency of economic production. In 2010, global energy intensity was 5.6 megajoules (1.6 kWh) per US dollar of GDP. United Nations goals call for energy intensity to decrease by 2.6% each year between 2010 and 2030. In recent years this target has not been met. For instance, between 2017 and 2018, energy intensity decreased by only 1.1%. Efficiency improvements often lead to a
rebound effect The rebound effect, or rebound phenomenon, is the emergence or re-emergence of symptoms that were either absent or controlled while taking a medication, but appear when that same medication is discontinued or reduced in dosage. In the case of re- ...
in which consumers use the money they save to buy more energy-intensive goods and services. For example, recent technical efficiency improvements in transport and buildings have been largely offset by trends in
consumer behaviour Consumer behaviour is the study of individuals, groups, or organisations and all activities associated with the Purchasing, purchase, Utility, use and disposal of goods and services. It encompasses how the consumer's emotions, Attitude (psy ...
, such as selecting larger vehicles and homes.


Sustainable energy sources


Renewable energy sources

Renewable energy sources are essential to sustainable energy, as they generally strengthen energy security and emit far fewer greenhouse gases than fossil fuels. Renewable energy projects sometimes raise significant sustainability concerns, such as risks to biodiversity when areas of high ecological value are converted to bioenergy production or wind or solar farms.
Hydropower Hydropower (from Ancient Greek -, "water"), also known as water power or water energy, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, ...
is the largest source of renewable electricity while solar and wind energy are growing rapidly. Photovoltaic solar and onshore wind are the cheapest forms of new power generation capacity in most countries. For more than half of the 770 million people who currently lack access to electricity, decentralised renewable energy such as solar-powered mini-grids is likely the cheapest method of providing it by 2030. United Nations targets for 2030 include substantially increasing the proportion of renewable energy in the world's energy supply. According to the International Energy Agency, renewable energy sources like wind and solar power are now a commonplace source of electricity, making up 70% of all new investments made in the world's power generation. The Agency expects renewables to become the primary energy source for electricity generation globally in the next three years, overtaking coal.IEA (2022), Renewables 2022, IEA, Paris https://www.iea.org/reports/renewables-2022, License: CC BY 4.0


Solar

The Sun is Earth's primary source of energy, a clean and abundantly available resource in many regions. In 2019, solar power provided around 3% of global electricity, mostly through
solar panels A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
based on
photovoltaic cells A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.
(PV). Solar PV is expected to be the electricity source with the largest installed capacity worldwide by 2027. The panels are mounted on top of buildings or installed in utility-scale solar parks. Costs of solar photovoltaic cells have dropped rapidly, driving strong growth in worldwide capacity. The cost of electricity from new solar farms is competitive with, or in many places, cheaper than electricity from existing coal plants. Various projections of future energy use identify solar PV as one of the main sources of energy generation in a sustainable mix. Most components of solar panels can be easily recycled, but this is not always done in the absence of regulation. Panels typically contain
heavy metals upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals is a controversial and ambiguous term for metallic elements with relatively h ...
, so they pose environmental risks if put in
landfill A landfill is a site for the disposal of waste materials. It is the oldest and most common form of waste disposal, although the systematic burial of waste with daily, intermediate and final covers only began in the 1940s. In the past, waste was ...
s. It takes fewer than two years for a solar panel to produce as much energy as was used for its production. Less energy is needed if materials are recycled rather than mined. In
concentrated solar power Concentrated solar power (CSP, also known as concentrating solar power, concentrated solar thermal) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight into a receiver. Electricity is generated whe ...
, solar rays are concentrated by a field of mirrors, heating a fluid. Electricity is produced from the resulting steam with a
heat engine A heat engine is a system that transfers thermal energy to do mechanical or electrical work. While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, pa ...
. Concentrated solar power can support dispatchable power generation, as some of the heat is typically stored to enable electricity to be generated when needed. In addition to electricity production, solar energy is used more directly; solar thermal heating systems are used for hot water production, heating buildings, drying, and desalination.


Wind power

Wind has been an important driver of development over millennia, providing mechanical energy for industrial processes, water pumps, and sailing ships. Modern wind turbines are used to generate electricity and provided approximately 6% of global electricity in 2019. Electricity from onshore
wind farms A wind farm, also called a wind park or wind power plant, is a group of wind turbines in the same location used to produce electricity. Wind farms vary in size from a small number of turbines to several hundred wind turbines covering an exten ...
is often cheaper than existing coal plants and competitive with natural gas and nuclear. Wind turbines can also be placed offshore, where winds are steadier and stronger than on land but construction and maintenance costs are higher. Onshore wind farms, often built in wild or rural areas, have a visual impact on the landscape. While collisions with wind turbines kill both
bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...
s and to a lesser extent birds, these impacts are lower than from other infrastructure such as windows and
transmission lines In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmis ...
. The noise and flickering light created by the turbines can cause annoyance and constrain construction near densely populated areas. Wind power, in contrast to nuclear and fossil fuel plants, does not consume water. Little energy is needed for wind turbine construction compared to the energy produced by the wind power plant itself. Turbine blades are not fully recyclable, and research into methods of manufacturing easier-to-recycle blades is ongoing.


Hydropower

Hydroelectric plants Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...
convert the energy of moving water into electricity. In 2020, hydropower supplied 17% of the world's electricity, down from a high of nearly 20% in the mid-to-late 20th century. In conventional hydropower, a reservoir is created behind a dam. Conventional hydropower plants provide a highly flexible, dispatchable electricity supply. They can be combined with wind and solar power to meet peaks in demand and to compensate when wind and sun are less available. Compared to reservoir-based facilities,
run-of-the-river hydroelectricity Run-of-river hydroelectricity (ROR) or run-of-the-river hydroelectricity is a type of hydroelectric generation plant whereby little or no water storage is provided. Run-of-the-river power plants may have no water storage at all or a limited amou ...
generally has less environmental impact. However, its ability to generate power depends on river flow, which can vary with daily and seasonal weather. Reservoirs provide water quantity controls that are used for flood control and flexible electricity output while also providing security during drought for drinking water supply and irrigation. Hydropower ranks among the energy sources with the lowest levels of greenhouse gas emissions per unit of energy produced, but levels of emissions vary enormously between projects. The highest emissions tend to occur with large dams in tropical regions. These emissions are produced when the biological matter that becomes submerged in the reservoir's flooding decomposes and releases carbon dioxide and methane.
Deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
and climate change can reduce energy generation from hydroelectric dams. Depending on location, large dams can displace residents and cause significant local environmental damage; potential
dam failure A dam failure or dam burst is a catastrophic type of structural failure characterized by the sudden, rapid, and uncontrolled release of impounded water or the likelihood of such an uncontrolled release. Between the years 2000 and 2009 more than ...
could place the surrounding population at risk.


Geothermal

Geothermal energy Geothermal energy is thermal energy extracted from the crust (geology), crust. It combines energy from the formation of the planet and from radioactive decay. Geothermal energy has been exploited as a source of heat and/or electric power for m ...
is produced by tapping into deep underground heat and harnessing it to generate electricity or to heat water and buildings. The use of geothermal energy is concentrated in regions where heat extraction is economical: a combination is needed of high temperatures, heat flow, and permeability (the ability of the rock to allow fluids to pass through). Power is produced from the steam created in underground reservoirs. Geothermal energy provided less than 1% of
global energy consumption World energy supply and consumption refers to the global supply of World energy resources, energy resources and its Energy consumption, consumption. The system of global energy supply consists of the energy development, Refineries, refinement, a ...
in 2020. Geothermal energy is a renewable resource because thermal energy is constantly replenished from neighbouring hotter regions and the
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...
of naturally occurring isotopes. On average, the greenhouse gas emissions of geothermal-based electricity are less than 5% that of coal-based electricity. Geothermal energy carries a risk of inducing earthquakes, needs effective protection to avoid water pollution, and releases toxic emissions which can be captured.


Bioenergy

Biomass is renewable organic material that comes from plants and animals. It can either be burned to produce heat and electricity or be converted into
biofuels Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil. Biofuel can be produced from plants or from agricultural, domestic ...
such as
biodiesel Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats. The roots of bi ...
and ethanol, which can be used to power vehicles. The climate impact of bioenergy varies considerably depending on where biomass feedstocks come from and how they are grown. For example, burning wood for energy releases carbon dioxide; those emissions can be significantly offset if the trees that were harvested are replaced by new trees in a well-managed forest, as the new trees will absorb carbon dioxide from the air as they grow. However, the establishment and cultivation of bioenergy crops can displace natural ecosystems, degrade soils, and consume water resources and synthetic fertilisers. Approximately one-third of all wood used for traditional heating and cooking in tropical areas is harvested unsustainably. Bioenergy feedstocks typically require significant amounts of energy to harvest, dry, and transport; the energy usage for these processes may emit greenhouse gases. In some cases, the impacts of
land-use change Land use is an umbrella term to describe what happens on a parcel of land. It concerns the benefits derived from using the land, and also the land management actions that humans carry out there. The following categories are used for land use: for ...
, cultivation, and processing can result in higher overall carbon emissions for bioenergy compared to using fossil fuels. Use of farmland for growing biomass can result in less land being available for growing food. In the United States, around 10% of motor gasoline has been replaced by
corn-based ethanol Corn ethanol is ethanol produced from corn biomass and is the main source of ethanol fuel in the United States, mandated to be blended with gasoline in the Renewable Fuel Standard. Corn ethanol is produced by ethanol fermentation and distillati ...
, which requires a significant proportion of the harvest. In Malaysia and Indonesia, clearing forests to produce
palm oil Palm oil is an edible vegetable oil derived from the mesocarp (reddish pulp) of the fruit of oil palms. The oil is used in food manufacturing, in beauty products, and as biofuel. Palm oil accounted for about 36% of global oils produced from o ...
for biodiesel has led to serious social and environmental effects, as these forests are critical carbon sinks and
habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
s for diverse species. Since
photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
captures only a small fraction of the energy in sunlight, producing a given amount of bioenergy requires a large amount of land compared to other renewable energy sources.
Second-generation biofuels Second-generation biofuels, also known as advanced biofuels, are fuels that can be manufactured from various types of non-food biomass. Biomass in this context means plant materials and animal waste used especially as a source of fuel. First-gene ...
which are produced from non-food plants or waste reduce competition with food production, but may have other negative effects including trade-offs with conservation areas and local air pollution. Relatively sustainable sources of biomass include
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, waste, and crops grown on soil unsuitable for food production.
Carbon capture and storage Carbon capture and storage (CCS) is a process by which carbon dioxide (CO2) from industrial installations is separated before it is released into the atmosphere, then transported to a long-term storage location.IPCC, 2021Annex VII: Glossary at ...
technology can be used to capture emissions from bioenergy power plants. This process is known as bioenergy with carbon capture and storage (BECCS) and can result in net
carbon dioxide removal Carbon dioxide removal (CDR) is a process in which carbon dioxide () is removed from the atmosphere by deliberate human activities and durably stored in geological, terrestrial, or ocean reservoirs, or in products.IPCC, 2021:Annex VII: Glossar ...
from the atmosphere. However, BECCS can also result in net positive emissions depending on how the biomass material is grown, harvested, and transported. Deployment of BECCS at scales described in some climate change mitigation pathways would require converting large amounts of cropland.


Marine energy

Marine energy has the smallest share of the energy market. It includes OTEC,
tidal power Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods. Although not yet widely used, tidal energy has the potential for future electricity generation. T ...
, which is approaching maturity, and
wave power Wave power is the capture of energy of wind waves to do useful mechanical work, work – for example, electricity generation, desalination, or pumping water. A machine that exploits wave power (physics), power is a wave energy converter (WEC). W ...
, which is earlier in its development. Two tidal barrage systems in France and in South Korea make up 90% of global production. While single marine energy devices pose little risk to the environment, the impacts of larger devices are less well known.


Non-renewable energy sources


Fossil fuel switching and mitigation

Switching from
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...
to
natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...
has advantages in terms of sustainability. For a given unit of energy produced, the life-cycle greenhouse-gas emissions of natural gas are around 40 times the emissions of wind or nuclear energy but are much less than coal. Burning natural gas produces around half the emissions of coal when used to generate electricity and around two-thirds the emissions of coal when used to produce heat. Natural gas combustion also produces less air pollution than coal. However, natural gas is a potent greenhouse gas in itself, and leaks during extraction and transportation can negate the advantages of switching away from coal. The technology to curb methane leaks is widely available but it is not always used. Switching from coal to natural gas reduces emissions in the short term and thus contributes to
climate change mitigation Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include energy conservation, conserving energy and Fossil fuel phase-out, repl ...
. However, in the long term it does not provide a path to
net-zero emissions Global net-zero emissions is reached when greenhouse gas emissions and removals due to human activities are in balance. It is often called simply net zero. ''Emissions'' can refer to all greenhouse gases or only carbon dioxide (). Reaching net ze ...
. Developing natural gas infrastructure risks carbon lock-in and
stranded assets Stranded assets are "assets that have suffered from unanticipated or premature write-downs, devaluations or conversion to liabilities". Stranded assets can be caused by a variety of factors and are a phenomenon inherent in the 'creative destructi ...
, where new fossil infrastructure either commits to decades of carbon emissions, or has to be written off before it makes a profit. The greenhouse gas emissions of fossil fuel and biomass power plants can be significantly reduced through carbon capture and storage (CCS). Most studies use a working assumption that CCS can capture 85–90% of the
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
() emissions from a power plant. Even if 90% of emitted is captured from a coal-fired power plant, its uncaptured emissions are still many times greater than the emissions of nuclear, solar or wind energy per unit of electricity produced. Since coal plants using CCS are less efficient, they require more coal and thus increase the pollution associated with mining and transporting coal. CCS is one of the most expensive ways of reducing emissions in the energy sector. Deployment of this technology is very limited. As of 2024, CCS is used in only 5 power plants and in 39 other facilities. The report lists 50 facilities, of which 3 are direct air capture facilities and 3 are transport/storage facilities


Nuclear power

Nuclear power Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by ...
has been used since the 1950s as a low-carbon source of
baseload The base load (also baseload) is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants or dispatchable generation, depending on which approach has the best mi ...
electricity. Nuclear power plants in over 30 countries generate about 10% of global electricity. As of 2019, nuclear generated over a quarter of all
low-carbon energy Energy is sustainable if it "meets the needs of the present without compromising the ability of future generations to meet their own needs." Definitions of sustainable energy usually look at its effects on the environment, the economy, and so ...
, making it the second largest source after hydropower. Nuclear power's lifecycle greenhouse gas emissions—including the mining and processing of
uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...
—are similar to the emissions from renewable energy sources. Nuclear power uses little land per unit of energy produced, compared to the major renewables. Additionally, Nuclear power does not create local air pollution. Although the
uranium ore Uranium ore deposits are economically recoverable concentrations of uranium within Earth's crust. Uranium is one of the most common Chemical element, elements in Earth's crust, being 40 times more common than silver and 500 times more common than ...
used to fuel nuclear fission plants is a non-renewable resource, enough exists to provide a supply for hundreds to thousands of years. However, uranium resources that can be accessed in an economically feasible manner, at the present state, are limited and uranium production could hardly keep up during the expansion phase. Climate change mitigation pathways consistent with ambitious goals typically see an increase in power supply from nuclear. There is controversy over whether nuclear power is sustainable, in part due to concerns around
nuclear waste Radioactive waste is a type of hazardous waste that contains radioactive material. It is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, nuclear decommissioning, rare-earth mining, and nuclear ...
, nuclear weapon proliferation, and
accidents An accident is an unintended, normally unwanted event that was not deliberately caused by humans. The term ''accident'' implies that the event may have been caused by unrecognized or unaddressed risks. Many researchers, insurers and attorneys w ...
. Radioactive nuclear waste must be managed for thousands of years. For each unit of energy produced, nuclear energy has caused far fewer accidental and pollution-related deaths than fossil fuels, and the historic fatality rate of nuclear is comparable to renewable sources. Public opposition to nuclear energy often makes nuclear plants politically difficult to implement. Reducing the time and the cost of building new nuclear plants have been goals for decades but costs remain high and timescales long. Various new forms of nuclear energy are in development, hoping to address the drawbacks of conventional plants.
Fast breeder A breeder reactor is a nuclear reactor that generates more fissile material than it consumes. These reactors can be fueled with more-commonly available isotopes of uranium and thorium, such as uranium-238 and thorium-232, as opposed to the rare ...
reactors are capable of recycling nuclear waste and therefore can significantly reduce the amount of waste that requires geological disposal, but have not yet been deployed on a large-scale commercial basis. Nuclear power based on thorium (rather than uranium) may be able to provide higher energy security for countries that do not have a large supply of uranium. Small modular reactors may have several advantages over current large reactors: It should be possible to build them faster and their modularization would allow for cost reductions via learning-by-doing. They are also considered safer to use than traditional power plants. Several countries are attempting to develop
nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...
reactors, which would generate small amounts of waste and no risk of explosions. Although fusion power has taken steps forward in the lab, the multi-decade timescale needed to bring it to commercialization and then scale means it will not contribute to a 2050 net zero goal for climate change mitigation.


Energy system transformation


Decarbonisation of the global energy system

The emissions reductions necessary to keep global warming below 2°C will require a system-wide transformation of the way energy is produced, distributed, stored, and consumed. For a society to replace one form of energy with another, multiple technologies and behaviours in the energy system must change. For example, transitioning from oil to solar power as the energy source for cars requires the generation of solar electricity, modifications to the electrical grid to accommodate fluctuations in solar panel output or the introduction of variable battery chargers and higher overall demand, adoption of
electric cars An electric car or electric vehicle (EV) is a passenger automobile that is propelled by an electric traction motor, using electrical energy as the primary source of propulsion. The term normally refers to a plug-in electric vehicle, typ ...
, and networks of electric vehicle charging facilities and repair shops. Many climate change mitigation pathways envision three main aspects of a low-carbon energy system: * The use of low-emission energy sources to produce electricity *
Electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. In the context of history of technology and economic development, electrification refe ...
– that is increased use of electricity instead of directly burning fossil fuels * Accelerated adoption of energy efficiency measures Some energy-intensive technologies and processes are difficult to electrify, including aviation, shipping, and steelmaking. There are several options for reducing the emissions from these sectors: biofuels and synthetic carbon-neutral fuels can power many vehicles that are designed to burn fossil fuels, however biofuels cannot be sustainably produced in the quantities needed and synthetic fuels are currently very expensive. For some applications, the most prominent alternative to electrification is to develop a system based on sustainably-produced
hydrogen fuel The hydrogen economy is an umbrella term for the roles hydrogen can play alongside low-carbon electricity to reduce emissions of greenhouse gases. The aim is to reduce emissions where cheaper and more energy-efficient clean solutions are not avail ...
. Full decarbonisation of the global energy system is expected to take several decades and can mostly be achieved with existing technologies. In the IEA's proposal for achieving net zero emissions by 2050, about 35% of the reduction in emissions depends on technologies that are still in development as of 2023. Technologies that are relatively immature include batteries and processes to create carbon-neutral fuels. Developing new technologies requires research and development, demonstration, and cost reductions via deployment. The transition to a zero-carbon energy system will bring strong co-benefits for human health: The World Health Organization estimates that efforts to limit global warming to 1.5 °C could save millions of lives each year from reductions to air pollution alone. With good planning and management, pathways exist to provide universal
access to electricity Access may refer to: Companies and organizations * ACCESS (Australia), an Australian youth network * Access (credit card), a former credit card in the United Kingdom * Access Co., a Japanese software company * Access International Advisors, a hed ...
and
clean cooking One aspect of energy poverty is lack of access to clean, modern fuels and technologies for cooking. As of 2020, more than 2.6 billion people in developing countries routinely cook with fuels such as wood, animal dung, coal, or kerosene. Burning ...
by 2030 in ways that are consistent with climate goals. Historically, several countries have made rapid economic gains through coal usage. However, there remains a window of opportunity for many poor countries and regions to "
leapfrog Leapfrog is a children's game of physical movement of the body in which players vault over each other's stooped backs. History Games of this sort have been called by this name since at least the late sixteenth century.

Integrating variable energy sources

To deliver reliable electricity from
variable renewable energy Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable ener ...
sources such as wind and solar, electrical power systems require flexibility. Most
electrical grid An electrical grid (or electricity network) is an interconnected network for electricity delivery from producers to consumers. Electrical grids consist of power stations, electrical substations to step voltage up or down, electric power tran ...
s were constructed for non-intermittent energy sources such as coal-fired power plants. As larger amounts of solar and wind energy are integrated into the grid, changes have to be made to the energy system to ensure that the supply of electricity is matched to demand. In 2019, these sources generated 8.5% of worldwide electricity, a share that has grown rapidly. There are various ways to make the electricity system more flexible. In many places, wind and solar generation are complementary on a daily and a seasonal scale: there is more wind during the night and in winter when solar energy production is low. Linking different geographical regions through long-distance transmission lines allows for further cancelling out of variability. Energy demand can be shifted in time through
energy demand management Energy demand management, also known as demand-side management (DSM) or demand-side response (DSR), is the modification of consumer energy demand, demand for energy through various methods such as financial incentives and behavioral change through ...
and the use of
smart grids The smart grid is an enhancement of the 20th century electrical grid, using two-way communications and distributed so-called intelligent devices. Two-way flows of electricity and information could improve the delivery network. Research is main ...
, matching the times when variable energy production is highest. With
grid energy storage Grid energy storage, also known as large-scale energy storage, are technologies connected to the electrical power grid that store energy for later use. These systems help balance supply and demand by storing excess electricity from variabl ...
, energy produced in excess can be released when needed. Further flexibility could be provided from sector coupling, that is coupling the electricity sector to the heat and mobility sector via
power-to-heat Power-to-X (also P2X and P2Y) are electricity energy transformation, conversion, energy storage, and reconversion pathways from surplus renewable energy. Power-to-X conversion technologies allow for the decoupling of power from the electricity s ...
-systems and electric vehicles. Building overcapacity for wind and solar generation can help ensure that enough electricity is produced even during poor weather. In optimal weather, energy generation may have to be curtailed if excess electricity cannot be used or stored. The final demand-supply mismatch may be covered by using dispatchable energy sources such as hydropower, bioenergy, or natural gas.


Energy storage

Energy storage helps overcome barriers to intermittent renewable energy and is an important aspect of a sustainable energy system. The most commonly used and available storage method is
pumped-storage hydroelectricity Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing (electrical power), load balancing. A PSH system stores energy i ...
, which requires locations with large differences in height and access to water. Batteries, especially
lithium-ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. Li-ion batteries are characterized by higher specific energy, energy ...
, are also deployed widely. Batteries typically store electricity for short periods; research is ongoing into technology with sufficient capacity to last through seasons. Costs of utility-scale batteries in the US have fallen by around 70% since 2015, however the cost and low
energy density In physics, energy density is the quotient between the amount of energy stored in a given system or contained in a given region of space and the volume of the system or region considered. Often only the ''useful'' or extractable energy is measure ...
of batteries makes them impractical for the very large energy storage needed to balance inter-seasonal variations in energy production. Pumped hydro storage and
power-to-gas Power-to-gas (often abbreviated P2G) is a technology that uses electric power to produce a gaseous fuel. Most P2G systems use electrolysis to produce hydrogen. The hydrogen can be used directly, or further steps (known as two-stage P2G systems) ...
(converting electricity to gas and back) with capacity for multi-month usage has been implemented in some locations.


Electrification

Compared to the rest of the energy system, emissions can be reduced much faster in the electricity sector. As of 2019, 37% of global electricity is produced from low-carbon sources (renewables and nuclear energy). Fossil fuels, primarily coal, produce the rest of the electricity supply. One of the easiest and fastest ways to reduce greenhouse gas emissions is to phase out coal-fired power plants and increase renewable electricity generation. Climate change mitigation pathways envision extensive electrification—the use of electricity as a substitute for the direct burning of fossil fuels for heating buildings and for transport. Ambitious climate policy would see a doubling of energy share consumed as electricity by 2050, from 20% in 2020. One of the challenges in providing universal access to electricity is distributing power to rural areas. Off-grid and
mini-grid A mini-grid is an aggregation of Electrical load, electrical loads and one or more energy sources operating as a single system providing electricity and possibly heat, isolated from a main Electrical grid, power grid. A modern mini-grid may includ ...
systems based on renewable energy, such as small solar PV installations that generate and store enough electricity for a village, are important solutions. Wider access to reliable electricity would lead to less use of kerosene lighting and diesel generators, which are currently common in the developing world. Infrastructure for generating and storing renewable electricity requires minerals and metals, such as
cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...
and
lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...
for batteries and
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
for solar panels. Recycling can meet some of this demand if product lifecycles are well-designed, however achieving net zero emissions would still require major increases in mining for 17 types of metals and minerals. A small group of countries or companies sometimes dominate the markets for these commodities, raising geopolitical concerns. Most of the world's cobalt, for instance, is mined in the Democratic Republic of the Congo, a politically unstable region where mining is often associated with human rights risks. More diverse geographical sourcing may ensure a more flexible and less brittle
supply chain A supply chain is a complex logistics system that consists of facilities that convert raw materials into finished products and distribute them to end consumers or end customers, while supply chain management deals with the flow of goods in distri ...
.


Hydrogen

Hydrogen gas is widely discussed as a fuel with potential to reduce greenhouse gas emissions. This requires hydrogen to be produced cleanly, in quantities to supply in sectors and applications where cheaper and more energy efficient
mitigation Mitigation is the reduction of something harmful that has occurred or the reduction of its harmful effects. It may refer to measures taken to reduce the harmful effects of hazards that remain ''in potentia'', or to manage harmful incidents that ...
alternatives are limited. These applications include heavy industry and long-distance transport. Hydrogen can be deployed as an energy source in
fuel cells A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in req ...
to produce electricity, or via combustion to generate heat. When hydrogen is consumed in fuel cells, the only emission at the point of use is water vapour. Combustion of hydrogen can lead to the thermal formation of harmful NOx, nitrogen oxides. The overall lifecycle emissions of hydrogen depend on how it is produced. Nearly all of the world's current supply of hydrogen is created from fossil fuels. The main method of producing hydrogen is steam methane reforming, in which hydrogen is produced from a chemical reaction between steam and methane, the main component of natural gas. Producing one tonne of hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide. While carbon capture and storage (CCS) could remove a large fraction of these emissions, the overall carbon footprint of hydrogen from natural gas is difficult to assess , in part because of emissions (including Gas venting, vented and Fugitive gas emissions, fugitive methane) created in the production of the natural gas itself. Electricity can be used to split water molecules, producing sustainable hydrogen provided the electricity was generated sustainably. However, this electrolysis process is currently more expensive than creating hydrogen from methane without CCS and the efficiency of energy conversion is inherently low. Hydrogen can be produced when there is a surplus of Variable renewable energy, variable renewable electricity, then stored and used to generate heat or to re-generate electricity. It can be further transformed into liquid fuels such as green ammonia and green methanol. Innovation in Electrolysis of water, hydrogen electrolysers could make large-scale production of hydrogen from electricity Hydrogen economy#Costs, more cost-competitive. Hydrogen fuel can produce the intense heat required for industrial production of steel, cement, glass, and chemicals, thus contributing to the decarbonisation of industry alongside other technologies, such as electric arc furnaces for steelmaking. For steelmaking, hydrogen can function as a clean fuel and simultaneously as a low-carbon catalyst replacing coal-derived coke (fuel), coke. Hydrogen used to decarbonise transportation is likely to find its largest applications in shipping, aviation and to a lesser extent heavy goods vehicles. For light duty vehicles including passenger cars, hydrogen is far behind other alternative fuel vehicles, especially compared with the rate of adoption of battery electric vehicles, and may not play a significant role in future. Disadvantages of hydrogen as a fuel include high costs of storage and distribution due to hydrogen's explosivity, its large volume compared to other fuels, and its tendency to make pipes brittle.


Energy usage technologies


Transport

Transport accounts for 14% of global greenhouse gas emissions, but there are multiple ways to make transport more sustainable. Public transport typically emits fewer greenhouse gases per passenger than personal vehicles, since trains and buses can carry many more passengers at once. Short-distance flights can be replaced by high-speed rail, which is more efficient, especially when electrified. Promoting non-motorised transport such as walking and cycling, particularly in cities, can make transport cleaner and healthier. The Energy efficiency in transport, energy efficiency of cars has increased over time, but shifting to electric vehicles is an important further step towards decarbonising transport and reducing air pollution. A large proportion of traffic-related air pollution consists of particulate matter from road dust and the wearing-down of tyres and brake pads. Substantially reducing pollution from these Non-tailpipe emissions, non-tailpipe sources cannot be achieved by electrification; it requires measures such as making vehicles lighter and driving them less. Light-duty cars in particular are a prime candidate for decarbonization using Electric battery, battery technology. 25% of the world's Carbon dioxide, emissions still originate from the transportation sector. Long-distance freight transport and aviation are difficult sectors to electrify with current technologies, mostly because of the weight of Electric vehicle battery, batteries needed for long-distance travel, battery recharging times, and limited battery lifespans. Where available, freight transport by ship Rail freight transport, and rail is generally more sustainable than by air and by road. Hydrogen vehicles may be an option for larger vehicles such as lorries. Many of the techniques needed to lower emissions from shipping and aviation are still early in their development, with ammonia (produced from hydrogen) a promising candidate for shipping fuel. Aviation biofuel may be one of the better uses of bioenergy if emissions are captured and stored during manufacture of the fuel.


Buildings

Over one-third of energy use is in buildings and their construction. To heat buildings, alternatives to burning fossil fuels and biomass include electrification through heat pumps or Electric resistance heater, electric heaters, Geothermal heating, geothermal energy, central solar heating, reuse of waste heat, and seasonal thermal energy storage. Heat pumps provide both heat and air conditioning through a single appliance. The IEA estimates heat pumps could provide over 90% of space and water heating requirements globally. A highly efficient way to heat buildings is through district heating, in which heat is generated in a centralised location and then distributed to multiple buildings through insulated pipes. Traditionally, most district heating systems have used fossil fuels, but District heating#Fourth generation, modern and cold district heating systems are designed to use high shares of renewable energy.Cooling of buildings can be made more efficient through Passive solar building design, passive building design, planning that minimises the urban heat island effect, and district cooling systems that cool multiple buildings with piped cold water. Air conditioning requires large amounts of electricity and is not always affordable for poorer households. Some air conditioning units still use refrigerants that are greenhouse gases, as some countries have not ratified the Kigali Amendment to only use climate-friendly refrigerants.


Cooking

In developing countries where populations suffer from
energy poverty In developing countries and some areas of more developed countries, energy poverty is lack of access to modern energy services in the home. In 2022, 759 million people lacked access to consistent electricity and 2.6 billion people used dangerous a ...
, polluting fuels such as wood or animal dung are often used for cooking. Cooking with these fuels is generally unsustainable, because they release harmful smoke and because harvesting wood can lead to forest degradation. The universal adoption of clean cooking facilities, which are already ubiquitous in rich countries, would dramatically improve health and have minimal negative effects on climate. Clean cooking facilities, e.g. cooking facilities that produce less indoor soot, typically use natural gas, liquefied petroleum gas (both of which consume oxygen and produce carbon-dioxide) or electricity as the energy source; biogas systems are a promising alternative in some contexts. Improved cookstoves that burn biomass more efficiently than traditional stoves are an interim solution where transitioning to clean cooking systems is difficult.


Industry

Over one-third of energy use is by industry. Most of that energy is deployed in thermal processes: generating heat, drying, and refrigeration. The share of renewable energy in industry was 14.5% in 2017—mostly low-temperature heat supplied by bioenergy and electricity. The most energy-intensive activities in industry have the lowest shares of renewable energy, as they face limitations in generating heat at temperatures over . For some industrial processes, commercialisation of technologies that have not yet been built or operated at full scale will be needed to eliminate greenhouse gas emissions. Steelmaking, for instance, is difficult to electrify because it traditionally uses Coke (fuel), coke, which is derived from coal, both to create very high-temperature heat and as an ingredient in the steel itself. The production of plastic, cement, and fertilisers also requires significant amounts of energy, with limited possibilities available to decarbonise. A switch to a circular economy would make industry more sustainable as it involves recycling more and thereby using less energy compared to investing energy to mine and refine new raw materials.


Government policies

Well-designed government policies that promote energy system transformation can lower greenhouse gas emissions and improve air quality simultaneously, and in many cases can also increase energy security and lessen the financial burden of using energy.


Regulations

Environmental regulations have been used since the 1970s to promote more sustainable use of energy. Some governments have committed to dates for Coal phase-out, phasing out coal-fired power plants and ending new fossil fuel exploration. Governments can require that new cars produce zero emissions, or new buildings are heated by electricity instead of gas. Renewable portfolio standards in several countries require utilities to increase the percentage of electricity they generate from renewable sources. Governments can accelerate energy system transformation by leading the development of infrastructure such as long-distance electrical transmission lines, smart grids, and hydrogen pipelines. In transport, appropriate infrastructure and incentives can make travel more efficient and less car-dependent. Urban planning that discourages Urban sprawl, sprawl can reduce energy use in local transport and buildings while enhancing quality of life. Government-funded research, procurement, and incentive policies have historically been critical to the development and maturation of clean energy technologies, such as solar and lithium batteries. In the IEA's scenario for a net zero-emission energy system by 2050, public funding is rapidly mobilised to bring a range of newer technologies to the demonstration phase and to encourage deployment.


Carbon pricing

Carbon pricing (such as a tax on emissions) gives industries and consumers an incentive to reduce emissions while letting them choose how to do so. For example, they can shift to low-emission energy sources, improve energy efficiency, or reduce their use of energy-intensive products and services. Carbon pricing has encountered strong Politics of climate change, political pushback in some jurisdictions, whereas energy-specific policies tend to be politically safer. Most studies indicate that to limit global warming to 1.5°C, carbon pricing would need to be complemented by stringent energy-specific policies. As of 2019, the price of carbon in most regions is too low to achieve the goals of the Paris Agreement. Carbon taxes provide a source of revenue that can be used to lower other taxes or help lower-income households afford higher energy costs. Some governments, such as the EU and the UK, are exploring the use of carbon border adjustments. These place tariffs on imports from countries with less stringent climate policies, to ensure that industries subject to internal carbon prices remain competitive.


Pace

The scale and pace of policy reforms that have been initiated as of 2020 are far less than needed to fulfil the climate goals of the Paris Agreement. In addition to domestic policies, greater international cooperation is required to accelerate innovation and to assist poorer countries in establishing a sustainable path to full energy access. Countries may support renewables to create jobs. The International Labour Organization estimates that efforts to limit global warming to 2 °C would result in net job creation in most sectors of the economy. It predicts that 24 million new jobs would be created by 2030 in areas such as renewable electricity generation, improving energy-efficiency in buildings, and the transition to electric vehicles. Six million jobs would be lost, in sectors such as mining and fossil fuels. Governments can make the transition to sustainable energy more politically and socially feasible by ensuring a just transition for workers and regions that depend on the fossil fuel industry, to ensure they have alternative economic opportunities.


Finance

Raising enough money for innovation and investment is a prerequisite for the energy transition. The IPCC estimates that to limit global warming to 1.5 °C, US$2.4 trillion would need to be invested in the energy system each year between 2016 and 2035. Most studies project that these costs, equivalent to 2.5% of world GDP, would be small compared to the economic and health benefits. Average annual investment in low-carbon energy technologies and energy efficiency would need to be six times more by 2050 compared to 2015. Underfunding is particularly acute in the least developed countries, which are not attractive to the private sector. The United Nations Framework Convention on Climate Change estimates that climate financing totalled $681 billion in 2016. Most of this is private-sector investment in renewable energy deployment, public-sector investment in sustainable transport, and private-sector investment in energy efficiency. The Paris Agreement includes a pledge of an extra $100 billion per year from developed countries to poor countries, to do climate change mitigation and adaptation. This goal has not been met and measurement of progress has been hampered by unclear accounting rules. If energy-intensive businesses like chemicals, fertilizers, ceramics, steel, and non-ferrous metals invest significantly in R&D, its usage in industry might amount to between 5% and 20% of all energy used. Fossil fuel funding and energy subsidy#Fossil fuel subsidies, subsidies are a significant barrier to the energy transition. Direct global fossil fuel subsidies were $319 billion in 2017. This rises to $5.2 trillion when indirect costs are priced in, like the effects of air pollution. Ending these could lead to a 28% reduction in global carbon emissions and a 46% reduction in air pollution deaths. Funding for clean energy has been largely unaffected by the COVID-19 pandemic, and pandemic-related economic stimulus packages offer possibilities for a green recovery.


References


Sources

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External links

{{DEFAULTSORT:Sustainable Energy Sustainable energy, Climate change mitigation Climate change policy Emissions reduction Energy economics Environmental impact of the energy industry Sustainable development Sustainability Sustainability by subject Sustainability and environmental management Energy