A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Acceptance

Social acceptance is crucial for the transition of our energy supply system to renewable energy, such as for the costs associated with the energy transition, the construction of renewable energy plants as well as > energy storage or the expansion of electricity > grids. Participation in the associated processes can improve acceptance. Overall, surveys show that there is a constant social support for the energy transition.

Agrivoltaics

The term agrivoltaics refers to the combined use of land for agriculture and electricity generation with > solar photovoltaics (PV). The PV systems are mounted at a certain height on agricultural land, and crop production or animal husbandry can happen underneath the elevated panels or in-between rows for instance. Integrating solar technology into agricultural activities enhances climate resilience by providing movable shade, reducing water consumption, improving soil health, and protecting crops and livestock from extreme heat.

Artificial Intelligence (AI)

AI has the potential to support and accelerate the energy transition, as it can help to better manage the new challenge of > volatility and decentralised feed-in, for example through precise predictions of electricity generation and consumption within a fully renewable energy system, or through enhancing the > digitalisation of energy supply with intelligent control systems such as > smart grids. On the downside, AI also consumes enormous amounts of energy (e.g. through data centres), and the electricity for powering AI must first be generated.

B

Backup power

Backup power refers to any system that supplies immediate power when the regular power supply is interrupted, unavailable or insufficient to meet demand.

Base load power

Base load is the minimum amount of power that a country needs at a certain point in time. With the share of renewables in electricity generation increasing, the aim in future will shift from covering a fixed base load to flexibly and reliably supplementing wind and solar power to meet demand. As wind, solar, biomass, geothermal energy and hydropower can complement one another, renewable energy sources alone will increasingly be able to provide electricity in line with demand, supported by > flexibility from > energy storage technologies and behavioural changes. > Peak load power in contrast to base load power refers to periods of highest demand during daytime.

Bioenergy

Bioenergy is the umbrella term referring to all solid, gaseous and liquid energy carriers based on the organic matter of > biomass, such as > biofuels, > biogas and > biomethane.

Biofuel

Biofuels are liquid or gaseous fuels for transport that are obtained from > biomass (various crops such as rapeseed, sugar cane, sugar beets or corn, as well as residues, e.g. used cooking oil). They are used as substitutes for diesel fuel, petrol or gaseous fuels such as fossil gas. When burned, biofuels emit no more > CO₂ than was absorbed from the atmosphere during the growth of the plant. However, depending on how the biomass is sourced, the environmental impact of biofuels can differ largely.

Biogas

Biogas is a combustible > gas produced during the fermentation of > biomass, be it dedicated crops or waste and residues such as manure. It contains > methane and CO₂ as its main components, as well as various trace substances. Biogas is used as an energy carrier. It is burnt to produce electricity and/or heat, for instance in > cogeneration in combined heat and power plants. Purified biogas that is ready for injection into existing fossil gas grids is called > biomethane.

Biomass

Substances or mixtures of substances of biological origin, hence organic matter, are referred to as biomass. It can be provided as a solid, liquid, or gaseous energy carrier (see also > biofuel, > biogas). From those solid, gaseous or liquid energy carriers, it is possible to generate electricity, heat or provide a transport fuel. Biomass can be provided either from plants grown for energetic use or as a residual product from other forms of biomass use.

Biomethane

Methane is the main component of > biogas and can be fed into the existing fossil gas grid after purification. It is for example available for use in > cogeneration in combined heat and power plants or as fuel for vehicles. Methane obtained from biogas is known as biomethane.

Brown coal

See > Lignite

C

Carbon capture and storage (CCS)

The combustion of fossil fuels such as coal or oil produces > CO₂. This is one of the main drivers of to the global climate crisis. There is a technology that captures > CO₂ and stores it underground: carbon capture and storage (CCS). When parts of the > CO₂ are additionally used as a raw material, for example in the chemical industry, this is referred to as carbon capture, utilisation and storage (CCUS). The technology has not yet been comprehensively proven. Carbon leakage can undo the anticipated climate benefits, underground storage can pose a threat to groundwater, and it is expensive. The introduction of CCS may be reduced to areas where > CO₂ emissions are inevitable, e.g. in cement production.

Carbon capture, utilisation and storage (CCUS)

See > Carbon capture and storage (CCS)

Carbon dioxide

See > CO₂ emissions

Cities in the energy transition

Climate and energy policy is mostly decided upon at state level. However, the implementation is also the responsibility of local authorities and cities to a certain extent, which are advancing the energy transition at local level and promoting > energy democracy.

Climate crisis

Climate change has grown into a climate crisis due to human activities causing > greenhouse gas emissions. This leads to serious consequences such as a rise of the earth’s surface temperature, the rise of sea levels, more extreme weather events such as floods, wildfires, storms and droughts, and to a loss of biodiversity, to name only a few effects. The need for action to counteract these developments is huge. Although almost all countries worldwide have committed to climate protection through the > Paris Agreement, there is still not enough being done to mitigate emissions.

Climate neutrality

Climate neutrality refers to achieving a balance between > CO₂ emissions and the absorption of carbon from the atmosphere in carbon sinks (soil, forests, and oceans). To achieve > net zero emissions, all residual > greenhouse gas emissions worldwide must be offset by carbon absorption. The best thing, of course, is not to emit anything in the first place. The energy transition is leading to a shift away from fossil fuels (which cause emissions) towards clean energy that is climate-neutral.

Climate protection

Climate protection refers to measures to reduce effects that are harmful to the climate. Climate protection can be achieved in many different ways: for example, there is natural climate protection through intact ecosystems (forests, peatlands, soils, oceans). In everyday life, it can mean switching to a bicycle or public transport instead of taking the car, eating organic products and less meat, or recycling for example. At political level, the > Paris Agreement defined targets for reducing > greenhouse gas emissions. Measures to protect the climate in the energy sector are particularly important, as a significant part of emissions is caused by fossil energy supply.

CO₂ emissions

Carbon dioxide (CO₂) is a colourless and odourless > greenhouse gas which is a natural component of the atmosphere. However, during the combustion of carbon-based fossil fuels (coal, oil, gas), it is emitted as a waste product of energy generation, thereby significantly driving the > climate crisis. CO₂ emissions, among other things, cause glaciers to melt, sea levels to rise and extreme weather events to increase.

Coal

Coal is a fossil, finite fuel, formed by the long-term deposition of plant substances. Coal consists of more than 50 percent carbon by weight. There are different types of coal, such as > lignite or > hard coal.

Cogeneration

Cogeneration refers to the simultaneous supply of electricity and heat. In combined heat and power plants, the heat generated during electricity production is not released into the environment as > waste heat, but is made available for technical use through a heat exchanger.

Combined heat and power

See > Cogeneration

Community-owned renewables

The term community-owned renewables refers to the economic and operational participation in or ownership of citizens or a defined community of a renewable energy project. It is a crucial element in establishing public > acceptance and support for the development of > energy democracy. It leads, among other things, to accelerated access to renewable energy and can help to leverage renewables in the fight against > energy poverty.

Conference of Parties (COP)

The Conference of the Parties (COP) is the main decision-making body of the United Nations Framework Convention on Climate Change (UNFCCC), which has the main objective to prevent anthropogenic climate change by reducing greenhouse gas emissions. Through the UNFCCC, its parties (nearly 200 countries) have reached different binding agreements, the most prominent being the Kyoto Protocol with binding emission reduction targets, and the following > Paris Agreement, which aims to keep global warming well below 2°C and ideally under 1.5°C compared to pre-industrial times. The COP meets every year to assess the Convention’s implementation and to also take decisions for a successful implementation. Renewable energies are key to lower > greenhouse gas emissions.

Critical raw materials

For the energy transition, large amounts of critical raw materials are needed, e.g. for the deployment of wind and solar energy, for > electric mobility or for battery storage. These include for instance rare earths, cobalt, lithium, nickel and copper. The extraction and processing of these raw materials can cause serious environmental damage, and is often concentrated in few countries with large deposits, which leads to dependencies and geopolitical risks. However, many critical raw materials can also be recycled and reused.

D

Dark doldrums

The term dark doldrums efers to weather conditions with calm winds or darkness or low solar radiation, resulting in low electricity generation from wind turbines and solar panels. In an energy system with high shares of solar and wind power, dark doldrums are a challenge for the suppliers and > grid operators that need to make sure that electricity demand and supply perfectly match. However, potential risks can be anticipated thanks to today’s excellent weather forecasts. If too little electricity is generated at a particular point in time, several > flexibility options can jump in, e.g., electricity can be transported from neighbouring regions, through the existing > grids, consumers can temporarily reduce their demand or > energy storage can be drawn upon.

Decarbonisation

Transition of the energy industry with the objective of moving away from fossil (carbon-based) energy carriers (e.g. > coal, oil, > gas). Burning these energy carriers produces carbon dioxide (> CO₂), which is released into the atmosphere and thereby contributes to the global warming process and drives the > climate crisis.

Digitalisation

Refers to the increasingly automated collection and analysis of data on energy demand and supply. Based on this energy system data, the sectors of electricity, heat and transport (as well as the associated value chain of energy generation, storage and consumption) are being linked intelligently so that demand, supply and infrastructure use can be optimised in > smart grids. The digitalisation is becoming increasingly important due to electrification and decentralisation of the energy sector, as it helps improving the stability of a highly complex system.

Distributed energy

Distributed energy describes a large number of small and geographically decentralised generators (solar roofs, wind turbines, etc.) that supply energy, as opposed to a centralised system based on a few large power stations and centralised supply chains for fossil and nuclear fuels.

Distribution networks

A distribution network is a network that is not used for long-distance transport (as > transmission networks), but rather for the distribution of, for example, electricity, fossil gas or heat, to individual consumers.

District heating

Some buildings and industrial plants are not supplied by their own heating systems on premises, but receive heat and hot water from a remote heat generator. The heat in the form of hot water or steam is transported via insulated pipes directly from suppliers to connected heat consumers. Large district heating networks are often connected to a > combined heat and power plant, using the waste heat from the heat engine for district heating. > Waste heat from waste incineration plants can also be used, for example.

Dunkelflaute

See > Dark doldrums

E

Electricity grid

See > Grid

Electricity price

The term electricity prices refers to the cost of supplying electricity for consumers. Even though renewables have the lowest levelised costs of electricity generation (LCOE), the retail electricity price for final customers (including taxes, levies and network charges) is usually much higher. As long as other energy sources such as > fossil fuels and > nuclear power are part of the electricity mix, their costs also influence the electricity price.

Electric mobility

Electric mobility refers to trains, trams, cars, buses and bikes running on electricity. Electric mobility is a key component in reducing emissions, as electric vehicles do not rely on burning fossil fuels such as diesel, for example. The infrastructure for electric mobility, such as charging stations, needs to be expanded in parallel to the growing number of electric vehicles.

Electrolysis

Electrolysis is a technique that breaks down a chemical compound using electricity. In the context of the energy transition, electrolysers split water into > hydrogen and oxygen. Hydrogen can be stored and used later for producing electricity, heat or running other production processes in energy-intensive industries. If the electrolyser uses exclusively renewable electricity, the hydrogen supplied is almost emission-free. This renewable hydrogen is considered the key for phasing out > fossil fuels in sectors that are very difficult to decarbonise, such as the steel and chemicals industry, aviation and long-distance shipping.

Emissions trading

Emissions trading is a market-based instrument in environmental policy to reduce emissions. It is based on the concept of internalising into the polluters’ economic activities the external environmental costs caused by a polluter. In the European Union’s Emissions Trading System (EU-ETS), > greenhouse gas emissions in a specified sector, such as for all electricity generators are limited to a total amount and distributed in the form of tradable emission allowances to polluters. Hence, the more emissions one polluter causes, the more allowances the polluter needs, and the more expensive it becomes to emit emissions. The shrinking amount of available emission allowances and the increasing cost of tradable allowances sends a strong signal to polluters to cut their emissions, for instance by reducing > fossil fuel consumption and switching to > renewable energy sources.

Employment

The energy transition has positive effects on jobs creation. Across their entire production chain, > renewable energy technologies usually are more employment-intensive than > fossil fuels and > nuclear power. > Energy savings measures such as building renovation also create new and secure existing jobs.

Energiewende

Energiewende is the German term for energy transition, partly used interchangeably also in English.

Energy democracy

Energy democracy means a shift from a centralised, corporate energy system to local, affordable and community-based energy production, allowing more direct > participation in the energy transition to citizens through democratic decision-making and creation of value added. It also refers to the freedom to choose an energy provider and to produce your own power, for instance through a > solar PV system on your roof or through > community owned renewables installations under the umbrella of a citizens’ energy cooperative.

Energy efficiency

Energy efficiency is the ratio between the required initial energy input on the one side and the usable final energy output for consumption, be it for electricity generation, heating and cooling buildings, driving a vehicle or running an industrial production process. Energy efficiency describes the losses of this conversion process. In a highly energy efficient process, the same performance is provided reducing energy consumption. Energy efficiency can lead to > energy savings and needs to be differentiated from > energy sufficiency.

Energy poverty

Large parts of the world’s population, especially in developing countries, suffer from energy poverty. This means that important needs cannot be met (partially) because the energy required to meet them is either unavailable or cannot be paid for. The European Union defines energy poverty as a household’s lack of access to essential energy services including adequate heating, hot water, cooling, lighting and energy to power appliances, caused by a combination of factors including at least non-affordability, insufficient disposable income, high energy expenditure and poor > energy efficiency of homes.

Energy savings

Energy savings encompass a range of activities designed to reduce energy consumption, e.g. by cutting energy demand and/or by increasing the > energy efficiency of an energy conversion process. In this way, energy costs can be reduced, dependencies can be minimised, and the environmental impact can be limited. Energy savings form a contrast to > energy sufficiency and > energy efficiency.

Energy security

Most countries have to import > fossil fuels and nuclear fuels (uranium), i.e., buy them from other countries that have access to these energy sources on their territory. This leads to dependency on these other countries, for example in terms of price fluctuations or the political situation, which in turn can lead to insecurity. > Renewable energy sources contribute to energy security because they are accessible in every country and thus can reduce dependencies.

Energy sources

Energy is available in the form of energy sources. A distinction is made between > primary energy sources, which are directly extracted from nature and only minimally processed (e.g. > coal and fossil > gas), and > secondary energy sources, which are converted using technology – for example, electricity, > hydrogen, > biogas or diesel fuel.

Energy storage

Energy can be stored in different ways. Energy storage systems are available for different forms of energy, e.g. for electrical energy (for instance batteries or > hydrogen) or for heat (thermal storage such as boilers).

Energy sufficiency

Energy sufficiency refers to the deliberate reduction of consumption, i.e. limiting consumption to a necessary, moderate level and avoiding excessive consumption, thus reducing raw material and energy usage. The concept of energy sufficiency goes beyond > energy savings and > energy efficiency.

European Green Deal

The European Green Deal is a package of more than 100 legislative initiatives and action plans that was launched by the European Commission during its term from 2019 to 2024. Its target is to achieve > climate neutrality in Europe by 2050, with > greenhouse gas emissions to be reduced by 55 percent by 2030. The European Green Deal is designed to promote sustainable growth and links social, environmental and economic factors. It is therefore an important contribution to the implementation of the > Paris Agreement.

European Energy Union

The European Commission in 2015 launched the Energy Union as a strategy to foster > security of supply, solidarity and trust; a fully integrated internal energy market; > energy efficiency; climate action and the > decarbonisation of the economy; as well as research, innovation and competitiveness.

F

Feed-in tariff

A feed-in tariff is a remuneration for the generation of electrical energy at a fixed price set through regulation. It serves to promote selected energy generation technologies, in particular > renewable energy. It determines the prices per > kilowatt-hour of a system over its lifetime, plus a return on investment.

Final energy

Final energy is the energy that reaches a consumers’ doorstep as fuel, heat or electricity. In other words, losses in production and transport are not included. The term gross energy is used to describe energy consumption that includes distribution losses.

Flexibility

To complement weather-dependent renewables, whenever the sun is not shining or the wind is not blowing, for example during > dark doldrums, or during times of high > volatility, the electricity system needs more flexibility to ensure that demand will always be met. There is a broad range of flexibility options, such as consumers ramping up and down their consumption, different > energy storage technologies, import and export through existing and newly built > grids, as well as dispatchable renewable electricity generation that does not depend on the weather, such as > hydropower, bioenergy and geothermal energy.

Fossil fuels

Non-renewable energy sources that have been formed from > biomass over millions of years under high pressure and high temperatures, for instance oil, > coal, or fossil > gas. Their combustion releases > greenhouse gases such as > CO₂, which is a major contributor to climate change.

Fossil fuels import dependency

Not every country has deposits of > fossil fuels for energy supply on its territory. As a result, many countries have to purchase energy carriers from other countries, which leads to dependencies. > Renewable energy and > energy efficiency help reducing imports significantly, since they can be used nearly everywhere.

G

Gas

Gas can refer to fossil gas and renewable gas. Whereas fossil gas is per definition a finite energy carrier, consisting mainly of > methane and gets extracted from underground sources for combustion, renewable gas is either based on > biogas, a > bioenergy carrier produced through digestion of organic matters, or on > hydrogen that has been produced through > electrolysis with renewable electricity.

Geothermal energy

Geothermal energy is the natural thermal renewable energy from the ground that can be transported upwards for > renewable heat supply and/or for electricity generation.

Gigawatt (GW)

A gigawatt refers to a unit of electrical power and equates to one billion watts. It describes the maximum electricity output of the installed capacity of a power station or of a heating station. For areas where the amounts of energy are high, the total installed capacity is often expressed in gigawatts for simplicity. The electricity produced is expressed in gigawatt-hours (one billion kilowatt-hours).

Green Deal

See > European Green Deal

Green energy

A very broad term, oftentimes used as a synonym for > renewable energy.

Greenhouse effect

The gases in the atmosphere that surrounds the earth ensure that the sunlight that hits the earth is not immediately reflected into space. The > greenhouse gases ensure that part of the solar irradiation is kept. Consequently, the earth surface does not fully cool off but can reach a temperature levels that allow life on earth. A distinction is made between this natural and an anthropogenic (man-made) greenhouse effect. Man-made emissions of greenhouse gases increase their concentration in the atmosphere. The greenhouse effect then intensifies and global average temperature levels increase, causing the detrimental effects of climate change.

Greenhouse gas (GHG)

Greenhouse gases (e.g. carbon dioxide, methane, or nitrous oxide) contribute to the greenhouse effect. The largest anthropogenic emitters of greenhouse gases is the combustion of fossil fuels, such as coal, gas and oil, as well as agriculture.

Green transition

A very broad term that can be used for the energy transition and related transformations.

Grid

The electricity grid is the network of power lines that allows electricity to flow from one place to another. The voltage levels of electricity grids differ depending on the distance of transmission and distribution and on the quantity and of electricity that flows through the cables. Power stations need to connect to the electricity grid to generate electricity and transport it to consumers.

Grid access

Grid access refers to a generator’s physical connection to the larger electrical > grid. If homeowners install > solar PV panels, they should have the right to be connected to the > distribution network, to feed in power they do not consume on premises for own purposes into the grid and to get a remuneration for injecting their power into the grid.

H

Hard coal

There are different types of coal, such as > lignite or hard coal, a fossil fuel formed by carbonisation of plant remains. Hard coal is a higher quality coal (in comparison to lignite) that was formed under higher pressure over longer periods of time. It is therefore usually found at greater depths, i.e. extracted in coal mines.

Heat pump

A technical device that increases the temperature level of available thermal energy, e.g. ambient energy or > geothermal energy. The heat pump compresses a refrigerant that collects and transports the thermal energy. With the compression of the refrigerant, its temperature level also increases. It can then supply heat for the space heating of buildings, for hot water or production processes. The principle of changing temperature levels through compression can also be found in the opposite sense in refrigerators, where it is used for cooling. Heat pumps have a huge potential for replacing > fossil fuels for heating because they are very energy efficient. For running the process, heat pumps only consume little electricity and supply up to three to four times more > renewable heat than the input electricity.

Hydrogen

A combustible > gas that can be used as an energy carrier. By splitting water through > electrolysis, hydrogen and oxygen are generated. If renewable electricity is used for the electrolysis, it is also referred to as renewable or ‘green’ hydrogen. If based on renewable electricity, hydrogen is a promising source of energy that can contribute to the > decarbonisation of various sectors, especially hard-to-abate sectors. Hydrogen can also be stored for long time before use, hence serve as a > backup power for weather-dependent renewable energy. In this case, hydrogen during those times when the sun is not shining and the wind is not blowing, is burned for electricity generation, e.g., in gas turbines.

Hydropower

Hydropower refers to generating electricity from water, usually by damming rivers or through turbines placed in rivers. The water drives a turbine that in turn drives a generator to produce electricity.

I

Intergovernmental Panel on Climate Change (IPCC)

The Intergovernmental Panel on Climate Change is an institution of the United Nations. It consists of leading climate scientists that deliver regular and comprehensive scientific assessments on climate science, to provide policymakers with information on climate change and its implications.

International Energy Agency (IEA)

The International Energy Agency (IEA) is an independent organisation within the Organisation for Economic Cooperation and Development (OECD). It advises the governments of its member countries on energy matters and aims at contributing to a secure, sustainable and economical energy supply. The IEA has 30 member countries, including the European Union.

International Renewable Energy Agency (IRENA)

The International Renewable Energy Agency (IRENA) is a leading global intergovernmental organisation of 168 member states (2024) driving the energy transition. It acts as a key platform for international collaboration, assisting countries in their shift to > renewable energy and offers data as well as analyses on policy, innovation, or technology for instance.

J

Jobs

The energy transition and research as well as development in the field of > renewable energy are driving job creation, generating lots of new employment opportunities. The loss of jobs in the > fossil fuel sectors is therefore not an argument against the energy transition. Through reskilling and training, many jobs can be moved from the fossil fuel sector to the renewable energy sector. According to the > International Energy Agency, the transition to renewables will lead to an overall increase in energy sector jobs.

Just transition

The global energy transition comes with consequences for individuals. For example, many people are and have been employed in the > fossil fuels industry, but as the energy transition moves forward, more and more of these jobs disappear. Workers therefore need retraining and jobs in other sectors, and this must be taken into account in the energy transition so that it is fair and socially just for everyone. At the same time, structural change is creating new jobs, for example in the > renewable energy sector. The energy transition at the same time aims to minimise injustices by making affordable clean energy accessible to all: currently, industrialised countries and rich nations are responsible for the majority of emissions from their use of fossil fuels, causing the > climate crisis. Poorer countries struggle with access to affordable energy sources and suffer the most from the consequences of industrialised countries’ fossil fuel consumption, which is not fair.

K

Kilowatt (kW)

Kilowatt (kW) is a unit of measurement for power, it stands for the amount of energy that is consumed or generated per second. It indicates how much energy an appliance requires or provides at a given time. One kilowatt corresponds to 1,000 watts. Kilowatts (kW) and > kilowatt-hours (kWh) are often confused with each other. While kW defines how much energy can be consumed or produced at a given moment, kWh describes the power output over a certain period of time.

Kilowatt-hour (kWh)

Kilowatt hours, abbreviated as kWh, indicate how much energy is consumed or produced when operating a device with an output of 1 kW for one hour. > Kilowatts (kW) and kilowatt hours (kWh) are often confused with each other. While kW defines how much energy can be consumed or produced at a given moment, kWh describes the power output over a certain period of time.

Kyoto Protocol

The Kyoto Protocol was adopted by the third Conference of Parties (COP) of the United Nations Framework Convention on Climate Change in 1997 in Kyoto/Japan and entered into force in 2005. It was the first binding treaty under international law on the mitigation of climate change, which obliges the participating countries to reduce > greenhouse gas emissions. The emissions reduction was supposed to happen where it can be realised most cost-effectively. For this reason, the Kyoto Protocol also offered the option of fulfilling commitments abroad through ’flexible mechanisms’ of emissions trading in addition to domestic reductions. Following the Kyoto Protocol, the > Paris Agreement was adopted in December 2015.

L

Lignite

Lignite (also named brown coal) was formed during millions of years under low pressure, contains identifiable plant parts and has a low calorific value in comparison to other fossil fuels. It is mostly used for electricity and heat production.

Liquefied Natural Gas (LNG)

Liquefied natural gas (LNG) is the result of the liquefaction process of natural > gas through extreme cooling. LNG plays a role in areas where transportation via pipeline networks is not possible. It can be transported by ship, for example.

Local value added

See > Strengthening local economies

Lock-in effects

The ‘lock-in effect’ refers to a situation where decisions or investments made in existing systems (e.g. fossil infrastructure or subsidies for a given period of time) make it difficult to switch to more sustainable alternatives. In the energy industry, this can lead to further dependence on > fossil fuels and higher costs for the energy transition.

M

Megawatt (MW)

Watt is a unit of measurement for power, with 1,000 watts corresponding to one > kilowatt (kW) and 1,000 kilowatts corresponding to one megawatt (MW). Megawatts are typically used to measure the installed generation capacity of large power plants.

Methane

Methane is a hydrocarbon and combustible > gas. It is the main component of fossil gas (also called ‘natural gas’) and of > biogas. Alongside carbon dioxide (> CO₂), it is one of the most significant man-made > greenhouse gases. Over a period of 20 years, methane is approximately 86 times more climate-damaging than CO₂.

N

National Energy and Climate Plans (NECPs)

In their National Energy and Climate Plans (NECPs), the Member States of the European Union provide comprehensive information on their national energy and climate policies for a period of 10 years. The aim is to enable comparison and coordination of the energy and climate policies of EU Member States and to track the achievement of the EU’s overall energy and climate targets for 2030 and beyond. The legal basis for this is the EU Regulation on the Governance of the Energy Union and Climate Action.

Net zero

The ‘net zero’ objective refers to the state where > greenhouse gas emissions are reduced to a minimum, with any remaining emissions offset by carbon removal processes – either through natural sinks or technological solutions – so that the total amount of emissions added to the atmosphere is net zero. Achieving net zero emissions latest by 2050 is essential to limiting global warming to 1.5°C, in line with the objectives of the > Paris Agreement.

Nuclear power

Nuclear power (or nuclear energy) is energy released as a result of nuclear reactions. The most important use of nuclear energy is the generation of electricity in nuclear power plants, the construction of which is extremely expensive, takes a very long time and is usually heavily subsidised. The use of nuclear power plants involves great risks for health and environment, starting with the extraction and processing of > uranium ore, the nuclear fuel needed for producing power from a nuclear reactor. Severe reactor accidents can contaminate large areas with radioactivity, posing a threat to humans and nature. After use, the spent nuclear fuel (uranium) remains radioactive, which is why it must be stored safely in repositories for thousands of years. Given its costs and deployment times, nuclear power does not have the potential to play a major role in future world energy supply and in view of climate protection, even though a nuclear power plant does not directly emit > greenhouse gases. Nuclear energy is also used for military purposes in nuclear weapons. Spreading nuclear technology thus implies the risk of proliferation, posing a threat to global stability and peace.

O

Offshore wind energy

Wind turbines generate electricity on land and on sea. Onshore wind turbines are usually installed on open spaces or on hills and use wind currents on land to generate electricity, whilst offshore wind turbines are built in the sea. Offshore, wind conditions are stronger and more constant, which increases energy yields.

Onshore wind energy

See > Offshore wind energy

P

Paris Agreement

The Paris Climate Agreement was adopted in Paris in 2015 and entered into force in 2016. It follows on the > Kyoto Protocol from 1997. The main targets are to keep global warming below ideally 1.5°C, or 2°C, compared to pre-industrial levels; to reduce emissions on a pathway towards > net zero, adapt to climate change and steer financial resources in line with climate protection targets; and to strengthen resilience against the impacts of climate change. The agreement is binding and all parties must elaborate and implement nationally determined contributions (NDCs).

Participation in the energy transition

The decentralised character of > renewable energy sources and the accessibility of small-scale renewable energy technologies make it easy for citizens to engage in electricity and heat production on the local level. The energy transition thus offers both democratic participation in the planning and operation of renewable energy installations, as well as financial participation in the benefits. Acceptance of the energy transition can only be achieved if decisions are made with consulting the public. One approach is to involve citizens through the provision of information, via consultations, or through local > community-owned renewables and reskilling of staff.

Passive house

A passive house is a highly efficient building (residential or otherwise) that ’passively’ uses solar heat (sunshine) to drastically reduce the need for ’active’ heating and cooling, such as from an air conditioner and heating system.

Peak load

Peak load describes a certain period in time when the demand for power in the electricity > grid is the highest. It usually occurs with peaks of electricity consumption around midday and in the evening. To cover peak load in a grid, power plants or electricity storage that can be quickly adjusted to generate electricity are used to feed the additional energy required into the grid. Alternatively, electricity consumers can also ramp down their demand during peak load hours in order to ease the grid and avoid high electricity costs. Import and export through existing and newly built > distribution networks and > transmission networks, is another > flexibility solution to reduce pressure on infrastructure and on prices during peak load.

Photovoltaics (PV)

See > Solar Photovoltaics (PV)

Power-to-X

Power-to-X is a term for different processes where electrical energy that isn’t used for other purposes is turned into chemical energy or heat. The X hence stands for > gas, liquids, or heat for instance, resulting in concepts like power to gas, power to liquid, or power to heat.

Primary energy

Primary energy sources are energy sources that occur naturally, including > fossil fuels, and > renewable energy sources. They are not yet converted into secondary, usable energy for final consumers, e.g. such as electricity and heat.

Q

Quotas for renewable energy

Countries have implemented different systems to encourage investments in renewables – one of these is determining quotas for companies to meet a minimum share of renewable energy in the > final energy they sell to customers.

R

Raw materials for the energy transition

See > Critical raw materials

Redispatch

Electricity > grids can only operate in a stable way if the power fed into the grid matches exactly the power withdrawn, including transmission losses, at all times. Normally, electricity generators trade and dispatch their future electricity production to cover precisely the expected demand. If this balance is disturbed, e.g. because of grid congestion, technical failures or other events, the electricity > transmission grid operator intervenes by ramping down or up certain electricity generators so that an expected mismatch of supply and demand is prevented.

Renewable energy

Renewable energy is the umbrella term for all energy sources that rely on > bioenergy, > solar energy, > wind energy, > geothermal energy and > hydropower. In contrast with fossil energy carriers such as crude oil, fossil > gas, > hard coal and > lignite, renewable energy sources are not finite but replenish themselves naturally.

Renewable heat

Renewable heat refers to heat generated from renewable resources, such as > biomass, > geothermal energy or > solar energy. The term statistically can also encompass the recovery of > waste heat for heating applications. Electric > heat pumps and the electrification of heat with renewable electricity also represent renewable heat.

Repowering

Repowering refers to the process of replacing old power plant components used for electricity generation with new components with higher efficiency and/or higher capacity at the same location, while continuing to use parts of the existing plant and infrastructure onsite. In the context of the expansion of > wind energy, repowering refers to the replacement of older, less efficient wind turbines with higher and more productive ones.

S

Secondary energy

Secondary energy is energy in secondary energy sources, i.e. energy sources that are not taken directly as > primary energy from nature but have been artificially produced or significantly altered (refined) to make them more usable. These include, for example, electrical energy (e.g. produced from the primary source of > solar energy through > solar PV panels) or petrol (e.g. from the primary energy source of crude oil).

Sector coupling

Sector coupling refers to the interconnection and interaction of sectors of the energy industry that were mostly organised separately before, such as electricity, heating and transport. These sectors need to be integrated more closely in order to replace > fossil fuels with > renewable energy in the most efficient way. For instance, renewable electricity use increases in the transport sector through > electric mobility, requiring adaptations in energy infrastructure. Renewable gases such as > hydrogen or > biomethane replace fossil > gases in industry which also requires a better coordination of renewable electricity generation, fossil gas supply and gas infrastructures.

Sector integration

See > Sector coupling

Security of supply

Security of supply, i.e. ensuring that the required amounts of energy are available at all times to cover energy demand, is one of the central objectives of energy policy. It entails the reliable supply of > primary energy, its conversion and distribution to final customers without interruption.

Smart grids

A smart grid is an umbrella term for an optimised and digitalised electricity > grid involving many producers and consumers that can interact amongst each another as well as with the grid infrastructure as such, allowing for an economically more attractive and stable operation through fine control based on > smart meters. This is important because electricity consumption and decentralised renewable electricity generation is rising worldwide. In the shift from a centralised system with a few fossil fuel-powered plants to many small producers using > renewable energy, a smart grid is a key solution for matching more volatile demand and supply in a cost-efficient way.

Smart meters

Smart meters or smart metering systems are digital electricity meters with a communication module that measures the energy consumed or fed into the > grid close to real time, making the information potentially accessible for consumers, producers, traders and electricity grid operators. Their purpose is to realise cost efficiency potentials by displaying actual, current energy consumption and/or production. Electric vehicle drivers, for instance, can charge their battery and save money if a smart meter informs them about an excess of low-price electricity during certain hours. Smart meters are key components for the functioning of > smart grids, which in turn support the energy transition with its shift away from centralised to decentralised energy systems with higher > volatility.

Social acceptance

See > Acceptance

Social justice

The use of > renewable energy has a potential for increasing social justice. Firstly, households can find their way out of energy poverty with renewable energy technologies. These technologies do not require constant payments for expensive > fossil fuels, thus offer a way out of > energy poverty. Renewable energy technologies such as > solar PV panels and > heat pumps ease the bills of vulnerable households because they have become affordable for them, at least on the mid- and long-term. Citizens’ engagement in > community-owned renewables projects also can help turning the classic top-down supply of energy into an > energy democracy. Secondly, renewable energy allows for intergenerational justice. While the use of > fossil fuels leads to emissions and thus to a worsening of the > climate crisis, and while the use of nuclear fuels produces enormous quantities of radioactive waste for which there is still no final repository and which future generations will have to deal with, renewable energy protects the climate so that our planet can remain a liveable place for future generations.

Solar energy

Solar energy is the renewable > primary energy source of the sun’s irradiation. Firstly, it can be converted through > solar photovoltaics into electricity. Secondly, solar thermal energy is the umbrella term for the use of solar energy as heat supply, typically through solar thermal collectors, which in a next step can then be converted into useful energy. It is used to supply hot water and, depending on the size of the system, also heat for space heating or for industrial production processes.

Solar photovoltaics (PV)

A photovoltaic system converts radiation from the sun or light into electrical energy (solar power) with the aid of solar panels. This provides a renewable source of electrical energy.

Strengthening local economies

Local > community-owned renewables provide great economic payback to investing communities in terms of local value added. Instead of huge global corporate groups extracting and selling > fossil fuels, local companies, cooperatives and other organisations can make profits from installing and operating renewable energy installations. This creates and secures local jobs and local purchase power. In addition, local authorities can benefit more from renewable energy installations thanks to increasing local tax revenues. A huge offer of domestic affordable renewable energy then turns into a clear competitive advantage for the hosting region.

Sufficiency

See > Energy sufficiency

Sustainable Development Goal 7 (SDG7)

In 2015, the United Nations adopted 17 Sustainable Development Goals (SDGs) to protect the planet, to end poverty, and to foster peace and prosperity. One of them is SDG7 (Affordable and Clean Energy) aiming at ensuring access to affordable, reliable, sustainable and modern energy for all.

T

Transmission losses

Transmission losses occur during the transmission and transformation of electrical energy in the > transmission network. In order to keep losses for transmissions over longer distances at a minimum, the voltage of the electrical energy in the > grid is increased with the help of transformers.

Transmission network

Energy carriers (for instance fossil > gas) and electricity usually have to be transported over long distances from the place where they are extracted or generated to the place where they are needed or where they are further distributed via the > distribution network. For this purpose, there are transmission networks. Gas is transmitted via a network of pipes, whereas electricity is transmitted via overhead lines or underground cables.

Transmission System Operator (TSO)

Transmission system operators are responsible for operating, maintaining and expanding the > transmission networks such as the cross-European high-voltage electricity network and fossil gas pipelines. They grant producers and consumers access to their > grids. The transmission system operators also have the duty to balance out grid fluctuations and are responsible for guaranteeing > security of supply at all times, e.g. through > redispatch measures.

U

Uranium

Uranium is a chemical element, a toxic and radioactive heavy metal that can be extracted from certain ores. It is essential as key component of the nuclear fuel for the generation of > nuclear power in nuclear reactors. The extraction of uranium ore, its processing, transformation and enrichment are energy-intensive expensive and have negative impacts on the environment and on human health. After its use as nuclear fuel, uranium remains highly radioactive, which is why it must be stored safely in repositories for thousands of years.

V

Volatility

Power generation from the two renewable energy sources > solar energy and > wind energy is dependent on the weather. It is therefore subject to fluctuations. Solar energy is dependent on sunlight, which is naturally available during day time and particularly abundant during certain weather periods. Wind energy is dependent on wind speed, which in turn is available depending on weather constellations. Whenever the sun is not shining and the wind is not blowing, there are several solutions to remedy this volatility, e.g. the use of > energy storage technologies as a > backup power, ramping up or down flexible power plants such as > hydropower plants, > geothermal plants, or plants running on > biomass. Alternatively, well-connected energy networks allow to fill the gaps trough > transmission network imports from neighbouring regions or to get rid of excess production. Postponing or anticipating certain energy consumption can also help to better match demand with weather-dependent supply.

W

Waste heat

Waste heat refers to heat that is generated as a by-product of a process. It often leaks unused into the environment, but it can also be utilised (heat recovery) as a measure to increase > energy efficiency. Waste heat from industrial processes, for instance, is partly used by the same industry and partly used for heating purposes via local > district heating networks. Waste heat can also be used as a heat source by > heat pumps.

Wind energy

Wind energy is a form of renewable energy. Winds, or air movements in the atmosphere, carry large amounts of mechanical energy. Wind turbines (windmills) capture wind energy by transferring it to a rotating axis, which is then used to drive a generator to produce electrical energy. Wind turbines can be operated > onshore and > offshore.

Wood pellets

Wood pellets consist of combustible material from dried, natural wood waste (sawdust, wood shavings, forest waste wood) pressed into small sticks. Wood pellets are mainly used as > biomass fuel: modern, fully automatic central heating systems can be operated with it.

World Energy Outlook

The > International Energy Agency’s annual World Energy Outlook is a global reference for energy analysis and projection, based on fact-based analysis. It examines the most significant trends in energy supply and demand, offering insights into their implications for economic development, energy security, and emissions.

Z

Zero emissions

See > Net zero