Glossary

Abated fossil fuels refer to fossil fuels whose carbon dioxide (CO2) emissions have been reduced or mitigated through carbon capture, utilisation, and storage (CCUS) technologies. These technologies capture CO2 emissions produced during the combustion of fossil fuels, preventing them from entering the atmosphere. The captured CO2 is then either stored underground or utilised for other purposes.

In the context of Nationally Determined Contributions (NDCs), absolute emissions reductions refer to a country’s commitment to cut greenhouse gas emissions by a specific amount compared to a fixed baseline year. This approach leaves little room for interpretation, as it sets a clear, quantifiable target. For example, the UK has pledged to reduce economy-wide emissions by at least 68% by 2030, relative to 1990 levels. Absolute targets are widely seen as the most rigorous form of emissions commitment and are commonly adopted by Annex I countries under the Paris Agreement.

Under the UN Framework Convention on Climate Change (UNFCCC), Annex I countries (or 'parties') include the industrialised countries that were members of the OECD (Organisation for Economic Co-operation and Development) in 1992, plus countries with economies in transition. These countries are expected to take the lead in reducing greenhouse gas emissions due to their historical contributions to climate change.

The ASEAN Power Grid is an initiative to develop a regional grid network that connects the electricity systems of ASEAN countries. Initially, the connection is made on a bilateral basis, with plans for gradual integration into a fully connected regional power system. The goal is to enhance energy security, optimise energy use, and facilitate cross-border electricity trade among ASEAN nations.

Asset managers oversee the financial and operational performance of energy infrastructure, ensuring assets meet investment goals and regulatory requirements.

Asset owners hold direct ownership and make strategic decisions about investment, maintenance, and upgrades. Both play a key role in managing complex project financing, securing construction loans, equity, tax equity, and project debt to fund energy developments.

The Association of Southeast Asian Nations is an inter-governmental international organisation comprising of 10 countries, namely Brunei Darussalam, Cambodia, Indonesia, Lao PDR, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam.

Availability is the ratio between the maximum number of hours a technology can operate at full capacity in a year and the total number of hours in a year (8,760).

For example, a nuclear power plant with planned maintenance outages might have an availability of 90%, meaning it can operate at full capacity for 7,884 hours per year (0.90 × 8,760). A wind turbine, subject to variable wind conditions, might have a lower availability of 50–60%. Availability is typically expressed as a percentage and is a key input in energy system modelling for assessing reliability, capacity planning, and economic viability.

Baseload power is the minimum amount of electricity required by the electrical grid at any given time, such as over a day or week, to meet the continuous demand of essential services. It is traditionally supplied by power plants that operate at a constant output and cannot ramp up or down quickly, such as coal and nuclear plants. The remainder of electricity demand, which fluctuates throughout the day, is typically met by peaker plants, flexible generation, or energy storage.

A battery energy storage system (BESS) stores electricity for later use, helping balance supply and demand. It captures excess energy during low-demand periods and releases it when demand is high, supporting the integration of renewable energy and improving grid stability.

Behind the meter refers to energy generation, storage, or management that occurs on the consumer’s side of the electricity meter — within their home, business, or facility — rather than on the utility-controlled grid. The term is applied most often to rooftop solar, and residential battery energy storage systems (BESS).

Business as usual (BAU) refers to a scenario where current trends and practices continue without any significant changes or interventions. In energy and climate modelling, BAU assumes that no major policy actions are taken to reduce emissions or transition to renewable energy. This makes BAU a reference scenario for understanding what might happen if current energy systems and practices persist. A key weakness of BAU is that it often underestimates the potential for future changes, especially policy shifts, technological advancements, and societal transformations that could alter future outcomes.

Capacity is the maximum output an electricity generator can physically produce, measured in megawatts (MW). It represents the highest level of electricity generation a plant can sustain under optimal conditions.

A capacity expansion models simulate generation and transmission capacity investment, given assumptions about future electricity demand, fuel prices, technology cost and performance, and policy and regulation.

Capacity factor is the ratio of the actual output of a power plant or energy generation system over a period of time, to the maximum possible output if the plant were running at full capacity during that time. It reflects the efficiency with which a plant operates.

A captive power generation asset is managed by an industrial or commercial facility for the company's own energy consumption. It can be operated off-grid or connected to the grid to exchange excess power generation. Captive power plants can also be referred to as autorproducer, or embedded generation.

Carbon-free energy, also known as 24/7 carbon-free energy (24/7 CFE) is the goal of a fully decarbonised energy system, ensuring that every kilowatt-hour of electricity consumption is met with zero-carbon sources at all times and in all locations. Unlike traditional renewable energy procurement, which often relies on annual matching, this approach ensures a continuous supply of clean electricity every hour of every day. The movement is coordinated by Sustainable Energy for All (SEforALL), the United Nations, and a growing coalition of companies, organisations, and governments which are committed to transforming electricity procurement and accelerating the transition to a carbon-free grid.

Climate finance refers to financial resources allocated to addressing climate change, including efforts to reduce greenhouse gas emissions, enhance climate resilience, and support sustainable energy transitions. It is sourced from public and private entities, including governments, financial institutions, and corporations. At the international level, climate finance is essential for supporting developing countries in achieving their climate and energy goals.

TransitionZero's Coal Asset Transition tool is an open data product to help refinance and replace coal plants in an affordable and just way. Explore the tool and download the data.

TransitionZero's Coal-to-Clean Price Index is an open data product that tracks the operating cost of coal and gas versus the cost of new onshore wind or utility-scale solar PV plus four hours of battery storage in 25 countries. The tool can be used to understand how price volatility can impact fuel competitiveness. Explore the tool and download the data.

Common but differentiated responsibilities is a principle of international environmental law establishing that all states are responsible for addressing global environmental destruction yet not equally responsible. CBDR puts more onus on the higher-income industrialised nations to take more ambitious action on climate change because of their historical responsibility for the majority of emissions and their greater capacity to act.

In the context of Nationally Determined Contributions (NDCs), relative emissions reduction targets can be conditional or unconditional, depending on the support required to achieve them. Unconditional targets are commitments a country makes without reliance on external assistance. These reductions will be implemented using domestic resources, policies, and capabilities. Conditional targets depend on external factors such as international climate finance, technology transfer, or capacity-building support. Many developing countries submit conditional targets alongside unconditional ones, aiming for greater emissions reductions if sufficient assistance is provided. This distinction reflects the varying capacities of countries to fund and implement climate action, particularly in non-Annex I nations.

In energy system modelling, a constraint is a rule or limit that the model must follow when finding the best solution. Constraints can represent physical limits, like how much electricity a power plant can generate, or economic and policy restrictions, such as emissions limits or budget caps. They help to ensure that the model’s results are realistic and follow real-world conditions.

In modelling, descriptive models represent or describe a system as it currently exists, without attempting to predict future behaviour or prescribe specific actions. Unlike normative models, which identify solutions, these models typically aim to capture the structure, relationships, and behaviours of a system in its current state, helping to understand how the system works or how different components interact.

A dispatch model is a type of optimisation problem used to determine the operational pattern of a power system. It plays a crucial role in influencing the security, efficiency, and economics of the system. By optimising the generation and distribution of electricity, dispatch models ensure that supply meets demand in the most cost-effective and reliable manner, considering factors such as fuel costs, system constraints, and system stability.

Distributed energy resources are small-scale power generation assets under 10MW —such as solar panels, diesel generators, small wind turbines or batteries— which are usually located close to load centres, that can be used responsively to provide flexibility to the grid. Virtual DERs are a collection of many small-scale assets that may not be physically near each other but, using specialist software, have been aggregated into one collective asset that grid operators can control as if it were one power plant.

Distribution network operators are the companies that are responsible for distributing electricity to homes and businesses, via power cables and other infrastructure. DNOs manage the local electricity distribution network but are separate from energy suppliers and do not bill consumers for electricity usage.

An electricity system operator is a national body responsible for system operation and balancing of the national electricity grid, turning generation assets on and off to balance demand and generation at all times.

Emissions refer to the release of gases into the atmosphere that contribute to climate change, particularly greenhouse gases (GHGs) like carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These gases trap heat in the atmosphere, leading to climate change.

An emissions factor is a value used to estimate the amount of greenhouse gases (GHGs) emitted per unit of activity, energy, or material consumed. It helps quantify emissions from various sources, such as fuel combustion or industrial processes, and is used in calculating a country’s or company’s carbon footprint.

The amount of energy used to produce a specific amount of output, such as a product or service. It is usually measured as the energy input required for each unit of output produced. Energy intensity is the opposite of energy efficiency—higher energy intensity means more energy is used for less output, while lower energy intensity indicates greater efficiency.

An energy system model is a simulation of an energy system, representing energy sources, conversion pathways, distribution networks, and end uses. These models are used to analyse how different energy technologies, policies, and market dynamics interact over time.

For policymakers and stakeholders, energy systems models are essential for evaluating future energy scenarios, assessing policy impacts, and identifying cost-effective pathways for decarbonisation and energy security. By integrating economic, environmental, and technological factors, these models provide evidence-based insights to support strategic decision-making and the transition to sustainable energy systems.

Energy transition mechanism is a climate finance initiative backed by the Asian Development Bank (ADB) supports the early closure of carbon-intensive energy generation assets, such as coal-fired power plants. The initiative aims to reduce greenhouse gas emissions by providing financial assistance to accelerate the transition to cleaner, more sustainable energy sources. It helps countries and companies manage the economic and social impacts of shifting away from fossil fuels, promoting a just and low-carbon transition.

In modelling, an ensemble refers to a set of simulations run multiple times with varying input parameters, assumptions, or scenarios to capture uncertainty and explore a range of possible outcomes. These simulations might include different variables like fuel prices, technology costs, or policy changes. By analysing the ensemble, modellers can assess how uncertainty in inputs can affect system performance, providing a more robust understanding of potential futures. Ensembles are commonly used in Monte Carlo sampling, a statistical technique where multiple random samples are generated to explore a range of outcomes based on probability distributions. Ensembles are typically used in meteorological and other forecast data.

A gas system operator is a national body responsible for the operation and balancing of the gas network. The GSO ensures a stable and reliable supply of gas by coordinating the flow of gas, managing storage facilities, and maintaining the infrastructure needed to meet demand while ensuring system stability.

A unit of electricity equal to 1 billion watts.

TransitionZero's Global Steel Cost Tracker is an open data product that estimates the plant-level steel production costs of blast furnace (BF), basic oxygen furnace (BOF) and electric arc furnace (EAF) production routes representing around 90% of global steel production. The cost estimates are broken down by raw materials, energy, labour, and other costs. Explore the tool and download the data.

Global warming potential (GWP) is a metric used to compare the climate impact of different greenhouse gases over a specific timeframe, usually 100 years (GWP100). It measures how much heat a gas traps in the atmosphere relative to carbon dioxide (CO2), which has a GWP of 1. For example, methane (CH4) has a GWP100 of about ~28, meaning it traps ~28 times more heat than CO2 over a century, while nitrous oxide (N2O) has a GWP100 of ~273, meaning that it traps ~273 times more heat than CO2 over the same period.

Green hydrogen is the production of hydrogen by electrolysis — splitting water into hydrogen and oxygen — using electricity from renewable sources. Producing hydrogen is a very energy-intensive process, but if the energy comes from renewables, there are no direct carbon emissions. This makes green hydrogen a useful fuel for fossil-based industries that are hard to decarbonise, like heavy industry and long-haul transportation. However, the high level of energy loss means it is less efficient at powering technology that can be powered by renewable energy directly.

Greenhouse gases (GHGs) refer to the seven direct greenhouse gases covered under the Kyoto Protocol that trap heat in the atmosphere: carbon dioxide (CO2) methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). These gases were selected because they are the most significant contributors to human-made climate change.

Grid intensity refers to the measure of how clean the electricity grid is, based on the amount of carbon dioxide (CO2) emitted per kilowatt hour of electricity generated. It provides an indication of the environmental impact of the electricity being supplied, with lower grid intensity indicating cleaner energy sources and higher intensity reflecting more carbon-intensive power generation.

Gross domestic product measures the monetary value of goods and services produced in a country in a given period of time. It is a key indicator of a country's economic performance and is used to assess the size and health of its economy.

Ground truth is real word data that is known to be true, based on direct observation and measurement, which is used to train and test machine learning models. For example, ground truth could include historical data about emissions, energy production, or temperature, which can be compared with predicted values from a model to ensure its reliability.

The Group of Seven is an intergovernmental political and economic group of high-income industralised nations, including: Canada, France, Germany, Italy, Japan, the United Kingdom and the United States; additionally, the European Union (EU) is a 'non-enumerated member'.

An independent power project (IPP) is a privately owned power generation project that is developed, financed, and operated by a company or consortium outside of government-owned or regulated utilities. IPPs generate electricity for sale to the grid or directly to consumers, often under power purchase agreements (PPAs) with governments or utility companies. These projects can include a variety of energy sources, such as renewables (wind, solar) or conventional fuels (coal, gas).

An integrated assessment model combines data and methodologies from multiple scientific disciplines, including both human and Earth systems, to assess the interactions between climate, energy, economy, and other sectors. IAMs are used to evaluate the impacts of different policy options and provide actionable insights for addressing complex challenges such as climate change, sustainability, and energy transitions.

Interconnectors are high-voltage cables that connect the electricity systems of neighbouring countries, enabling cross-border power transfer. They enhance energy security, improve grid stability, and support decarbonisation by allowing surplus renewable energy to be shared. By balancing supply and demand across regions, interconnectors help reduce costs, integrate renewables, and increase the efficiency of the overall energy system.

The Intergovernmental Panel on Climate Change is a United Nations body that assesses scientific research on climate change, its impacts, and potential responses. It provides policymakers with objective, evidence-based reports to inform climate action and international negotiations.

Intermittent energy sources are sources that are not continuously available but fluctuate in their availability and output over a short timescale, such as solar, wind, wave and tidal power. While solar and tidal energy follow predictable daily and seasonal patterns, they are sometimes referred to as variable rather than intermittent. Coal, gas and nuclear power can also be intermittent because they can sometimes fail due to extreme weather or technical faults. Intermittency and variable renewable energy can be addressed with the use of energy storage and smarter energy demand management.

The International Energy Agency is a Paris-based autonomous intergovernmental organisation, established in 1974, that provides policy recommendations, analysis and data on the global energy sector. The 31 member countries and 13 association countries of the IEA represent 75% of global energy demand.

The International Renewable Energy Agency is an intergovernmental organisation with the aim of advancing the transition to renewable energy, including through greater understanding and cooperation between countries.

JETPs are an emerging climate finance mechanism aimed at supporting coal-dependent emerging economies to fund early retirement of coal plants, ramp up renewable energy and address the socioeconomic impacts of the energy transition on workers and communities. The first JETP was announced at COP26 in Glasgow, where $8.5 billion was promised to South Africa from the UK, US, France, Germany and the EU. Other JETP agreements have been signed with Indonesia (November 2022), Vietnam (December 2022), Senegal (June 2023).

Kilogrammes of carbon dioxide equivalent (kgCO₂e) measure the global warming impact of greenhouse gas emissions in terms of the equivalent amount of CO₂. This standardised metric accounts for different greenhouse gases by converting their impact into CO₂ terms, typically using a 100-year global warming potential (GWP100). It allows for the comparison and aggregation of emissions from various sources, enabling a clearer assessment of their contribution to climate change.

A unit of power equal to 1,000 watts.

A unit of measurement equivalent to using a 1,000 watt appliance for 1 hour.

Land use refers to the amount of land required to produce a certain resource, such as electricity or food. Different power generation sources have vastly different land use requirements. For example, renewable energy sources like solar and wind often require large areas of land for installations, while fossil fuel-based energy generation has smaller direct land footprints but other significant environmental impacts.

Least cost refers to a principle in system modelling aimed at minimising total system costs. This approach mirrors the goals of efficient system planning and market-based policies, making it a good representation of liberalised markets.

To add realism, modellers can introduce constraints for non-market behaviours, such as regulations, and apply external factors like taxes, quotas, or changes in resource availability to address specific research questions.

A load flow model is used to analyse the steady-state operation of an electrical power system. It calculates the flow of electrical power through the system, determining how power is distributed across the network from generation to load centres. Load flow models help assess voltage levels, power losses, and the performance of system components, ensuring that the grid operates efficiently and within safe limits.

A unit of power equal to 1 million watts.

Merit order is a ranking system used in power grid management which determines the order in which power plants should be deployed to meet energy demand in the most optimal and economically efficient way.

MTCO₂e stands for million tonnes of carbon dioxide equivalent. It is a standard unit used to measure and compare the climate impact of different greenhouse gases by converting them into the equivalent amount of carbon dioxide (CO₂) based on their global warming potential (GWP). This allows for a consistent way to assess total emissions across different gases. For example, if a country’s annual methane emissions are estimated at 100 MT, and methane has a GWP100 of about 28, this would be equivalent to 2,800 MTCO₂e.

A model is a simplified representation of a real-world system. A model can be used to simulate different scenarios and test various assumptions. For example, a climate model may be used to predict how global temperatures will change in response to different levels of greenhouse gas emissions.

An Nationally Determined Contribution is a climate action plan submitted by countries under the Paris Agreement to reduce emissions and adapt to climate impacts. Each Party is required to establish and update their NDC every five years.

The first NDCs were set at COP21 in 2015, when 197 countries committed to emissions targets designed to keep global temperatures "well below 2°C" compared to pre-industrial levels, with the intention to limit warming to 1.5°C. The NDCs were intended to increase ambition and keep the Paris Agreement's climate goals within reach. Although countries are encouraged to submit more ambitious NDCs every five years, the level of ambition has not significantly increased to date.

Negative emissions refer to the removal of carbon dioxide from the atmosphere to counterbalance ongoing emissions, helping to achieve a net zero or carbon-negative balance. Unlike absolute zero emissions — where no emissions are produced at all — negative emissions offset residual emissions through various natural and technological methods. Natural approaches include reforestation, afforestation, and soil carbon sequestration, which enhance the ability of ecosystems to absorb and store carbon. Technological solutions, often referred to as negative emissions technologies (NETs), include direct air capture (DAC), which chemically extracts CO2 from the air, and carbon capture and storage (CCS), which prevents emissions from reaching the atmosphere in the first place. Other experimental methods, such as ocean fertilisation, aim to boost carbon uptake in marine environments. While negative emissions play a crucial role in achieving climate targets they are not a substitute for immediate and deep emissions reductions. Instead, they are seen as a necessary complement to mitigate unavoidable emissions.

Net zero refers to the state where any emissions released into the atmosphere are offset by equivalent ‘negative emissions,’ resulting in a final balance of zero. This differs from absolute zero emissions, where no emissions are released at all. The term can apply to individual assets, sectors, or entire economies. Negative emissions refer to any process — whether natural or technological — that removes carbon from the atmosphere. Examples include direct air capture (DAC), carbon capture and storage (CCS), reforestation, and changes in land use.

In modelling, node demand is the demand for electricity at a specific location. The node could be a substation, city, province or entire country, depending on the spatial resolution of the model or analysis.

A normative model is designed to prescribe or recommend specific actions or outcomes based on defined objectives or criteria. Unlike descriptive models, which explain what is happening, normative models focus on identifying optimal or desirable solutions under certain conditions. They are often used in decision-making, optimisation, and policy analysis to suggest how systems should behave, such as minimising costs, maximising efficiency, or achieving specific environmental or economic goals.

The Open Source Energy Modelling System (OSeMOSYS) is an open-source tool designed for long-term energy planning and integrated assessment. It has been employed to develop energy systems models ranging from global scales to individual countries, regions, and villages.

The Paris Agreement is a legally binding international treaty on climate change, drafted by the parties to the United Nations Framework Convention on Climate Change (UNFCCC) during the 21st Conference of the Parties (COP21) held in Paris in 2015. Signed by 196 nations, it addresses climate mitigation, adaptation, and finance, with the main goal of limiting global temperature rise to well below 2°C above pre-industrial levels, and striving to limit it to 1.5°C. The agreement aims to strengthen global efforts to reduce greenhouse gas emissions and support countries in adapting to the impacts of climate change.

Parts per million (PPM) is a unit of measurement used to express the concentration of a specific gas in a mixture. It represents the number of parts of a substance per million parts of the total mixture. In environmental science, ppm is often used to measure the concentration of GHG pollutants, such as CO2 in the atmosphere.

Peaking power plants, also known as peaker plants or simply ‘peakers’, are power stations that operate during periods of high electricity demand. Unlike baseload power plants, which run continuously, peakers provide short-term additional power to the grid when supply from other sources is insufficient. They are typically fuelled by natural gas but can also use oil, diesel, or even battery storage. While essential for grid stability, traditional peaker plants tend to be less efficient and more expensive to run per unit of electricity generated compared to baseload or renewable sources.

In an energy system model such as OSeMOSYS, perfect foresight means that all inputs and constraints are visible to the model across the entire time horizon. This assumption allows the model to make decisions based on complete knowledge of future conditions, ensuring that the system’s optimisation is based on all available information.

Photovoltaic (PV) technology refers to the use of solar cells to convert sunlight into electricity. A PV cell is a non-mechanical device made from semiconductor materials, most commonly silicon, which absorbs sunlight and generates an electric current through the photovoltaic effect. When multiple PV cells are connected together, they form a solar panel, which can generate larger amounts of electricity. Solar panels are used in various applications, from small residential rooftop systems to large-scale solar farms. The technology is widely regarded for its reliability, low maintenance, and ability to produce renewable energy without any moving parts.

A power development plan is a national long-term strategic policy framework that outlines the development, expansion, and modernisation of a country's power system. It typically includes projections of electricity demand, generation capacity planning, transmission and distribution infrastructure, and strategies for integrating renewable energy sources. It is often developed by government agencies, regulatory bodies, or utilities and is periodically updated to reflect technological advancements, policy changes, and evolving energy needs.

A power purchase agreement is a long-term contractual agreement between an electricity generator and an offtaker, such as a utility company. Lasting around 5-25 years, it outlines the terms of sale, such as the amount of electricity to be supplied, the price, and any penalties. It provides price stability for the offtaker and an assured revenue stream for the generator.

Probabilistic refers to methods or models that incorporate uncertainty and the likelihood of different outcomes. In a probabilistic approach, instead of providing a single deterministic result, a range of possible outcomes is presented, each with a certain probability. This is particularly useful in areas like energy systems modelling, where future scenarios are uncertain, and decision-makers need to assess risks and probabilities rather than fixed predictions.

A projection is an estimate of future outcomes based on current data and assumptions about trends or conditions. It describes the numbers that represent possible future scenarios, and can be probabilistic — offering an ensemble of futures or distributions of key parameters. Projections are commonly used in modelling to explore a range of potential outcomes, such as energy demand or emissions, accounting for uncertainty and variability in the assumptions.

PyPSA is an open-source toolbox designed for simulating and optimising modern power and energy systems. It includes capabilities for modelling conventional generators with unit commitment, variable wind and solar power generation, energy storage, integration with other energy sectors, and networks that combine both alternating and direct current systems.

Ramping capability refers to the maximum rate at which a power generation technology can increase or decrease its output. It is a key factor in grid stability, allowing power systems to respond to changes in electricity demand, fluctuations in renewable energy generation, or unexpected outages. Technologies like gas turbines and hydroelectric plants typically have high ramping capabilities, while coal and nuclear plants ramp more slowly.

Raster data is a type of spatial data in which the geographical area is divided into a grid of pixels, with each pixel corresponding to a specific location. The value of each pixel can either be continuous, such as elevation or temperature, or categorical, such as land use or vegetation type. Raster data is commonly used in geographic information systems (GIS) to represent a variety of spatial features, offering a detailed, pixel-based depiction of the landscape.

Rated capacity is the maximum sustainable power output of a generation asset, measured in megawatts (MW), under ideal conditions. While some assets may temporarily exceed this limit, operating above rated capacity can accelerate wear and reduce the asset’s lifespan. This metric helps planners assess system reliability and ensure long-term efficiency in power generation.

In the context of Nationally Determined Contributions (NDCs), relative emissions reductions refer to targets set in relative terms rather than absolute figures. These are often based on a ‘business as usual’ (BAU) emissions projection for a future year or a carbon intensity metric, such as emissions per unit of GDP. While relative targets can demonstrate progress, they leave room for interpretation and do not always guarantee an overall decline in emissions. A country may achieve reductions relative to an alternative scenario while still increasing absolute emissions at a rate inconsistent with global climate goals. Most non-Annex I countries include relative reduction targets in their NDCs, which can be either unconditional or conditional on external support.

Renewable energy comes from natural sources that are continuously replenished on a human timescale, such as sunlight, wind, water (producing hydropower, wave, and tidal energy), and geothermal heat from within the Earth. These sources produce little to no carbon emissions and do not deplete over time, making them key to sustainable energy systems and climate change mitigation.

The renewable energy potential estimates the maximum capacity of a renewable energy technology (e.g., onshore wind, or solar power) that could be generated in a given geography based on topography, system performance and land use constraints.

Renewable profiles are data sets that describe the potential energy output of renewable technologies based on location and time period. These profiles take into account factors such as the availability of resources at specific times and in specific locations. For example, a solar profile would show the expected electricity generation based on sunlight intensity throughout the day, while a wind profile would reflect expected generation based on wind speeds at different times of the year. Renewable profiles are crucial in energy system modelling, as they help estimate how much power renewable sources can contribute to the grid, considering seasonal and daily fluctuations.

A report is the output or result of a model run, summarising the findings and key insights derived from the simulation. It typically includes data, visualisations, and analysis that describe the performance of the energy system under the specified inputs and constraints. Reports are used to communicate the outcomes of model runs to stakeholders, helping inform decision-making and policy planning.

In energy system modelling, residual capacity refers to the existing assets, such as power plants or infrastructure already in place at the beginning of the modelling period. This capacity is considered as part of the model’s baseline, providing a foundation for future investment or upgrades.

A run or model run refers to the execution of a model using a specific set of inputs. It involves numerically solving the optimal energy system based on the economic logic and constraints provided. This process generates a result in the form of a report that shows how the system would perform under the given conditions, helping to inform decision-making or assess different scenarios.

In modelling, a scenario is a description of a possible future based on a set of assumptions about how different variables may evolve over time. Scenarios help analyse uncertainties, compare different pathways, and support decision-making in areas like energy planning, climate policy, and economic forecasting.

TransitionZero's Solar Asset Mapper is an open access, asset-level dataset of solar facilities, powered by machine learning. Explore the tool and download the data.

A solver is an algorithm designed to find solutions to mathematical problems, often used in optimisation, simulation, and decision-making. Solvers are implemented in programs or libraries to efficiently tackle similar problem types across various applications, such as energy modelling, engineering, and finance.

Spatial resolution refers to the level of geographic detail used in a model to represent a system. In energy system modelling, higher spatial resolution means more detailed representations of geographical areas (e.g., specific regions, cities, or even smaller units), which allows for a more accurate depiction of local energy production, demand, and infrastructure. Lower spatial resolution uses broader geographic units (e.g., entire countries or regions), simplifying the model but potentially overlooking local variations.

Temporal resolution refers to the time intervals used in a model to represent changes over time. In energy system modelling, higher temporal resolution means more frequent data points (e.g., hourly or sub-hourly), which allows for a more detailed representation of dynamic changes, such as energy demand fluctuations or generation variations. Lower temporal resolution uses larger time intervals (e.g., daily or yearly), which may simplify the model but reduce accuracy in capturing short-term system behaviour.

In modelling, the time horizon refers to the timeframe over which a model is applied. It should be long enough to capture all the most relevant impacts, including technological developments, policy changes, and environmental effects. In energy system modelling, the time horizon typically spans several years or decades, depending on the focus of the study. The choice of time horizon is critical as it influences the assumptions made about future scenarios and impacts long-term planning and decision-making.

Unabated coal refers to coal combustion for power generation without the use of Carbon Capture and Storage (CCS) technology. This includes all forms of coal-fired power generation, even those with high-efficiency technologies, as they are still considered unabated unless equipped with CCS to reduce emissions.

The United Nations Economic and Social Commission for Asia and the Pacific (UN-ESCAP) is the largest of the UN’s five regional commissions. It consists of 53 member states and 9 associate members, mostly from the Asia-Pacific region. It was founded to foster economic growth and cooperation between the region and the rest of the world. UN-ESCAP is involved in energy policy development through its efforts to promote sustainable development, energy access, and regional energy cooperation.

The United Nations Framework Convention on Climate Change (UNFCCC) is the UN's international body responsible for managing climate diplomacy. Established in 1992, its primary goal is to address global climate change through international cooperation and negotiations. The UNFCCC provides a platform for countries to discuss and implement measures to mitigate and adapt to climate change, including the negotiation of legally binding agreements like the Paris Agreement.

Variable Renewable Energy are energy sources which produce a variable amount of electricity according to the time of day, season, location and weather conditions - such as wind and solar PV. These sources are not considered to be dispatchable unless paired with energy storage. See also: intermittency.