A nitrogen and hydrogen-based chemical compound widely used in the production of fertilisers and industrial chemicals. Ammonia (NH3) can be used as a carrier of hydrogen, since it can transport large amounts of energy over long distances in little space and there is already a globally established infrastructure for transporting ammonia safely and efficiently.

Hydrogen produced with CO₂ emissions, but the CO₂ is captured and sequestered and stored permanently.

A hydrogen bus is a public transportation vehicle powered by hydrogen. Hydrogen fuel cell buses are electric buses which generate electricity through a chemical reaction between hydrogen and oxygen, producing water as the only byproduct. These buses have a fuel cell stack that converts hydrogen stored in onboard tanks into electricity, which then powers an electric motor to drive the vehicle. Hydrogen Internal Combustion Engine (ICE) buses are vehicles powered by an internal combustion engine that burns hydrogen instead of traditional fossil fuels like diesel or gasoline. These buses use a similar engine design to conventional ICE vehicles but are adapted to combust hydrogen, producing water vapor as the primary emission, with significantly lower emissions of pollutants such as NOx.

The process of mixing hydrogen with natural gas in existing natural gas pipelines to reduce carbon emissions

An energy storage device that produces electricity by means of chemical action. There are one or more electric cells where each cell has all the parts and the chemicals compounds needed to produce electricity.

A technology used to capture carbon dioxide emissions from industrial processes or power generation and store them underground.

Combined Heat and Power (CHP), also known as cogeneration, is the use of a power station to simultaneously generate both heat and electricity.

A greenhouse gas produced by burning fossil fuels and other industrial processes. Reducing CO₂ emissions is essential for mitigating climate change and is a key goal in the decarbonization of energy systems, which aims to shift from carbon-intensive energy sources to renewable, low-carbon alternatives.

Hydrogen gas compressed to a high pressure and stored at ambient temperature.

Mixtures of hydrocarbon gases and vapors, consisting principally of methane in gaseous form that has been compressed.

The process of reducing or eliminating carbon gases emissions, especially carbon dioxide, being released into the atmosphere as the result of activities such as the burning of fossil fuels, with the aim of achieving a net-zero carbon footprint.

A hydrogen ecosystem refers to the interconnected network of stakeholders, infrastructure, policies, technologies, and markets involved in the production, distribution, storage, and utilization of hydrogen as an energy carrier within a limited territorial area.

Device that uses electricity to split water molecules (H₂O) into hydrogen gas (H₂) and oxygen gas (O₂) through an electrochemical reaction (see Electrolysis). Electrolysers, are a critical technology for producing low-emission hydrogen from renewable electricity.

A process that uses electric current passed through a substance to effect a chemical change. It is commonly used to split water by dividing its molecules in hydrogen and oxygen, commonly used for producing green hydrogen.

An envisioned future where hydrogen is a central energy carrier, supporting a wide range of applications from transportation to industry.

A conductor through which electrons enter or leave an electrolyte in an electrolyzer. Batteries and fuel cells have a negative electrode (the anode) and a positive electrode (the cathode).

A substance that conducts charged ions from one electrode to the other in a fuel cell, battery, or electrolyzer.

A device that generates electrical power throygh the chemical reaction of Hydrogen and Oxigen gases fuels to cleanly and efficiently produce electricity. If hydrogen is the fuel, the only products are electricity, water, and heat

Individual fuel cells connected in a series. Fuel cells are stacked to increase voltage.

Hydrogen produced without CO₂ emissions from clean and renewable electricity, such as wind, solar, or hydroelectric power, resulting in zero carbon emissions.

Hydrogen produced from natural gas or other fossil fuels with CO₂ emissions (typically through steam methane reforming).

Warming of the Earth’s atmosphere due to gases in the atmosphere that allow solar radiation (visible, ultraviolet) to reach the Earth’s atmosphere but do not allow the emitted infrared radiation to pass back out of the Earth’s atmosphere.

Gas in the Earth’s atmosphere that contributes to the greenhouse effect and global warming. Key greenhouse gases include carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), with CO₂ being the most prevalent due to activities like fossil fuel combustion and deforestation. Although less abundant than CO₂, methane is over 25 times more effective at trapping heat in the atmosphere than over a 100-year period and significantly contributes to global warming.

A vehicle powered by hydrogen fuel cells, producing only water and heat as emissions.

Hydrogen is the most abundant element in the universe, but it is generally bonded to another element. Hydrogen gas (H₂) is a diatomic gas composed of two hydrogen atoms and is colorless and odorless, and flammable when mixed with oxygen over a wide range of concentrations. Hydrogen can be used as an energy carrier, produced through various methods, e.g., water electrolysis using renewable energy (green hydrogen), steam reforming of natural gas (grey hydrogen). Hydrogen is used as fuel in combustion processes, as chemical feedstock, or in fuel cells to generate electricity.

Industries that rely on processes or energy sources that are difficult to decarbonize with current technologies, due to technological limitations or high energy requirements. These sectors include cement, steel, chemicals, paper, glass , and contribute significantly to global greenhouse gas (GHG) emissions, because they face challenges in adopting low-carbon alternatives.

Hydrogen Valleys are hydrogen ecosystems that cover a specific geography ranging from local or regional focus (e.g., industrial cluster, ports, airports, etc.) to specific national or international regions (e.g., cross border hydrogen corridors). Hydrogen Valleys showcase the versatility of hydrogen by supplying several sectors in their geography, such as mobility, industry and energy end uses. They are ecosystems or clusters where various final applications share a common hydrogen supply infrastructure. Across their geographic scope, Hydrogen Valleys cover multiple steps in the hydrogen value chain, ranging from hydrogen production (and often even dedicated renewable energy production) to the subsequent storage of hydrogen and distribution to off-takers.

A type of engine in which fuel combustion occurs within the engine itself, typically in a chamber where air and fuel mix. The combustion process generates high-pressure gases that drive pistons or a turbine, producing mechanical power. While traditionally powered by fossil fuels like gasoline or diesel, ICEs can also be adapted to use hydrogen as a cleaner alternative fuel.

Hydrogen in liquid form. Hydrogen can exist in a liquid state but only at extremely cold temperatures. Liquid hydrogen typically has to be stored at -253°C (-423°F). The temperature requirements for liquid hydrogen storage necessitate expending energy to compress and chill the hydrogen into its liquid state.

An organic substance in liquid or semi-solid states that store hydrogen by catalytic hydrogenation and dehydrogenation processes over multiple cycles. Hydrogen is stored inside the liquid hydrogen carriers via a catalytic reaction. The liquid has a low viscosity which seems like water, and once hydrogenation, the viscosity increases with the material resembles honey. LOHC is also flame-retardant, making it ideal for safe transportation.

Chemical compounds formed when hydrogen gas reacts with metals. Used for storing hydrogen gas.

A process that breaks down methane into hydrogen and solid carbon without producing carbon dioxide emissions.

The separating layer in a fuel cell that acts as electrolyte (an ion-exchanger) as well as a barrier film separating the gases in the anode and cathode compartments of the fuel cell.

A net zero term is used in a situation where global GHG emissions derived from human activity are in balance with emissions reductions. At net zero, COH₂ emissions are still generated, but an equal amount of COH₂ is is removed or absorbed from the atmosphere as is released into it. The result is a zero net increase in emissions.

Various methods of generating hydrogen, including electrolysis, steam methane reforming, and biological processes.

A type of fuel cell where hydrogen and oxygen react across a membrane to produce electricity, water, and heat. See term Fuel Cell

The conversion of electrical power into hydrogen or synthetic natural gas for storage or transportation purposes.

A hydrogen pipeline is a dedicated infrastructure system designed to transport hydrogen gas from production facilities to end-users, such as industrial plants, distribution centers, or hydrogen refueling stations.

Practices and regulations ensuring the safe operation of pipelines carrying hazardous substances like hydrogen.

A facility designed for dispensing hydrogen fuel to vehicles. These stations store hydrogen in pressurized tanks and deliver it to vehicles through specialized nozzles, similar to gasoline or diesel oil stations.

Energy derived from natural sources that are replenished at a higher rate than they are consumed. An example of such sources are sunlight, wind and hydropower, which can be used to produce electric energy for the production of green hydrogen through water electrolysis.

A chemical process in which hydrogen-containing fuels react with steam, oxygen, or both to produce a hydrogen-rich gas stream.

Energy storage devices that can function as both a fuel cell and an electrolyzer, generating power and producing their own fuel. They are used in applications requiring large amounts of stored electricity, such as off-grid power sources, emergency power generation, zero-emission vehicles, and aerospace systems.

An approach to social, economic, and environmental planning that attempts to balance the social and economic needs of present and future human generations with the imperative of preserving, or preventing undue damage to, the natural environment.

Also known as a snowcat or piste basher, it is a specialized vehicle used in snow sports and in ski areas and resorts to maintain and prepare snow covered surfaces, such as ski slopes and cross-country trails. It tipically uses diesel oil as fuel, but hydrogen-fuelled prototypes are emerging.

A process in which the natural gas or other methane stream reacts with steam in the presence of a catalyst to produce hydrogen and carbon dioxide. It is the most widely used process for producing hydrogen from fossil methane (grey hydrogen).

Methods and technologies for storing hydrogen, that include compressed gas, liquefaction, and solid-state storage (metal hydrides).

See fuel cell stack.

The entire system including the production, storage, transportation, distribution, and use of hydrogen as a fuel or input. This includes the generation of hydrogen (e.g., through electrolysis), its safe storage, transportation (via pipelines, trucks, or ships), and eventual delivery to end-users such as industries, power plants, or fuel stations. The supply chain is crucial for enabling the use of hydrogen in various applications, including clean energy, transportation, and industrial processes.

A hydrogen train is a type of railway vehicle powered by hydrogen fuel cells, which generate electricity to drive electric traction motors. These trains operate similarly to traditional electric trains but use hydrogen as a clean alternative to diesel or overhead electrification.

Vehicles that produce no emissions of greenhouse gases or other pollutants during operation.