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Energy Essentials: A Guide to Hydrogen

Climate change and air quality concerns have pushed clean energy up the global agenda. As we switch to new technologies and cleaner fuels, our experience of using power, heat and transport will change, transforming the way we live, work, or travel.

Hydrogen, historically produced in large quantities for use as a chemical feedstock and in refineries, is now attracting attention for its potential as a versatile energy carrier - a substance containing energy that can be converted to useful mechanical, heat, or electrical energy. It is found in various energy sources and water, from which it can be extracted. With high energy content, clean combustion, and the ability to produce electricity via fuel cells, hydrogen could play an important role in the future energy system.

Despite its promise, hydrogen’s widespread adoption as an energy carrier remains limited. There are numerous technological, economic, safety, and user-acceptance challenges that must be addressed for it to scale effectively. Explore the sections below to find out more.

  • Hydrogen is the simplest and most abundant of all chemical elements.
  • Hydrogen is an ‘energy carrier’ - a substance containing energy that can be converted to useful mechanical, heat, or electrical energy.
  • When extracted from water using electrolysis powered by renewable electricity, so-called “green” hydrogen may be used as a carbon-free substitute for fossil fuels.
  • In certain applications, such as industrial heating and long-distance shipping, hydrogen may be the best - or even the only - low-emission alternative to the direct use of fossil fuels. In other areas, like residential heating and short-distance transport, other low-carbon options may be more suited or cost-effective.

Hydrogen (the chemical symbol H for a single hydrogen atom), is the simplest and most abundant element in the universe. It has the atomic number 1. Hydrogen gas (H2) is one of only seven naturally occurring homonuclear diatomic (consisting of two identical atoms) molecules.

At normal room temperature and pressure, hydrogen is a non-toxic gas. It has no taste, colour, or smell, and it has the lowest density of all gases. If cooled to extremely cold temperatures (-253°C or lower) or put under pressure, it becomes a liquid or under extreme conditions, solid. It is extremely volatile and easily ignites in air, burning at over 2,000°C with a very pale blue, near-colourless flame.

When hydrogen burns, it reacts with oxygen in the air to produce water – its name even broadly translates to ‘water-maker’. As a carbon-free fuel, the combustion of hydrogen does not produce carbon dioxide (CO₂). However, at high temperatures, nitrogen in the air reacts to form nitrogen oxides (NOx). These acidifying pollutants can directly cause damage to buildings and ecosystems, particularly through acid rain, and contribute to greenhouse gases by producing ozone via photochemical reactions in the atmosphere. Fortunately, NOx emissions can be managed with established low-NOx burner technologies.

Whilst hydrogen can exist in natural geological environments (known as “white”, “geologic”, or “gold” hydrogen), it is very reactive and forms chemical bonds with many other elements. Consequently, nearly all hydrogen used today comes from substances such as natural gas (~63%), coal (~20%) and as a by-product in refineries and in the petrochemical industry (~15%).Only a very small fraction is produced from biomass and through the electrolysis of water.

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As well as using hydrogen as a chemical feedstock (e.g. ammonia and methanol manufacture) or as a reducing agent in primary iron extraction for the steel industry, hydrogen has several potential energy carrier applications:

  • High-grade heat for industrial processes (e.g., glass, cement, etc.)
  • Replacement for fossil fuels in transport (e.g., shipping, aviation, HGVs, etc.)
  • In power generation, either as a replacement for natural gas in gas turbine generation, or in hydrogen fuel cells for utility scale or distributed power generation
  • Storing surplus renewable electricity to support load balancing and enhance grid stability
  • Low-grade heat (e.g., domestic, commercial, and industrial)

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While hydrogen has broad potential applications, several factors could constrain its use in a future low-carbon economy. These include its current relatively high costs compared to alternatives, limited availability, and high flammability. For instance, hydrogen may be the most effective - or even the only - substitute for fossil fuels in certain applications like heavy industrial processes, heavy haulage, and sea freight transportation. However, in other areas, such as residential heating and light, or personal transport, there may be more suitable or cost-effective alternatives like heat-pumps or electric vehicles. This view may differ depending on regional circumstances and may change over time as technologies and markets evolve.

  • Hydrogen can be extracted from fossil fuels like oil, gas, or coal through processes such as steam reforming, partial oxidation, pyrolysis, and gasification.
  • Renewables and nuclear power can all be used to produce low-carbon hydrogen. Biomass gasification is also being explored as another production pathway.
  • The environmental impact of making hydrogen depends on the methods and feedstock used to produce it.

Although hydrogen is the most abundant element in the universe, its propensity to bond with other molecules means that the occurrence of natural deposits of hydrogen is generally uncommon. Consequently, it is necessary to extract (or separate) it from other sources using various methods. Currently, the most common methods are steam methane reforming, gasification, and electrolysis. Other methods include thermochemical processes that convert biomass into gas or liquids to then separate out hydrogen, photolytic processes that use solar energy to split water into hydrogen and oxygen, and biological processes that use microbes, such as bacteria and microalgae.

Today, over 95% of the hydrogen used is produced through natural gas or coal reforming processes that emit generate greenhouse gases since they are rarely paired with carbon capture technologies.

Hydrogen produced from fossil fuels

One common method of producing hydrogen today is steam methane reformation (SMR) of natural gas which combines methane from natural gas and water at very high temperatures (approximately 900°C) to produce a mix of carbon monoxide (CO), carbon dioxide (CO₂) and hydrogen (H2), so-called synthesis gas (or “syngas”). By controlling the amount of air, water, and methane in the reaction, operators can alter the SMR process and change the amount of energy required and the mix of waste gases produced.

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Hydrogen can also be extracted from coal in a process called gasification. In this process, syngas is created using coal and water at high temperatures (above 750°C). The coal is also used to provide the heat needed for the reaction.

A major downside to using fossil fuels for hydrogen production is the associated CO₂ emissions. However, by integrating carbon capture, usage and storage (CCUS) technologies to the process, around 90% of the CO₂ emissions can be captured and either used in the production of other products or processes, or stored underground. Although CCUS currently has high costs, which limit its widespread deployment, ongoing projects aim to advance the technology and reduce these costs.

Hydrogen made using electricity

A more sustainable way of producing hydrogen is through electrolysis powered by renewable electricity, which significantly reduces its carbon footprint. Electrolysis is a process that uses electricity to bring about non-spontaneous chemical reactions. Electrolysers, the devices used for this process, use electricity to split water into its constituent hydrogen and oxygen elements.

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Electrolysis operates at temperatures typically between 20-100°C and can produce hydrogen at a range of scales, from small home-based units (e.g. generating hydrogen for residential fuel cell applications) to large industrial systems (e.g. ammonia production, or steel manufacturing). In addition, the purity of hydrogen produced through electrolysis is much higher than that of reformed hydrogen, which makes it more compatible for use in fuel cells without the need for expensive purification processes.

However, due to the high costs of equipment and energy, less than 1% of dedicated hydrogen production uses electrolysis today. Production costs are expected to decrease as the cost and size of electrolysers improve, and the cost of renewable generation continues to fall.

An important consideration in the production of hydrogen through electrolysis is the availability of water. With electrolysis requiring around nine litres of water for every kilogram of green hydrogen produced, freshwater access is likely to be a barrier to widespread deployment in water-stressed regions, though integrating desalination could help address this limitation.

Classifying Methods of Hydrogen Production

Hydrogen is often colour-coded to indicate where it comes from (the feedstock), the source of energy used to drive the process, and whether carbon capture is involved. For example, hydrogen produced via electrolysis powered by electricity generated from renewables such as wind and solar is called “green hydrogen”, whilst hydrogen produced from natural gas reforming is referred to as "grey hydrogen," which becomes "blue hydrogen" if carbon capture and storage (CCUS) is applied. Naturally occurring deposits of hydrogen are classified as “white” or “gold” hydrogen.

TerminologyTechnology Feedstock/
Electricity source
GHG footprint
Production
via Electricity
Green Hydrogen Electrolysis Wind | Solar | Hydro
Geothermal | Tidal
Minimal
Pink / Purple Hydrogen Nuclear
Yellow Hydrogen Mixed-origin grid energy Medium
Production
via Fossil Fuels
Blue Hydrogen Natural gas reforming + CCUS
Gasification + CCUS
Natural gas | coal Low
Turquoise Hydrogen Pyrolysis Natural gas Solid carbon
(by-product)
Grey Hydrogen Natural gas reforming Medium
Brown Hydrogen Gasification Brown cool (lignite) High
Black Hydrogen Black coal
Found
in geological
 formations
White Hydrogen Naturally occurring N/A Minimal

Recently, the classification of hydrogen has been looking beyond colour labels and focusing more on carbon intensity, taking into account its full life-cycle emissions, including processing and transportation.

  • Currently, hydrogen is primarily used in non-energy applications, such as petroleum refining and chemical manufacturing, with nearly all of it being produced from fossil fuels.

Since its discovery in the 1700s, hydrogen gas has been used in various ways, including in dirigibles and airships, fertiliser production, and converting crude oil into petroleum products. It was also used in homes as town gas - a manufactured gas that is a mix of hydrogen and carbon monoxide - for lighting and heating before natural gas became widespread.

While global demand for hydrogen has experienced modest growth in the 2020s, production has reached around 100 million metric tonnes (Mt), with over 99% still derived from fossil fuels. It is primarily consumed in non-energy applications, such as the petroleum refining and chemical sectors, using fossil fuels as a feedstock and without CCUS.

China is leading in both production and consumption, accounting for nearly 30% of global demand - about twice the share of the second-largest consumer, the United States.

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Today, the most common uses for hydrogen are:

1. Petroleum refining – hydrogen plays a crucial role in reducing the amount of harmful sulphur/sulfur (the IUPAC standard) oxides contained in fuels and transforming crude oil into fuels like ethane and liquid petroleum gas.  Hydrogen use in refining represents about 43% of total global hydrogen demand.

2. Ammonia production – ammonia is commonly used as a feedstock to manufacture fertilisers to enhance crop yields and quality by providing essential nutrients. Ammonia production accounts for around 33% of global hydrogen demand.

3. Methanol production – methanol serves as a base chemical material used in manufacturing of plastics, paints, fabrics and fibres, and other chemical products. It can also be used as a transport fuel instead of petrol, diesel, or fuel oil. Methanol production accounts for around 17% of the global hydrogen demand.

4. Steel production – hydrogen is used in the steel industry with initiatives exploring its potential to fully replace coal, as a fuel for furnaces and as a reducing agent to extract iron from iron ores. Notable projects include those by SSAB, LKAB, and Vattenfall in Sweden, and by Salzgitter in Germany. Steel production accounts for around 6% of global hydrogen demand.

5. Other uses – hydrogen is also used in manufacturing processes for plastics, resins, flat sheets of glass and silicon microchips, as well as a coolant for large electrical generators.

By the mid-2020s, over 1,500 hydrogen projects had been announced worldwide, covering the entire supply chain, with the majority concentrated in Europe, the US, and China.

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  • Hydrogen is the lightest and ‘leakiest’ gas, making it more difficult to store and handle compared to other gases. It requires specialised and expensive equipment to either compress or liquefy it.
  • Transporting hydrogen in gas pipelines necessitates high-pressure compression. Due to its small molecular size, particular attention must be given to the design, maintenance, and operational safety to prevent leaks.
  • Research is ongoing to develop alternate transportation methods using hydrogen-carriers such as ammonia or Liquid Organic Hydrogen Carriers (LOHC).

Like fossil fuels, hydrogen is often produced far from its end-use locations. However, its unique physical properties – being the lightest element with small molecules and a high diffusion rate - make it difficult to transport, store, and handle safely throughout the supply chain. These characteristics can lead to leakage and material damage if not properly managed.

Furthermore, hydrogen burns with a near-colourless flame that is difficult to detect, posing safety risks that require advanced detection equipment for safe use and handling.

Hydrogen has a high energy density by weight but low energy density by volume compared to conventional fuels. Storing the same amount of energy as hydrogen requires three to four times the volume of natural gas at the same pressure. To match the energy content of one litre of petrol, over 18 litres of hydrogen would be needed, at high pressure (200 bar) necessitating stringent safety measures. Additionally, specially designed materials are essential for storing hydrogen as it can easily penetrate materials and cause hydrogen embrittlement, which weakens the integrity of transport and storage infrastructure.

These factors must be carefully considered when designing hydrogen transport and distribution infrastructure, storage facilities, valves and joint support systems, and control instrumentation.

Compressed gas and liquid hydrogen

Transporting and storing hydrogen poses challenges due to the need to enhance its energy density through energy-intensive methods like compression or liquefaction. Although technologies such as high-pressure cylinders and liquid hydrogen storage exist, they require significant amounts of energy for compression or cooling. For instance, high-pressure storage involves compressing hydrogen to between 350 to 700 times atmospheric pressure, demanding substantial energy input and strict safety measures, before it is stored in specialized containers, known as tubes, and transported by trucks, commonly referred to as “tube trailers”.

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Alternatively, hydrogen can be liquefied by cooling it to -253°C. In its liquid state, hydrogen is 800 times denser than its gaseous form in the atmosphere. Liquefaction technology, widely used since the 1960s for transporting natural gas in specialized LNG tankers, is significantly more costly and energy-intensive when applied to hydrogen. This is primarily due to the much lower temperature needed for liquefaction (-253°C for hydrogen compared to -162°C for natural gas).

Once liquified, hydrogen can be transported by road, rail, or ship, depending on the distance and the volume. However, over time, heat gradually leaks into the cold store, causing the liquid hydrogen to evaporate or “boil off”, increasing the likelihood of leakage and losses as it returns to a gaseous state.

Hydrogen pipelines

For long-distance transport, hydrogen can also be pumped through pipelines. Currently, there are over 5,000 kilometres (km) of hydrogen pipelines worldwide, mainly in Europe and the US, compared to over 1 million km for natural gas. Europe has about 1,600km of hydrogen pipelines, with an additional 3,300km network under construction across Austria, Germany, and Italy.  The US has over 2,500km of dedicated hydrogen pipelines already in operation. Some countries, such as the UK, have extensive natural gas pipeline networks that could be converted to carry pure hydrogen or into which hydrogen could be injected and blended with natural gas.

Hydrogen networks require more monitoring and maintenance than natural gas networks, as well as larger compressors. These factors contribute increased capital and operating costs, as well as higher operational energy requirements.

Future options for distributing hydrogen

Research is ongoing to develop solid or liquid materials that can store hydrogen, aiming to overcome the challenges of its transportation. One pathway being explored is converting it to ammonia by reacting hydrogen and nitrogen. When liquified, ammonia is much easier to handle and transport than liquid hydrogen. However, while the infrastructures for ammonia production are well established, the process of cracking it back to hydrogen is still relatively new, energy-intensive, and requires with additional steps to purify the hydrogen post-cracking. In addition, ammonia is a toxic substance that, if leaked, can severely impact air, soil, water quality, and human health. Nevertheless, the feasibility of using ammonia for hydrogen storage and transport warrants further exploration and development.

Another alternate pathway involves using Liquid Organic Hydrogen Carriers (LOHC), which are liquids capable of absorbing hydrogen via a hydrogenation reaction. The chemical reaction occurs under elevated pressure and temperature with the help of a catalyst. LOHCs can then simply be stored or transported. When hydrogen is needed, the LOHC is dehydrogenated in a process requiring elevated temperatures and a catalyst. The overall process is relatively cost-effective and safe, producing a petrol-like substance that can be transported under atmospheric pressure and ambient temperatures. However, dehydrogenation requires significant energy for heating, increasing the cost for large-scale operations. Additionally, the production of LOHCs may generate CO2 emissions, depending on whether green electricity is used.

On site generation of hydrogen is an alternative to transportation. By generating hydrogen close to where it will be used, the need for extensive transportation networks is reduced. This is mostly used currently at large industrial sites.

  • Sustainably produced hydrogen could play a crucial role in decarbonising energy-intensive industries.
  • Low-carbon hydrogen applications in ammonia production, crude oil refining, and process heat can cut emissions and enable carbon-free alternatives like green ammonia, synthetic e-fuels, and hydrogen-based steelmaking.

Global demand for hydrogen has experienced modest growth in the 2020s. It is currently primarily consumed in non-energy applications, such as the petroleum refining and chemical sectors, using fossil fuels as a feedstock and without CCUS. However, growing concerns about climate change are prompting countries to explore its sustainable production and potential in energy-related applications.

According to the International Renewable Energy Agency (IRENA), global hydrogen demand could increase from around 100 Mt in 2023 to approximately 614 Mt by 2050, depending on climate change goals, sector-specific developments, energy-efficiency measures, electrification, and the adoption of carbon capture technologies. This would represent about 12% of the world’s final energy demand, with most production needing to come from green hydrogen.

Explore the sections below to learn about hydrogen's potential to transform various sectors, including industrial processes, transport, heating, and storage, as part of the transition to a low-carbon economy.

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Heavy industry and manufacturing

Globally, the heavy industry sector accounts for approximately 20% of CO2 emissions and is widely considered as more technologically and economically challenging to decarbonise than sectors like power generation or road transportation. The complexities stem from the nature of industrial processes, often reliant on high temperatures or continuous heating, making it difficult to substitute fossil fuel energy sources. These requirements limit the available technological and cost-effective options to facilitate a transition.

Hydrogen, particularly green or blue hydrogen, holds greater potential than electrification for meeting the operational and process requirements of heavy industry. However, to achieve this sustainably, the focus will need to be on sourcing naturally occurring hydrogen along with producing green and blue hydrogen - pathways that are all nascent today. Blue hydrogen production faces additional challenges, as it still relies on fossil fuels, raising concerns that it could both extend the reliance on the oil and gas industry and result in captured CO₂ being released back into the atmosphere if used rather than stored.

Ammonia production

Hydrogen could play a significant role in reducing the carbon footprint of the ammonia industry, which is currently responsible for about 1% of global greenhouse gas emissions, by replacing fossil fuels used in industrial heating processes.

Additionally, hydrogen has long been combined with nitrogen to produce ammonia, a well-established industrial process. The key opportunity now is to use green hydrogen to create green ammonia - a low-carbon alternative with potential applications in power generation, maritime transportation, and various industrial sectors.

Crude oil refining

Hydrogen already plays a major role in refining, enhancing the efficiency and quality of refined products by removing sulphur/sulfur and other impurities from crude oil and upgrading heavy oil into lighter crudes for products like petrol and diesel.

Besides, hydrogen could be used as a feedstock to produce low-carbon synthetic fuels, known as e-fuels, such as methanol, which are liquid or gaseous fuels made from hydrogen and CO2 to replace conventional fossil fuels in hard-to-electrify sectors such as aviation, maritime shipping, and long-distance haulage.

High-grade process heat

The production of materials like steel, aluminium, cement, glass, and ceramics is highly energy- and carbon-intensive, with significant high-grade heat requirements. In primary steel production, hydrogen has the potential to replace coal and coke in the direct conversion of iron ore into metallic iron . Alternatively, high-temperature electrical heating offers another pathway for meeting these heat demands while reducing emissions.

Hydrogen could also be used to power furnaces and ovens for producing materials critical to the energy transition, such as steel for wind turbine towers, and cement for wind farm construction, as well as aluminium and ceramics for high-voltage transmission, alongside recycling scrap metals and other materials.

Hydrogen could also be used to power furnaces and ovens for producing materials essential to the energy transition, such as steel and cement for net-zero infrastructure and construction, as well as aluminium and ceramics for high-voltage transmission. Additionally, it could support the recycling of scrap metals and other critical materials used in renewable energy and electrification technologies.

  • Alongside electricity and biofuels, hydrogen is one of the few options for decarbonising transport.
  • Fuel cell vehicles (FCEVs) and hydrogen internal combustion engines (H2-ICEs), are particularly suited for heavy-duty transport, long-haul trucking, and industrial vehicles.
  • However, hydrogen-powered transport solutions face significant challenges, including high costs and limited infrastructure development.

Currently, the transportation sector relies heavily on fossil fuels, including petrol, diesel, jet fuels, and bunker fuels, accounting for nearly a quarter of global CO2 emissions. Despite this significant environmental impact, fuel demand in transportation continues to grow. While hydrogen, alongside electric vehicles and biofuels, offers a pathway to a more sustainable future, its use will likely be limited to specialized applications.

At present, the hydrogen technologies for road transport – both in light-duty vehicles like passenger cars and vans, and in heavy-duty vehicles such as trucks, buses, and coaches - are fuel cells and hydrogen internal combustion engines.

Fuel cell electric vehicles (FCEVs) incorporate a fuel cell that generates electricity on-board using hydrogen and oxygen from air as its feedstock. The chemical reaction between hydrogen and oxygen is an efficient and clean process that generates electricity, with water as the only waste by-product. Each fuel cell uses a catalyst, usually containing platinum, for chemical stability and improved performance. Notable FCEV models include the Toyota Mirai, Hyundai Nexo, and Honda Clarity.

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Hydrogen internal combustion engines (H2ICEs) involve the combustion of hydrogen in an internal combustion engine (ICE). They present an opportunity to adapt or retrofit existing conventional ICEs and leverage their well-established supply chains. However, their application in road transport is expected to be limited to long haulage, heavy-duty goods vehicles. Toyota showcased an experimental H2ICE vehicle in December 2021 whilst China’s SINOTRUK and Weichai launched the first heavy-duty H2-ICE vehicle in June 2022.

Refuelling

Hydrogen-powered vehicles can be refilled at hydrogen refuelling stations (HRS) in the same manner as petrol and diesel vehicles. HRS are designed to store gas above the ground in open areas to ensure that any leaks or fires can be managed safely. The hydrogen nozzle is designed to be an exact fit with the fuel tank opening and it automatically dispenses the gas once it is locked into place with an airtight seal. Additionally, fuelling stations should be equipped with safety controls, including infra-red sensors for hydrogen leak detection, and mandatory safety distances between buildings, fuel pumps, and pipework.

The current number of hydrogen refuelling stations worldwide remains relatively low, at approximately 1,000, with over 50% concentrated in East Asian countries.

Certain regions have implemented regulations aimed at significantly increasing the number of HRSs. For example, the EU’s Alternative Fuels Infrastructure Regulation (AFIR) requires that by 2030, EU member states must ensure HRS are placed every 200 km along the core Trans-European Transport Network (TEN-T) and that each urban node has at least one station available. Also, the U.S. Department of Energy aims to support the development of HRS through various programs and policies.

Vehicle emissions

While FCEVs produce zero tailpipe emissions, H2ICEs emit nitrogen oxides and small amounts of CO2 due to lubricating oil burned within the engine. However, the “well-to-wheel” greenhouse gas emission footprints associated with H2ICEs and other low-carbon transport alternatives depend on the source of the fuel. For instance, vehicles powered by green or blue hydrogen will have a lower carbon footprint than those powered by grey hydrogen.

Light-duty vehicles (passenger cars and vans)

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Hydrogen cars are only just starting to become commercially available, with Honda, Hyundai, and Toyota each releasing models using hydrogen fuel cells. As of 2023, hydrogen cars  remain relatively scarce with only around 80,000 on the road worldwide, mainly in South Korea, US, China, and Japan. Additionally, they tend to be more expensive than similar sized battery electric, petrol, or diesel cars. The current lack of refuelling infrastructure further hampers their uptake. There is broad consensus that EVs are likely to dominate light-duty transport.

Heavy-duty vehicles (trucks, buses, and coaches)

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According to the International Energy Agency (IEA), although trucks and buses represent fewer than 8% of vehicles (excluding two- and three-wheelers), they are responsible for more than 35% of direct CO2 emissions from road transport. As a fuel, hydrogen is well suited for powering heavy-duty vehicles, particularly long-haulage trucks, as it offers a comparable range of 500-750 miles and a refuelling time of 15 mins. By 2023, the global fleet of hydrogen trucks exceeded 8,000 vehicles, with 95% of them in China. The deployment of hydrogen buses is progressing with the goal of reducing air pollution in congested urban areas, although their adoption has been uneven. These buses offer a longer range than their battery electric equivalents and can be refuelled quickly at depots. As of 2023, around 7,000 hydrogen buses were in operation worldwide, mainly in China. In the UK, hydrogen fuel cell buses are being used in Aberdeen and London in demonstration projects.

Forklifts and other material handling equipment

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Among all hydrogen vehicles, forklifts are the most prevalent, with over 60,000 fuel cell-powered forklifts in operation in the US alone in 2022. For a given range, the fuel cell system - comprising a hydrogen tank, fuel cell, and often a small battery storage unit - typically takes up less space than electric battery equivalents, and only take a few minutes to refuel. The hydrogen company Plug Power currently dominates the fuel cell market in this space.

Hydrogen may also be used for powering heavy industrial, construction, quarrying, mining, and agricultural vehicles such as diggers, dumper trucks, and tractors. These vehicles often need to operate for 8 to 12 hours between refuelling, and where the weight from low-energy density of batteries may be excessive. Another drawback to batteries in these applications is that these machines are often used in remote areas with limited or zero electricity grid connectivity. However, large mining companies, such as Fortescue, are increasingly turning to electric vehicles even in the heaviest-duty of use cases.

Trains

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Trains are typically powered by diesel or electricity, fed through overhead lines or a third rail. Electricity could also be generated on-board using hydrogen fuel cells. The world’s first hydrogen train, the Coradia iLint™, was launched by Alstom in Germany, marking a significant step toward sustainable rail transport. Since then, hydrogen-powered trains have seen trial runs in various countries, e.g. the FCH2Rail in Spain, HydroFlex in the UK or ZEMU in the United States, demonstrating their potential for reducing emissions. However, several planned projects were abandoned due to challenges such as cost and the need for specialized infrastructure, highlighting the complexities of implementing hydrogen technology on a larger scale.

Aviation

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Using hydrogen as a fuel for passenger aeroplanes is challenging. Due to its relatively low energy density compared to kerosene-type jet fuels, it would be difficult for a plane to carry enough fuel for long-haul flights, although potentially feasible for short-haul flights. There is growing research in the short-haul flights area, with the world’s first hydrogen fuel cell powered flight of a commercial-grade aircraft completed by ZeroAvia in September 2020. Additionally, H2FLY has developed an electric aircraft powered by liquid hydrogen, and the first four piloted flights have taken place, including one that lasted for over three hours.

The UK government, in partnership with industry stakeholders, has established the Jet Zero Council to drive efforts towards accelerating decarbonisation, with the goal to deliver zero emission transatlantic flights within a generation. Similarly, the Hydrogen in Aviation Alliance (HIA) was formed in the UK in September 2023 by key players in the aviation and renewable energy sectors to explore hydrogen’s potential, especially for short-haul fights. Airbus has announced its ambition to develop and launch a zero-emission hydrogen propulsion large commercial aircraft by 2035.

Shipping

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The shipping industry accounts for 3% of global greenhouse gas emissions and is considered one of the most challenging sectors to decarbonise. Cargo ships are invariably powered by heavy fuel oil, or bunker oil, which is cheap but highly polluting. Hydrogen could be used to make ammonia as an alternative fuel, that, whilst having a greater energy density, is also highly toxic. It also is a potential feedstock to manufacture low carbon methanol. On a smaller scale, there are several pilot projects exploring hydrogen-powered ferries, including the HyDIME feasibility study conducted onboard a commercial ferry operating between Shapinsay and Kirkwall in Orkney, which aims to investigate how hydrogen technologies could be safely integrated in the marine industry .

In addition to hydrogen, liquefied natural gas (LNG) is being explored as a cleaner and more immediately viable alternative to conventional marine fuels.

Space vehicles

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Hydrogen was first used for space exploration by NASA in the 1960s and has remained an important part of space travel ever since. NASA and the European Space Agency use hydrogen as a propellant in rocket fuel as it is very light and burns at a high temperature. Hydrogen fuel cells are also used as a power source for spacecraft and space vehicles once they are in orbit. On the Space Shuttle, three fuel cells were used to power all the electronics in the craft with water as their by-product.

  • Currently, hydrogen is expected to play a limited role in the decarbonisation of residential and commercial low-grade heating. However, in regions where policies support its adoption, hydrogen may see greater use, including the potential for blending up to 20% into existing gas networks.

A wide range of sustainable methods for providing low-grade heating in residential and commercial buildings is already in use worldwide, to varying degrees. These methods include  (electric) heat pumps or low-carbon district heating.

The use of low-carbon gas such as hydrogen, synthetic natural gas, and biogas for low-grade heating in buildings remains minimal at present; however, numerous research projects and trials are exploring their potential worldwide, including initiatives like HyDeploy and H100 Fife in the UK.

Using hydrogen safely at homes

Replacing fossil fuel in heating is a complex and costly process that faces several technical and economic barriers, with solutions likely varying by region. Key obstacles include the high upfront costs of renewable heating technologies, the need to retrofit the existing fuel and heat distribution systems, limited consumer awareness and trust in alternative low-carbon options, inconsistent policy support and incentives, the limited availability and accessibility of renewable energy sources, and the potential environmental and social impacts of some of the alternatives.

If natural gas is replaced with 100% hydrogen, heating and cooking appliances will need to be adapted or replaced due to hydrogen's different properties, such as its higher combustion temperature and increased flammability. To address these challenges and ensure safety in homes, several precautionary measures are recommended, including enhanced ventilation (which may involve permanent vents), the installation of hydrogen detectors, and the incorporation of other safety measures. For more details, refer to the What are the main challenges and potential solutions? section.

Companies such as Worcester Bosch, Giacomini, and BDR Thermea (BAXI) are already developing hydrogen-ready appliances for use in homes. These appliances would work normally with natural gas but could also be used with hydrogen if the gas supply switched over. In the UK, research projects like Hy4Heat and HyHouse have evaluated the risks associated with using hydrogen in residential applications, contributing valuable insights into safety requirements and mitigation strategies.

Implementing these safety measures and utilizing hydrogen-ready appliances are crucial steps toward safely integrating hydrogen into residential energy systems.

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Boilers: Natural gas boilers are equipped with a flame failure device, which uses sensors to stop the gas flow if the flame extinguishes. The sensors used in natural gas boilers are incompatible with hydrogen, but engineers are working on new safety technologies that use infra-red or ultra-violet light. To ensure the safety of hydrogen boilers, these devices will need to be fast-acting and reliable.

Fires: Hydrogen burns with a pale blue flame which is almost invisible to the naked eye. To enhance both visibility and safety, a chemical colourant could be added to the flame, making it more noticeable and visually appealing. Ongoing research aims to find a suitable colourant that is cost-effective, non-toxic, and compatible with hydrogen. Another alternative would be to design a heating element that glows when in use.

Cookers and ovens: Hydrogen cookers would require re-designed burners to manage the higher temperatures at which hydrogen burns and to limit the release of harmful NOx gases. Elevated levels of nitrogen dioxide (NO₂), a common NOx gas, can damage the human respiratory tract and increase vulnerability to respiratory infections and asthma. Long-term exposure to high levels can even lead to chronic lung disease. To mitigate this, design modifications such as reducing the size of burner holes, using new materials, or other methods of limiting oxygen concentration at the point of ignition may be necessary. Importantly, using hydrogen is not expected to impact cooking performance or require new kitchen utensils.

Hydrogen blending

An interim step for using hydrogen in residential heating could involve blending up to 20% into the existing natural gas supply. This approach would require relatively little investment in existing pipelines and cause less disruption to household appliances. However, it would only result in a relatively modest CO₂ saving of around 6%, and concerns about hydrogen's availability and sustainability are likely to persist. Additionally, safety and flammability issues must be addressed - though they are less critical at this lower concentration compared to the challenges posed by 100% hydrogen.

  • Hydrogen may enhance grid stability by providing flexibility and storage solutions for power networks.
  • Hydrogen enables seasonal storage through multiple methods, including compressed gas, liquid hydrogen, subsurface storage (e.g., salt caverns), and chemical carriers like ammonia and organic liquids.

Hydrogen could potentially help to balance and maintain grid stability by providing flexibility and storage solutions for power networks. Stable and safe operation of electricity grids is maintained by continuously matching supply with demand. As the share of intermittent renewable energy generation such as wind and solar - which depend heavily on weather conditions and the time of day - increases, the challenge and cost of maintaining grid stability rises.

Linking electrolysers to renewable power generation to produce green hydrogen offers an effective way to prevent the curtailment and loss of generation at times when there is a surplus supply. Rather than foregoing renewable electricity, it could be stored as hydrogen gas, which can later be used to generate electricity through fuel cells or transported to other locations and uses.

Additionally, hydrogen can serve as a direct combustion fuel in conventional combined cycle gas turbine (CCGT) power generation, either as an H₂/natural gas blend or as 100% hydrogen. This approach is currently being explored in feasibility reports, such as one by Energy Institute’s Technical + Innovation function.

Whilst grid-scale battery technologies are increasingly deployed, they primarily offer short term storage capability, lasting hours or days. Creating green hydrogen could deliver more optionality and long-term storage capability, spanning weeks, months, or even seasons.

Common methods for short-term hydrogen storage include:

  • Compressed gas cylinders: Hydrogen is stored as a high-pressure gas in metal or composite cylinders, ranging from smaller laboratory-scale cylinders, approximately 1.2 metres in length, to larger industrial tubes that are several metres long. While this method is simple and widely used, it requires significant space and energy to compress the gas. The application is small-scale storage.
  • Liquid hydrogen tanks: Hydrogen is stored as a cryogenic liquid in insulated tanks. This method offers high energy density but requires very low temperatures to liquefy the gas, and “boil-off” losses occur over time. The application is medium to large-scale storage.

Common methods for the long-term storage of hydrogen include:

  • Subsurface: Hydrogen can be stored as a high-pressure gas in both natural and artificial geological formations, such as salt caverns, depleted oil and gas fields, and aquifers. Salt caverns are particularly well-suited for hydrogen storage due to their ability to securely contain gas even under high pressure. These caverns have been used effectively for hydrogen storage for many years, with long-established facilities in places like Teesside, UK or Texas, USA, serving as examples. While these storage options offer significant capacity and relatively low costs, they require careful consideration of geological suitability and integrity to mitigate potential risks of leakage or contamination over time.

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  • Ammonia: Hydrogen can be stored as ammonia, a compound of nitrogen and hydrogen produced through a chemical reaction. This method offers high energy density and utilizes existing infrastructure, but converting ammonia back into hydrogen requires a catalyst and energy input. While ammonia is an effective hydrogen carrier, its high toxicity presents environmental and health risks.
  • Organic liquids: Hydrogen can be stored as a liquid in organic compounds such as methanol, ethanol, or formic acid. This method has a high energy density and can utilise existing infrastructure, but it requires a catalyst to convert the organic liquids back into hydrogen and may cause greenhouse gas emissions.
  • Methane: Hydrogen can be stored as a gas in methane, a compound of hydrogen and carbon. This method has a high energy density and can use existing infrastructure. While methane can be used directly as a fuel without the need to convert it back into hydrogen, converting it back to hydrogen could potentially reduce CO₂ emissions, depending on how the hydrogen is produced.
  • A significant challenge lies in scaling up the hydrogen production capacity, storage and distribution infrastructure, and end-use technologies needed to replace the energy delivered by existing energy systems.
  • A major hurdle to hydrogen making a meaningful contribution to net-zero targets is ensuring its production becomes sustainable. As of 2023, only around 0.1% of global hydrogen production was green hydrogen and only around 3% blue hydrogen.
  • More pilot projects are needed to prove the economic, environmental, and social benefits to businesses and communities. Addressing regulatory and public acceptance concerns, particularly regarding the safety and integrity of new technologies, will be vital.

Scaling the production, storage, and distribution of hydrogen will require significant energy, investment, and resources, alongside effective risk mitigation. The main challenges include safety, economic viability, and scaling production of sustainable, low carbon supplies. Additionally, securing acceptance from policymakers, regulators, and end-users - whether industrial, commercial, or residential - is crucial. Without strong demand signals, developers and investors across the supply chain may struggle to gain traction and grow.

The UK’s Hydrogen Strategy also highlights technical, policy, and regulatory uncertainty as hurdles to overcome, alongside the need for infrastructure development, supply-demand coordination, and securing ‘first-of-a-kind’ and ‘next-of-a-kind’ investments to advance and scale emerging technologies.

Public acceptance

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One of the biggest challenges, particularly in demonstrating the role hydrogen could play in residential heating, is to gain the public’s trust. Concerns are often centred on hydrogen’s safety and cost for such use of hydrogen. Beyond residential applications, broader societal acceptance will also be critical for hydrogen-carrying pipelines, fuel cell vehicles, hydrogen storage and dispensing at depots. Proving the viability of these technologies and providing transparent, balanced information on the safety, reliability and cost implications of choosing hydrogen over non-hydrogen alternatives for heating, transport, or storage is essential for building trust.

Safety

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Concerns regarding hydrogen’s safety and flammability must be addressed. As a non-toxic gas with no colour, taste, or smell, hydrogen burns with a nearly invisible pale blue flame, producing no hot ash or smoke. This makes it difficult to detect both when it is burning and when it is leaking.

Beyond leakage risks, hydrogen can also act as an asphyxiant at high concentrations, posing additional safety challenges. To mitigate these risks, an odorant such as mercaptan - a harmless but strong-smelling compound - may need to be added, similar to how natural gas is treated for household use. However, odorant additives can potentially contaminate fuel cells, which require a high level of hydrogen purity.

To ensure safe hydrogen use in homes, several precautionary measures are recommended, including enhanced ventilation (which may involve permanent vents) and the installation of hydrogen detectors or other advanced monitoring systems to identify leaks and ensure safety.

Regulation and codes of practice

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For hydrogen to be used in new applications, industries and sectors, either new regulations and codes of practice will need to be developed, or existing ones extended or adapted. Since its first use in industrial applications in the 1930s, companies and governments have worked together to create regulations and codes that promote the safety and minimise the risk of using hydrogen. A range of international standards already apply to hydrogen, including those developed by the Energy Institute, the International Standards Organisation (ISO), the International Electrotechnical Commission (IEC), the European Industrial Gases Association (EIGA), the International Partnership for Hydrogen and Fuel Cells in the Economy (IPHE), and the European Hydrogen Safety Panel. These standards cover a wide range of aspects, from how to store hydrogen securely to guidance on the types of pipes and valves to be used.

Sustainability

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Developing international standards is also crucial for verifying the source of any hydrogen being supplied.

While the different colour-coded sources of hydrogen (green, blue, grey, pink, etc.) are chemically identical, their production costs and carbon intensities vary significantly across the entire value chain, as demonstrated by a comprehensive life-cycle analysis conducted by the Energy Institute. This highlights the need for new standards and certification to clearly define what qualifies as low-emissions hydrogen and to ensure its origin. In 2023, the UK government launched a consultation seeking views on the design elements of a low carbon certification scheme.

Equipment costs

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Whilst technologies for producing low-emissions hydrogen already exist, at present they tend to be more expensive than other production methods or alternative fuels. Significant investment is needed to scale up new production facilities and supply chains, build the necessary equipment for plants and infrastructure, ensure adequate supply, and reduce unit costs.

The installed cost of electrolysers has increased significantly in recent years, due to increases in materials and labour costs, along with wider system issues impacting the energy sector. However, the IEA anticipates that these capital costs could start to decline due to economies of scale through mass production by 2030. Based on announced new projects, the cost of an installed electrolyser might reduce by 60% by 2030 compared to 2023, reaching about USD 720-810/kW of installed capacity.

Infrastructure and technology development

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Technology will be critical to the role hydrogen plays in the wider energy transition going forward. In some instances, new technologies - particularly in electrolysis and storage - must be developed, commercialised, and scaled. In other cases, it may be possible to leverage and re-purpose existing technologies and infrastructure, such as parts of existing natural gas networks. However, in areas where new technologies are needed, the hydrogen industry is starting from a very small baseline, especially with green hydrogen.

Support from both public and private investors will be essential to kick-start the development of new hydrogen infrastructure. In addition to government support, funding for new hydrogen projects could come from a range of sources, including gas companies, car manufacturers, transporters, shippers, or engineering firms. For instance, the UK Hydrogen Council is an initiative involving several companies across the energy, transport, and industrial sector, all aiming to boost investment in hydrogen and fuel cells. However, private investment is unlikely to occur without significant policy support or tax incentives to reduce financial risk, stimulate demand, and support the competitiveness of low-carbon hydrogen.

Moreover, certain segments of the hydrogen industry will depend on the development of enabling technologies. For instance, blue hydrogen depends entirely on the successful development, commercialisation, deployment, and operation of CCUS technologies. Today, the use of CCUS across its potential applications is extremely limited, with its development, deployment, and cost reduction significantly undermined by a combination of market, social, and political barriers.

New jobs and skills

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Alongside the broader energy transition, the emergence of a hydrogen economy holds the promise of creating a significant number of new and skilled jobs in the construction, manufacturing, and machinery industries. Skilled technical workers will be particularly needed in companies focused on hydrogen-related and enabling technologies, vehicles, and appliances. Additionally, once hydrogen plants are operational, there will also be ongoing demand for roles in plant operation, maintenance, safety management, and logistics, ensuring a continued need for a skilled workforce throughout the hydrogen value chain.

However, while the promise of new jobs is seen as a major benefit, a key challenge facing the entire energy transition - including the development of hydrogen economies and the achievement of net zero targets - is the availability of workers, particularly those with skills in clean energy technologies. In recent years, global demand for workers in the renewable energy sector has grown faster than in other industries, and this pressure continues to mount.

A report by the Boston Consulting Group (2023) concluded that by 2030, there will be a global shortage of seven million skilled workers needed for the critical climate and energy projects, such as installing solar panels, heat pumps, electric car charging stations, and wind farms. In the UK alone, there is an estimated current gap of around 200,000 workers, which poses a challenge to meeting net-zero targets. As well as competing within itself for talent, the renewables industry is competing with other sectors for the same highly sought-after skills.

About Energy Essentials

Produced and published by the Energy Institute (EI), the Energy Essentials series aims to explain energy topics in an accurate, concise and accessible format. The guides are intended to promote greater understanding of energy, and are suitable for students, professionals whose work crosses over into the energy sector, or anyone with an interest in energy.

Energy Essentials guides are designed to provide foundation-level understanding with a scientific basis. The information, tailored for non-experts, is presented in a format intended to be accessible, neutral and based on sound science.

Due to the constantly evolving nature of energy technologies and markets, all data and information is current as of the date of publishing (21February 2025). For more information, visit the Energy Institute Knowledge Service, or get in contact using knoweldge@energyinst.org.uk

Other titles in this series

Energy Essentials: A guide to shale gas
Energy Essentials: A guide to energy and carbon management
Energy Essentials: Transitioning energy-intensive industries to net zero

For more on hydrogen

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About the Energy Institute

The Energy Institute is the professional membership body bringing global energy expertise together. We gather and share essential knowledge about energy, the skills that are helping us use it more wisely, and the good practice that keeps it safe and secure. We articulate the voice of energy experts, taking the know-how of around 20,000 members from 120 countries to the heart of the public debate. And we’re an independent, not-for-profit, safe space for evidence-based collaboration, an honest broker between industry, academia and policy makers.


References

Technical and innovation: Hydrogen, Energy Institute

Hydrogen - fuels and technologies, International Energy Agency (IEA), 2020

Global Hydrogen Review 2024, International Energy Agency (IEA), 2024

Global Hydrogen Review 2023, International Energy Agency (IEA), 2023

The hydrogen council - an introduction, Hydrogen Council, 2020

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