• 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”.

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.