• 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.

• 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.