The energy transition is generating renewed interest in hydrogen to decarbonize the global energy system. Today, almost all H2 is produced on-site in chemical facilities and used immediately, eliminating the need for long-term storage and distribution. However, the planned deployment of progressively larger water electrolysis facilities and emerging industrial use cases will require a more flexible infrastructure, and storage will be a critical part of that. In this blog post, we highlight the established and emerging approaches to H2 storage. These are:
- Compressed gas storage: H2 gas storage in pure form at either 350 bar or 700 bar (35 MPa to 70 MPa) inside special tanks. Tanks are commonly made from carbon fiber, with a polymer or metal lining. Carbon fiber is necessary to sustain high pressures but drives the cost of these tanks. Compressed gas storage is the main commercial method of storage today, but there is still substantial room for improvement. Key innovation areas include tank design, tank manufacture, and carbon fiber cost reduction. Safety and cost are the major pain points. Notable innovative startups include Infinite Composites Technologies and Noble Gas Systems.
- Liquid storage: H2 storage as a pure liquid; requires cryogenic temperatures because the boiling point of hydrogen at 1 atm is −252.8 °C. Liquid storage has the advantage of being more energetically dense than gas storage but requires highly insulated tanks to prevent liquid boiling. In addition, the energy input for liquefaction is higher than that of compression, increasing costs. Decreasing liquefaction energy is the main area of innovation; H2 liquefaction is an emerging solution at pilot scale today. This approach is being piloted by the Hydrogen Energy Supply Chain, a $343 million joint Australian-European project to produce H2 from Australian coal, liquefy it, and ship it to Japan.
- Carrier storage: Carrier storage relies on reaction or adsorption of H2. This approach theoretically eases fueling challenges while lowering storage pressures and often increasing overall energy density. Within carrier storage, there are three main approaches:
- Adsorption: H2 is stored via physical adsorption into a solid. Metal organic frameworks and graphene have both been proposed as possible carrier materials.
- Interstitial storage: H2 is stored in a metal lattice or an anion; approaches include magnesium-based metal hydrides like those developed by Hydrexia or borohydrides like those from EnergyNova.
- Chemical bonding: H2 is stored via the formation of a covalent bond with a liquid, such as the liquid organic hydrogen carriers (LOHCs) developed by Hydrogenious LOHC Technologies or Hynertech. This approach is currently at pilot scale. Alternatively, hydrogen can also be stored in chemicals like ammonia, methane, formic acid, and methanol.
Carrier storage is the least mature approach overall. While some approaches have major challenges due to costs or potentially hazardous materials, LOHCs are a promising option for low-pressure H2 storage and distribution.
H2 storage has been dominated by compressed gas approaches, but as industrial and energy applications become more crucial, other forms of storage will get their chance to shine. LOHC carriers and liquefaction are both front-runners among emerging approaches, but process improvements in MOF production or advances with metal hydrides could make these approaches competitive in the future. In addition, compressed gas storage will continue to improve as carbon fiber production scales up (especially in China) and costs fall. The future H2 storage landscape will be complex with multiple viable solutions, so different businesses and applications needs to align to the solution that best fits their needs.
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