With almost 99% of current hydrogen production reliant on fossil fuels, it is clear that the green hydrogen economy is still some way off. However, recent advances in the search for hydrogen storage solutions suitable for large-scale applications demonstrate that exciting progress is now being made.
It is widely understood that hydrogen represents an important step on the road to achieving net zero targets. It’s high energy density means it is uniquely placed to help decarbonise some of the most polluting industries and applications that do not readily lend themselves to electrification, such as aerospace and other long distance transportation sectors, steel production, and residential heating systems.
However, much of the world’s hydrogen is currently produced using carbon-intensive processes. Common techniques include Steam Methane Reforming (SMR), which produces around 8-10 kg of carbon dioxide per kg of hydrogen produced. The search is therefore on for alternative technologies and solutions to enable a low-carbon ‘green hydrogen’ economy that is not reliant on fossil fuels.
Research scientists are already making progress in finding safe and reliable means of generating sufficient low-carbon green hydrogen, to meet future clean energy demands. Electrolytic techniques enable the production of hydrogen using renewably generated electricity, for example. As well as finding ways to produce green hydrogen viably and at scale, innovative solutions are needed to facilitate its distribution and storage.
Main barriers
There are three main barriers to the green hydrogen economy which must be overcome to realise its full potential as a renewable energy source. Firstly, there is the cost of green hydrogen which is significantly more expensive to produce than fossil fuels and other forms of hydrogen, such as ‘blue hydrogen’, produced mainly from natural gas. Secondly, using green hydrogen as a primary energy source will require significant investment in infrastructure including storage, pipelines and a means of delivery. Thirdly, international standards and regulations will be needed to standardise its production, delivery and use.
As the green hydrogen economy is still relatively underdeveloped, some industrial manufacturers and their innovation partners have been exploring interim solutions which use hydrogen alongside other sources of energy to reduce their operational carbon footprint. For example, Tevva Motors, a British maker of commercial electric vehicles (EVs), is currently developing hydrogen as a range extender for its hydrogen-electric trucks, with a view to launching a production 7.5 tonne truck, followed by a 19 tonne model. Compressed hydrogen gas is stored in lightweight, onboard cylinders, developed by Luxfer Gas Cylinders, which are made from aluminium and carbon-composite materials.
Research scientists at Sheffield University have developed an innovative means of making hydrogen storage tanks for aerospace applications. Using Wire Arc Additive Manufacturing (WAAM), the project team has constructed a demonstrator storage tank for liquid hydrogen made from aluminium alloy and additive manufacturing techniques were used to produce associated parts. Other innovators are exploring different solutions for aerospace hydrogen storage. Recently granted US patent, US 11795029 B1. describes fabrication equipment to enable the construction of lightweight carbon fibre pressure vessels capable of storing hydrogen. European patent, EP4286281A2, concerns equipment for the cryo-compressed storage of hydrogen for use in aerospace applications.
Storage solutions
As well as developing storage vessels for specific end-use applications, innovators are creating bulk storage solutions to support large-scale green hydrogen production. These storage solutions bring additional benefits by helping to smooth out peaks and troughs in renewable electricity production. Renewable energy sources such as wind and solar cannot be relied upon to deliver a continuous flow of power due to the variable nature of weather conditions. Green hydrogen on the other hand, can be created via electrolysis, using electricity generated at times of peak production, stored, and then utilised at times when energy production is low.
The California Energy Storage Alliance (CESA) has shown that it is possible to store large quantities of green hydrogen over a long period of time in salt caverns to meet seasonal/variable energy storage demand and facilitate a continuous source of supply to the grid. Harnessing these existing, man-made cavities to provide a long-term, scalable storage solution for green hydrogen, which could be integrated into a hydrogen pipeline, could potentially accelerate the decarbonisation of the grid. The idea of utilising salt caverns is not new. For example, a US patent granted in 2016 discusses using a barrier to prevent high-purity hydrogen permeating the walls of a salt cavern.
German power company, RWE, has recently announced that it is aiming to complete the construction of the first hydrogen cavern storage facility by 2026. Feasibility studies for similar projects are underway in many territories including India, Australia, Newfoundland, Northern Ireland and Wales. Large-scale hydrogen storage does not necessarily need to be underground – RWE also filed patent application WO 2021/156158 A1 directed to offshore hydrogen storage, providing floating storage close to offshore production sites.
Despite this progress, there is still a lack of infrastructure readiness and the use of green hydrogen as a primary energy source is not yet viable, due to the cost of the renewable energy needed to produce it. The cost of solar and wind energy would need to fall significantly, and existing infrastructure such as plants and pipelines would need to be replaced or modified to enable the green hydrogen economy.
In the meantime, innovators at the MIT Energy Initiative in the US are exploring ways to make greater use of hydrogen by blending a small amount with natural gas. Blending natural gas and green hydrogen could potentially facilitate the continued use of legacy plants and pipelines as a distribution network. In the UK, a pilot project carried out recently in Gateshead by Northern Gas Networks has demonstrated that a 20:80 hydrogen to natural gas blend could be used to support the decarbonisation of domestic heating systems. Implementing blended hydrogen/natural gas requires specialist infrastructure for both the blending process and distribution. A recent patent application filed in the US by Sagebrush Pipeline Equipment Co - US 2023/0357657 A1 - relates to an automated system for blending hydrogen with natural gas.
Green hydrogen holds much promise as a means of decarbonising energy-intensive industries and transport-related applications, so it is encouraging to see vigorous and continued innovation in this space. Research in both industry and academia has a critical role to play in developing the storage, infrastructure and distribution solutions required to enable its wider use. For innovators, there is also an important opportunity to secure patent protection for early-stage technologies that could become standard essential in the future.
John-Paul Rooney is a partner and Andrew Hey is a senior associate at European intellectual property firm, Withers & Rogers. Both are patent attorneys with specialist knowledge of the cleantech and transportation sectors.
