TELF AG examines an innovative method for hydrogen storage
The strategic role of existing infrastructures
Over the years, green hydrogen has progressively emerged as one of the most interesting innovations in the renewable energy sector. It stands out above all for its potential applications in very different fields. Green hydrogen stands out for its peculiar production methods, based on water electrolysis and renewable energy sources such as wind and solar. In addition to its possible use to produce electricity or to store energy, making it usable when it is most needed, this resource can also be effectively used for domestic and industrial heating, representing a valid alternative to natural gas. Despite this evident potential, the large-scale adoption of green hydrogen has been limited by some important obstacles, such as production costs and the need to develop adequate infrastructure for its practical and operational management, such as storage systems.
A recent study published in Nature Communications focused precisely on this last point. For hydrogen storage, some researchers have, in fact, proposed using existing infrastructures at the bottom of lakes and reservoirs made with a particular material that would be perfectly capable of carrying out this task very well. These are high-density polyethylene pipes are already used at the bottom of lakes or hydroelectric storage systems for water management.
Nowadays, hydrogen storage solutions can vary depending on the specific ways in which hydrogen is stored. For compressed hydrogen storage, specialized high-pressure tanks are needed, while liquid hydrogen must be stored at very low temperatures. Finally, underground storage depends mainly on the region’s characteristics and the deposit where the resource is stored, such as depleted natural gas tanks or salt caverns. However, the limitation of these solutions is that they may not be available in the locations where hydrogen storage is most needed.
The main advantages
Storage through polyethylene pipes on the bottom of lakes or reservoirs would, therefore, be a much more applicable solution, especially since the infrastructures in question already exist. Despite some operational obstacles, such as the lack of bathymetric data and precise information on the characteristics of these submerged areas, researchers believe that this storage method could have a good chance of success.
Up until now, high-density polyethylene pipes have been used mainly for water management in reservoirs. Still, they could also be used for water transport in agriculture and for other purposes. Their main characteristic is that they are made of a material specifically designed to resist high underwater pressures and corrosion. All these characteristics would also be beneficial if these pipes were used for other purposes, such as storing green hydrogen. Inside these infrastructures, hydrogen could be injected from above, keeping the internal pressure of the hydrogen at the same level as the external water pressure to prevent the resource from expanding excessively. To maintain constant pressure in the pipes, there would be special safety valves to regulate the flow of water and hydrogen. Furthermore, hydrogen is insoluble in water, which would make this method risk-free for aquatic life.
According to the researchers who carried out some experiments in a California reservoir, this method, in terms of space, would be even more efficient than solar energy generation, as it would require an area 38 times smaller than the space required for solar panels. Moreover, one of the main advantages of this method would be its proximity to strategic points where energy demand is highest, such as cities or industrial districts. Globally, the study says, the capacity for storing hydrogen underwater, in lakes or reservoirs, would be 15 PWh (petawatt-hours), with the Caspian Sea alone accounting for more than half of this amount.
