Introduction
Sales of electrolyzers are currently exploding. Hydrogen is in demand by governments and markets. On the one hand, public authorities in Europe are committed to the medium-term creation of a vast low-carbon hydrogen market. On the other hand, the share prices of companies specializing in the hydrogen economy are soaring on the stock market. Development prospects are particularly favorable in Europe and Asia, where several governments have recently revised their carbon neutrality ambitions upwards.
In this general rush for market share, the multiplication of reports is also helping to accelerate the pro-hydrogen narrative. Accelerating both the message of the falling cost of low-carbon hydrogen, and of applications where hydrogen would provide a unique advantage.
Most of the projections are based on the industrial solutions that currently exist. They do not take into account possible technological leaps (in the more or less near future) in the various links of the hydrogen economy. This is the case in particular for the storage solutions link, which today constitutes a limiting factor due to their high cost, both physically (energy efficiency) and economically (monetary cost). Storage is one of the central applications envisaged for hydrogen in energy systems that are heavily based on renewable sources, but also for hydrogen used directly as a fuel (for example, to power aircraft turbines).
However, alternative hydrogen storage technologies have been under investigation for many decades. They have provided solutions for some niche uses in the past, but have never become viable on a larger scale. Is it reasonable to expect a technological breakthrough in storage, one that could shake up the current comfort and predictability zone? The answer is yes, through the synergy between two hitherto distinct lines of development.
Storage: the high physical cost of existing industrial solutions
Hydrogen is the lightest gas in the universe. It combines a high mass-energy density with a low volume energy density. Existing petrochemical infrastructures cannot be used to store hydrogen. The solutions used in the industry today are based on compression and/or cooling processes :
- Compression at 700 bar, an operation that reduces energy efficiency by 13%. It takes about 4.6 liters of hydrogen compressed at 700 bar to provide the same energy as a liter of gasoline. Heavy hydrogen vehicles such as buses use hydrogen compressed to only 350 bars;
- Cooling to -252.8°C, an operation that reduces energy efficiency by 40%.
These storage solutions require special tanks, which benefit from incremental improvements thanks to the R&D efforts of major hydrogen suppliers.
Innovation in storage: conventional tracks
Two storage methods exploit existing infrastructures:
- The existing gas network: it is possible to inject hydrogen into the natural gas network, in moderate quantities (5%-15%, above hydrogen, weakens and destroys normal gas pipes);
- Salt caverns and other underground reservoirs used by the petrochemical industry. The distribution of salt caverns in space is not uniform, many regions are devoid of them.
Other alternative storage methods can be divided as follows:
- Absorbent materials: several families of porous materials perform hydrogen adsorption on their surface and can store hydrogen; requires high pressure;
- Metal hydrides: some metals can charge and discharge their interstices with hydrogen;
- Chemical hydrides: some gases or liquids can similarly charge and discharge hydrogen. Included in this class are ammonia and LOHC (liquid organic hydrogen carrier).
All of these methods have in common significant variations in heat during charging and discharging. In addition, the speed and energy cost of these two processes is highly variable.
Metal hydrides find niche applications but result in a high mass of the storage unit. Research to identify a lightweight solution continues.
The great advantage of LOHCs is that they are designed to be stored using existing petrochemical storage infrastructures. Similarly, the storage and transport of ammonia are based on existing infrastructures. According to Ben Schwegler, Fellow Presans, what is missing from these promising approaches is a way to reduce the energy cost of charging and discharging.
A synergy with biochemistry for a new leap in performance
As this whitepaper by Presans shows, disruptive innovation tends to result from the meeting of research universes that initially evolve independently.
This condition is realized in the case of the encounter between the hydrogen industry and the world of biochemistry. Among the technologies developed by the latter, there are methods of biohydrogenation by enzymatic TRL 3 that would provide a solution to the problems encountered by the storage of hydrogen in chemical hydrides.
“Biochemistry is the most effective road to tackle these problems. Indeed, hydrogen is essential for all living systems, as nature has developed an elaborate set of reactions to get around its lack of solubility. These reactions are all based on biological enzymes and biological “hydrogen transporters”. The level of specificity possible in enzymatic reactions gives substantial value to hydrogen as a source of reducing equivalents for chemical reactions”. – Ben Schwegler, Presans Fellow
Conclusion
Which companies have the strategic vision and industrial judgment to shake up the current technical comfort zone and economic predictability? Who is going to take the lead in large-scale hydrogen storage? Go to the Synergy Factory of Presans to find out more!
