1) Perspectives and evolutions

Hydrogen, the smallest chemical element, emerged shortly after the Big Bang and is abundant on Earth, where it is often bonded to other molecules, most notably oxygen in water. However, hydrogen in its gaseous form (dihydrogen), which is of interest for industrial applications, is extremely rare. Currently, only one small natural deposit is being exploited in Mali. In Europe, debates persist regarding the evaluation of hydrogen reserves within rock formations, and its environmental extraction and purification impacts remain uncertain. This natural form of hydrogen is referred to as « white hydrogen. »

At present, hydrogen is primarily produced from natural gas using steam methane reforming. It serves in various applications, including refining petroleum products, synthesizing ammonia for fertilizers, and reducing iron ore. This form, known as gray hydrogen, is carbon-intensive, emitting 11 tons of CO₂ for every ton produced. It accounts for 95% of global hydrogen production. When CO₂ emissions are captured during production, it is classified as blue hydrogen, which has a lower carbon footprint.

The most promising form for energy applications, particularly in sectors that are hard to decarbonize, is green hydrogen, produced via water electrolysis powered by renewable energy sources. However, significant challenges persist for its large-scale deployment.

III.1.2 Challenges in Producing Green Hydrogen

The first challenge is industrial-scale production. Alkaline electrolysis, currently the only decarbonized hydrogen production process, has limitations:

• Efficiency loss: About 30% of the electrical energy is lost during conversion to hydrogen, with an additional 10% lost during storage and 30% if reconverted to electricity.
• Startup delays: Electrolyzers take time to reach full capacity, making them less suitable for intermittent renewable energy sources.

To address these issues, emerging technologies include:

• Proton Exchange Membrane (PEM): Using polymer membranes as electrolytes, PEM systems can quickly reach full capacity. Air Liquide’s Quebec facility, operational since 2021, produces 8 tons of hydrogen per day using hydroelectric power.
• Solid Oxide Electrolysis (SOEC): Operating at high temperatures (600–800°C), SOEC systems are faster but require nearby unused heat sources.

Materials like iridium and platinum remain costly and raise concerns about long-term sustainability, while the variability of renewable energy causes premature aging of installations.

Decarbonizing the 95 million tons of hydrogen used annually is already a challenge. New applications—such as heavy transport and synthetic fuel production—could increase demand to 140 million tons by 2030, according to the IEA. Producing the additional 55 million tons through electrolysis powered by renewables would incur significant costs: green hydrogen currently costs €3–6/kg compared to €1–2/kg for gray hydrogen, It is therefore clear that the development of the green hydrogen sector development will highly depend on market regulation.

III.1.3 Hydrogen Storage and Transport

Hydrogen’s gaseous form is highly explosive, complicating storage and transport. Its low density requires solutions such as:

• Compression: Storing hydrogen at 350–700 bars consumes 15% of its energy content.
• Liquefaction: Although liquefaction increases density 800-fold, it incurs a 30–35% energy loss and is mainly used in aerospace applications.

Short-distance transport involves insulated pipelines, while cryogenic tankers or high-pressure cylinders are used for longer distances. Multi-layered storage tanks (carbon fibers and resins) provide safety and rigidity but remain expensive.

Research into new storage solutions, such as materials that absorb and release hydrogen at moderate conditions (e.g., the Hycare project), is ongoing.

III.1.4 Applications and Recycling

Hydrogen powers fuel cells, which operate like reverse electrolyzers. Although fuel cells were discovered in the 19th century, they were overshadowed by internal combustion engines. Today, fuel cells are used in industrial facilities, building, trains, and vehicles such as the Toyota Mirai and Hyundai ix35.

Challenges include extending the lifespan of fuel cells and reducing costs, especially for platinum electrodes (€29,000/kg) and membranes (hundreds of euros per m²). Developing a recycling system will be essential to make this technology sustainable and economically viable.

III.1.5 Additional Potential: Methanation

Hydrogen can also be used in methanation, where synthetic methane is produced from CO₂ (or CO) and hydrogen through the Sabatier reaction. Methane is more widespread and can utilize existing gas infrastructure. However, the conversion process incurs energy losses of around 50%.

III.1.6 Conclusion

While hydrogen shows promise, it remains an emerging sector. The primary challenge lies in decarbonizing current hydrogen production. Scaling up the industry requires decarbonized electricity production, technological innovations for production and storage, new applications, and an appropriate recycling ecosystem. Hydrogen is expected to reach maturity in the 2040s

Source:

IAE global hydrogene review 2023: https://www.iea.org/reports/global-hydrogen-review-2023

https://iea.blob.core.windows.net/assets/deebef5d-0c34-4539-9d0c-10b13d840027/NetZeroby2050-ARoadmapfortheGlobalEnergySector_CORR.pdf

Les dossier de science et avenir n219octobre/ decembre 2024 : Quelle energies pour demain?

https://www.h2-mobile.fr/dossiers/lh2-hydrogene-liquide-definition/

https://demaco-cryogenics.com/fr/cryogenie/tout-sur-lhydrogene-liquide/

https://hycare-project.eu/