Pourquoi il faut fabriquer de l’hydrogène vert et comment ? - Monsieur Bidouille

Summary

This video explains the role of hydrogen in the energy transition, focusing on its production, storage, and transportation challenges. It details how hydrogen is stored at high pressure or as a liquid, and how it can be converted into methane for easier storage and distribution through existing infrastructure. The video also covers the process of capturing and utilizing CO2 to produce synthetic methane, highlighting its potential for reducing carbon emissions. While hydrogen is a promising energy source, the complexities of handling, compressing, and transporting it remain key obstacles to widespread adoption.

Takeaways

• 😀 Hydrogen is a highly energetic gas with low volumetric density but high mass energy density, making it an efficient energy carrier by weight.
• 😀 Storing hydrogen requires high pressure or liquefaction due to its low density, with pressures reaching up to 700 bars for vehicle storage.
• 😀 When hydrogen storage systems are idle or under maintenance, they are filled with nitrogen to prevent explosive mixtures with oxygen.
• 😀 Hydrogen can be used to create synthetic methane (CH4) through a process that involves capturing CO2, providing a more manageable energy storage form.
• 😀 Liquefying hydrogen, while more efficient for storage, requires extremely low temperatures (below -252°C), which is energy-intensive.
• 😀 The process of converting hydrogen to synthetic methane, also known as 'power-to-gas,' helps in carbon recycling and may assist the energy transition.
• 😀 The synthetic methane produced from hydrogen and CO2 can be injected into existing natural gas networks, facilitating its integration into industrial and domestic applications.
• 😀 A critical aspect of the hydrogen-to-methane process is the use of high-temperature catalytic reactions, which generate more heat than they consume.
• 😀 The use of synthetic methane in existing gas networks is a viable solution since it requires less compression and can be transported more easily than hydrogen.
• 😀 Despite its potential, hydrogen remains valuable for specific applications like decarbonizing sectors where other solutions are not feasible.
• 😀 Various countries, including France, are investing heavily in hydrogen technologies, contributing to a broader European and global transition to cleaner energy solutions.

Q & A

Why is nitrogen used to replace oxygen in hydrogen systems when they are not in operation?

Nitrogen is used because it is an inert gas. When hydrogen systems are not in operation, they are filled with nitrogen to prevent explosive mixtures of oxygen and hydrogen, which could lead to dangerous reactions.

What is the main challenge with hydrogen's volumetric energy density?

Hydrogen has a low volumetric energy density, meaning that in order to transport significant amounts of energy, hydrogen must be compressed or stored as a liquid. This requires large amounts of energy for compression or cooling, especially when compared to more dense gases like methane.

How does hydrogen compare to methane in terms of energy per kilogram?

Hydrogen has a higher energy density by mass than methane. For example, 1 kg of hydrogen contains more energy than 1 kg of methane, making hydrogen a more efficient energy carrier in terms of weight.

Why is hydrogen stored at high pressures, like 700 bar, in vehicles?

Hydrogen is stored at high pressures, such as 700 bar, to compress the gas into a smaller volume. This allows vehicles to carry enough energy without requiring extremely large storage tanks, as hydrogen has a low volumetric energy density.

What is the alternative to compressing hydrogen for storage and transport?

The alternative is to liquefy hydrogen by cooling it to extremely low temperatures (around -252°C). In its liquid state, hydrogen occupies much less volume, making it easier to store and transport, though the liquefaction process consumes a significant amount of energy.

What is synthetic methane, and how is it produced?

Synthetic methane, or 'iméthane,' is methane produced by reacting hydrogen with carbon extracted from CO₂. This process can utilize captured carbon from industrial emissions, converting it into methane that can be injected into the existing gas network.

How does the production of synthetic methane compare to the production of hydrogen in terms of energy efficiency?

Producing synthetic methane from hydrogen is less energy-efficient than producing hydrogen directly. However, it has the advantage of being able to leverage existing infrastructure for storage and transport, which makes it a more practical solution for large-scale use.

Why is synthetic methane beneficial for the transition to renewable energy?

Synthetic methane is beneficial because it can be injected into the existing natural gas network, which is already widely developed. It also allows for the use of hydrogen in a more manageable form, improving the overall efficiency of energy distribution and storage.

What are the technical limitations of injecting hydrogen into the current gas network?

One major limitation is that the current gas network cannot handle pure hydrogen. Only small amounts (typically no more than 2%) can be mixed with methane without risking damage to infrastructure or compromising system integrity.

What role does carbon capture and utilization (CCU) play in this process?

Carbon capture and utilization (CCU) plays a crucial role by extracting CO₂ from industrial emissions, which is then used to produce synthetic methane. This process not only helps recycle carbon but also reduces overall greenhouse gas emissions by capturing and reusing carbon that would otherwise contribute to global warming.