Hydrogen Network: Principal Barriers and Interests of the Power to Gas

Renewable energies are currently one of the most promising alternatives for coping with the future scarcity of conventional fossil fuels and the effects of greenhouse gas emissions. However, in the current state of knowledge, each resource (solar, wind, hydraulic, geothermal, biomass) is still subject to technological constraints, the most important of which is intermittency. To get around this problem, the development and use of energy carriers seems to be an appropriate solution, and among the known energy carriers, hydrogen seems to be the ideal candidate insofar as it enables energy to be stored on a massive scale for long periods of time. This stored energy can then be used in a wide variety of systems, such as mobility, heat or industrial processes. What's more, it has no impact on the carbon footprint, and its combustion with oxygen produces only water.

Hydrogen (H ₂ ) then appeared as a "miracle" solution to reduce our dependence on fossil resources. However, 95% of hydrogen is currently produced by steam reforming of natural gas! It therefore needs to be produced by other techniques using renewable energy sources such as water, biomass, sun and wind.

The hydrogen produced can be used for mobile or stationary applications, using fuel cells or direct combustion. However, these technologies are not yet technically and economically optimal, and there is also the problem of distribution, which needs to be developed and optimized to meet demand. What's more, its use depends heavily on its storage, which currently represents a crucial problem, particularly for mobility and embedded applications. At present, only two on-board hydrogen storage techniques are available: low-temperature liquid storage and high-pressure storage. However, these temperature and pressure conditions are extreme (20 K and 70.0 MPa) and an alternative means of storage at moderate temperatures and pressures needs to be developed. With this in mind, solid-state hydrogen storage is recognized as a promising option. Nevertheless, further progress in fundamental research is still needed to better understand the potential of this technology and to be able to exploit it.

Finally, because of its intrinsic energy properties, hydrogen appears as a promising solution to society's future energy problems, but before this is possible, advances in its production, storage, distribution and use are essential. In this article, the various techniques and technologies used today to produce, store, distribute and use hydrogen are presented. The technical and economic obstacles associated with the various stages of the process will then be highlighted, to give an overview of the use of hydrogen in relation to the process as a whole. Finally,...