Green hydrogen in the energy transition: a review.

An unprecedented worldwide momentum is pushing forward the development of hydrogen since it is a fuel that can be synthesised using low-carbon sources. When the source is renewable energy, the hydrogen is referred to as ”green”. As such, it could have a key role in the fight against climate change and in the global reduction of greenhouse gases emissions. This paper is a literature-based review that aims to give an overview of the current situation regarding hydrogen: its current and future uses, its production routes and its related technical, environmental and economical challenges. It provides additional information about the situation in France and on the ways hydrogen can be produced from renewable electricity. Those production modes are then compared economically. From the economic analysis, it seems that it is not economically feasible to produce hydrogen only when prices are low (in periods of overproduction). Green hydrogen is also expected to become cost-competitive against the current fossilbased hydrogen by the 2030’s. The review concludes on two major comments. The first comment is the importance of remaining critical and remembering that every consumption leads to greenhouse gases emissions. Hence, hydrogen is only a very limited part of the answer to our current issues. The second comment is the importance to support the development of low-carbon hydrogen to reduce emissions in key sectors. While current production of fossil-based hydrogen represents around 2% of the global CO2 yearly emissions, this could be avoided by switching to green hydrogen. Furthermore, low-carbon hydrogen could also directly replace some fossil fuels further lowering CO2 emissions. For example, hydrogen is one of the only feasible solution to produce steel without requiring coke (currently accounting for around 7 % of CO2 emission). Therefore, the development of green hydrogen is required and it will have a major role in the energy transition of the 21st century.