Today, 98% of the hydrogen consumed worldwide comes from fossil sources, so its production process involves the emission of large amounts of CO2 (between 10 and 20 tons of CO2 per ton of Hydrogen); an amount approximately equivalent to the emissions of the United Kingdom and Indonesia jointly. Unlike this hydrogen that comes from fossil sources and which is called Grey Hydrogen, Green Hydrogen is obtained from the electrolysis of water using energy generated from renewable sources. The adoption of Green Hydrogen is essential if we are to reach the emission reduction targets in certain production processes as described below.
The decarbonisation of most sectors can be undertaken through direct electrification, which is generally a more efficient way to decarbonise than by using Green Hydrogen, since the conversion efficiency of commercial electrolysers currently stands at about 60%. However, there are sectors where the road to electrification in order to reduce emissions is not the most efficient or is simply not possible; these are the so-called "hard-to-kill sectors", and these include the oil refining sector, ammonia production, methanol production, steel production and industries with high temperature requirements. These are energy-intensive sectors that can be efficiently decarbonised using Green Hydrogen. Our efforts should concentrate on these sectors and Green Hydrogen given its proper place in energy transition; we should be aware that this technology has not yet been fully developed, it is not yet competitive and its operation requires large amounts of renewable electricity. That is why research needs to continue and, meanwhile aid should be made available that enables technological development and greater implementation (scale) to make Green Hydrogen technology feasible, which is exactly what happened with electric mobility just a few years ago.
Due to the low density of hydrogen, it is significantly less efficient and competitive to use if it needs to be stored for long periods of time or transported over medium and long distances. That is why it is important for it to be produced in close proximity to the industries that will consume it, avoiding its transport as far as possible. When energy needs to be transported, a number of studies have shown that it is more efficient to transport energy in the form of electricity, and to install the electrolyser next to the consumption centre, rather than to transport the hydrogen. Especially when the capillarity of the existing electricity grid is much greater than that of the gas/hydrogen network as is the case in Spain. It should also be noted that the reliability of the electrical network is very high while that of a hydrogen network is yet to be demonstrated.
Furthermore, the environmental impact, the risk to the safety of living beings and the difficulty of developing the permitting associated with the large, long pipes used to transport Hydrogen is much greater than for the transport of energy through existing power lines. It should also be noted that the installation of pipelines to transport Hydrogen represents a less flexible alternative to the installation of equivalent power lines since firstly, electricity has a much broader selection of uses then Hydrogen, and secondly, the flow of energy in a pipeline is unidirectional while in power lines it is bidirectional.
To conclude, it should be added that Green Hydrogen will be a key element in energy transition as a complement to electrification in those sectors with emissions that are difficult to reduce (oil refining, ammonia and industries that require high temperature). Given the current and incipient state of Green Hydrogen technology and the costs and efficiencies associated with it, this resource should only be used in sectors where there is no other more efficient alternative for decarbonisation and we should avoid the transport of Hydrogen over long distances.