The Role of Green and Blue Hydrogen in the Energy Transition—A Technological and Geopolitical Perspective

Abstract

Hydrogen is currently enjoying a renewed and widespread momentum in many national and international climate strategies. This review paper is focused on analysing the challenges and opportunities that are related to green and blue hydrogen, which are at the basis of different perspectives of a potential hydrogen society. While many governments and private companies are putting significant resources on the development of hydrogen technologies, there still remains a high number of unsolved issues, including technical challenges, economic and geopolitical implications. The hydrogen supply chain includes a large number of steps, resulting in additional energy losses, and while much focus is put on hydrogen generation costs, its transport and storage should not be neglected. A low-carbon hydrogen economy offers promising opportunities not only to fight climate change, but also to enhance energy security and develop local industries in many countries. However, to face the huge challenges of a transition towards a zero-carbon energy system, all available technologies should be allowed to contribute based on measurable indicators, which require a strong international consensus based on transparent standards and targets.

The Future Is Colorful—An Analysis of the CO2 Bow Wave and Why Green Hydrogen Cannot Do It Alone

“…Both literature and practice use a color scheme to categorize hydrogen production according to the applied procedure [6,9]. Green hydrogen refers to the application of electrolysis (see Section 2.2) which only generates hydrogen and oxygen-hence no emissions at all.…”

“…Lately, yellow hydrogen has been added to the color scheme, which is only mentioned for the sake of completeness-especially because the definition is ambiguous: some authors mean hydrogen produced using solar power (and electrolysis) and some refer to hydrogen production using nuclear power [9].…”

Recent Progress in Mixed-Matrix Membranes for Hydrogen Separation

“…However, being an energy carrier and not an energy source, hydrogen has to be first produced from primary energy sources that inevitably involve fossil fuel [ 4 ]. Hence, to enable hydrogen as a low-carbon energy resource, two approaches are at present widely undertaken and researched upon: (1) leveraging renewable electricity to drive an electrolysis process, which produces hydrogen (termed as green hydrogen) from water [ 5 , 6 ], and (2) cleaning the carbon emissions from hydrogen produced from natural gas to yield blue (decarbonized) hydrogen by means of carbon capture, storage and utilization (CCSU) [ 6 , 7 , 8 ]. As of 2020, green hydrogen is costly to produce, which is priced between USD 3.00–6.55 per kg hydrogen, due to the limited electrolysis capacity and the high cost of tapping on renewable energy [ 9 ].…”

A System Integration Analysis of a Molten Carbonate Electrolysis Cell as an Off-Gas Recovery System in a Steam-Reforming Process of an Oil Refinery

“…To achieve long-term climate neutrality targets by 2050 as imposed by the EU (European Commission, 2018), transition technologies, which have the capability of efficiently exploiting unavoidable CO 2 streams in synergy with renewable energy sources (RES), must be further investigated and deployed in the global energy sector. In such a context, hydrogen is an energy vector that can effectively contribute to the energy transition due to its wide applicability, both in terms of sector and scale (Noussan et al, 2020). Electrochemical systems can connect gas and electricity networks, which provide an opportunity to integrate clean technologies into industrial processes and to reduce their environmental impacts.…”