Green hydrogen

The focus of this book is mainly on electricity storage technologies and other approaches facilitating that, for example, thermal energy storage. Such technologies are important not only for peak-shaving and on-demand power production but also for stabilizing the grids via the utilization of excess renewable electricity for a vari­ety of purposes in different sectors that are being more electrified every day. Such technologies guarantee a fast and secure transition to the 100% renewable-based energy matrix of the future, where more than half of the whole energy demand is to be covered by solar and wind energy. As discussed in the first chapter, the pathway for large-scale electricity storage is to a very good extent paved (though efforts for pilot-scale technology demonstrations and implementations are still ongoing), where other electrified sectors such as heat, cold, and light transportation, could also benefit from that. However, the heavy transportation sector (heavy trucks, air­planes, trains, ships, etc.) is very challenging to be electrified, and it is responsible for a massive amount of fossil fuel use and thus the emission of greenhouse gases. This is what has brought us here to find hydrogen as the energy topic of the day. The outstanding solution, on which the majority of energy experts have a concrete agreement, is to utilize excess/off-peak wind/solar electricity for hydrogen produc­tion (so-called green hydrogen). The green hydrogen can then be either directly combusted or processed with nitrogen or carbon for producing ammonia or various types of hydrocarbons, which can be suitable fuels for the heavy transportation sec­tor. This whole process, which is called power-to-X (PtX), is under the spotlight of research, development, and demonstration activities of many leading energy compa­nies, and a major portion of national and private funding on energy is allocated to it. Since hydrogen is the cornerstone of PtX technologies and there is so much to learn about it, this chapter is exclusively dedicated to it, and the next chapter dives into the supplementary processes of hydrogen for producing other fuels. The current chapter presents thorough information about hydrogen production methods with a focus on various electrolysis technologies/approaches, mathematical modeling required for technoeconomic analysis of hydrogen production systems, including a parametric study of them, and a discussion of the future of green hydrogen from research and commercial perspectives. Note that, besides hydrogen production by renewable electricity, there are several more hydrogen production methods that are not covered comprehensively in this chapter.