Hydrogen has been proposed as the currency of future energy systems, both in science-fiction and technical literature. The limitations of fossil fuel supply and the need for decarbonisation of energy systems presage the dawn of the hydrogen economy. However, realising the vision of the hydrogen economy will require developing and implementing solutions to the engineering and technology challenges in the arenas of hydrogen production, storage, utilisation and distribution. Hydrogen: Science, Engineering, and Energy Systems presents a comprehensive overview of the issues related to hydrogen. The historical evolution of the energy systems is provided to accentuate the potential future role of hydrogen. Hydrogen production alternatives are examined and the competing options analysed on the basis of fundamental scientific principles. Similar discussions are included on other aspects of the hydrogen economy, not only answering questions of "how" and "what," but also explaining the observed phenomena by seeking answers to questions of "why" through an understanding of the basic properties of hydrogen. This discussion of hydrogen is integrated with societal energy needs and demands, to enhance an understanding of the place of hydrogen in energy systems. Suitable for both industry and academia, working professionals and students, Hydrogen: Science, Engineering, and Energy Systems is an indispensable text on this important topic.