This book provides a systematic and comprehensive introduction to the fundamentals of hydrogen energy, hydrogen energy-related technologies and systems, and the environmental and economic impacts of hydrogen energy. This book is rich in content, combining theory with practice and reflecting the latest world achievements in hydrogen energy utilization and research. It is used by a wide range of scientific and technologists engaged in the development and utilization of hydrogen energy and other energy sources. It is also referenced for technical workers in power engineering, aerospace, chemistry, chemical engineering, refrigeration, metallurgy, and those engaged in safety management, as well as for teachers and students of related disciplines in higher education institutions. Furthermore, this book makes some modest contribution to the development of hydrogen energy by strengthening the hydrogen energy research teams.