Handbook of Power-to-X Systems: Processes, Technologies, and Simulation Models is a comprehensive guidebook on Power-to-X technologies, leading the energy engineer from fundamental principles of these electrochemical techniques to complex practical applications for conversion and management in energy systems. This book begins with an overview of the Power-to-X background, clarifying fundamental questions of components, frameworks, uses in sustainable energy, and the history of the technology. This is followed by in-depth analysis of the essential techniques electrolysis and carbon capture, including methods of modelling and practicalities for implementation. Additional chapters break down the role of various power-to-X processes, with Power-to-Gas, Power-to-Liquids, Power-to-Chemicals, Power-to-Heat, and Power-to-Power assessed, along with pragmatic guidance on regulatory and policy frameworks and assessments of environmental and social impacts. Finally, the book covers innovations and future technologies and provides a wealth of resources for the energy engineer to build understanding.