This book is open access under a CC BY 4.0 license. It focuses on the global cycles of energy, water, and carbon, which are essential to our main energy carriers, the fossil fuels, and are also the building blocks of life. The book offers an overview of the basic scientific facts and relationships needed to understand today's energy generation and use, how they relate to global climate, the water cycle, and other resources, as well as the complexities of energy policy. Building on the work of the Desertec project, it presents the main technological options available in a world after the "Energiewende" and discusses possible future solutions for a sustainable world. The book is written in an engaging, descriptive style that can be understood by those without specific knowledge of science or economics, allowing readers to form their own conclusions.