This textbook provides readers with a practical understanding of the key aspects of energy. This latest edition includes two new chapters on Decarbonization and Energy Transition Beginning with fundamental definitions, the textbook explores primary and secondary energy types, internal energy, enthalpy, energy balance, heat of reaction, and heat transfer. Each chapter features fully solved examples and practice problems to reinforce learning and application. Topics covered include: Energy production, conversion, and conservation Energy storage and coupling Sustainability in energy systems Renewable energy solutions Energy management and economics Decarbonization and energy transition Designed for students across engineering and science disciplines, this comprehensive guide is ideal for courses in energy technology, sustainable energy systems, energy conversion and management, decarbonization and energy transition. It also serves as a valuable reference for engineers, researchers, and industry professionals. An updated solutions manual is available to course instructors upon request from the author or online via Springer Nature Link.