Thermal energy storage systems constitute an important part of the energy distribution landscape in today's world. This comprehensive compendium covers the development of thermal energy storage, from the most fundamental principles to recent developments and case studies in the field. Key focus is on the context of urban and commercial thermal management such as district cooling and heating systems and decentralised energy systems. State-of-the-art advancements in both academia and industrial applications highlights the current direction of innovation and trends in the field.