This book explores the prospective applications of Phase Change Materials (PCMs) in energy storage systems, thermal system temperature control, peak shifting, and energy management. It starts with definitions and a brief history of energy storage systems, followed by an exploration of different types of PCMs, encapsulation techniques, heat transfer enhancement methods, and the applications and challenges of PCMs. The book provides a comprehensive overview of PCM applications in building envelopes, free cooling, electrical appliances, lithium-ion batteries, textiles, solar panels, vehicles and logistics, and more across 14 chapters.