Modelling of Energy Systems explores the principles, methods, and tools used to design, analyse, and optimize diverse energy systems. Covering both conventional and renewable energy technologies, the book integrates theoretical foundations with practical modelling approaches to address real-world challenges in energy generation, conversion, and utilization. It emphasizes system-level thinking, incorporating aspects such as energy flow, thermodynamics, solar geometry, thermal systems, and advanced computational methods. With clear explanations, case studies, and illustrative examples, this work serves as a valuable resource for students, researchers, and engineers aiming to develop efficient, sustainable, and innovative energy solutions for a rapidly evolving global energy landscape.