This book is to provide in-depth information on fundamentals of different renewable energy resources. In this textbook, the primary emphasis is on fundamentals of thermodynamics and heat transfer aspects of renewable energy gadgets and their actual applications. Various renewable energy systems are described and their fundamental analyses are described.This book contained seventeen chapters and provides state of art of renewable energy systems and their applications. The opening chapter of this book highlighted the different energy sources and current renewable energy scenario in India. Energy and exergy analysis approach iscovered in second chapter. Subsequent chapters cover the heat transfer, solar radiation computation solar thermal, solar drying and photovoltaic, heating and cooling of building, bioenergy, hydro power, OTEC, MHD, and energy economic assessment. Solved numerical problem in relevant chapter are also included for better understanding.This book will be valuable to undergraduate and post graduate engineering students, researchers, and others interested in the field of renewable energy.