This book explores the field of energy and its sustainable use. Energy is an essential requirement of today's world. But this dire requirement results in unstable usage and wastage. Thus, using energy like hydroelectricity, solar energy, wind energy, etc. which is sustainable is a wise choice. This book covers in detail some existent theories and innovative concepts revolving around sustainable energy. It aims to present path-breaking techniques that transformed this field. From theories to research to practical applications, case studies related to all the contemporary topics of relevance to this field have been included in this book. It will provide comprehensive knowledge to the readers and prove to be an essential guide for both academicians and experts.