The aim of this book is to understand: Classification of Energy Sources, Energy resources (conventional and non-conventional), Energy needs of India, and energy consumption patterns. Worldwide potentials of these sources. Energy efficiency and energy security. Energy and its environmental impacts, Distributed generation. Solar Energy: Solar thermal Systems: Types of collectors, Collection systems, efficiency calculations, applications. Photo voltaic (PV) technology: Present status, solar cells, cell technologies, characteristics of PV systems, equivalent circuit, array design, building integrated PV system, its components, sizing and economics. Peak power operation. Stand alone and grid interactive systems.