Renewable energy is a rapidly expanding field, welcomed by many as part of the answer to climate change and energy security concerns. This book offers a comprehensive, authoritative and up-to-date overview of this globally-expanding field, including a thorough review of fluid-driven mechanical power, heat-based systems and light conversion. It also examines the challenges involved with the unpredictable nature of renewable energy sources, and how these variable energy inputs can be balanced and integrated into a viable energy supply system. Finally, the book discusses both the developing technologies and support policies from around the world. This second edition has been extensively revised and updated and remains an invaluable reference text for scientists and professionals involved with the technology, policy and implementation of renewable energy. It is essential reading for renewable energy courses. Part of IOP Series in Renewable and Sustainable Power.