From a scientific point of view, several challenges to renewable energy come from the intermittent nature of energy sources such as wind, solar photovoltaic and solar thermal. These problems are currently being addressed with research on power electronics converters, storage systems, Artificial Intelligence techniques, new materials and production technologies, numerical analysis techniques, among others. This research endeavours to reduce costs and find alternative energy sources that are competitive with fossil fuels. Consequently, these efforts of the scientific community will contribute to improving the quality of life on the planet. This book summarises ten years of contributions to these topics, and contains a selection of the best papers presented at the International Conferences on Renewable Energy and Power Quality (ICREPQ) from 2003 to 2012. These contributions have been selected by a team of voluntary reviewers, with two to four reviewers assigned to each paper. At the end of this process only about 5% of all presented papers were selected. Considering each paper had been reviewed before, in order to be accepted for the conference, the selected papers represent “the best of the best”. The contributors to this book represent some of the leading authorities in their areas of expertise. This book will be of particular interest to professional engineers and researchers dealing with renewable energy exploitation, but will also prove useful to postgraduate level students. In addition, it can be used as a reference book for engineers, physicists and mathematicians who are interested and involved in the operation, project management, design, and analysis of renewable sources equipment.