Worldwide, many regions have a great potential to cover part of their pressing water needs by renewable energy powered water treatment processes using either thermal or membrane based technologies. Not only arid and semiarid regions are increasingly suffering from water shortage but also many other regions face a limitation of freshwater resources either by increasing contamination of surface water bodies or groundwater resources unsuitable for drinking and irrigation purposes either due to their high grade of mineralization or their contents of toxic components. In many areas without centralized water supply, treatment techniques using locally available renewable energy resources such as wind, solar and geothermal can provide an economical, social and environmentally sustainable option for clean water production from seawater and from highly mineralized or otherwise unsuitable ground- and surface water. This book provides an overview on possible cost-efficient techniques and application opportunities for different scales and shows why the implementation of these technologies faces numerous technological, economic and policy barriers and provides suggestions how they can be overcome. It serves as a synoptic compendium of the fundamentals of freshwater production using renewable energies, applicable to all types of water, ranging from brackish to marine water and also including industrial and communal residual water. The book is aimed at professionals, academics and decision makers worldwide, working in the areas of water resources, water supply,land planning, energy planning, greenhouse gases emission mitigation and rural development.