This book provides a comprehensive review of resources, technologies and applications in the salinity gradient power field. Its publication is another indication of the fast-growing interest in this area. It includes a chapter dedicated to salinity gradient heat engines, where all possible concepts are described. Among these are also the concepts explored in the RED Heat-to-Power project. There is explicit reference to our project, mentioning it as one of the leading R&D efforts currently on-going on a global scale. Also the chapters dedicated to assessment of the resources, the economics and the environmental impacts, cover separately the heat engine applications, recognising it as one of the most promising applications of salinity gradient technologies.