Salinity gradients can be applied for storage of electricity and conversion of thermal differences (e.g. solar heat, industrial waste heat) into sustainable electricity, all by means of harmless environmentally safe technology. These closed systems are scalable, universally applicable and constructed from abundant materials. The main materials are NaCl solutions. Additionally, the content of the system can be controlled and fouling reduced to an absolute minimum. Salinity gradient systems constitute a promising alternative to fossil fuels and might turn out to be a versatile tool in transforming our energy supply and storage.