Osmotic power systems use a variety of means to generate energy from salinity (salt content) differences in two sources of water. Such systems are clean, renewable and low-impact – and they provide a steady source of energy. In contrast, the energy produced by renewables such as solar and wind power may fluctuate greatly during the course of a day, depending on weather conditions. Although the concept was first proposed in 1975,14 osmotic power systems could not be adopted at the time due to limitations of membrane performance, including inadequate flows through the membrane and insufficient power produced even in larger area systems.15 To address both issues, recent advances have yielded new materials,16,17 and system designs18 that facilitate flow through membranes. There are two general designs for osmotic power systems. One, called pressure retarded osmosis (PRO), uses a specially designed semipermeable membrane that only allows water to move from a low- to high-salinity environment. The increased amount of water on one side of the membrane generates a pressure difference that can be used to drive a turbine that spins a generator to produce electricity. Another type relies on reverse electrodialysis (RED),19 which uses ion-exchange membranes that selectively allow cations (positive charge) and anions (negative charge) to move to opposite sides of the membrane – the impetus to do so again being differences in the salt content between two sides of the membrane. That flow of charge in this instance directly generates electricity. These advances are both in lab trials and being developed into commercial power plants. One commercial effort, for instance, the OsmoRhône 1 by Sweetch Energy, began system installations in 2024. A Danish company, SaltPower,20 founded in 2015, already generates power using the super-concentrated salt solutions that well up from geothermal sites. In a form of circular economy, the Mega-ton Water System Project in Fukuoka, Japan21 extracts energy from a seawater desalination plant’s output of highly saline solution left over after purified water is produced.22 In addition to power generation, techniques such as RED have been shown to potentially be relevant to producing purified water, and recovering lithium, nitrogen and carbon dioxide (CO2) from the water employed in the process. Remaining challenges to full emergence are largely technical and economic in nature. Previous generations of osmotic power stations suffered from membrane fouling and high costs, although recent advances have improved performance. The technology is otherwise based on clear and uncontroversial scientific principles for extracting energy from differences in salinity. Beyond licensing processes and effective environmental and social impact assessments, there appear to be relatively few hurdles to wide adoption once sufficient financial investments are made into osmotic power systems.Katherine Daniell Director and Professor, School of Cybernetics, Australian National University Alison Lewis Dean of the Faculty of Engineering and the Built Environment, University of Cape Town Boxed Icons Establish demonstration projects – Create public-private partnerships to build pilot osmotic power plants in diverse geographic locations to validate the technology across different environments.Ecosystem readiness map Boxed Icons Develop community engagement programmes – Implement educational initiatives in potential host communities that clearly demonstrate osmotic power’s dual benefits for clean energy generation and water management.KEY ACTIONS TO ACHIEVE SCALE TechnologicalSocial Economic EnvironmentalPolicy Image: Osmotic power generates steady, renewable energy from salinity differences, with advancing membranes improving efficiency and viability. Credit: Midjourney and Studio Miko. Prompt (abbreviated): “Flow of energy between two sources of water, creating electricity.” Read more: For more expert analysis, visit the osmotic power systems transformation map. Authored by: Odne Burheim. Top 10 Emerging Technologies of 2025 13