Salt gradient power reverse electrodialysis (SGP-RE) or simply reverse electrodialysis (RED) is a novel method for converting chemical salt gradient energy into electrical energy across a stack composed of multiple repeating units (called cell pairs). River waters are typically very low in salinity, which provides an advantage over potentially available salinity gradients. Due to its high salinity, sea water has a higher osmotic pressure than fresh water. His two main technology types, reverse electrodialysis (RED) and pressure-retarded osmosis (PRO), use a semi-permeable membrane that creates an osmotic potential that can be used to generate electricity in Delta's turbines. The major environmental issues associated with salinity gradient technology typically include changes in water quality and impacts on the physical environment. The natural process of mixing freshwater and seawater creates unique brackish water habitats that wash away nutrient-poor water and yield nutrient- and oxygen-rich water, making for some of the most productive ecosystems. The regions of are used by many organisms and are biologically and physically diverse. Potential impacts may result from acceleration of mixing processes, changes in freshwater and saltwater balances, or risks to organisms at points of intake or release. This effect can be mitigated by dumping the resulting brackish water in the centre of the water column and covering the intake pipe with a screen. The most important socioeconomic problem with salt gradient technology is the diversion of freshwater resources for power generation, which can be negated by avoiding water stress or water stress areas. Due to the limited deployment and information of these technologies, there is a high degree of uncertainty about their environmental impacts and further research is needed to fully understand the potential impacts. Saline gradient or osmotic energy is one of the new renewable energy sources available in many countries with ocean access. Two basic concepts of power generation from salt gradients are presented. Systems with pressure delayed osmosis (PRO) and reverse electrodialysis (RED). Discuss the advantages and disadvantages of the salt gradient system. Basic formulas for estimating energy from salinity gradients are illustrated using similar calculations for estimating energy requirements for water desalination systems. The sizing of a PRO system is explained using an example and the latest net power density output from a recently achieved design. An example is also provided if you are interested in calculating the required membrane area for domestic applications. The chapter also discusses specific applications and locations for potential salt gradient projects. Finally, we list the limits and factors that affect performance, such as performance and cost. A simple payback time calculation for a salt gradient system is also presented using an example of a real pilot system. Large-scale utilization of salt gradients presents barriers that must be incorporated into the design. Engineers must consider suitability, sustainability, and reliability in order to be widely adopted. The ocean is an important source of renewable energy, all of which can be used, including currents and tides, wave energy, temperature and salinity gradients. Due to the property of absorbing seawater and freshwater with organic matter. Anyway, biofouling is a big problem with both PRO and RED. This is one of the most important features. Elements of membrane science. To date, there is no cost-effective and satisfactory solution. It has not yet been found, but many research projects have been initiated focusing on it. This topic is related to salinity gradient energy technology. In stand-alone salt gradient power plants, significant amounts of fresh water flow through the system and brackish water exits the process.