We can build a better or secure energy future with different methods. For example, with the search for renewable energy sources, the world now relies heavily on fossil fuels (oil, natural gas or coal). And we know that fossil fuels are not renewable. The resources of these fossil fuels are limited and these resources are starting to become abundant. So we need fuels or energy sources that are infinite or easily renewable. The need for clean and sustainable energy sources is quite evident, since fossil fuels have a number of drawbacks: such as greenhouse gas emissions, depletion of limited sources and dependence on some oil-exporting regions in the world. Current energy conversion techniques considered sustainable include solar, wind, biomass and hydroelectric energy. There are other sources of sustainable energy including, but not limited to, tidal energy, ocean wave energy, and ocean thermal energy conversion. Significant potential for obtaining clean energy exists from mixing streams of water with different concentrations of salt. This salt gradient energy, also called Blue Energy, is available around the world where freshwater streams flow into the sea. Global energy production from estuaries is estimated at 2.6 TW, which represents approximately 20% of current global energy demand. Large quantities of blue energy can also be made available from natural or industrial brines. Several techniques for salinity gradient energy conversion have been proposed in the literature: pressure-delayed osmosis, reverse electrodialysis and use of vapor pressure difference. The main disadvantage of these membrane-based conversion techniques was the high price of the membranes. However, the decrease in prices of membranes for desalination...... middle of paper ......dient energy is a more promising energy source for electricity generation with the high available potential compared to another renewable energy source. There are many places in the world where salt gradient energy is available, so installing plants at river mouths can be produced and support the huge amount of global electricity demand in the future. This study paper presented the excessive review of salinity gradient energy and discussed the important techniques (i.e. RED and PRO) to harness the energy from this type of renewable energy source. The demand for energy continues to grow unabated, so it is essential now to introduce alternative methods of producing electricity to secure an energetic future. Various methods are available to renew energy and meet the needs of the population, but health and income security should be a priority.