# The Synergy of Renewable Energy and Desalination:
## 2 Overview of Desalination Technologies
### Membrane-Based Methods
There is an osmotic pressure differential between the two solutions because the solute concentration in the draw solution is significantly larger compared to the one in the feed solution. Water molecules migrate over the FO membrane from the feed solution to the draw solution due to this osmotic pressure differential. Unlike reverse osmosis, FO does not require high pressure; instead, it relies on a more concentrated solution to pull water from a less concentrated feed solution [42; 43]. This characteristic makes FO an attractive option for applications where energy efficiency is crucial. FO has garnered attention for its potential in desalination and wastewater treatment. The process is advantageous because it minimizes fouling issues commonly associated with other membrane technologies. Additionally, FO can operate under low hydraulic pressures, reducing energy costs significantly compared to traditional methods like RO. There are still challenges that remain regarding the selection of suitable draw solutions and the recovery of clean water from the draw solution after processing. Research is ongoing to develop more effective membranes and optimize operational parameters. As technology advances, forward osmosis holds promise for sustainable water management solutions, particularly in regions facing water scarcity or requiring innovative approaches to wastewater reuse. Electrodialysis (ED) is an electrochemical separation process that uses an electric field to drive the movement of ions through selective ion-exchange membranes. This technology is primarily employed for desalination and the treatment of brackish water but can also be used for various industrial applications, including the recovery of valuable byproducts from wastewater. In ED systems, cation-exchange membranes allow positively charged ions (cations) to pass through while blocking negatively charged ions (anions), and vice versa for anion-exchange membranes. This selective ion transport creates a flow of freshwater on one side while concentrating salts on the other. One of the main advantages of electrodialysis is its lower energy consumption compared to reverse osmosis, especially when treating low-salinity feedwater. Additionally, ED systems can be easily scaled up or down depending on the specific application needs. A number of variables affect the functioning of ED systems, such as the voltage curve, the electrolyte concentration, the feed seawater concentration, and the particular working circumstances. Recent research has shown that raising the voltage gradient, raising the concentration of the electrolyte and feed saltwater, and lowering the system's flow rate can all greatly improve the desalination functionality of the ED system. Among the challenges are membrane fouling and the need for regular maintenance to ensure optimal performance. Recent advancements focus on improving membrane materials and configurations to enhance efficiency and longevity. Electrodialysis presents a promising alternative for sustainable desalination and resource recovery efforts in various sectors. There are several advantages to membrane-based desalination techniques. Since membrane-based technologies do not lose energy through evaporation or condensation, they consume less energy than thermal-based technologies. These include lower energy and capital costs, less physical space needed, greater recovery ratios, less vulnerability to corrosion and scale because the membrane operates at room temperature, and the membrane's capacity to reject microbial contamination. The total dissolved solids (TDS) concentration of brackish and saltwater can be treated using any of the above-mentioned technologies. In addition, the maximum salinity of the feed water threshold for membrane-based technologies is lower than that of thermal-based technologies. It is crucial to establish pertinent criteria in order to select the best membrane-based desalination technique among a variety of possibilities. Energy consumption is one important consideration when choosing a desalination method.