Salty Batteries
On Aug. 11, the Korea Institute of Energy Research announced that one of its research teams headed by Dr. Jung Nam-jo succeeded in developing a core tech to generate kW-level power using the difference in salt concentrations between sea water and fresh water. The tech is eco-friendly, since it does not emit greenhouse gases at all during the electricity generation process.
The total amount of energy that could be produced by this method based on the amount of sea water is 2.6 TW worldwide, which is roughly equivalent to the total amount of electricity produced by 2,600 nuclear power plants each year.
The research team has successfully secured core original techs for reverse electro-dialysis (RED) and pressure-retarded osmosis (PRO) for the first time in Korea, which are representative methods to generate power using differences in salt concentrations.
RED produces power using a potential difference occurring when ions between sea water and fresh water are separated and move through ion-exchange membranes in a mechanism. The research team was able to develop a technique to make a kW-level module by developing a 500 W level RED stack, thereby improving the performance of ion exchange membranes.
The newly-developed stack makes it possible to steadily produce power, since it can minimize energy losses resulting from pressure inside the stack and increase energy to the maximum capacity. It means that the tech solved the shortcoming of existing electricity generation methods using the difference in salt concentration, where a great deal of energy is lost due to pressure in the stack when generating power.
Ion exchange membranes were also made in a pore-filling type, which fills nano-sized pores with ion exchange polymers. Thus, in terms of power density, the product performance improved by more than 10 percent compared to other products on the market made by Dutch companies, and the cost of production was lowered by half. The research team developed reverse osmosis membranes based on hollow fibers, which are the main materials for electricity generation, and secured an original tech that can modularize them.
Straw-shaped hollow-fiber osmosis membranes proved to be able to maximize the movement of water across a membrane from an area of low solute concentration to an area of high solute concentration, compared to flat membranes based on paper. Hollow-fiber osmosis membranes were also found to have 9 W level power density. In addition, they are likely to be used in not only electricity generation, but also other fields including seawater desalination equipment based on osmosis membranes or water purifiers.
Advanced countries like the Netherlands and Japan are leading the efforts to develop pilot plant technologies to generate dozens of kW-level electricity generators using the differences in salt concentration. The construction of MW-level power plants is expected to be feasible after 2025.