2022 Volume 76 Issue 3 Pages 170-176
Pressure-retarded Osmosis （PRO） is a promising system for renewable energy. The system utilizes a spontaneous hydraulic water stream driven by the osmotic pressure difference between brine with high concentration of salts and freshwater, and then the hydraulic water stream is subsequently converted into electricity using a turbine and generator. Because a spontaneous hydraulic water stream is produced by a semi-permeable membrane, the development of high-performance PRO membranes with long-term stability is quite important for making the PRO system commercially feasible. Since this system uses membrane technology, the core item is a semi-permeable membrane. Based on well-established membrane technology for more than 40 years, Toyobo has developed and commercialized hollow-fiber PRO modules consisting of cellulose triacetate.
SaltPower, a start-up company in Denmark, uses high salinity solutions （more than 10 wt％） as draw solutions （DS） that can be used to achieve a commercial PRO plant. Toyoboʼs PRO modules have been officially adopted by SaltPower, and two pilot-scale PRO plants have been demonstrated using high salinity solutions provided by （1） the salt industry and （2） geothermal water. In the case of （1）, we successfully achieved high gross power of 7000 W for 700 h, and this result accelerates SaltPowerʼs first commercialized PRO plant, which will start up within this year.
