Hollow fiber forward osmosis (FO) membranes manufactured by Toyobo Co., Ltd. have been adopted at a first of its kind osmotic power plant in Denmark. The pilot plant is operated by Danish venture firm SaltPower ApS with support from industrial machinery maker Danfoss A/S and engineering firm Semco Maritime A/S. The plant started a demonstration in September and aims to put the membrane to continuous operation.
The FO membrane, in which hollow fibers are densely packed in a cylindrical pressure vessel, is a kind of semipermeable membrane that permeates water molecules and filters out molecules and ions above a certain size. Toyobo developed hollow fiber semipermeable membrane in the 1970s, applying spinning technology nurtured in its textile production business. Since the early 1980s, Toyobo’s reverse osmosis (RO) membrane using the technology, which filters saline water into fresh water, has crafted an excellent reputation for its filtering capabilities and durability, and has been adopted at desalination facilities mainly in the Middle East Countries.
The osmotic power plant generates electricity by using energy derived from the difference in the salt concentration between fresh water and geothermal water, or saline water pumped up from underground wells. When saline water comes in contact with fresh water over the FO membrane, which filters out salt content from saline water, water currents are created in the saline water due to the difference in osmotic pressures. These currents turn the turbine for generating electricity. Osmotic power using geothermal water is attracting attention as a novel renewable energy that, unlike solar or wind power, is unaffected by weather or time of day.
Toyobo’s FO membrane has an internal structure in which densely packed hollow fibers enable water to flow efficiently, generating stable water currents at a low pressure loss for turning the turbine. In addition, the membrane is robust enough to withstand the high water pressure needed for efficient osmotic power generation, a property that Toyobo’s RO membranes possess. These features prompted the Danish osmotic power plant to use the FO membrane.
Toyobo, SaltPower and other entities are scheduled to build a one-megawatt-class osmotic power plant that harnesses Toyobo’s FO membrane in Denmark by the end of 2021 and later in other European countries. Toyobo plans to actively market the FO membrane to energy-saving desalination plants and industrial wastewater concentration systems.