Scientists believe saltwater could become a reliable source of renewable energy through a process known as osmosis. Japan has now taken a major step in that direction.
Earlier this month, Japan officially launched its first osmotic power plant in Fukuoka, a large city to the west of Tokyo. That makes Japan the second country in the world to bet on osmotic power, after Denmark. Fukuoka’s plant is expected to generate about 880,000 kilowatt hours of electricity each year, enough to supply approximately 290 Japanese households.
For now, the facility’s first task is to power Fukuoka’s desalination plant, which supplies fresh water to neighboring areas. Its success could lead to the proliferation of osmotic power, a natural and low-risk alternative to fossil fuels that hasn’t quite taken off due to practical challenges.
How it works
Osmosis is a simple process that reflects nature’s tendency to even things out. In an osmotic power plant, a special membrane separates layers of freshwater and seawater, with the latter subjected to slightly more pressure. Over time, osmosis leads to freshwater flowing toward the seawater layer to balance the concentration of salt on both sides of the semipermeable membrane. This causes a pressure increase that turns a turbine in the plant, which in turn generates electricity.
This is also an energy source unaffected by the whims of nature, such as weather or time of day. Unlike solar or wind power, osmosis is essentially a “stable source of electricity generation that can operate 24 hours a day, for every day of the year,” Kenji Hirokawa, director of the Seawater Desalination Center at the Fukuoka District Waterworks Agency, which operates the plant, told the NHK (translated from Japanese).
Just two plants so far
In principle, osmosis seems to offer a simple alternative to the shortcomings of fossil fuel alternatives. Realistically, however, researchers will need to overcome several technical hurdles before it can be a viable option. For instance, we’ve yet to resolve the massive energy losses from pumping the water into the plant and again as it travels through the membranes, Sandra Kentish, a chemical engineer at the University of Melbourne in Australia, told the Guardian.
“While energy is released when the salt water is mixed with fresh water, a lot of energy is lost in pumping the two streams into the power plant and from the frictional loss across the membranes,” Kentish said. But researchers are hard at work improving membrane and pump technology to minimize these issues, she added.
Fukuoka’s officials appear optimistic about their goal of harnessing osmosis as a reliable energy source for Japan, according to Hirokawa. “It’s a meaningful plan—the start of a plan, perhaps—in our response against climate change,” he said.
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