Osmotic energy, also known as salinity energy or blue energy, is a growing new energy source that is expected to generate electricity without producing carbon dioxide and other greenhouse gases. It has advantages over other renewable energy sources because it can operate 24 hours a day, regardless of weather conditions, allowing for continuous and predictable electricity production. This technology relies on mixing fresh and saltwater, allowing for a continuous flow of energy day and night, providing a stable source of electricity.

What is osmotic energy?
Osmosis is a natural process where water moves through a semipermeable membrane from a solution of lower concentration to a solution of higher concentration, attempting to maintain a concentration balance on both sides. It's the same process that allows plants to absorb water from the soil for moisture.

Imagine a cup divided vertically by a thin, permeable layer. If one side contains saltwater and the other contains pure fresh water, the water will flow to the salty side to dilute it, since the salt cannot pass through the membrane. Osmotic power plants use the same principle. Water molecules naturally flow from an area of high water concentration (e.g., fresh water) to an area of low water concentration (e.g., saltwater) through a semipermeable membrane.

In the case of energy generation, this movement of water can be harnessed to rotate turbines that generate electricity. The plant in Fukuoka uses a thin barrier to separate treated wastewater from concentrated seawater. As the water flows to maintain concentration balance, it creates pressure that drives the turbines.

The Fukuoka power plant is the second power plant in the world to use osmotic energy. The first to use this energy is in Marieger, Denmark, built in 2023 by the joint venture SaltPower, said Professor Sandra Kentich of the University of Melbourne.
The Japanese plant is larger than the Danish one, even though it has a similar generating capacity. There have also been pilot demonstrations in countries such as Norway, South Korea, Spain, and Qatar. Australia also attempted a similar project during the COVID-19 pandemic, but it was unsuccessful.

Although the concept is simple, it has drawbacks, like many new technologies. Because the technology works well in small-scale laboratories, it is difficult to implement in the real world on a large scale while maintaining efficiency. Professor Kentich said that a significant amount of energy is lost in pumping water into the plant and as water flows through the membrane.
Some research also indicates that this form of energy production is not economically viable because it is significantly less competitive than other renewable energy sources such as wind and solar power. But advances in membrane and pump technology are helping to mitigate these problems, Kentich added. “Another notable thing is that the Japanese plant uses concentrated seawater, which is the brine remaining after dewatering in a desalination plant, as a feedstock.” It helps to increase the difference in salt concentration and available energy.”

Kentish and Altaë agreed that this power plant in Japan represents an exciting time for osmotic energy, as it further proves that the technology can be used to produce large-scale power. Altaë said that the pilot plant at the University of Australia (UTS) could be reactivated if government funding is provided, which would increase its potential for wider application in Australia, similar to the power plant in Fukuoka.

If these problems can be solved, osmotic energy has the potential to meet up to 15% of global electricity demand by 2050 if adequately utilized. In a world seeking more environmentally friendly energy sources, this clean energy source represents an underutilized opportunity that could complement solar, wind, and other renewable energy sources as the world reduces its reliance on fossil fuels.