Potential revolution in green energy as new power plant in Japan is the second in the world to exploit the well-known effect of mixing seawater with fresh water
There’s a great deal of buzz in the green energy sector about in a new power plant opened recently in Fukuoka, south-west Japan.
Photo by Sime Basioli / Unsplash
The plant promises to generate clean, sustainable energy. What makes this one so interesting is that it’s just the second plant in the world to harness osmotic power. That has a key advantage over other green energy sources such as wind and solar in that it can produce a regular, steady supply of power around the clock.
Osmotic power is relatively new and untested. There have been pilot schemes and trials in countries such as Norway, South Korea, Australia, Spain and Qatar. The venture company SaltPower opened the first full-scale osmotic power plant in Denmark in 2023.
This new, second plant, in Japan, is larger than the one in Denmark and expected to generate some 800,000 kilowatt hours of electricity per year, equivalent to the energy needs of more than 200 homes. If it works as hoped, and can demonstrate the effectiveness of osmotic power, more such projects will surely follow – and could see a revolution across the sector.
So, how does it work?
Osmosis is well-understood natural process in living cells – one that many of us have studied at school, doing experiments with cut-up potato in water.
You start with two solutions of water, one with more salt or sugar (a concentrated solution) than the other (a dilute one). The two solutions are separated by a membrane akin to a cell wall. The salt or sugar can’t pass through the membrane but water molecules can.
What happens is that, over time, water molecules in the dilute solution diffuse through the membrane, evening out the concentration of both solutions.
The osmotic power plant harnesses this principle but uses freshwater on one side of the membrane and salty seawater on the other. The seawater is kept under pressure. As the less salty freshwater diffuses through the membrane, it increases the volume of seawater inside – and increases pressure. In the process, the movement of water drives a turbine to generate power.
The issue is ensuring that the power generated is significantly greater than the energy required to pump in the two sources of water in the first place – if not, it’s not an effective way of generating power.
Using more concentrated sources of saltwater and reducing friction as water molecules pass through the membrane will help improve levels of power generated – the question is to what degree. It may be that this method can produce only modest levels of power.
On the other hand, this method can generate power on a continuous basis, whereas other forms of green power generation such as solar and wind are dependent on weather conditions. Saltwater is also in ready supply in lakes and seas, so it may be possible to generate significant volumes of power by deploying this method at scale.
The point is that we don’t know yet and more work needs to be done to understand the potential of this process. That’s why this new plant in Japan is of such interest – it’s success could lead to a whole new line in green energy production. Or perhaps that should be a ‘fresh wave’…
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