Water Power: An Under-Exploited Resource
What is Osmotic power?
This Blue energy is released when fresh and salty water meet. It has the capability to power our homes. But how can we exploit this natural effect?
Well, in fact, if we separate via a semi-permeable membrane in a container the fresh water from the salty water, the fresh water will naturally go to the salty side. This action increases the level of salty water and generates a pressure of a 120m waterfall. If we combine this pressure with turbines, we can generate power and therefore electricity to our homes.
Throwback On Its Evolution
The first notion of Blue power or Osmotic Power was first described in 1954 by R.E.Pattle. But it is only in the 1970’s that an Israeli scientist, Sidney Loeb, had the idea of an Osmotic power plant. Indeed, he wanted to create it at the confluence of the Jordan river with the salty Dead Sea.
However, to become reality, we had to wait until 2009 when the first Osmosis power plant was opened in Tofte, Norway. This power plant could generate up to 10kW. Nevertheless, its operating costs were too important compared to what it could generate and the plant had to be shut down in 2013.
Nowadays, another company works on the project in Leeuwarden, The Netherlands, but using a different osmosis technique.
Above, the Confluence of the Jordan River and the salty Dead Sea.
What Are The Different Osmosis Power Techniques Currently Used?
- Pressure-Related Osmosis (PR)
This technique implies that a power plant works best when the flow rate is not at its highest level across the membrane but rather slowed down a bit. To be able to do so, you can squeeze the salt water so that there exists pressure to slow down the influx of freshwater into the salty water tank.
- Reverse Electrodialysis (RED)
This process differs from the first one in the extent that it allows the salt ions instead of the water molecules to pass through the membrane.
Two types of membrane currently exist:
- One that allows positively charged sodium ions to go through
- One that allows negatively charged chloride ions to go through
- Capacitive Mixing (CapMix)
Finally, this last technique lies in the fact that electrodes are placed in two separate chambers in which the freshwater and salty water are stored alternatively. Thanks to this process, you can also raise voltage and therefore produce electricity. However this voltage could be doubled if the fresh water is warmed-up. This warming process could be done thanks to industrial water already warm, so the use of fossil fuels could be avoided.