Osmotic power plants. Another type of generation in alternative energy

If we start talking about alternative energy, then the majority of people come up with images of solar panels or wind turbines. The disadvantages or their limitations in work are known. Geothermal, tidal power plants are complex and geographically limited to a few locations on the planet. Biogas plants operate smoothly only in warm countries. It is possible to place MicroHPPs (floating or low-speed generators on a pile foundation) along the banks of rivers, but this direction is not progressing either.

I think for those who are interested in this topic, information about osmotic power plants, which in our century nanotechnology, polymer membranes, can become a very serious increase in the total share of electricity generated by planet.

So, what are we talking about? Theory first. In physics, the effect of osmosis is known:

This phenomenon occurs when two liquids with different salt concentrations begin to mix through a semi-permeable membrane. Those. a liquid with a lower salt concentration dilutes a liquid with a higher concentration. The membrane works in one direction - it allows practically only water molecules to pass through and in one direction. Thus, in the container where there was salt water, water will either be added and its column will rise, or pressure will be created. And since water is incompressible, then this excess pressure can be used to rotate the turbine and generator.

Thanks to this phenomenon, it is possible to raise the water column by 240 m or create a pressure of up to 24 atmospheres (when diluting salt water with a salinity of 35 g / liter)! The phenomenon of osmosis is used by nature itself even more effectively in plants and trees (the rise of moisture along the trunk).

Since the middle of 1980. the direction of membranes for osmotic water purification and its desalination is actively developing. And from this period, it became possible not theoretical, but already practical application of this effect for the generation of electricity. The first osmotic power plant was implemented by Norwegian scientists with the support of the local energy company Statkraft. Were used Loeb membranes made of modified polyethylene on a ceramic base. They can withstand tremendous pressure. It all looks like this:

They adapted a building in Toft, which is located on the banks of a river flowing into the sea. Water from the river flows by gravity into the building. There it is purified and fed to spiral membrane plants for mixing with salt water, which is pumped from the sea and also fed to the plant (second slide). Due to the obtained pressure in the salt water, the turbine is set in motion and the generator rotates through it. Installation diagram:

Roll-type osmotic chambers. Similar to those used in sewage treatment plants. The pumps supplying water to the osmotic plant are powered by the electricity generated by the plant. Third-party electricity is only needed to start the station. Mixed river and sea water is discharged into the sea.

The station was spent on a state grant from the government of Norway $ 20 million. The station started with the generation of only 4 kW * h of electricity. Plans for 2015 was to increase the capacity to 25 MW. Whether it worked or the project was frozen - I did not find information.

A source: http://www.chekltd.com/node/673

The fact is that the commercial use of such a technology makes sense if the membranes are effective at values 5 W / m2 from the membrane area. At the osmotic station in Toft, only 1 W / m2 from the membrane area.

But progress does not stand still. In physics, carbon nanotubes are known. Membranes based on them are very effective. Such membranes will increase the performance up to 4000 W / m2. This efficiency exceeds the indicators of any generating sources!

And ultra-thin graphene films will increase the indicator to 10 kW / m2 from the membrane area, since only water molecules can pass in one direction. Imagine, an osmotic plant the size of a 50 liter gas cylinder with a constant supply of salt and fresh water to it can create pressure to rotate the turbine and 5-10 kW of the generator! It all comes down to the cost of producing such membranes.

With such a rate of currencies, our Rusnano would take control of the niche. for graphene films, we have a huge lead:

Graphene nanotubes are 150 times stronger than any steel. And Russia has become the largest producer of it - 50 tons per year. I'm directly surprised if Mr. Chubais really did something useful?

With all this information in mind, estuary osmotic power plants could become leaders in alternative energy in the near future. They are silent, do not emit any harmful impurities into the atmosphere or water. It is advisable to locate the equipment below the water level in the river and sea - there will be no industrial buildings and structures on the surface.

Currently, such osmotic stations are most efficiently located near desalination plants. Because water leaving desalination plants is 10 times saltier than sea water.

And one more idea, which is still a distant future: osmotic power plants in the oceans near major cities. It is known that the salinity of water depends not only on the content of salts in it, but also on temperature. And it is different at different depths in the oceans. A floating station with columns lowered to a depth of several hundred meters and with water supply to them from sea ​​surface, can generate environmentally friendly electricity almost anywhere in the seas and oceans.

All of this reminded me of futuristic articles and drawings from the magazines Technology of Youth, Young Technician of the USSR times.

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Photos are taken from open sources, from Yandex. Pictures

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