[kublikhan]

Generating energy on a large scale by mixing salt and fresh water is both technically possible and practical. The worldwide potential for this clean form of energy -- 'blue energy' or 'blue electricity' -- is enormous. However, it will be necessary to work actively on several essential technological developments and to invest heavily in large-scale trials. The principle of generating electricity by mixing salt and fresh water, taking advantage of the difference in charge that results, has been known for more than 100 years. It was first tested in practice in a laboratory in the 1950s. There are two methods for generating blue energy: pressure-retarded osmosis and reverse electrodialysis.

Post investigated the possibility of recovering energy from the Rhine and the Maas rivers. He estimated the technical potential of both rivers to be 2.4 gigawatts per year. He believes it would be economically feasible to recover 1.5 gigawatts. A power station of around 200 megawatts -- comparable with a park containing 200 wind turbines -- could be placed at the Afsluitdijk (the famous Closure Dike in the Northern part of the Netherlands) which, according to Post, is a rather suitable place for the large-scale trials that need to be carried out. This test location on the Afsluitdijk could be combined with the redesign of the dike that is already being planned. Heavy investment is necessary but this type of clean energy is extremely promising and, since it is essential to look for alternatives to fossil energy, this investment would be worthwhile in every respect.

It will be at least ten years before the first commercial power stations are operational, Post says. Post believes that in the next few years it will be necessary to work even more intensively on two technological developments that will bring down the present, rather high, price of generating blue electricity. An appropriate membrane technology should be developed and, furthermore, such membranes should become much cheaper by introducing mass production. The technique should also be robust enough to work both when the water is polluted and when living organisms accumulate on the membranes (biofouling). His research showed that both hindrances could be removed in the future.

Blue Energy Seems Feasible And Offers Considerable Benefits

[ian807]

As with so many of these things, I sure hope it works, but I'll believe it when I see it.

[Tanada]

OK this system works based on the ion potential difference between differing levels of salinity in the water used. What this brought to my mind is the possibility of building a bunch of power plants along the coast of the Black Sea in Eurasia, the stagnant bottom water is highly saline while the surface waters are merely brackish. If this system really works you could pump highly saline bottom water and brackish surface water through a power plant and generate considerable power, repeated dozens of times over because you could ring the entire sea with a series of them a hundred km or so apart from one another. This would give both the Ukraine and Turkey a massive bounty of electricity to sell to the European power grid.

[katkinkate]

OK this system works based on the ion potential difference between differing levels of salinity in the water used. What this brought to my mind is the possibility of building a bunch of power plants along the coast of the Black Sea in Eurasia, the stagnant bottom water is highly saline while the surface waters are merely brackish. If this system really works you could pump highly saline bottom water and brackish surface water through a power plant and generate considerable power, repeated dozens of times over because you could ring the entire sea with a series of them a hundred km or so apart from one another. This would give both the Ukraine and Turkey a massive bounty of electricity to sell to the European power grid.

Do you get enough energy out of it to cover the energy used to pump all that water?