River Power

Not that we needed it, but here’s another reason to be impressed with the creative thinking of chemists: the chemical reactions that occurs when fresh water in rivers runs into salty sea water could one day become a viable commercial power source.

Two European projects, in Holland and Norway, are testing systems to capture the energy released in estuaries, and though the concept is still in the very early stages, they estimate that the world’s estuaries could, in theory at least, put out enough power to meet 20 percent of the word’s electricity needs.

The basic idea is that when fresh water meets more concentrated salt water, the salt water, which is more concentrated, sucks in the fresh water as the two types of liquid seek equilibrium. In the process, the water becomes warmer, by about 0.1 degree C, and as we know, changing temperature requires power.

The two projects are both using specialized membranes to convert that temperature change into electricity, but with slight variations. The Dutch project captures salt particles in the process, and the salt crystals produce electrical current. The Norwegian one is trying to harness the physical force as the salt water sucks the fresh through the membrane; one researcher said the energy is comparable to the kinetic energy produced by water falling 270 meters.

Of course, there are plenty of complications, not the least of which is protecting a delicate membrane that stretches for acres and is vulnerable to tears and pollution. Oh, and one more thing. The membranes being tested are based on ones used in commercial desalination plants, which convert sea water to drinking water, But there isn’t really any design available that could be used in a commercial power plant, and there probably won’t be one available for a decade or more.

Still, I love the creative thinking that goes into finding new ways to harness the always-changing earth. And, let’s not forget that while the sun only shines in the daytime, and wind only blows when it wants to, the rivers and the tides never stop.