Generating Electricity With Mixing Entropy: The Weird Science Of Salinity Cells

Physicists have long held that there's energy abounding in naturally occurring chemical reactions, and one of their most prime candidates from which to harness this energy has been the process known as salination, wherein freshwater rivers drain into the salty ocean. The notion of collecting the energy lost to entropy during salination has been only theoretical since the process came to light, however a paper by University of Milan-Bicocca physicist Doriano Brogioli is due to be published in the scientific journal Physical Review Letters describing a power cell that converts this lost energy into electricity.

The strange physics of mixing entropy are intuitive to understand. Imagine you're at a bar, and there's dancing music playing. You're feeling very acutely the long day behind you, so you order a Red Bull and vodka, the perfect drink for dancing. The bartender pours half a can of Red Bull into a glass, then pours 3 ounces of vodka. You are now officially ready to party. But wait! The resulting solution is less than the sum of it's constituent parts! This loss of energy is called the entropy of mixing and is precisely the physical process that the salination cell aims to capture.

The device itself is more difficult to describe. It's functional core is comprised of two electrically-charged chunks of activated carbon that collect negative and positive ions from salt water. When fresh water is flushed in, the ions are released from the carbon chunks, increasing the voltage of the charge and generating electricity. Scientific abstracts and illustrated diagrams are out there, but the weird science of it places real understanding somewhat beyond the reach of layfolks. Suffice it to say, the lab models work, and the science suggests it can be scaled up to provide a new source of renewable clean energy.

As usual, there are skeptics. Many in the scientific community are quick to point out the logistical difficulty in scaling the lab models up from experimental devices to the megawatt-generating plants needed to make capturing the energy inherent in the process of salination worthwhile, noting that the relative scarcity of places where a great deal of fresh water hits the ocean makes the new technology potentially less than ubiquitous. Others such as Fred Schlachter, retired staff scientist at Lawrence Berkeley National Lab in California, go further to say that the figures cited by proponents of the technology don't account for the enormous upkeep and maintenance overhead necessary when dealing with the very corrosive properties of ocean water.

Still, those figures are impressive. Scientists who first described the physics underlying mixing entropy deduced that the potential energy inherent in the process worldwide is equivalent to every river in the world ending in a 223 meter waterfall. Those numbers, along with the presumed success of a large-scale salination plant, suggest that salination energy might one day comprise a significant chunk of the renewable, green energy that offset brokers resell.

(Source: http://www.physicscentral.com/buzz/blog/index.cfm?postid=8192106608311312838)