Saltwater + Freshwater = Blue Energy

Blue energy, or reverse electrodialysis, generates electricity through the convergence of fresh and salt water using artificial semi-permeable membranes. The technology is currently in use in the Netherlands, but the possibilities for its application exist wherever saltwater and freshwater mix. It’s not a new discovery, but until now, the cost of the membranes has been prohibitive for most applications.

photo by spisharamBlue Energy
Blue Energy

Also called osmotic power or pressure retarded osmosis, blue energy capitalizes on the chemical differences between saltwater and freshwater. A concentrated salt solution and fresh water are brought into contact through an alternating series of anion exchange membranes (AEM) and cation exchange membranes (CEM). The chemical potential difference generates a voltage over each membrane and the overall potential of the system is the sum of the potential differences.

Here’s a short animation of the process:


Sound like Greek to you? I have to admit that I don’t fully understand the scientific principle behind the technology, but because this is a sustainable, non-polluting energy source, applicable wherever a large estuary is located, I can really get behind it. There are many places around the globe where this could be deployed, bringing safe, renewable energy to the masses through a natural energy source. One estimate is that blue energy could supply up to 7% of the world’s energy needs. That’s significant.

Written by Derek Markham

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