Plenty of Energy Where River Meets Sea

Mix one part fresh water with one part salt water, stir in a bit of activated carbon, and jump-start.

Voila: you've produced electricity.

With just $3 worth of activated carbon and a steady flow of water, you could produce enough electricity to run a small home — indefinitely.

Sound too good to be true? It isn't! Turns out that mixing fresh and salt water together results in net energy production. The only catch is — you need a great deal of fresh and salt water mixing together. To find that in nature, you have to go where the river meets the sea. That means places like the Mississippi Delta, along with various estuaries and deltas around the United States and throughout the world.

Until recently the idea sounded great, but the technology wasn't available to make the dream a reality. Now Doriano Brogioli, a researcher in Milan, has developed a system that could, in theory, be scaled up to serve entire communities.

The system would have very little impact on the environment: The only waste product is slightly brackish water that can be poured directly into ponds where plants and animals thrive on slightly salty water. Even better, there's no need to use potable fresh water to produce electricity: polluted, slightly salty water works beautifully. Preliminary studies suggest that it's possible to scale up quickly to produce salinization plants to run entire cities. So far, though, skepticism is holding the process up. Some worry that the approach will only work in certain areas; others are concerned that too much salt will corrode machine parts, destroying the plants from the inside.

Brogioli is sure that his approach has legs, and he's ready to get moving toward full-scale implementation. From his point of view, any type of low cost renewable energy is a bonus and he wants to see his brainchild grow up to become as significant as solar cells or wind farms.

Photo courtesy of Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite.