Clean Power stanford researchers create renewable energy system based on salt and entropy

Published on March 28th, 2011 | by Tina Casey


Where River Meets Sea, Salt Makes Renewable Energy Happen

March 28th, 2011 by  

stanford researchers create renewable energy system based on salt and entropyA team of researchers from Stanford University has estimated that rivers could provide about 13 percent of the world’s current energy needs, but they’re not talking about hydropower. Instead, they envision renewable energy based on the principle of entropy, as energy is produced when fresh water from rivers disperses into salt-laden seawater. While 13 percent might be something of an overreach given the current state of the technology, the team has developed a new entropy based system that could lead to the widespread use of river-generated renewable energy.

Renewable Energy when Salty Meets Fresh

The idea of using the interaction of salt water and fresh water to generate energy has been around for a while. In nature, the diffusion of river water into salty seawater leads to a slight rise in temperature, and this energy could be captured to generate electricity. The conventional means of capture has been through osmotic power. Fresh water and salt water are separated by a membrane, and the salt water draws fresh water through the membrane, causing an increase in pressure. The pressure can then be used in a variety of ways, for example to turn a turbine. The Norway-based company Statkraft is testing one such osmotic power facility.

Power from Entropy

Though promising, osmotic power does have one drawback, and that is the bulk of the membrane. The Stanford team approached the problem from a different angle and came up with a more compact system. As reported by Andy Extance at the Royal Society of Chemists, the Stanford system uses a battery to draw energy through a crystal lattice made of manganese dioxide nanorods, which pack a large surface area into a small space.

Salt and Sustainability

Salt is shaping up to play some interesting roles in the sparkling green future. Molten salt, for example, is being developed as a storage solution for solar power installations. Another exciting development is a fuel cell that combines desalination, wastewater treatment, energy generation and hydrogen gas production in a single process.

Image: Salt by genista on

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • Ghowe

    Hi Tina,
    We’d like to contact you with some renewable technology updates – can you contact me at
    Graham Howe

  • Pingback: NGN Daily: Earthquakes, Photosynthesis, and Entropy | NetGreen News()

  • John

    So in the desert southwest of the US, we may need to turn to desalination in order to meet fresh water needs. Meanwhile, we have a proposal like this to generate power from fresh water pouring into the ocean (presumably the biggest source would be the Mississippi).

    But I wonder what the energy cost would be of somehow diverting the fresh water of the Mississippi to the desert southwest instead of letting it flow into the ocean. Perhaps an aqueduct+pump system powered by wind turbines in the plains states? (during the day, wind power could meet normal demand for electricity, but at night it could be used to pump water) And how would that power cost compare to the cost of desalination?

    • FromLV

      The pumping station that moves water from Northern California over the Tehachapi Mountains consumes more energy than the entire city of San Francisco. Does that give you an idea of the energy needed for such a plan?

  • love this idea — curious to see if it goes anywehre

  • love this idea — curious to see if it goes anywehre

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