Nanomaterial Boosts Efficiency of Salinity Power Technology

The work of Yi Cui, Associate Professor of Materials Science and Engineering at Stanford University, has garnered a great deal of interest, especially with his paper "High Performance Silicon Nanowire Field Effect Transistors" that has become the second most cited paper in the ACS journal Nano Letters over the past 10 years.

A few years back, I noted his work in replacing the lithium in the anodes of li-ion batteries with silicon nanowires and thereby increasing the battery life of a laptop to over 20 hours.

Now Cui and his colleagues have developed a material that improves on the technique of generating electricity by exploiting the difference in salinity between freshwater and saltwater.

The technique of using the combination of fresh and saltwater to generate electricity has become known as pressure-retarded osmosis and is being used in a working prototyple plant in Norway run by Statkraft

While Statkraft has claimed a goal of converting 80 percent of the available chemical energy this technique to electricity, Cui is quoted as believing that the best efficiency they can really hope for is 40 percent.

The material that Cui has developed is a manganese-dioxide nanorod that makes up the electrode, and, according to Cui, because this material offers 100 times more surface area for the sodium ions to interact with and allows those ions to attach and detach more quickly from the electrode.

The result is that Cui’s team was able to convert 74 percent of the potential energy that exists between the fresh and salt water into electricity, and, if the electrodes are brought closer together, could possibly achieve 85 percent efficiency.

Cui offers some pretty stunning calculations on how much energy could be produced if “all of the freshwater from all of the world's coastal rivers were harnessed.” He calculates that roughly 2 terawatts of electricity would be produced under such circumstances, or 13 percent of the world’s current energy demand.

Needless to say, nobody is going to undertake such a project on that scale since not only would it disturb sensitive aquatic habitats but also it would likely have large energy costs as well. 

But an outfit like Statkraft might take an interest in the new material to see if it will bump some salinity power technology over the 80 percent efficiency mark.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

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Dexter Johnson
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