The salinity difference between seawater and river water is a renewable source of enormous entropic energy, but extracting it efficiently as a form of useful energy remains a challenge. Here we demonstrate a device called “mixing entropy battery”, which can extract and store it as useful electrochemical energy. The battery, containing a Na2−xMn5O10 nanorod electrode, was shown to extract energy from real seawater and river water and can be applied to a variety of salt waters. We demonstrated energy extraction efficiencies of up to 74%.
With the entropy battery, costs are much lower than other ways of accomplishing the same thing due to the absence of replaceable membranes. Because the entropy battery operates in both warm and cold conditions it is a completely renewable resource; one that might lead to mass energy production in both developed countries and those in the third world.
Batteries for Efficient Energy Extraction from a Water Salinity Difference Fabio La Mantia, Mauro Pasta, Heather D. Deshazer, Bruce E. Logan, and Yi Cui
Nano Lett., Publication Date (Web): March 17, 2011 (American Chemical Society)