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 Na2xMn5O10 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%. Considering the flow rate of river water into
oceans as the limiting factor, the renewable energy production could potentially reach
2 TW, or ∼13% of the current world energy consumption. The mixing entropy battery is
simple to fabricate and could contribute significantly to renewable energy in the future.
KEYWORDS: Salinity-gradient power, mixing entropy, sodium intercalation, energy
harvesting