The Amazon River meets the sea - potential site for future non-dam salinity-based hydro? Photo retrieved from: www.internationalrivers.org
“Battery-operated electric vehicles are cutting CO2 emissions and raising awareness of our transportation carbon footprint. Recent cutting edge research now shows that batteries can also be harnessed in rivers and estuaries as a non-dam and hopefully low-impact form of electricity generation.
According to Stanford University, a team lead by Yi Cui (Associate Professor of Materials Science and Engineering), has developed a battery that takes advantage of the difference in salinity between freshwater and seawater to produce electricity.
The battery is simple, consisting of a positive and negative electrode immersed in water containing electrically charged particles, or ions – in this case, sodium and chlorine (i.e. table salt).
Battery in freshwater/saltwater cycle. Retrieved from: www.internationalrivers.org
- Step 1: A small electric current charges the battery, pulling ions out of the electrodes and into the water.
- Step 2: The fresh water is replaced with seawater, thereby increasing the amount of charged ions. Salty seawater contains 60 to 100 times more ions than freshwater.
- Step 3: The salt water increases the electrical potential, or voltage, between the two electrodes, allowing the battery to generate far more electricity than the amount used to charge it. Electricity is then drawn from the battery for use, draining the battery of its stored energy.
- Step 4: Seawater is discharged and replaced with river water, and the cycle starts again.
The impacts and limitations
According to the Stanford article, the potential environmental impact of the battery should be low. They recognize that river mouths and estuaries are environmentally sensitive areas. They chose manganese dioxide for the positive electrode, in part because it is environmentally benign. The discharge water would be a mixture of fresh and seawater, released into an area where the two waters are already mixing, at the natural temperature.”
Read more: International Rivers
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