Page 24 - AW SEPOCT 2019

TECHNO NEWS

Harnessing energy from a mixture of

fresh and salt water

esearchers at Stanford University have harnessed The new Stanford battery floods a tank with salt-free
Rblue energy, an immense and untapped source of water (which can be wastewater effluent. The tank
renewable energy by developing a “mixing entropy contains electrodes which release sodium ions (Na+) and
battery” (MEB) that can harness energy from the mixing chlorine ions (Cl–) from the electrodes into the solution.
of fresh and salt water. The energy created this way This motion of ions also causes a current to flow from the
is sometimes called “blue energy.” According to a anionic electrode to the cationic electrode. Then, a rapid
Stanford news release, the team’s objective is to apply exchange of the wastewater effluent with seawater allows
the technology to coastal wastewater treatment plants the electrodes to reincorporate the sodium and chloride
and to use the electricity generated to make the plants ions, reversing the electric current flow. Energy is recovered
energy-independent and carbon-neutral. during both the freshwater and seawater flushes. This
The Stanford battery isn’t the only technology available means that the battery is constantly discharging and
to capture blue energy, but it’s the first to use battery recharging without needing any input of energy. As
electrochemistry instead of pressure or membranes. The reported in a paper in the journal ACS Publications, energy
present work is based on earlier research at Stanford that is recovered during both the freshwater flush (43.6% of the
tapped into salt gradients to produce electricity, but that total energy recovered) and the seawater flush (56.4%
effort required an expensive electrode made from silver, of the total energy recovered), with no upfront energy
and an initial energy input to begin the process. investment.

22 SEPTEMBER/OCTOBER 2019 Asian Water