Page 27 - Newsletter

27

LARGE STORAGE BATTERIES:THE MISSING LINK TO RENEWABLE ENERGY

With the emergence of renewable energy, the usage of non renewable fuels have
come down by only a marginal amount. The culprit for this disappointing
numbers is the lack of an efficient energy storage. Regardless of retrieving power
from wind, solar and water, a stable medium for their storage still remains an

issue that needs solving. Around 7 years back, a professor from MIT, Donald
Sadoway gave a TedTalk on the same issue titled " THE MISSING LINK TO
RENEWABLE ENERGY". In that talk he spoke of a battery that he was developing
along with his student and a group of PhD scholars. In his words, he was
"working on a battery miracle-an inexpensive, incredibly efficient, three layered
battery using 'liquid metal'". During the course of the talk, the professor spoke of
everything, starting from the first battery ever made, by Alessandro Volta to the
current stage of the battery that he was developing. Over the course of the talk,
he maintained a light hearted ambiance and has a calm demeanor. Speaking of
the first battery made, he mentioned that it was made of a stack of coins made
of zinc and silver both of which is separated by a cardboard soaked in brine

solution. In such a system the two metals act as the electrodes and the salt water
acts as the electrolyte. However he admited that he has left out a few details on
the same. Then he went ahead and talked about the requirements of these
power grids, which are "uncommonly high power, low service lifetime and super-
low cost". He later began suggesting that the ideal way to approach problem in
hand is to "invent in the price point of the elecricity market", I.e., using
something locally sourced and commercially viable. He moved on to speak about
his personal journey that started 6 years prior. And he claimed that what served

as an inspiration for his invention, was the process of production of aluminium,
which consumes an enormous amount of energy. He proceeded to state out the
difference between the conventional battery and the aluminium production ,
"Volta's battery works at room temperature. it's fitted with solid electrodes and
an electrolyte that's a solution of salt and water. The Hall-Heroult cell operates at
high temperature, a temperature high enough that the aluminium metal product
is liquid. The electrolyte is not a solution of salt and water, but rather salt that's
melted. It's this combination of liquid metal, molten salt and high temperature
that allows us to send high current through this thing". It is this very basic idea
that helped him develop a fully liquid battery. His liquid battery had two molten
electrodes and molten salt acting as the electrolyte. The battery had a low
density liquid (magnesium) at the top, a high density liquid(antimony) for the

bottom and molten salt sandwiched between the two.