[NewCandle] Aluminum-Air Battery

[Frederick Sparber]

Is this what Nick is shooting for?

http://en.wikipedia.org/wiki/Aluminium-air_battery

"Aluminium batteries are commonly known as aluminium-air batteries or
Al-air batteries, since they produce electricity from the reaction of
oxygen in the air with aluminium. Aluminium batteries have the highest
energy density of all batteries. Yet they are not widely used because
of their high cost and very limited shelf-life which have restricted
their use to mainly military applications. An electric vehicle with
aluminium batteries could potentially have four times the range of
lead-acid batteries, which have only one-fifth of the energy per unit
volume."

"Al-air are primary batteries, i.e., non-rechargeable, and can also be
considered to be fuel cells. Once the aluminum anode is consumed by
its reaction with atmospheric oxygen at a cathode immersed in a
water-based electrolyte to form hydrated aluminum oxide, the battery
will no longer produce electricity. However, it may be possible to
mechanically recharge the battery with new aluminum anodes made from
recycling the hydrated aluminum oxide. In fact, recycling the formed
aluminum oxide will be essential if aluminum air batteries are to be
widely adopted"

"There are a number of technical problems that need to be solved in
order to make Al-air batteries suitable for powering electric
vehicles. Anodes made of pure aluminum get corroded by the
electrolyte, so the aluminum is usually alloyed with tin or other
proprietary elements. The cathode is made from high molecular weight
polymers, i.e., plastics and advanced membrane technology which allow
the oxygen to diffuse through the salt water electrolyte and reach the
aluminum anode. Further development work on cathodes is necessary. The
hydrated alumina that is created by the cell reaction forms a gel-like
substance at the anode and reduces the electricity output. This is an
issue that is being addressed in the development work on Al-air cells.
Additives have been developed which make the alumina to be formed as a
powder rather than a gel."

"Aluminum as a "fuel" can be comparable in price to gasoline. At
present, the typical wholesale price for aluminum is under $3 per
kg[3]. A kg of aluminum produces about 16 000 kJ (4.5 kWhr) of energy
when it reacts with oxygen. A kg of gasoline, i.e., 1.25 liters, has
an energy content of 45 000 kJ and costs about $1.3[4]. Assuming 80%
energy conversion efficiency in a battery and only 20% for a gasoline
engine then Al-air is not competitive. But in Europe, where gasoline
can be three times more expensive than the USA, aluminum power becomes
very viable. Using recycled aluminum however changes the situation in
the USA too: Recycled aluminium is also $1.3/kg[5] which makes the
cost per kg equivalent to gasoline. That is for a static engine, but
since an electric vehicle with Al-Air cells would be much lighter,
owing to the lack of an engine or transmission, it would have a lower
cost per kilometer"

Fred