Large-scale energy storage

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					Large-scale energy storage.
Chemical energy provides the most versatile form of stored energy, which is why
fossil fuels have powered our modern way of life. Conversion of electrical energy
generated by alternative energy sources- -viz. wind, wave, radiant solar or nuclear
energy- -into chemical energy is done in an electrochemical or
photoelectrochemical system. The most efficient way to convert chemical energy
back into electrical energy is in an electrochemical system: a fuel cell, a battery,
or an electrochemical capacitor.
Professors at the University of Texas at Austin have played a leading role in the
development of electrode materials for Lithium rechargeable batteries and the
solid oxide fuel cell. They also have experience with materials for
electrochemical capacitors. The plug-in hybrid automobile powered by Lithium
rechargeable batteries and electrochemical capacitors are under development
world wide; this development represents a transformational
technology. Distributed CO2 emissions from cars and trucks cannot be
captured; the storage of off-peak electrical energy as chemical energy in the
batteries of commuter plug-in hybrid cars would reduce distributed CO2
emissions dramatically. However these batteries suffer from limitations on the
amount of energy that can be stored in the battery per unit weight and volume as
well, at present, as by cost and safety concerns. These batteries use a liquid
electrolyte and solid insertion-compound electrodes. An alternative strategy
under investigation at the University of Texas at Austin is the use of a solid Li+-
ion or Na+-ion electrolyte that separates a non-aqueous liquid anolyte from an
aqueous catholyte. With a Lithium anode and Fe(NO3)3 in aqueous solution as
the cathode, a rechargeable cell giving 3.6 V and a large capacity has already been
demonstrated, but optimization of the cell is on-going. This technology promises
to offer storage of of electrical energy from distribute wind energy and solar cells
as an alternative to storage in the grid; it also would provide sufficient capacity
for longer-range all-electric cars. A challenge for this technology is the
development of a solid electrolyte capable of operating adequately below freezing

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