A recent patent issued to compressed air energy storage (CAES)
company SustainX could provide a significant improvement in grid
storage of energy, especially for wind farms and solar power
arrays. Compressed air is one of the preferred methods for
storing excess energy from renewable sources during periods of
peak production. When there is increased demand, it can then be
readily harnessed to provide additional electricity, instead of
relying on fossil fuel burning 'peaker plants' or other, less
desirable alternatives. The problem with compressing air comes
from thermodynamic effects. "Without heat transfer, a gas will
increase in temperature as it is compressed; and as it gets
hotter, it tends to resist further compression (i.e., each
increment of compression must be performed on a volume of gas
that is at higher pressure than if it had not been heated by
prior compression)." SustainX has developed technology to
provide isothermal compression and expansion which gives their
system conversion efficiencies of