The elementary principles related to compressed air are presented,
describing the basic compression and expansion characteristics. The adiabatic,
polytropic and isothermal phenomena are described together with the definitions of the
energy content of a given volume. Different loss factors related to compressed air are
enumerated together with the advantages and drawbacks of pneumatic technology.
Then, the possibility of storing energy under low pressure conditions as the so-called
Underwater CAES system is discussed. Such systems have the interesting property of
being realized with a very low amount of grey energy.
Keywords: Adiabatic characteristic, Compression of air, Expansion of air, Energy content, Isothermal characteristic, Loss factors, Low pressure storage, Properties of energy storage, Polytropic characteristic, Pressure reduction valve, Underwater CAES.
