Energy stored in a pressure fluid compressed at the pressure p. The storage of energy within a volume of gas or fluid as a result of pressure is comparable to the storage of energy when a mechanical spring is compressed (energy content of a fluid). With fluids, it is almost possible to assume that a constant bulk modulus and isothermal compression apply. The result is as follows:
where V K = Compression volume
With gases, the compression energy is dependent on the thermodynamic change of state (the capacity of air to store energy).