*2.4. Compressed Air Storage*

The basic idea on which the proposed approach is based is the shift of the peak aeration load to low energy cost periods, introducing a storage system able to sustain the aeration during peak energy cost periods. In order to evaluate the economic convenience of the proposed technology, the energy required to compress the air in the tank, *Ecompr* (kJ), is calculated as follows (Equation (2)):

$$E\_{\text{cumpr}} = P\_{\text{starge}} \times V \times \ln{\frac{P\_{\text{@}}}{P\_{\text{starge}}}} + \left(P\_{\text{starge}} - P\_{\text{@}}\right) \times V \tag{2}$$

where *V* represents the storage tank volume (m3), *Pstorage* is the pressure inside the tank (MPa), and *P@* (MPa) is atmospheric pressure.
