Dynamics of dissolution for underwater compressed air energy storage

Underwater Compressed Air Energy Storage takes advantage of the hydrostatic pressure in deep water to provide a means of storing large amounts of pressurized air without expending very large sums of money on pressure containments. A key attractive feature of all underwater storage of pressurised air is that the containment may be largely isobaric (i.e. the pressure of the stored air remains relatively constant irrespective of the level of fill). One of the common issues for isobaric containments is air dissolution into water. The dissolution is controlled by the concentration of the air in the water and Henry's law can be applied to determine the steady-state concentration of dissolved air in seawater. The charge/discharge process is clearly dynamic. In dynamic processes, steady state is never reached. This paper examines whether the dynamic effects may be useful. Experiments are performed to investigate air dissolution in a water tank. The results reveal that the mass of the air dissolved in water in first 0.1s accounts for 97.5% of total mass determined by Henry's law. This means time of air dissolution is in the order of 0.1s. UWCAES systems are often used for long duration energy storage in the order of hours. The time of air dissolution is short enough to cause air loss in UWCAES systems.