Apparatus and method for eliminating champagne effect in compressed air energy storage systems

In a compressed air energy storage system, said storage system including a reservoir of water at ground level, an underground storage cavern and a fluid path connecting the cavern and the reservoir, apparatus for providing a continuous hydrostatic head on the water in the cavern by controlling the flow of bubbles forming in the water along the fluid path, the apparatus comprising:

• a generally vertical hydraulic compensating shaft in said fluid path along which the bubbles form and having a central axis and an upper end fluidly communicating with the reservoir;
• means for fluidly coupling a lower portion of said shaft to said cavern;
• a plurality of vanes mounted to the inner surface of said shaft configured to induce movement of the air bubble and water mixture in a direction of rotation as the air bubbles rise in said shaft for concentrating the air bubbles along the axis of said shaft;
• at least one nozzle disposed adjacent an inner surface of said shaft at a discharge level, said nozzle being adapted to cause water forced therethrough to enter said shaft in said direction of rotation thereby forcing the bubbles to collect along the axis of said shaft;
• and
• said fluid path including a water intake port within said reservoir, said shaft having an opening at an entry level located above the discharge level, and a water intake path fluidly connecting said intake port and said opening in said shaft to provide a substantially bubble free column of water in the fluid path above the entry level.