Abstract:
A hydraulic actuator (200) adapted to be coupled to one or more pistons of a compressed air energy storage (CAES) system includes a housing (205) forming a plurality of aligned bores (220a-220c), with a shaft (250) disposed therein for reciprocating movement. For a three bore configuration, the shaft has three pistons (250 230a-230c) subdividing the three bores into six pressure chambers (260a-260f). Four valves (270a-270d) fluidically connected to the six chambers selectively provide pressurized hydraulic fluid, permitting three levels of hydraulic shaft force for each direction of shaft motion.