The energy density of hydraulic drive trains is inferior in comparison to electrical and mechanical systems. A solution to this problem is to improve the energy storage density by storing potential and rotating kinetic energy in a flywheel-accumulator. A flywheel-accumulator is a cylindrical pressure vessel with oil and gas volumes separated by a piston that is rotated about a central axis. A low-energy prototype was created and tested to verify an increase in energy density and to validate that a parabolic pressure distribution exists on the oil side due to centripetal acceleration. If an increase in energy density is proven, the flywheel-accumulator has the potential to revolutionize compact hydraulic energy storage
