The present disclosure concerns liquid ring systems, including (i) a fixed or rotating casing adapted to contain a liquid, (ii) a rotor located within the casing and having at least one impeller, (iii) a liquid ring formed by rotation of the rotor or the casing, and (iv) a plurality of gas cells formed between the inner surface of the liquid ring and vanes of the impeller. For example, at least one compressing gas cell is in fluid connection with at least one expanding gas cell integrated with the rotor. A liquid valve may include a small gas cell with a reciprocating liquid surface and at least two fluid connections having a free pathway between the connections during an angle of rotation of the rotor and a closed pathway between the connections during 360° minus the angle of rotation.