An energy storage process comprising - an energy storage step wherein air is sucked in at the inlet (1.1) of a one-or more-stage compressor, its pressure is increased to a value higher than ambient pressure, the air is liquefied by isenthalpic expansion and fed into a thermally insulated storage tank, the cold air vapor produced during the air liquefaction process being fed back to the inlet (1.1) of the compressor through at least one counterflow heat exchanger that allows heat exchange of the compressed air with the cold vapor behind the at least one stage of the compressor, the compressed air being divided into two partial flows after the counterflow heat exchanger, and the second mass flow being routed through a liquefaction-expansion turbine, and the energy obtained in the liquefaction-expansion turbine being fed to the compressor, the first mass flow being cooled by means of a Claude heat exchanger by the second mass flow exiting from the liquefaction-expansion turbine and the other cold vapor produced during the air liquefaction process, - and an energy removal step, in which the liquid air is removed from the storage tank and regasified, wherein the air pressure is increased by means of a pump and/or by means of thermal compression and then the air temperature is increased to at least the ambient temperature, the compressed air produced in this way driving a main turbine, characterized in that the temperature level of the liquid air removed from the storage tank is additionally used to condense a low-boiling coolant at the lowest stage of a one- or more-stage Rankine cycle process, the energy produced in the Rankine cycle process being brought together with the energy produced in the main turbine. - an energy storage step wherein air is sucked in at the inlet (1.1) of a one-or more-stage compressor, its pressure is increased to a value higher than ambient pressure, the air is liquefied by isenthalpic expansion and fed into a thermally insulated storage tank, the cold air vapor produced during the air liquefaction process being fed back to the inlet (1.1) of the compressor through at least one counterflow heat exchanger that allows heat exchange of the compressed air with the cold vapor behind the at least one stage of the compressor, the compressed air being divided into two partial flows after the counterflow heat exchanger, and the second mass flow being routed through a liquefaction-expansion turbine, and the energy obtained in the liquefaction-expansion turbine being fed to the compressor, the first mass flow being cooled by means of a Claude heat exchanger by the second mass flow exiting from the liquefaction-expansion turbine and the other cold vapor produced during the air liquefaction process, - and an energy removal step, in which the liquid air is removed from the storage tank and regasified, wherein the air pressure is increased by means of a pump and/or by means of thermal compression and then the air temperature is increased to at least the ambient temperature, the compressed air produced in this way driving a main turbine, characterized in that the temperature level of the liquid air removed from the storage tank is additionally used to condense a low-boiling coolant at the lowest stage of a one- or more-stage Rankine cycle process, the energy produced in the Rankine cycle process being brought together with the energy produced in the main turbine.