Method for generating electrical energy in a combined energy generation plant (100, 200) which comprises an air treatment unit and a power plant unit, wherein • in a first operating mode, in the air treatment unit, air is successively compressed, cooled and expanded and used for obtaining an air liquefaction product (LAIR), • in a second operating mode, in the air treatment unit, an air liquefaction product (LAIR) is vaporized or pseudo vaporized at superatmospheric pressure and used for obtaining electrical energy in the power plant unit, and • in a third operating mode, in the air treatment unit, air is compressed and used in the power plant unit for obtaining electrical energy, characterized in that • the air in the first operating mode is successively cooled in counterflow against a first liquid coolant and against a second liquid coolant in a heat-exchange system to which the first coolant is fed at a first temperature level and is taken off after heating to a second temperature level, and to which the second coolant is fed in part at a third temperature level and in part at a fourth temperature level and is taken off after heating to a fifth temperature level, • in that the air liquefaction product (LAIR) in the second operating mode is successively warmed in counterflow against the second coolant and against the first coolant in the heat-exchange system to which the second coolant is fed at the fifth temperature level and is taken off, after cooling, in part at the fourth temperature level and in part at the third temperature level, and to which the first coolant is fed at the second temperature level and is taken off after cooling at the first temperature level, • in that the air in the first operating mode is successively compressed from a first pressure level to a second pressure level, to a third pressure level and to a fourth pressure level, • in that the air liquefaction product (LAIR) is warmed in the second operating mode to a fifth pressure level that is beneath the fourth pressure level, and • in that the air is compressed in the third operating mode at a first fraction to the third pressure level and at a second fraction to the fourth pressure level, or the fifth pressure level, wherein the first fraction and the second fraction are introduced separately from one another into the power plant unit. • in a first operating mode, in the air treatment unit, air is successively compressed, cooled and expanded and used for obtaining an air liquefaction product (LAIR), • in a second operating mode, in the air treatment unit, an air liquefaction product (LAIR) is vaporized or pseudo vaporized at superatmospheric pressure and used for obtaining electrical energy in the power plant unit, and • in a third operating mode, in the air treatment unit, air is compressed and used in the power plant unit for obtaining electrical energy, • the air in the first operating mode is successively cooled in counterflow against a first liquid coolant and against a second liquid coolant in a heat-exchange system to which the first coolant is fed at a first temperature level and is taken off after heating to a second temperature level, and to which the second coolant is fed in part at a third temperature level and in part at a fourth temperature level and is taken off after heating to a fifth temperature level, • in that the air liquefaction product (LAIR) in the second operating mode is successively warmed in counterflow against the second coolant and against the first coolant in the heat-exchange system to which the second coolant is fed at the fifth temperature level and is taken off, after cooling, in part at the fourth temperature level and in part at the third temperature level, and to which the first coolant is fed at the second temperature level and is taken off after cooling at the first temperature level, • in that the air in the first operating mode is successively compressed from a first pressure level to a second pressure level, to a third pressure level and to a fourth pressure level, • in that the air liquefaction product (LAIR) is warmed in the second operating mode to a fifth pressure level that is beneath the fourth pressure level, and • in that the air is compressed in the third operating mode at a first fraction to the third pressure level and at a second fraction to the fourth pressure level, or the fifth pressure level, wherein the first fraction and the second fraction are introduced separately from one another into the power plant unit.