In a method for operating a combination of a gas turbine process and a steam turbine process, in which the superimposed boosted gas turbine process is operated with compressed air and a combustible fluid, and the steam turbine process is operated via a fluidized bed furnace with a carbonaceous solid fuel, whereby the combustion in the fluidized bed furnace is performed with the oxygen-containing exhaust gases of the superimposed gas turbine process and electrical energy is generated with both processes, the efficiency is increased by expanding the exhaust gases of the superimposed gas turbine process only to an extent to which the fluidized bed furnace is operable as a pressurized fluidized bed and subjecting the exhaust gases of the pressurized fluidized bed furnace, after removing solid particles, to a second gas turbine process for further expansion and then to a heat exchange with the compressed air of the superimposed gas turbine process; the air for the superimposed gas turbine process is subjected to a two-stage compression with recooling, whereby the compressing energy for the first stage is derived from the second gas turbine process and the compressing energy for the second stage is derived from the superimposed gas turbine process.