In a power generation plant having at least one gas turbine cycle with heat-recovery boiler (4) and at least one steam turbine cycle operated via the heat-recovery boiler (4), the gas turbine cycle being designed to be semi-closed and essentially free of emissions and essentially comprising a compressor (1), a combustion chamber (2) arranged downstream of the compressor (1), a gas turbine (3) arranged downstream of the combustion chamber (2), a heat-recovery boiler (4) arranged downstream of the gas turbine (3), and at least one generator (8) coupled to the gas turbine (3), modes of operation with the gas turbine cycle stopped and start-up using fresh air are made possible by first means (12) being arranged which alternatively or additionally allow hot gas to be fed into the hot-gas path (23) between gas turbine (3) and heat-recovery boiler (4), and by second means (15) being arranged which alternatively or additionally allow exhaust gas to be expelled from the exhaust-gas path (40) downstream of the heat-recovery boiler (4).