In a power generation unit, especially in a gasturbo group, a gaseous process fluid is guided in a closed cycle. The gaseous process fluid flows through a
compression device (1), a heater (6) and an expansion device (2), especially a
turbine. Downstream from the expansion device at least one
heat sink (11, 13) is arranged in which the gaseous process fluid is cooled before it is returned to the compressor device (1). At least one
heat sink includes a
waste heat steam generator in which an overheated amount of steam (26) is generated that is added to the compressed gaseous process fluid. Together with the gaseous process fluid the steam flows through the heater (6) if necessary and is expanded together with it. The expanded steam condenses in the
waste heat steam generator (11) and another
heat sink (13); the condensate is processed in a filter (16) and is returned to the
waste heat steam generator (11) under pressure via a
feed pump (18). Due to the closed process any kind of process fluid and process filling for controlling performance can be used.