The invention relates to a device comprising an expansion machine for generating mechanical energy by expanding the steam in a working medium; a generator which is connected to a shaft of the expansion machine and which is used to generate electric energy from mechanical energy of the expansion machine. Said expansion machine and the generator form a structural unit together with a waste stream chamber between the expansion machine and the generator, and when the expansion machine is in operation, the working medium expanded in the waste steam chamber contacts the generator; and means for guiding, in particular for injecting, a liquid working medium into the waste steam chamber. The invention also relates to an ORC device comprising the claimed device and to a method for operating the claimed device.