A device is provided comprising an expansion machine for generating mechanical energy by expanding vapor of a working medium; a generator connected to a shaft of the expansion machine and used for generating electric energy from mechanical energy of the expansion machine; wherein the expansion machine and the generator form a structural unit with an exhaust vapor chamber between the expansion machine and the generator, and wherein, when the expansion machine is in operation, working medium expanded into the exhaust vapor chamber contacts the generator; and means for feeding, in particular injecting, a liquid working medium into the exhaust vapor chamber. Also provided is an ORC device comprising the device and a method for operating the device.