An object of the invention is to minimize energy loss to be generated at a driving shaft and a shaft seal device, when an electric rotating device is driven by an expansion-and-compressor device. According to a feature of the invention, a first driving shaft is rotationally supported by a housing and transmits a driving force from an engine to a second shaft of the expansion-and-compressor device, wherein a shaft seal device is provided on the first driving shaft for air-tightly sealing the inside of the housing from the outside of the housing. A power transmission control device (electromagnetic clutch or one way clutch) is operatively provided in a path between the first driving shaft and the second shaft, so that power transmission from the second shaft to the first driving shaft is cut off, to suppress any energy loss to be generated between the first driving shaft and the shaft seal device.