that the intermediate heat transfer medium heater can be reduced in size and also the direct contact heat exchanger can be reduced in size because direct contact heat exchange is effected between the intermediate heat transfer medium and the turbine operating medium additionally said intermediate heat transfer medium can be used as the lubricant for the bearings of the turbine and generator so that decrease in the capacity of lubrication can be prevented in addition to the above the condensate of turbine operating medium can be used for cooling the intermediate heat transfer medium used for the lubrication of the bearings and the turbine operating medium can be preheated so that the production of gaseous turbine operating medium is facilitated in the direct contact heat exchanger and the direct contact heat exchanger can be reduced in size further detailed description will hereunder be given of the direct contact heat exchanger 10 with reference to fig3 the intermediate heat transfer medium which has been heated by the intermediate heat transfer medium heater 8 shown in fig2 enters the intermediate heat transfer medium tank 51 through the intermediate heat transfer medium inlet 9 shown in fig3 where it gives heat to the turbine operating medium which has been blown out from the turbine operating medium nozzle 52 and upon vaporizing the turbine operating medium flows out of the intermediate heat transfer medium outlet 25 on the other hand the gaseous turbine operating medium which has been vaporized in the intermediate heat transfer medium tank 51 passes through a demister 54 and upon the removal of liquid droplets included therein flows out of the gaseous turbine operating medium outlet 53 next description will be given of the control unit shown.