JPH0214997B

PURPOSE:To improve the coefficient of result of a device, by controlling the capacity of a compressor so as to hold a water turbine to a fixed speed, when the water turbine is operated within the range of a quantity of supply water smaller than the rated quantity of supply water. CONSTITUTION:Normally a signal of a speed adjusting meter 12 and a water turbine-guide valve potentiometer 14 of a water turbine 5 controls a water turbine-guide valve servo motor 13 so as to adjust a quantity of water and hold the water turbine 5 to its rated speed. Then the quantity of water, when it is in a range smaller than the rated quantity of water decreasing a speed of the water turbine 5, is detected from a water level in a storage water tank 17, and a slide valve-controlling solenoid operated valve 6 of a compressor 1 is controlled in accordance with a signal of the water level so as to reduce a load of the compressor 1, preventing the speed of the water turbine 5 from decreasing, thus holding the speed to a fixed value.