To cool a large-sized refrigerator through heat exchanging with a heat exchanger and to enable a strong farce to be applied to a turbine for use in driving a generator by a method wherein fluid of supplied liquefied natural gas is received at the heat exchanger and the liquid flowed from the heat exchanger is utilized divededly for a cooling operation and for the generator. SOLUTION: Fluid of liquefied natural gas supplied through a liquefied natural gas liquid feeding pipe 1 is received at a heat exchanger 3 and then fluid flowed from the exchanger 3 is utilized dividedly for a cooling operation and for a power generating operation. Fluid is flowed out of the heat exchanger 3 under its pressure reduced condition and then the fluid is completely changed into gas by a heat exchanger 17 such vaporizer or the like, the fluid completely gasified is utilized to drive a turbine and a generator 20 is operated to generate electricity. Then, heat contained in the exhaust gas of an engine generated under an operation of the generator 20 is recovered and then an air conditioning in cooling or heating carried out under utilization of heat recovered by an absorbing type cold water or hot water generation machine 29 and energy of cold heat.