Patent ID: 8646284

Claim:
A heat-source system comprising: a centrifugal-chiller including a centrifugal-compressor driven by electricity and having a variable rotational frequency, the centrifugal-compressor compressing refrigerant, a condenser that condenses the refrigerant compressed by the centrifugal-compressor into liquid, an expansion valve that expands the refrigerant condensed into liquid by the condenser, and an evaporator that evaporates the refrigerant expanded by the expansion valve; a cooling-water pump driven by electricity that supplies cooling water for cooling the refrigerant by heat exchange in the condenser; a cooling tower that cools the cooling water guided from the condenser by the cooling-water pump by bringing the cooling water into contact with the outside air to perform heat exchange; a cooling-tower fan driven by electricity and provided on the cooling tower, the cooling-tower fan introducing the outside air into the cooling tower; a chilled-water pump driven by electricity that supplies the chilled water cooled by the heat exchange in the evaporator to an external load side; and a control unit that controls the centrifugal-chiller, the cooling-water pump, the cooling tower, the cooling-tower fan, and the chilled-water pump, wherein a plurality of the centrifugal-chillers are provided, a plurality of the cooling towers are provided so as to have a cooling-tower capacity corresponding to the total capacity of the rated capacities of the respective centrifugal-chillers, the cooling towers being commonly connected to the plurality of centrifugal-chillers, the control unit can change the number of cooling towers to be operated so that the cooling-tower capacity can be changed, the control unit preliminarily stores an optimum cooling-tower capacity relationship representing the cooling-tower capacity of the cooling towers with which the heat-source system efficiency, taking into consideration the centrifugal-chillers, the cooling-water pump, the cooling towers, the cooling-tower fan, and the chilled-water pump, is higher, in relation to the outside-air wet-bulb temperature and the centrifugal-chiller partial load factor, and the control unit determines the number of cooling towers to be operated by referring to the optimum cooling-tower capacity relationship, on the basis of the outside-air wet-bulb temperature and the partial load factor of the centrifugal-chillers during operation.