Packaged air conditioner incorporating free cooling cycle for data centers

Aiming to improve energy saving in regard to data centers, the authors have developed a high-efficiency air conditioner for use in data centers. In consideration of application to data centers, which are considered “mission-critical” facilities, development of air conditioners using a refrigerant - which have no effect on ICT equipment even in the event of leakage - has been continuing. A key feature of air conditioners for data centers is that they must provide sufficient cooling all year round, to handle the huge amount of heat generated by ICT equipment, and this is the key to energy saving. Given those circumstances, by improving compression efficiency in regard to outside environments in the low- to mid-temperature range and expanding the operational range at low pressure ratio, the authors developed a high-efficiency air conditioner [1]. Aiming to further reduce electrical power consumption, the authors developed an air conditioner whose pump cycle is juxtaposed on the conventional compression cycle. In more concrete terms, the pump cycle is configured so that low-temperature outside air (hereafter, “cold”) is imported into the refrigeration cycle via a heat exchanger (HEX) inside an outdoor unit. In the HEX, the cold is transferred to a refrigerant, which carries it into a computer room by means of a refrigerant pump. As one kind of indirect outside-air cooling method, this configuration does not degrade the quality of the air inside the computer room. Since the refrigerant pump (which consumes less power than the compressor) works when the outside air temperature is low, energy consumption is significantly reduced. In comparison with conventional air conditioners, the developed air conditioner can reduce annual power consumption by 54%, 50%, and 38% in the cases of Sapporo (Japan), New York (USA), and Austen (Texas, USA), respectively. We are sure that it will significantly contribute to reducing energy consumption of air conditioners used for data centers.