The energy consumed by data centers accounts for about 1.4% of global electric power consumption, and the accumulated electric power consumption by 111 domestic data centers is about 2.6 billion KWh or approximately 36% of the power generated by one unit of nuclear power plant (7 billion KWh). Therefore, data centers are compared to hippos eating electric power, and reduction of cooling energy (40% of power consumed by data centers) emerges as an important factor in national policies in relation to computing and data centers.

Moreover, demand for data centers is rapidly increased by the explosion of volume of information and concentration of information resources in data centers caused by the rapid conversion into cloud computing and big data environment.

Accordingly, the technology for enhancing the efficiency of cooling system to cool large-capacity, high-density servers and the application of various cooling systems using outdoor air are required.