Power usage effectiveness analysis of a liquid-pump-driven hybrid cooling system for data centers in subclimate zones

Free cooling technology can effectively reduce the cooling energy consumption of data centers, but its energy efficiency is greatly affected by regional and meteorological conditions. This study investigates the liquid-pumpdriven free cooling/mechanical refrigeration hybrid cooling system of a data center with 40 racks through a demonstration case and tests. The annual hourly energy efficiency in 20 subclimate zones and 37 typical cities in China of the hybrid cooling system designed with 5 and 10 degrees C temperature differences was analyzed with different meteorological parameters. The annual power usage effectiveness (PUE) values corresponding to the energy efficiency ratio (EER) in different regions were presented. Results showed that the annual average EER of the liquid-pump-driven free cooling mode was 7.07-14.18, and the annual average EER of the hybrid system was 4.22-14.10 when the temperature difference was 5 degrees C. The annual average EER range and the design temperature difference of the hybrid system for different climate regions were recommended. The PUE values of other regions, except for Guangzhou and Haikou, were lower than 1.40. The results provide references for the EER and PUE of the hybrid system in different climate regions.