Effect of climate conditions on the thermodynamic performance of a data center cooling system under water-side economization

Abstract

This paper evaluates the potential of water-side economizers in the refrigeration system of data centers under different climate conditions. Due to the wide range of conditions along the country (Desert, Mediterranean, Temperate rainy and Tundra climate), Chile is selected as case study. The number of hours per year in which economization is possible is estimated using the data base of 22 weather stations along the country. The refrigeration system is modeled in steady state through a set of thermodynamic equations simultaneously solved using the Engineering Equation Solver (EES). The system performance is evaluated by calculating the Coefficient of Performance (COP) and the Water to Energy Ratio (WER). The latter is a new metric proposed to compare the volume of water required by the system to save 1 MWh of cooling energy. The thermodynamic analysis shows that the chiller decreases its energy usage if water-side economizers are implemented in favorable climates such as cool-summer Mediterranean with winter rain (Csc), temperate rainy (Cfb) and tundra (ET) climates. Here, the use of economizers allows a monthly increase in the COP of 50 to 120% (compared to the conventional operation) and an annual average COP ranging from 7.8 to 9.7. These climates also offer an additional gain of lower water requirements, with annual WER values ranging from 11 to 17 m3/MWh. Desert climates, on the other hand, prevent implementing economizers, offering the lowest annual average COP values (5.6–5.7). In climates in which the complete economization is impossible, the partial use of economizers allows a monthly increase in the COP of 10 to 45%. The costal influence decreases the system performance, reducing the COP and increasing the WER.