Development of a thermal storage combined water-side economizer system: Enhancing cooling energy reduction in data centers through expanded free cooling performance

Abstract

A thermal energy storage (TES) is utilized for emergency cooling (EC), while a water-side economizer (WSE) system is applied for free cooling in data centers, with each serving distinct purposes. These systems play a pivotal role in enhancing cooling operation reliability and reducing cooling energy consumption. However, their application methods and effects remain limited. Therefore, this study proposes a novel system that combines a WSE system, which reduces chiller energy consumption by utilizing low-temperature outdoor air, with a TES, which charges a chilled heat source at night for use during the day, thereby improving the energy efficiency of cooling systems. Additionally, an on/off control algorithm was developed and implemented to enable the TES to charge and discharge thermal energy solely through free cooling, thereby evaluating its energy reduction potential. As a result, the free cooling operation rate was increased by 39.7 percentage points during intermediate and winter seasons, achieving reductions of 34 % in chiller energy consumption and 13 % in cooling tower energy consumption, which led to an overall 27 % reduction in cooling energy consumption for the designated data center.