Model-based Optimal Control for a Water-side Economizer System in a Data Center

Abstract

Economizers play an important role in reducing the cooling energy in data centers. They are generally combined with chillers since it is difficult for economizers to meet the cooling demand throughout a year. To achieve energy-efficient operation in such hybrid systems, it is crucial to switch between operational modes and allocate the proper cooling load to the subsystems according to the outdoor conditions and cooling demand. This study aims to optimize the operation of a water-side economizer system functioning in a cold climate. A simple semi-optimal control was realized by adjusting the control setpoints using polynomial regression equations that represent the relationship between boundary conditions and optimal setpoints based on simulation-based optimization results. The operational data showed that the use of the semi-optimal control resulted in an increase in the system efficiency from 7.5 to 13.2. Additionally, the results suggest the importance of optimizing the cooling load allocation to the subsystems by leveraging the cooling potential of outdoor air while avoiding inefficient operation.