Robust enhancement of chiller sequencing control for tolerating sensor measurement uncertainties through controlling small-scale thermal energy storage

Reliable chiller sequencing control strategy is crucial to enhancing control robustness and energy efficiency of the multiple-chiller systems. However, the commonly used conventional chiller sequencing control strategy, which determines the chiller stage by comparing the measurement instantaneous cooling load with the chiller's cooling capacity, often deviate significantly from its desired results due to the presence of measurement uncertainties. Different from the existing solutions focusing on improving the accuracy of measured cooling load using complicated models fed with large amounts of measurement information, this study presents a novel solution from a new perspective, tolerating rather than dealing with measurement uncertainties directly through introducing and controlling a small-scale thermal energy storage integrated with the chiller plant. Two schemes, namely robustness-enhancement scheme and chiller operating efficiency enhancement scheme, were developed and collaboratively utilized to achieve two objectives simultaneously: enhancing the robustness of the sequencing control and improving the operating efficiency of chillers even under measurement uncertainties. The results of case studies demonstrate that, compared with the conventional strategy, the proposed strategy can reduce the switching frequency by up to 77.42% as well as save the total energy use of chilled water systems by up to 4.44% without sacrificing indoor thermal comfort. © 2023 Elsevier Ltd.