Distributed load regulation strategy for enhancing energy efficiency of chiller plants

Chiller plants exhibit high Coefficients of Performance (COPs) only within narrow favorable bands of Part-Load Ratios (PLRs), while time-varying building cooling demand often drives operation outside these bands. To address this, chiller plant load regulation becomes essential, which aims to keep the chiller plant operating within the favorable range without disrupting the building's cooling demand through artificially increasing or decreasing chiller load. This process necessitates the use of thermal energy storage (TES), normally latent heat thermal energy storage (LHTES). LHTES units are typically integrated centrally, connecting to the chiller water supply/return head pipes and operating in parallel with air-handling units (AHUs). Unlike centralized TES charged/discharged by chilled-water supply/return, where the available temperature difference is typically below 5 °C, each AHU-level LHTES charges with chilled supply water (5–10°C) and discharges to warm inlet air (>25°C), ensuring higher charge/discharge rates and improved storage effectiveness. We formulate load regulation as a constrained nonlinear optimization that determines AHU-level charging/discharging power based on the chiller COP–PLR curve, LHTES constraints, and predicted AHU loads. A regulation algorithm for this distributed load regulation strategy is developed. Case studies demonstrate that the strategy narrows the operating PLR band, improves the minimum COP from 7.21 to 8.35 in Case 1 and from 6.17 to 8.53 in Case 2, and reduces daily chiller energy consumption by 11.15% and 9.86%, respectively, depending on the degree of load synchrony across zones. These results indicate that distributed LHTES can effectively regulate chiller loading to sustain high COP and deliver meaningful energy savings with minimal impact on cooling service. © 2026 Elsevier Ltd