Optimizing Subway HVAC Control Strategies for Energy Savings Using Dymola Simulation

Water distribution and pumping systems consume a large share of energy in metro HVAC operations and remain a major challenge to energy-efficient performance. This study, grounded in a practical metro project, investigates four control strategies for chilled water systems, focusing on chiller sequencing, pump frequency modulation, and variable flow regulation. A dynamic system model was developed using Dymola to simulate and evaluate the performance of each strategy. The results indicate that Strategy 2, which integrates real-time outdoor weather parameters into the frequency control logic, enhances operational stability and maintainability while achieving a 4.42% reduction in total energy consumption compared to the baseline. Strategy 4 employs a genetic algorithm to optimize chiller load distribution, resulting in improved system efficiency and energy savings of up to 8.62%. Further analysis reveals that chillers account for approximately 80% of the system’s total energy consumption, underscoring their central importance in system-wide energy optimization. Additionally, cooling towers show significant energy-saving potential under low wet-bulb temperatures. A 1 °C decrease in wet-bulb temperature results in an estimated 7% reduction in energy use. These findings offer quantitative insights and practical guidance for the low-carbon optimization of metro chilled water systems.