Abstract
To enhance the energy performance of a central air-conditioning system, an effective control method for the chilled water system is always essential. However, it is a real challenge to distribute exact cooling energy to multiple terminal units in different floors via a complex chilled water network. To mitigate hydraulic imbalance in a complex chilled water system, many throttle valves and variable-speed pumps are installed, which are usually regulated by PID-based controllers. Due to the severe hydraulic coupling among the valves and pumps, the hydraulic oscillation phenomena often occur while using those feedback-based controllers. Based on a data-calibrated water distribution model which can accurately predict the hydraulic behaviors of a chilled water system, a new Model Predictive Control (MPC) method is proposed in this study. The proposed method is validated by a real-life chilled water system in a 22-floor hotel. By the proposed method, the valves and pumps can be regulated safely without any hydraulic oscillations. Simultaneously, the hydraulic imbalance among different floors is also eliminated, which can save 23.3% electricity consumption of the pumps.
Highlights
The energy consumptions in the buildings sector account for almost 40% of the total final energy consumption [1,2]
Research on the Model Predictive Control (MPC) method has attracted a lot of attention in the past few years due to its many advantages, such as: performing anticipatory control instead of corrective control [7] and ability to deal with constraints and uncertainties [8]
With the help of the automation system and information technologies, the dynamic hydraulic balance was achieved without any hydraulic oscillations in the tested chilled water system
Summary
The energy consumptions in the buildings sector account for almost 40% of the total final energy consumption [1,2]. The contributions are mainly in two aspects: (1) A new MPC method is proposed to achieve the dynamic hydraulic balance for the chilled water distribution system In this procedure, a system model is developed with considering the hydraulic characteristics of the chillers, terminal units, throttle valves, pumps and pipe network in detail. An optimization model using a GA algorithm is presented to provide the calibrated parameters for the system model; (2) two types of MPC-based controllers at the local level are elaborately designed for adjustments of throttle valve and variable-speed pump, respectively. Instead of those PID-based controllers, the local MPC-based controllers can work more smoothly with the supervisory MPC platform. With the help of the automation system and information technologies, the dynamic hydraulic balance was achieved without any hydraulic oscillations in the tested chilled water system
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