| Optimizing the design of air-conditioning chiller plants and developing adjustment methods of chiller plants operation parameters are the important ways to reduce the energy consumption of air-conditioning system.It is of great significance for China to achieve carbon peak and carbon neutral strategic goals.Compared to the conventional chiller plants without using natural cooling,the water-side economizer(WSE)system integrated with chiller plants can significantly reduce the energy consumption of the air-conditioning system through the usage of natural cooling sources.The current chiller plants integrated WSE system has some limitations in terms of control performance analysis and system operating parameter adjustment: the energy consumption characteristics of the chiller plant integrated WSE system are not clear;the conventional chiller plant simulation model is difficult to capture the operation event status and control transient of parameters,it is also difficult to systematically evaluate the control performance of WSE in various configuration scenarios;the adjustment method of WSE system operating parameters is mainly based on engineering experience,and insufficient consideration of the overall energy consumption optimization of the chiller plant.Based on these limitations,this paper has carried out the research on modeling simulation and optimal control of the chiller plant integrated WSE system.The main research contents and results are as follows:(1)The chiller plant integrated with WSE system model and control model were established by using the equation-based Modelica language,and a complete simulation platform was built by coupling these two models.The accuracy of the chiller plant model was verified through experiments data.In order to demonstrate the flexibility of the simulation platform in evaluating the control performance of the chiller plant integrated with WSE system.The 40 system scenarios were studied,including 2 system configurations,2 WSE operating mode control strategies,2 load types,and 5 typical climate zones.The simulation results show that chiller plant models can reflect the dynamic physical characteristics of the equipment,and capture the transient characteristics of the parameters during the operation of the system.The main operation control parameters of chiller plants,such as chilled water supply temperature,condenser water supply temperature,and indoor air supply temperature,can meet the design values most of the time.But there still is fluctuation within ±2°C.The fluctuation is caused by system control mode conversion or device switching,and the fluctuation time is usually within 320 seconds.(2)Two types of operation mode control models were established for the WSE system,namely CWST-based control and CHWST-based control.The above two control models can adjust the operating modes of the individual equipment during the WSE operation,and reduce the operating energy consumption of chiller plants by reducing chillers running time and cooling load.The case simulation results show that the WSE system can obtain a significant energy savings with two operating mode control strategies.Compared with the conventional chiller plant,the WSE system can significantly reduce the running time of chillers in cold climates,but has limited impact on the running time of chillers in warm and hot climates.For example,the series WSE system under constant cooling load can reduce the operating time of chillers in Harbin and Beijing by 47.4% and 31.7%,and reduce the energy consumption of chiller plants by 50% and 37.4%;for warm climates such as Kunming and Guangzhou,the WSE system can reduce the energy consumption of chiller plants by 16.3% and 6.7% through reducing the return temperature of the chilled water.(3)The changes characteristics of chiller plants integrated with WSE system in terms of energy efficiency and operating economy were analyzed.40 WSE system cases show that: the cooling energy efficiency ratio(EER)of chiller plants has a strong relationship with climates.The EER of chiller plants gradually decreases from 11.5 to 6.3 from cold to hot and humid climates under constant load.The EER varies from 13.2 to 8.1 under variable load.The operating economy of chiller plants is not only related to energy consumption,but also affected by area peak-to-valley electricity prices.For example,the energy consumption of the parallel WSE system under constant load in Kunming is 88.6% of Guangzhou,but due to the lower peak-to-valley price of the former,the annual operating cost of chiller plants is only55.1% of Guangzhou.(4)Developed model predictive control technology to realize the real-time optimization and adjustment of the operating parameters for chiller plants integrated with WSE system.Based on the goal of optimal energy consumption in chiller plants,a mathematical model of energy consumption optimization in chiller plants is established,and the operating parameters of chiller plants are optimized and adjusted time by time using genetic algorithm and load prediction technology.The continuous optimization method of operation parameters was proposed,which solved the problem of initializing parameter value during model predictive control optimization.The optimization results show that,the optimized EER of chiller plants can reach more than 6.9,improved by more than 9.7% compared to without optimization.The use of model predictive control optimization to adjust the control parameters of chiller plants in advance to keep the optimal operating status is of great significance for improving the energy efficiency of chiller plants and reducing the energy consumption and carbon emissions of the building. |
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