Energy Efficiency Analysis Of Central Air Conditioning Cooling Water System

The shortage of resources has always been a serious problem facing our country.Today,with the rapid development of economy,the sharp increase in the number of large public buildings leads to the increasing proportion of building energy consumption in the total energy consumption of society.Central air conditioning is an integral part of large public buildings,and its energy consumption accounts for more than 60% of building energy consumption.However,due to the immaturity of the control technology of central air conditioning system and the imperfection of the optimization method of operation parameters,unnecessary waste is caused in the operation process,so there is still a lot of room for energy saving of central air conditioning system.The cooling water system is a significant part of the central air conditioning system,and its optimized operation has a great impact on the energy consumption of the entire system.Therefore,in order to achieve energy-saving control of central air-conditioning system,the first task is to do a good job in energy-saving optimization of cooling water system.Based on the operation data of the central air conditioning cooling water system in a large shopping mall in Shenzhen,this thesis establishes and validates the mathematical models of chillers,cooling towers and cooling water pumps by analyzing the operation principles and characteristics of each component of the cooling water system.Then,using TRNSYS software,self-defined modules are built according to the mathematical model of each component,and embedded in MATLAB module.Through linking these modules and TRNSYS self-contained modules,a dynamic simulation platform for central air conditioning cooling water system is constructed,and the accuracy of the platform is verified by the measured data.Through the analysis of the operation characteristics of each part of the cooling water system,it is found that the energy efficiency of chillers is mainly affected by the supply temperature of cooling water and the return temperature of cooling water.The higher the supply temperature of cooling water,the lower the return temperature of cooling water,and the higher the energy efficiency of chillers.The heat-sinking capability of cooling towers is more affected by air volume than by water volume.The energy-saving effect of synchronous frequency conversion operation of four cooling towers is better than that of synchronous frequency conversion operation of three cooling towers.The simulation platform of cooling water system proves that the variable air volume and variable water volume operation of cooling water system can save energy under partial cooling load.At the same time,it is found that the adjustment order of the air volume and the water flow rate of cooling tower also affects the energy saving effect.When the load rate of central air conditioning system is more than 70%,the priority regulation of cooling water flow can achieve better energy saving effect.Through the analysis of the operation parameters of cooling water system,the appropriate optimization parameters are selected,using the energy consumption model of each component to determine the objective function and constraint condition,thus the parameter optimization model of cooling water system is established.After comparing and analyzing the optimization algorithms,the genetic algorithm is selected to solve the parameter optimization model of cooling water system.Taking meteorological conditions and refrigeration capacity of water chiller as known conditions on a certain day,the energy consumption before and after parameter optimization is compared and analyzed by using the dynamic simulation platform of cooling water system.It is proved that the optimization of cooling water system parameters based on genetic algorithm can save 8.4% energy.