Research On Low Energy Consumption Of Central Air-conditioning Cooling Water System Based On High-efficiency Machine Room

With the development of social economy and technology,people pay more and more attention to the comfort of building environment.The central air-conditioning system,as an important system for improving the comfort of the building environment,requires a huge amount of energy,accounting for about 60% of the building's energy consumption.Because the air-conditioning system is designed and selected according to the most unfavorable conditions in the design stage,but the air-conditioning system operates under partial load conditions most of the time in the operation stage,which results in the current situation of high energy consumption and waste of resources in the central air-conditioning system.Therefore,improving the energy utilization rate of the air conditioning and refrigeration system and building a high-efficiency air-conditioning machine room are crucial for achieving energy saving in buildings.Guangdong Province first issued the " Standard for energy efficiency measurement and assessment on chiller plant systems in centralized air conditioning systems ",which provides an executive standard for the design and transformation of high-efficiency air conditioning room.As the most complex part of the central air-conditioning system,the cooling water system greatly affects the energy consumption of the whole air conditioning system.Therefore,the optimization of energy-saving control of cooling water system has become the key to reduce the energy consumption of air conditioning system.In this paper,DeST software is used to simulate and calculate the hourly distribution of air-conditioning cooling load of a shopping mall building in Yantai during the cooling season and divide the load rate range.Through the load time frequency,it is determined that the working time of 51.7% in the cooling season is at the load rate of 10%~40%,which verifies the necessity of exploring the optimal operation of the air conditioning system under partial load.In this paper,the energy consumption mathematical model of the cooling water system equipment,including chiller,cooling water pump and cooling tower,is established based on the operation records of the air conditioning system equipment and the experimental data of the equipment manufacturer in a commercial building in Yantai.By using the mixed penalty function optimization algorithm,the optimal operation scheme of the same type and different type of chillers under different load rates is obtained.In the design and selection stage and actual operation stage of chillers,attention should be paid to how to make the chillers operate efficiently in the low load rate range.Variable flow operation of cooling water is an important measure for energy saving operation of cooling water system,Variable flow operation of cooling water is an important measure for energy-saving operation of cooling water system.In this paper,the equipment and total energy consumption of constant temperature and variable flow cooling water system and variable temperature and variable flow cooling water system are compared: the whole cooling season of constant temperature and variable flow cooling water system saves about 64000 kwh of energy compared with variable temperature and variable flow cooling water system.The energy consumption of chiller in constant temperature and variable flow cooling water system is significantly lower than that in variable temperature and variable flow cooling water system.However,the energy consumption of cooling water pump and cooling tower is slightly increased.By comparing the energy consumption of the cooling water system with constant temperature and variable flow in each load interval,the optimal group control operation scheme of the cooling water system is obtained: when the load rate is 100%~80%,the variable temperature and variable flow cooling water optimal control system is adopted;when the load rate is 80%~5%,the variable temperature and variable flow cooling water optimal control system is used.Taking a shopping mall building in Yantai as an example,the paper compares and analyzes the energy consumption of the existing cooling water control mode and the optimized cooling water control mode.It is obtained that: under the optimized control mode,the chiller can save 120,000 kWh and the energy saving rate 22.6%;the cooling water pump can save 21,000 kwh and the energy saving rate 22.6%;cooling tower energy saving of 21,000 kWh,energy saving rate of 36.9%;total system energy consumption of 162,000 kWh,energy saving rate of 23.9%.