Study On The Optimization Of Energy-saving Operation Of Central Air-conditioning System In An Office Building In Shenzhen

With the rising severity of the energy situation and the increasing prominence of energy consumption in Chinese public buildings,the issue of energy efficiency in large public buildings is constantly being emphasized and given more attention.The energy consumption of central air-conditioning systems account for a large proportion of the total energy consumption of public buildings in China,and there are many problems related to energy wastage in the daily operation process.The energy consumption of the water chiller accounts for a large proportion of the overall system operation,so it is important to carry out energy-saving optimization studies on the operation of the water chiller.The research object of this paper is the central air-conditioning system of an office building in Shenzhen.Mathematical models of the impedance of the water chiller,pumps,cooling towers and pipe network was established by using the measured operational data of the central air-conditioning system and their accuracy was verified.Then,a dynamic load model was established in the De ST and calculated the building hour-by-hour load data.The programming source code of water chiller model was imported into the TRNSYS to develop the magnetic bearing water chiller module-Type200.The variable-speed pumps,cooling towers and other auxiliary modules were built using the modules included in TRNSYS.Finally,the hour-by-hour load data of the office building was imported into the TRNSYS load reading module and the modules were linked and the operating parameters were set to establish a central air-conditioning system operation simulation platform.The TRNBuild software was also used to model the most disadvantaged rooms in the office building and verifies the accuracy of the model,then linked to the TRNSYS-based central air-conditioning operation system simulation platform to established an indoor thermal comfort-Integrated operation simulation platform for central air-conditioning systemsThe data from the magnetic bearing water chiller operation was analyzed and the best energy efficiency ratio operating point for the magnetic bearing water chiller was found to be at 27.7% of the load factor,rather than near the rated operating point.The existing start-stop strategy for the central air-conditioning system in the building was also analyzed and found that unreasonable.Three operation control schemes of chilled water supply temperature for magnetic bearing water chiller that were building load factor control,dry bulb temperature control and air enthalpy control were proposed because of the impact of energy efficiency and necessary of chilled water supply temperature on central air-conditioning system。The system was optimized by means of the simulation platform for central air-conditioning systems.TRNSYS-Gen Opt software was used to optimize the control strategy for different chilled water supply temperatures by using a particle swarm optimization and it was found the results that k2,k3,k4 was increased with growing chilled water supply temperature.Three variable chilled water control schemes were optimized by using the indoor thermal comfort-central air-conditioning system integrated operation simulation platform.The optimization results show that the scheme with the best energy saving effect is the variable chilled water temperature control scheme based on the enthalpy of outdoor air.After applying the outdoor air enthalpy-based variable chilled water temperature control scheme and the optimized start-stop strategy,the total energy consumption of the system is 970,754 k Wh,compared to the measured energy consumption of 1281655 k Wh,and the energy saving rate is 24.26%.Using the operating conditions of the central air-conditioning system on 23 September 2019 as a background,the system operation after applying the integrated optimization scheme is analysed by means of the indoor thermal comfort-central air-conditioning system integrated operation simulation platform,and the results show that the integrated optimization scheme has good feasibility and energy efficiency.