Central Air Conditioning Terminal Optimization Control Based On System Energy Efficiency

With continuous emergence of large buildings and universal application of central air-conditioning, the proportion of building energy consumption is more and more large, among which, central air-conditioning energy consumption accounts for about 50%～60%. Therefore, energy-saving control of central air-conditioning system has a very important position in the field of energy conservation.In practice, the energy consumption of central air-conditioning system is mainly generated by a variety of mechanical and electrical equipment of the system, which can be divided into two parts according to their different roles, namely, hot and cold source system equipment such as chillers, pumps; air terminal system equipment such as valve, blower. In the terminal system, the traditional concept of energy-saving control is mainly for the single device and has obvious energy-saving effect. However, from the perspective of the entire system, its energy-saving effect is unsatisfied.In this paper, based on the theory of system energy efficiency, aimed to improve central air-conditioning terminal system energy efficiency, a new rating system about central air-conditioning terminal system energy efficiency is established. We explain its evaluation method, energy-saving ideas and design related energy-saving controller. Experimental data shows that the method is helpful to improve energy-saving effect of air-conditioning terminal system.Firstly, central air-conditioning terminal system energy efficiency rating system is built. Based on the theory of energy efficiency, central air-conditioning terminal system energy efficiency's concept, value and simplified algorithm are expounded. As two main factors, the terminal system overall cooling load and energy consumption are also analyzed in detail.Secondly, an energy-saving control system of central air-conditioning terminal is introduced, and an energy-saving controller of central-station AHU is designed. In the article, the structure and function of the terminal energy-saving system are introduced, and the hardware and software design of central-station AHU energy-saving controller is described. In the design, using Microchip's PIC24 MCUs as the main control unit, taking the embedded operating system as the platform, the system is divided into different tasks, which are reasonably scheduled to achieve different functions. In the control strategy, the relationship among different devices is fully considered to seek the maximize energy efficiency of the central air-conditioning terminal system.Thirdly, a small-scale semi-centralized central air-conditioning terminal system is built to verify the evaluation system and test the controller's performance. A small air-cooled chiller, a set of AHU and four sets of cooling-coil are contained in the experimental system. The rated energy efficiency of the experimental system, REERei is 2.33, and in the terminal system, RCOPei is 9.32. A large number of related data and equipment running state are collected after a month of stable operation.Finally, the experimental results show that, during operation the minimum value of the system's EERsi is maintained about 3.75, and in the terminal system, COPei is maintained about 12. Therefor, the central air-conditioning terminal system energy efficiency rating system is reasonable. With the rating system as the guiding ideology, the energy-saving effect of central air-conditioning terminal system is improved obviously and energy-saving is about 25%.