Design And Development Of Chilled Water Storage Air-conditioning Control System

With the rapid development of Chinese economy and technology, the energy demand is increasing continuously in domestic industry, and the electricity consumption is growing rapidly especially in summer. In recent years, water storage air conditioning, as a new air conditioning system, is very effective to adjust summer electricity demands. The operation mode of the new system is "store energy in night, while release cold energy during daytime", which release the cold energy stored as cold water in night when needed, in order to achieve the purpose of peak load shifting and reducing daytime power consumption. At the same time, because of the lower environment temperatures and higher cooling efficiency in nighttime, the system can achieve better cooling performance. Chilled water storage air conditioning system has been widely used in many large public building facilities at home and abroad, and achieved good results in energy saving and emission reduction. Therefore, the control system design and development of water storage air conditioning, has a very important practical significance and theoretical value in improving the economic and social benefits.The difference between Water storage air conditioning and conventional air conditioning is the addition of a reservoir which could store chilled water. However, water storage air conditioning system with the reservoir possesses more control devices, making the automatic control system become complex and difficult, and also putting forward higher requirements for the system running status monitoring. In this paper, taking account of the design requirement and the current problems in the control system, we designed and developed a chilled water storage air conditioning control system for a company’s new plant, the main work is as follows:Firstly, as there are so many different types of devices and communication protocols, so we designed a three-layer network architecture for the control system, and developed a communication protocol conversion box to unify the communication format from master to transfer equipment. Taking the security and stability of the automatic control system into account, the control system used a private network independent of the office network, thus to achieve the goals of network access, decentralized control, centralized management and display, and easy to extend system.Secondly, different from a conventional chilled water storage control system using PLC, we chose the more stable Advantech IPC module as the master core, which can run multi-threads and sophisticated control algorithms. There is also equipped with a high resolution touch screen to display the human interface, which is convenient for operators to run the system.Thirdly, in order to ensure the stable operation of the system and deal with the sudden failure, we designed a manual and automatic mode switching circuit, and designed a circuit by using PLC to achieve the control and status monitoring of switching valves, and the collection of temperature information.Finally, the software design used object-oriented programming and modular structure, so we could expand and maintain the system conveniently. The simple and convenient user interface can fully demonstrate the running status of the air conditioning system.After the hardware and software design and development, we debugged the whole system. Through the commissioning of six months, the present water storage air conditioning automatic control system proved to be more stable and reliable, with higher control speed and greater precision. In a word, the control system obtained the good performance of the system, and achieved the purpose of transferring electric energy and reducing the operation cost of air conditioning.