An optimal control strategy for complex building central chilled water systems for practical and real-time applications

This paper presents an optimal control strategy for online control of central chilled water systems in complex building air-conditioning systems to enhance their energy efficiency. The optimal control strategy is formulated using a systematic approach by considering the system level and subsystem level characteristics and interactions among the overall system. The requirements and constraints of practical applications are also carefully considered during the development of this strategy. This optimal control strategy consists of the model-based performance predictor (i.e., simplified models), cost estimator (i.e., cost function), optimization technique, supervisory strategy and a number of local control strategies. The local control strategies are used to ensure the robust operation and keep track of control settings considering the dynamic characteristics of the local process environment. The performance of this strategy is tested and evaluated in a simulated virtual environment representing the complex central chilling system in a super high-rise building by comparing it with that of other control strategies. The results showed that this strategy is more energy efficient and cost effective than the other strategies for online applications. This strategy is being implemented in the super high-rise building under study for field application and validation.     

A fault-tolerant and energy efficient control strategy for primary-secondary chilled water systems in buildings

Primary-secondary chilled water systems with decoupled bypass in building air-conditioning often cannot work in healthy condition as desired in practical operation, due to excess secondary flow demand resulting in deficit flow in the bypass line. This paper presents a fault-tolerant and energy efficient control strategy for secondary chilled water pump systems to solve this operation and control problem providing enhanced operation performance and energy efficiency of chilled water systems. The strategy employs the flow-limiting technique that ensures the water flow of secondary loop not exceed that of the primary loop while still maintaining highest possible delivery capacity of cooling to terminals. The strategy is also integrated with a differential pressure set-point optimizer to determine the optimal set-point. The performance of this strategy is evaluated in a simulated real-life environment representing the chilled water system in a super high-rise building by comparing it with two conventional control strategies. Results show that the proposed strategy can effectively eliminate the deficit flow at both starting and normal operation periods. The energy saving in the secondary chilled water pumps can be up to over 70% and 50% at system starting and normal operation periods respectively compared with the other strategies.     

Online fault detection and robust control of condenser cooling water systems in building central chiller plants

This paper presents a robust strategy for online fault detection and optimal control of condenser cooling water systems. The optimal control strategy is formulated using a model-based approach, in which simplified models and a hybrid quick search (HQS) method are used to optimize the performance of the overall system by changing the settings of the local process controllers. A system level online fault detection scheme is embedded into the control system and used to monitor whether the system operates in a healthy condition. The faults considered are mainly the component performance degradations. When a fault is detected, the control system will be reconstructed to regain the control through using robust schemes. The performance of the proposed strategy is tested and evaluated against on a simulated virtual system representing the actual condenser cooling water system in a super high-rise building. The results show that the fault detection scheme is effective in identifying system performance degradations and the fault-tolerant control strategy with online fault detection and optimal control can enhance the overall system performance significantly when the operation of condenser cooling water systems suffers from performance degradations, as compared to that using optimal control only.     

楼宇自控在学校类建筑中央空调系统中的应用

论述了学校类建筑物中央空调系统设置楼宇自控系统的重要性和必要性,分析了空调监控系统的构成,对空调监控系统的监控原理及方法进行了详细介绍,以实现对建筑内空调设备有效、合理的监控和管理,使其达到最佳状态。     

空调冷热水循环泵变转速节能控制方法

分析比较了最小阻力控制和定末端差压控制的节能性。通过定量计算,明确了前者的节能效果优于后者。分析了最小阻力控制的可行性,认为最小阻力控制在系统构成和控制方法上均比定末端差压控制简单。     

智能化控制在地源热泵中央空调系统中的应用

结合太原武宿国际机场办公综合楼项目,探讨了智能化控制在地源热泵中央空调系统中的应用,简要介绍了该项目空调设计的选型及智能化控制系统要求,并阐述了地埋管、空调机房系统等不同系统中智能化控制的设计应用,为今后同类工程提供了指导。     

变频调速装置在空调水系统中的应用

分析了空调水系统的特点和当前常用的空调水系统流量调节方式，指出变频调速装置应用于变流量系统是最为节能的运行方式，并以工程实例说明应用变频调速系统经济上的可行性。     

邯钢经营大楼集中空调控制系统简介

介绍了邯钢经营大楼集中空调控制系统的划分,阐述了防排烟系统、冷冻水系统的控制原理,论述了制冷机理、制冷系统群控的方法,指出空调系统的自动控制及智能建筑将得到广泛应用。     

用变速泵和变速风机代替调节用风阀水阀

通过５个工程实例，探讨在供热空调系统中利用变速风机和变速泵代替调节用风阀水阀实现风和水系统的调节的可能性，分析表明，这样做可以节省运行能耗，同时改善系统的调节品质，系统的初投资一般也不会增加。水泵和风机能耗约占供热空调系统总能耗的４０％，这些能耗中的１／３左右被各种调节阀门所消耗，但这样大的代价并没有换来好的调节效果，反而导致系统中许多问题发生。     

集中空调系统控制策略

结合中央空调系统受多种因素干扰,控制参数多,各个环节之间互相耦合,控制过程时间滞后大等特点,从中央空调机组基本参数的测量、能量调节、冷热源及水管系统的全面调节与控制等方面考虑,探讨了智能控制策略在中央空调节能控制中的应用。     

变频泵及其供水系统效率曲线的确定

应用相似定律,得出了变速泵及其供水系统效率曲线的确定方法,为计算变速水泵的能耗提供了理论依据.     

空调水系统变流量节能控制分析

分析了变频调速水泵在三种控制(压差控制、温差控制、末端压差控制)方式下的运行过程、运行效果和节能效果,认为应综合考虑空调水系统的规模、负荷组成和分布、空调控制精度要求等因素选择最合适的控制方式。     

Energy simulation in the variable refrigerant flow air-conditioning system under cooling conditions

As a high-efficiency air-conditioning scheme, the variable refrigerant flow (VRF) air-conditioning system is finding its way in office buildings. However, there is no well-known energy simulation software available so far which can be used for the energy analysis of VRF. Based on the generic dynamic building energy simulation environment, EnergyPlus, a new VRF module is developed and the energy usage of the VRF system is investigated. This paper compares the energy consumption of the VRF system with that of two conventional air-conditioning systems, namely, variable air volume (VAV) system as well as fan-coil plus fresh air (FPFA) system. A generic office building is used to accommodate the different types of heating, ventilating, and air-conditioning (HVAC) systems. The work focuses on the energy consumption of the VRF system in the office buildings and helps the designer's evaluation and decision-making on the HVAC systems in the early stages of building design. Simulation results show that the energy-saving potentials of the VRF system are expected to achieve 22.2% and 11.7%, compared with the VAV system and the FPFA system, respectively. Energy-usage breakdown for the end-users in various systems is also presented.     

空调两级泵水系统变频调速的自控设计

分析了变频调速离心水泵的并联特性和变流量水系统的管路特性。结合具体工程,着重介绍了多台变频二级泵并联的自控方案及验证过程。指出了两级泵变频调速水系统的适用场合和成功不多的原因。     

VRV空调系统在嘉骏大厦中的应用

文中介绍了一个采用ＶＲＶ空调系统的工程实例及在设计中应注意的事项，最后对ＶＲＶ系统与常规空调系统的经济性进行了简要比较。     

Effects of alternative control strategies of water-evaporative cooling systems on energy efficiency and plume control: A case study

This paper reports the evaluations of energy efficiency, plume potential as well as plume control of a huge chiller plant using water-evaporative cooling towers for heat rejection for a super high-rising commercial office building in a subtropical region of Hong Kong. The evaluations were carried out in a dynamic Transient Simulation Program (TRNSYS)-based simulation platform using alternative control strategies including set-point control logics of the supply cooling water temperature and cooling tower fan modulation control methods as well as different number control means of cooling towers. The results show that different control strategies have significant effects on the energy efficiency of the chiller plant. The quantification of the energy efficiency demonstrates significant energy-saving potential by using advanced technologies for implementing optimal control strategies in this cooling system. The results also reveal that the plume may occur frequently in spring and summer seasons and occasionally in other months due to the odd subtropical weather conditions. Control strategies also have significant effects on the frequency of the plume occurrence. The effective energy efficiency control and effective plume control using wet–dry (i.e., hybrid) cooling towers are also discussed.     

美国的空调程控节能系统

自动控制在空调系统的设计、运行中大量使用。从各取所适、分散作业、信息交流、人工智能几方面说明了美国空调程控系统总的发展趋势。     

谈中央空调冷却水管理

以医院中央空调系统冷却水的水质控制过程为例,对影响水质变化的物理性、化学性及气态杂质等生成原因做了简要分析,提出了避免空调系统换热效率下降,循环水量减少以及延长设备使用寿命的有效措施,以期为医院创造舒适的医疗环境。     

In situ performance of independent humidity control air-conditioning system driven by heat pumps

A liquid desiccant based independent humidity control (IHC) air-conditioning system driven by heat pumps is presented in this paper. The system consists of a liquid desiccant fresh air processor and a high-temperature chilled water system. The operating principles of the fresh air processor and the whole system are presented in detail. Based on the in situ system installed in an ecological building of Shanghai Research Institute of Building Sciences (SRIBS), a performance investigation was performed in summer, 2007. The measurement results show that (1) the indoor temperature and humidity both are in the specified range; (2) the supply water temperature of the high-temperature refrigerator is higher than the corresponding indoor air dew point temperature, so no condensed water would be formed on the fan-coil unit (FCU) surface; and (3) the average coefficients of performances (COPs) of the fresh air processor and the high-temperature refrigerator are 6.24 and 4.38, respectively, and the average COP of the whole IHC system is 5.28.     

定流量与变流量系统冷水温度节能控制策略

分析了冷水温度对冷水机组COP的影响.讨论了定流量系统和采用变压差阀位控制的变流量系统的冷水温度调节和节能控制的最佳运行策略.