Optimum control strategy for all-variable speed chiller plant

The optimum control strategy and the saving potential of all variable chiller plant under the conditions of changing building cooling load and cooling water supply temperature were investigated. Based on a simulation model of water source chiller plant established in dynamic transient simulation program (TRNSYS),the four-variable quadratic orthogonal regression experiments were carried out by taking cooling load,cooling water supply temperature,cooling water flow rate and chilled water flow rate as variables,and the fitting formulas expressing the relationships between the total energy consumption of chiller plant with the four selected parameters was obtained. With the SAS statistical software and MATHEMATICA mathematical software,the optimal chilled water flow rate and cooling water flow rate which result in the minimum total energy consumption were determined under continuously varying cooling load and cooling water supply temperature. With regard to a chiller plant serving an office building in Shanghai,the total energy consumptions under different control strategies were computed in terms of the forecasting function of cooling load and water source temperature. The results show that applying the optimal control strategy to the chiller plant can bring a saving of 23.27% in power compared with the corresponding conventional variable speed plant,indicating that the optimal control strategy can improve the energy efficiency of chiller plant.

Hybrid Chiller Plant Optimization Strategies for Hotel Building on Nile River of Egypt

Hybrid chiller plants (HCPs) using multiple chillers and different energy sources are highly recommended in several energy applications in non-residential buildings such as hospitals and hotels. Time of use and cooling load profiles are significant factors that should be carefully considered either in chiller plant design or in chiller sequencing operation. This article aims to present an operation planning of HCP which consists of both electric and non-electric chillers. Four operational strategies are proposed and solved to compare their coefficients of performance and economics of running costs. A typical hotel building located on the Nile river in Egypt is selected to perform the current thermal and economic case study. The total cooling load profile of this hotel building is 4000 refrigeration tonnage (TR), which is simulated to optimize chiller sequence of operation and to select optimal design conditions of both numbers for electric and non-electric chillers used in HCP. The results of this comparative study for running cost are defined using various design configurations with different several chiller sequences available for each configuration. Then, the results of COPs, and operational running cost and initial cost are presented in this article also. The comparison aims to find the optimal design and operational sequencing for HCPs on thermal basis and economic analysis which were attached in this article. Recommendations and suggestions for future work are attached at the end of this article.

A non-cooperative game-based distributed optimization method for chiller plant control

The heating,ventilation,and air-conditioning(HVAC)systems account for about half of the building energy consumption.The optimization methodology access to optimal control strategies of chiller plant has always been of great concern as it significantly contributes to the energy use of the whole HVAC system.Given that conventional centralized optimization methods relying on a central operator may suffer from dimensionality and a tremendous calculation burden,and show poorer flexibility when solving complex optimization issues,in this paper,a novel distributed optimization approach is presented for chiller plant control.In the proposed distributed control scheme,both trade-offs of coupled subsystems and optimal allocation among devices of the same subsystem are considered by developing a double-layer optimization structure.Non-cooperative game is used to mathematically formulate the interaction between controlled components as well as to divide the initial system-scale nonlinear optimization problem into local-scale ones.To solve these tasks,strategy updating mechanisms(PSO and IPM)are utilized.In this way,the approximate global optimal controlled variables of devices in the chiller plant can be obtained in a distributed and local-knowledge-enabled way without neither global information nor the central workstation.Furthermore,the existence and effectiveness of the proposed distributed scheme were verified by simulation case studies.Simulation results indicate that,by using the proposed distributed optimization scheme,a significant energy saving on a typical summer day can be obtained(1809.47 kW·h).The deviation from the central optimal solution is 3.83%.

某商业建筑高效制冷机房运行数据分析

制冷机房作为系统工程,其系统运行参数的变化(如冷冻水供回水温差)会对机房内不同设备的能效产生不同的影响,机房整体能效最优是机房节能运行的重要目标。针对现有建筑运行数据存储较多但对其分析较少的现状,采用数据挖掘技术,对某商业建筑制冷机房实际运行能耗、能效进行统计计算,并将其与负荷率、供回水温度、供回水温差等变量的相关性展开分析,揭示机房能效与各变量间的内在联系。研究结果显示:制冷机房单位面积制冷能耗约为16~17 kW·h/(m^(2)·a),冷水机组能耗占80%以上,冷水机组的能效表现主导了机房的整体能效表现,机房系统能效比(COPs)高于设计值6.06 kW·h/kW·h,达到了预期目标。机房整体能效与室外气温及负荷率、冷冻(却)水供回水温差、冷却水进水出水温度呈负相关关系,机房整体能效与冷冻水供回水温度主要呈正相关关系。冷水机组运行COP与机组负荷率和冷却水回水温度呈现一定相关性,且基本符合机组定冷却水温和AHRI变冷却水温工况下的选型曲线。

机场航站楼空调水系统深化设计方法与案例研究

为实现中国民航业的绿色可持续发展,中国政府提出了打造绿色低碳航空、提高服务保障能力、推进技术进步和节能减排等要求,对中央空调系统能效有更高的要求。对于新建航站楼,通过节能措施提升系统的整体能效是关键所在。文章以我国夏热冬暖地区枢纽机场航站楼为例,主要从中央空调系统的水系统方面开展研究,开展能效分析,提出节能措施,既为新航站楼中央空调的建设提供参考依据,又为现有航站楼中央空调系统的改造提供数据支持。

办公建筑高效制冷机房研究与实践

公共建筑空调系统能耗占建筑运行总能耗的40%~60%,研究并推广高效制冷机房技术是建筑行业实现“双碳”战略的有效手段。目前国内外技术标准及工程案例更多关注的是高效制冷机房整体能效比(EER),对高效制冷机房EER的影响因素及提升技术策略研究较少。本文结合理论及工程案例,研究明确了高效制冷机房EER的影响因素及其相互关系,提出了包含冷水机组选型优化适配、能源梯级利用、输配系统优化、精细化监测与控制等技术策略,并详细介绍了中国海外大厦项目应用实例,旨在为同类项目提供参考,助力高效制冷机房技术在办公建筑中产业化应用。

团体标准T/CRAAS1039-2023(T/CECA20026-2023)《高效空调制冷机房系统能效监测与分级标准》解析

介绍了团体标准T/CRAAS1039—2023(T/CECA20026—2023)《高效空调制冷机房系统能效监测与分级标准》中高效空调制冷机房系统的术语、基本规定、监测、能效分级等,为相关的工程技术人员正确理解并执行该标准提供了参考。

RTM在核级冷水机控制系统标准化设计中的应用研究

随着国内大量核电机组的新建,如何有效实现其中核级冷水机控制系统的设计标准化已成为亟待解决的问题。以某核级冷水机控制系统项目为样本,将需求管理中需求追踪矩阵(RTM)的方法和标准化的常见方法结合,提出一种标准化设计方法。该方法以需求为核心,建立核级冷水机组标准化设计流程,对核级冷水机的设计输入和输出进行分析和建模,实现了冷水机控制系统设计的标准化。通过对该标准化设计在其他实际项目的应用,证明该方法可提高设计质量和效率。该方法的提出与应用为后续其他核电厂主设备的控制系统标准化设计提供了参考。

An optimization-oriented modeling approach using input convex neural networks and its application on optimal chiller loading

Optimization for the multi-chiller system is an indispensable approach for the operation of highly efficient chiller plants.The optima obtained by model-based optimization algorithms are dependent on precise and solvable objective functions.The classical neural networks cannot provide convex input-output mappings despite capturing impressive nonlinear fitting capabilities,resulting in a reduction in the robustness of model-based optimization.In this paper,we leverage the input convex neural networks(ICNN)to identify the chiller model to construct a convex mapping between control variables and the objective function,which enables the NN-based OCL as a convex optimization problem and apply it to multi-chiller optimization for optimal chiller loading(OCL).Approximation performances are evaluated through a four-model comparison based on an experimental data set,and the statistical results show that,on the premise of retaining prior convexities,the proposed model depicts excellent approximation power for the data set,especially the unseen data.Finally,the ICNN model is applied to a typical OCL problem for a multi-chiller system and combined with three types of optimization strategies.Compared with conventional and meta-heuristic methods,the numerical results suggest that the gradient-based BFGS algorithm provides better energy-saving ratios facing consecutive cooling load inputs and an impressive convergence speed.

基于温度多元线性回归模型的空调制冷站在线预测控制方法研究

从实际应用角度出发,以制冷站全局COP为优化目标,综合考虑制冷站整体特性及各组件相互耦合特性,提出了一种基于多元线性回归模型的制冷站预测控制方法。该模型的输入变量为冷水进出口温差和冷却水进出口温差,分别对应冷水侧和冷却水侧的运行特性,输出变量为制冷站全局COP,能够反映制冷站系统的综合特性。该模型结构简单、输入参数易获取、可复制性高,可在线应用于大多数制冷站系统。试验结果表明,该预测控制方法可有效提升制冷站整体运行能效。

疫苗生产厂房冷水机组可移动式胶球清洗装置的应用

随着生物医药及大健康产业项目的飞速发展,生物厂房的建设和使用需求不断增加,冷水机组作为最基础的保障设施,使用数量和技术也随之提高,在冷水机组冷凝器胶球清洗的实践过程中,不仅需要解决设备成本、混合布管、胶球使用寿命等技术问题,也要根据实际情况选择高效运行装置的方法。通过剖析各类胶球清洗装置效果,以提升冷凝器清洗效率为目标,重点研究胶球清洗装置与疫苗生产厂房冷水机组的适配性,提出以移动式胶球清洗冷水机组冷凝器的解决方案。基于此,对移动式胶球清洗装置在冷水机组中的具体应用进论述和分析,为冷水机组冷凝器清洗提供新的技术和方法。

区域供冷系统冷却水管路水力仿真优化

建立了区域供冷系统冷却水管路精细化水力仿真模型,采用理论分析与实验相结合的方法,对深圳前海10号制冷站1期冷却水系统设计与运行数据进行了分析。实验校核结果表明,采用本文仿真模型能较精确地计算整个管路系统及分段管路压降,可以较为精确地预测冷却水管路水力学现象,并用于工程分析。利用仿真模型得到了管路所有管件的阻力及各个管件的机械功耗,提出了高效机房管路减阻优化方法。与传统设计计算模型的对比发现,传统水力计算中90°弯头、三通等管件的局部阻力系数取值偏大导致管路水泵扬程计算结果与实际值有较大偏差。

基于现场数据建模的冷机群控策略研究

冷站能耗在中央空调总能耗中占比大。通过优化冷机运行序列和负荷分配,可以在保证末端冷量需求的同时,实现节能。针对冷机性能主要受供冷量、蒸发器出水温度和冷凝器出水温度影响,设计了基于现场数据识别模型优化群控策略,同时以冷机现场可达到的实际最大供冷量和最小供冷量作为约束条件,缩小了冷机序列优化和负荷分配优化的搜索域,加速优化控制计算速度。同时,探讨了不同优化算法对寻优结果的影响。以武汉某烟厂作为案例,对冷机优化群控策略进行验证,结果表明:与传统冷机群控策略相比,采用基于现场数据识别模型的冷机群控策略均可以在整个制冷季实现约20%的节能率。

以某商业综合体为例实现制冷机房仿真设计及高效建造

建立高效制冷机房并保持高效、稳定运行是一项集成化的系统性工作,主要包含制冷机房高效设备的选型和匹配、管路系统优化、制冷系统的科学调试及良好运维。通过仿真设计平台对制冷机房进行节能设计,实现在项目初期进行系统设计优化与控制策略的定制与调整,对高效制冷机房的建造具有重要意义。现以顺德万达广场为例,通过建筑系统建模、负荷分析及多控制策略参数优化对制冷机房系统运行情况进行节能性分析,同时利用高效制冷机房标准化建造与智能运维手段,保证制冷机房系统以最优的设备配置和最节能控制策略运行,助力实现高质量、高效率的制冷机房设计与智能化建造。

某制冷机房能效比测试与分析

中国致力于走绿色可持续发展道路,力争在2030年前实现二氧化碳排放峰值,在2060年前实现碳中和。在此时代背景下,制冷机房高效化改造和建设项目逐年增多。如何有效地对制冷机房的能效比进行客观准确的评价,成为影响高效制冷机房行业发展的一个关键点。本文结合某机构制冷机房系统能效比的监测,就制冷机房水系统的流量、温差测试,从测试点的布置,传感器、采集器的选择等方面进行了分析,对该制冷机房系统进行实际监测,使用监测的数据对该机房系统的能效比计算和评价,对高效制冷机房的监测与评价存在一定的指导意义。

浅谈高效整体集成式冷水机房在电厂的应用——以某电厂优化改造项目为例

基于我国政策背景和产业发展需求,简要介绍高效整体集成式冷水机房的概念、优点和应用情况,并以某电厂传统冷水机房的优化改造项目作为研究内容,通过实例和相关数据对比验证高效整体集成式冷水机房的应用对电厂的运维具有积极经济效应,以期为高效整体集成式冷水机房的应用发展提供借鉴,为高效整体集成式冷水机房在电厂其他方面的应用研究抛砖引玉。

基于Near-Optimal整体能效控制的某制冷机房系统高效化改造

通过高效设备、高效控制、高效输配和智慧运维等技改措施对某酒店进行了既有制冷机房高效机房化改造升级,实现了预期的能效提升目标。其中在高效控制方面,采用了自主研发的中央空调强弱电一体化高效控制柜,该控制柜借鉴了ASHRAE Handbook中提出的基于单一变量函数关系的Near-Optimal整体能效控制理念,引入了整体高效调控策略(简称N-O策略),用于冷却塔台数和频率、冷却水泵频率的整体高效调控,实现了制冷机房冷却系统(冷机+冷却水泵+冷却塔)的整体高效调控,使冷源系统全年平均运行能效比从4.5提升到了5.11,实现了高效制冷机房改造目标。

热源塔液气比优化分析与实验研究

针对夏热冬冷地区对冬夏两季双高效供冷/供热空调设备的需求,提出了采用热源塔热泵达到夏季高效供冷而冬季高效供热效果的解决方法.对热源塔热泵的原理和工作过程及其与冷水机组和空气源热泵的异同点进行了分析,建立了叉流式热源塔装置,并在不同室外空气参数情况下,以水和溶液(乙二醇水溶液)作为介质且在不同液气比时,对热源塔换热性能进行了研究.实验结果表明:调节室外空气温度从5.5℃升高到18.5℃,分别运行乙二醇水溶液和水,热源塔液气比优化值基本保持在0.25～0.4,而热源塔作为冷却塔使用时液气比优化值为1.33～1.67左右.冷却塔/热源塔的液气比优化值在冬季时小于夏季,此结果将为热源塔的设计及其应用提供实验数据支撑.

群智能控制系统在高效制冷站的实践

群智能控制系统是一种新型建筑自动化控制系统,区别于传统楼宇自控系统,它将建筑机电设备系统划分为若干基本单元,为每个单元配置一个智能控制器,智能控制器之间按照基本单元的空间位置关系连接成一个无中心、扁平化的网络系统。结合某商业项目的工程实践,分析了制冷站群智能控制系统的设计原则和全年运行效果。该系统在商场开业前投入使用,实现了制冷站在无人值守下的自动高效运行;2019年6—10月制冷站平均能效达到4.50,相对国标制冷站能效限值3.31,节能率达到26.44%。群智能控制系统可适用于不同形式的制冷站,通过标准化设计、施工调试和通用控制策略软件下载,快速“复制”高效制冷站经验,解决我国公共建筑空调制冷站存在的自动化程度低、运行效率低、能耗水平高等问题。

分片线性规划及应用

提出通过分片线性逼近和分片线性规划,将非线性优化问题转化为一系列的线性规划进行求解的方法。讨论了分片线性规划的性质,证明了分片线性规划问题可以通过有限次线性规划得到求解,同时,给出了分片线性规划问题局部最优解的充要条件,并基于此构造了求解分片线性规划问题的下降算法。该算法与自适应链接超平面模型相结合,成功地对离心式冷水机组的工作点进行了优化。通过优化,机组的能耗比之当前工作点有了明显的下降,表明通过分片线性规划求解非线性优化问题的有效性。