Optimal control strategies of eight parallel heat pumps using Gaussian process emulator

This study describes the development of the optimal control strategies of eight parallel heat pumps in an existing building. The building consists of seven floors above ground and two floors underground with a total floor area of 22,440?m². The chilled water generated by each of the eight parallel heat pumps runs through a common primary pipe to multiple air-handling units in the building. Because only one flowmeter and two thermometers (entering and exiting) are installed in the primary pipe, the heat removal rate and efficiency of each heat pump are unknown. The existing control of the heat pumps is as follows: if the chilled water return temperature in the primary pipe becomes greater than a predetermined temperature, the controller increases the number of operating heat pumps. The heat removal rate and efficiency of each heat pump were first identified using a Gaussian process (GP) machine-learning algorithm to develop the optimal control strategy of the eight heat pumps. Two GP models, one for estimating the heat removal rate and the other for estimating the coefficient of performance (COP), were developed based on the measured data for 27 days in July at the sampling time of 15?min. After developing the GP models, the authors applied a COP-based sequencing control strategy to the eight parallel heat pumps. The new optimal control strategy is to switch on the heat pumps in order from highest to lowest COP. Compared with the existing control logic, the new optimal control can reduce energy consumption by 20.9%.     

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.     

地源热泵--建筑节能新技术

在建筑供热空调中采用热泵技术可以有效地提高一次能源利用率，减少温室效应气体CO2和其他大气污染物的排放。本文阐述了利用热泵供热比锅炉直接燃烧供热节能的原理，对主要的热泵供热形式，特别是地源热泵的技术特征、适用范围和经济性作了较详细的介绍。     

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.     

地表水水源热泵水输配系统的能效分析

为了分析水输配形式、水泵配置和运行方式等对地表水水源热泵系统能效的影响,通过建立水泵能耗模型,找到了取水高差与取水泵能耗的关系,并结合系统能效的限定值,提出地表水水源热泵临界取水高差的概念及计算分析方法。基于对取水水泵功率随流量变化规律的研究,并结合实例,研究了取水水泵一、二级两种配置方式的确定依据。综合分析流量对机组和冷却水泵的能耗的影响,对比了定、变流量运行下的能效,以系统整体能效最佳为目标,得到了研究实例中取水泵的节能运行方式。研究表明,与常规系统相比,水源热泵系统节能效果的实现,存在临界取水高差的应用限制;而且由于机组、水泵所占系统能耗比重的差异,运行方式应依据优化模型而确定。     

水环热泵与空气源热泵节能性对比分析

结合工程实例,对天津地区某办公建筑分别采用带有辅助热源的水环热泵、空气源热泵空调系统进行供冷、供热的工艺流程进行了比较。分析了负荷率对两种空调系统功耗的影响,比较了两种空调系统的系统造价及运行费用。负荷率为80％～100％时,水环热泵空调系统的功耗升高速率较快。水环热泵空调系统的系统造价及运行费用均低于空气源热泵空调系统。     

某湖水源热泵空调系统的诊断与改造分析

对某湖水源热泵空调系统进行诊断,分析得出：水源热泵主机选型、水泵选型、水系统中补水定压装置的设定、排气装置安装均严重影响了空调系统的运行效果。对本工程存在的问题提出了三种不同改造意见,为今后湖水源热泵系统工程的设计、诊断提供借鉴和参考。     

北京某小区多层建筑物热环境模拟分析及应用

为了实现北京某小区水源热泵空调系统的节能设计与运行管理,选择DeST热环境模拟软件对该小区建筑物室内热环境进行了模拟分析,得出了建筑物全年室内热环境特点,不同层位、不同方位房间室内热环境差异和特征,冬季高层和低层内部空间比中间层热环境差,北向房间比南向房间热环境差,角部房间比中部房间热环境差;建筑热环境的模拟对地热工程系统设备选型、管网和末端设备布置具有指导意义。通过对模拟结果的分析和总结,对该小区地源热泵采暖系统的节能设计和运行管理提供了理论依据。     

毛细管辐射空调系统运行的经济性分析

介绍了毛细管辐射空调系统概况。以天津地区某居住建筑为研究对象,采用BIN气象参数、部分负荷率下冷热源机组性能系数,对土壤源热泵＋风机盘管、土壤源热泵＋毛细管辐射空调系统、家用空调机＋集中供热的经济性进行了比较,土壤源热泵＋毛细管辐射空调系统的经济性最佳。     

异程管网热湿负荷分配次优解群及适应性

提出了一种基于次优解群统计分析的异程管网热湿负荷分配方法,采用变步长+随机走步的寻优计算方法,获得空调季不同负荷率下热湿负荷再分配的次优解群,分析次优解群的随机行为和统计规律,以此探索复杂变量约束下的冷冻水系统负荷分配的优化控制策略及其适应性。根据计算结果,在40%、60%、80%、100%这4种负荷率下末端人数次优解重叠率最高达到24%。研究表明,次优解群随机行为与管网热湿负荷分配策略存在相关性,离冷源侧越近,末端人数次优解重叠率越高,分配策略的负荷适应性越好,其权重越大。     

空调管网中加压泵的控制方法研究

对供热、空调水系统中使用加压泵的可行性进行了分析,并导出了节能率计算公式,指出当最不利环路阻力较次最不利环路的阻力达30％以上时,宜采用加压泵。分析了一次泵空调系统中加压泵的控制方法,认为常规控制方法仍可沿用,并提出了空调供冷和供热情形下加压泵的具体调节方法。     

A quasi-steady state mathematical model of an integrated ground source heat pump for building space control

This paper is concerned with the development of a mathematical model, capable of describing the quasi-steady state performance of an integrated ground source heat pump, which is used for heating and cooling of an institutional building located in a Mediterranean climate. The model is structured on functional basis according to the heat pump vapour compression or primary circuit, a secondary ground loop circuit and a secondary building loop circuit. Heat pump heating and cooling capacities, as well as COP, are considered to be dependent variables and are estimated in the model using performance fitted maps. Independent variables include: compressor speed, circulation pump speeds, ground loop return temperature and building circuit return temperature. The model is validated using data from a full-scale ground source heat pump installation. The validated model is used to examine system capacity and performance sensitivity to different control optimisation strategies, including set-point control of room air temperature, room air bandwidth temperature, building loop return water temperature and building loop return bandwidth temperature.     

常用水源热泵空调系统分析

对常用水源热泵空调系统的特点、设计要点及应注意的问题进行了综述分析，尤其是对土壤耦合式地源热泵空调系统，结合工程实例进行了着重探讨。结论表明：在条件允许的情况下，使用地源热泵、水源热泵和水环路热泵空调，无疑是一种利国利民的选择。     

水泵比例定律在供暖空调工程中的应用分析

通过分析指出,水泵变速工况符合比例定律的工程条件为:无背压系统,所有并联水泵同时变速(包括单台泵系统变速),管路特性曲线不改变。水泵变速节能分析应当依据实现同一流量目标条件下,水泵变速调节与其他流量调节方式的能耗比较,而不应当与设计工况比较。     

空调水系统变流量节能控制(续2):变频调速水泵的合理应用

分析了变频调速水泵应用中的相关问题,包括变频泵的特性、最小转速的控制范围、不同控制方式的节能效果、变频泵与定速泵并联运行时的控制等.     

桂林两江国际机场候机楼空调冷却水系统节能改造

为了配合桂林两江国际机场对空调系统的节能改造,作者对机场候机楼空调冷却水系统进行了测试。测试结果表明:在冷却水系统中,冷却塔冷却效率较低,气水比过高,能耗较大;在部分负荷时,冷却水泵只能通过手动控制运行台数,水泵的能耗也较大。针对上述现象,本文对冷却水系统提出了一些改造方案。根据该方案,改造后冷却塔每年可节约能耗32 088 kWh,冷却水泵每年可节约能耗18 228 kWh。     

解读地源热泵技术之运用

地源热泵技术是一种利用浅层地热资源的既可供热又可制冷的高效节能的空调技术。地源热泵相比于其他传统空调和采暖系统具有运用范围较广、低碳环保、节能经济等优势。我国部分城市建筑工程中已使用了地源热泵技术,且逐年递增。     

中央空调海水冷却系统自适应优化控制

在淡水缺乏的香港地区,中央空调系统通常采用海水进行冷却。在能源日益紧张的今天,对空调系统进行优化控制是提高能源效率及节省能源的一个重要途径。本文针对中央空调海水冷却系统提出了根据海水冷却水压力设定值调整的微分自适应优化控制方法实现空调系统能耗最小化,然后进一步对该自适应控制方法进行了基于模拟环境的实验验证。结果表明该方法可以降低系统能耗,提高能源使用效率。     

Study on hybrid ground-coupled heat pump systems

Although ground-coupled heat pump (GCHP) systems are becoming attractive air-conditioning systems in some regions, the significant drawback for their wider application is the high initial cost. Besides, more energy is rejected into ground by the GCHP system installed in cooling-dominated buildings than the energy extracted from ground on an annual basis and this imbalance can result in the degradation of system performance. One of the available options that can resolve these problems is to apply the hybrid ground-coupled heat pump (HGCHP) systems, with supplemental heat rejecters for rejecting extra thermal energy when they are installed in cooling-dominated buildings. This paper presents a practical hourly simulation model of the HGCHP system by modeling the heat transfer of its main components. The computer program developed on this hourly simulation model can be used to calculate the operating data of the HGCHP system according to the building load. The design methods and running control strategies of the HGCHP system for a sample building are investigated. The simulation results show that proper HGCHP system can effectively reduce both the initial cost and the operating cost of an air-conditioning system compared with the traditional GCHP system used in cooling-dominated buildings.     

对中央空调系统节能问题的几点建议

落实中央政府节能强制要求,从围护结构、空调冷热源、机组及末端、冷冻水系统、开发利用新能源、人员培训和集中空调收费等七个方面就中央空调系统节能问题进行简要阐述。