HVAC control strategies to enhance comfort and minimise energy usage

Good heating, ventilating and air conditioning (HVAC) control ensures comfort. It is usually also the most cost-effective way to improve energy efficiency of air-conditioned buildings. In this article, the comfort enhancement and energy saving potential with new control strategies are determined for the Human Science Building (HSB) at the University of Pretoria. A new software tool, QUICKcontrol, was used to perform the complex and fully integrated building, HVAC and control simulations. Various control strategies were investigated. These included air-bypass, reset control, setback control, improved start–stop times, economiser control and CO₂ control. The simulation models were firstly verified against measurements to ensure accurate and realistic retrofit simulations. It was then possible to ensure comfort and to predict savings of 60% in HVAC power consumption. This resulted in a simple payback period of 9 months. Preparing input data took about 2 days, while setting up the simulation model took another day. The typical run time for the fully integrated building, HVAC system and control simulation took approximately 90 s per day on an Intel™ Pentium 133 MHz personal computer.     

某会展中心暖通空调设计

介绍了该工程的空调冷热源、水系统、通风系统、控制系统设计,着重分析讨论了冰蓄冷系统冷源的设置、高大空间分层空调气流组织设计、空调系统在部分负荷时的节能运行.     

Anatomy of a successful high street shopping centre

High street shopping centres are at the core of cities. The continuing design challenge is to adapt a built environment inheritance to meet the present commercial needs of retailers, maximize the potential of the physical environment and address the social amenities that are expected from a city/town centre public realm. This paper addresses the question of what makes a successful high street shopping centre and seeks to understand the relationship between property values, location, physical characteristics, diversity of retailing and use, and social vitality in two successful city centre retailing environments. The research also demonstrates the blurring between commercial and public space, and supports Carmona’s argument that successful social space also creates economic value.     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.     

暖通空调系统优化控制与能量管理的现状及发展趋势

分析了暖通空调优化能量消耗的特点,介绍了暖通空调控制系统基础控制器参数整定、工作点优化和能量管理的现状。根据暖通空调系统的未来需求和相关技术的发展,提出了其控制技术的发展方向。     

上海某大商场空气品质调查

对上海某６层商场的室内空气品质作了为期４天的现场测试和主观调查。结果表明,该商场存在各层温度分布不均匀、换气量不足等问题。     

Application of an energy management and control system to assess the potential of different control strategies in HVAC systems

The significant and continuous increment in the global electricity consumption is asking for energy saving strategies. Efficient control for heating, ventilation and air-conditioning systems (HVAC) is the most cost-effective way to minimize the use of energy in buildings. In this framework, an energy management and control system (EMCS) has been developed to schedule electricity end-uses in the campus of the Universidad Politécnica de Valencia (UPV), Spain. This paper presents an evaluation performed by using the EMCS of different control strategies for HVAC split systems. It analyzed the effect of different schedules for a common air-conditioning device and demand response strategies are tested in several situations. The economic saving is calculated taking into account the electricity contract clauses. Finally, a test is made for the control of a group of similar devices in order to reduce the maximum peak power in consumption and to obtain a flexible load shape with the HVAC loads. The studies are then extrapolated to a larger system, the whole University campus, for which energy and economic savings are quantified.     

Konnex技术及HVAC控制应用

在分析现有总线技术应用现状的基础上,介绍了针对楼宇、家居现场控制应用领域开发的总线标准——Konnex,它融合了欧洲三大总线技术（BatiBUS,EIB和EHS）,在HVAC控制领域具有良好的应用前景。通过实例介绍了Konnex在HVAC控制中的应用和配置方式。     

Modelling and performance prediction of an integrated central cooling plant for HVAC energy efficiency improvement

The aim of this paper is to explore methods to reduce the energy consumption of a central cooling plant. To achieve this, we have developed a new design for heating, ventilating and air conditioning (HVAC) efficiency improvement. A storage tank together with an immersed heat exchanger is installed in the discharge line between the compressor and condenser. The heat exchanger uses the make-up water of the cooling tower to reduce the refrigerant temperature entering the condenser. To investigate the potential of energy savings, we used a real-world commercial building with a central cooling plant, located in a hot and dry climate, for our case study. The energy consumption and relevant data of the existing central cooling plant were acquired over the course of a typical week in summer. The integrated system has been modeled and analyzed to achieve energy conservation. The performance of the proposed cooling system was simulated using a transient simulation software package. Comparison of the proposed system with existing cooling plant is included in this paper to demonstrate the advantages of our new configuration. Results show that up to 18% power saving can be obtained by using our design.     

HVAC系统的碳足迹分析及环境评价指标

介绍了HVAC系统碳足迹的分析方法,提出了评价系统对环境影响程度的两个指标:碳排量和单位输出能量的碳排量.前者用作同一区域的多种设计方案的评价指标,后者用作任何系统的环境影响评价指标.这两个指标可作为规划阶段不同系统设计方案的环境影响评价指标,也可作为对运行系统碳排量监测的理论依据.另外,提出了设定HVAC系统的基准碳排量的思想.     

大型商场功能性和消防安全性的统一

针对商场设计中功能实现与防火分区设计的冲突,分析了含中庭的大型商场不同防火分区形式对商业功能实现、布局灵活性、空间连续性和消防安全性的影响,研究不同分隔方式的优势和局限性;综合分析功能性和建筑美观性提出了组合分隔方式的设计理念,并探讨了室内步行街设计方法在该类建筑防火分隔上的适用性.     

Evaluating the performance of shading devices and glazing types to promote energy efficiency of residential buildings

This study presents a novel residential envelope transmittance value (RETV) performance-based approach for determining the suitable external shading devices and glazing types to improve energy efficiency in residential buildings. The approach is applied to two residential buildings types, namely, point block and slab block, for any given orientation in an entire year. In this approach, a RETV equation for residential buildings was first developed. Employing this equation, we demonstrated how the design of shading devices and the selection of glazing type impact the cooling load of high-rise residential buildings. Comparing results from the model simulations, the half egg-crate louver was found to be the most suitable shading device for residential buildings facing the north and south orientations, whereas a horizontal projection with 30° downward tilt was appropriate for facade facing the east and west orientations to reduce cooling load. In addition, simulations also indicated low-E single clear glazing to be a suitable glazing since it results in relatively economical short payback periods.     

Energetic, economic and environmental performance of a solar-thermal-assisted HVAC system

A solar-assisted HVAC system was retrofitted in 2006-2009 onto an earlier (1980) energy-efficient building. A hybrid system of flat plate and vacuum tube solar collectors heats water in a large hot storage tank that is delivered to an absorption chiller in the cooling season or directly to heating coils in the heating season. Large chilled water storage tanks are charged off-peak and discharged during the day, cooling the building in parallel with the chiller. Measurements of the seasonal performance of the system are presented. Good overall agreement between actual measurements and earlier numerical modeling results is reported for our system, with one notable discrepancy attributable to the operation of the air terminal units, which requires tuning. In cold seasons, solar thermal energy can easily displace a large fraction of traditional heating sources. In the cooling season, the conversion of heat to cooling capacity incurs several parasitic losses, which if not accounted for properly in the design stage, have the capacity to completely offset any advantage gained from the solar system. The economics of building-scale solar thermal systems are strongly dependent on the cost of energy, and electricity in particular. The economics are favorable where electricity costs are high, and vice-versa.     

某数据中心空调系统设计与节能优化分析

从系统设计、设备的选择、系统的优化、运行费用、投资回收期和系统的安全可靠性等方面,详细分析了上海某IT企业研发中心大楼数据中心的空调系统设计及节能优化.     

建筑暖通空调工程的节能减排设计研究

分析了暖通空调设计中存在的问题,通过采用建筑暖通工程节能减排设计应遵循的基本原则,选择相应的建筑暖通空调工程的节能减排设计方案,从而达到减排目的。     

Environmental performance of a naturally ventilated city centre library

To tackle climate change it is essential to reduce carbon dioxide emissions. To this end, it is important to reduce the energy demands of non-domestic buildings. Naturally ventilated buildings can have low energy demands but the strategy is difficult to implement in deep plan, urban locations. The Frederick Lanchester Library at Coventry University, UK, incorporates natural ventilation, daylighting and passive cooling strategies. By using lightwells and perimeter stacks to supply and exhaust air, it can be ventilated by natural means despite its deep plan form and sealed façade. This paper describes the building and presents the energy consumption and the internal temperatures and CO₂ levels recorded in 2004/2005. The building's performance is compared to the original design criteria and good practice guidelines. Recommendations for the design of such buildings are made and the likely performance in other UK cities is assessed. It is concluded that the building uses under half the energy of a standard air-conditioned building and yet, in summer, can keep the interior comfortable and up to 5 °C below ambient. The design would perform equally well in the typical weather conditions experienced at 13 other UK cities, but not in London. It is concluded that deep-plan, naturally ventilated buildings with sealed facades, if well designed, could maintain thermal comfort in all but a very few UK locations, whilst consuming much less energy than even good practice standards.     

HVAC air-quality model and its use to test a PM2.5 control strategy

This paper presents a MATLAB^® Simulink air-quality model of a commercial building with a heating, ventilation, and air conditioning (HVAC) system in Fairbanks, Alaska. Outdoor and indoor real-time fine particulate matter (PM_2.5) levels were measured at this building during a summer wild-fire smoke episode and then during a winter period. The correlation coefficient between the model-predicted and the measured indoor concentrations was 0.99 for the summer and 0.98 for the winter, justifying the usability of the model for further studies. An HVAC control algorithm was developed that reduces the indoor PM_2.5 levels. The algorithm was tested using the HVAC Simulink model and the outdoor PM_2.5 data from the summer smoke episode. The average indoor PM_2.5 level with this control algorithm was 65% lower than with the regular control. Thanks to the PM_2.5 control strategy being automatically engaged only during episodes, it was shown to have the potential of significantly reducing the indoor PM_2.5 levels without significantly compromising the purpose of the original control strategy.     

Development of a testing method for control HVAC systems by emulation

CEN TC247 has prepared draft standards for main types of room controllers. These standards include a performance testing procedure that was designed to facilitate the introduction on the market of innovative controllers (adaptive controllers, fuzzy controllers …). The test procedure is based on the connection of the real controller to be tested to a virtual building and technical plants. The objective of the study which is part of the European SIMTEST project is the development of a testing method by emulation for control systems for heating ventilating and air conditioning applications. This study was focused on the development of numerical models of building and HVAC systems, which are the core of the test facility. The models developed are adapted to the needs of HVAC controller design and test. They take into account static and dynamic phenomena, which are necessary to assess, control functions in terms of comfort and energy consumption. These models are adapted to the test of all controllers, which are in the scope of the three draft standards CEN TC247, in particular to controllers for heating systems, fan coils, variable air volume systems and chilled ceilings. We present in this paper:

• (1)The testing method developed including the simulated environment with its models, the interfaces and the test procedure.
• (2)The validation of the testing method by inspection and comparison of the results obtained by emulation to the results obtained by real tests in a cell. Each application is tested with two different controllers: a high performance and low performance controllers. The same controllers are used in the two different testing methods.

     

Evaluating diverse patterns of occupant behavior regarding control-based activities in energy performance simulation

Simulation is recognized as an effective tool for building energy performance assessment during design orretrofit processes. Nevertheless, simulation models yield deviating outcomes from the actual building performance and a significant portion of this deviation originates from the dynamic nature of occupant behavior. Literature on occupant behavior indicates that occupant behavior is not integrated into building energy performance assessment procedures with appropriate resolution, instead they are acceptedas as sumedand fixed data sets that usually represent the presence of occupants. This study attempts to evaluate the effect of diverse patterns of occupant behavior on energy performance simulation for office buildings. Diverse levels of sensitivity of occupant behavior on control-based activities such as using lighting apparatus, adjusting thermostat settings, and presence in space are employed through three diverse occupant behavior patterns. These occupancy patterns are correlated with three identical office spaces simulated within a conceptual office building. EDSL Tas is used to run building energy performance simulations. Effects of occupant behavior patterns on simulation outcomes are compared for five sample winter and summer workdays, with respect to heating and cooling loads. Results present findings on how diversity of occupancy profiles influences the consumption outcomes.     

弹性基础隔振系统的简化性能指标和有源控制力

系统研究了基础弹性对单层隔振系统、双层隔振系统及浮筏隔振系统隔振性能的影响。分析了不同隔振系统与不同弹性基础间的振动耦合特性,讨论了不同隔振系统的振级落差和力传递率特性,给出了振级落差和力传递率的简化计算方法。针对不同隔振系统的有源隔振问题,比较了不同作动器安装方式所需的控制力。研究表明,对于所有隔振系统,增加基础的刚度和阻尼有利于提高振级落差和力传递率;对于浮筏隔振系统,增加筏架的刚度和阻尼有利于提高隔振性能和减少有源隔振所需的控制力。