Optimization based integrated control of building HVAC system

Improving the control strategy of building HVAC (heating, ventilation, and air-conditioning) systems can lead to significant energy savings while preserving human comfort requirements. This paper focuses on the analysis of the optimal control strategy of the whole HVAC system itself (such as set point value curves for different parts, number control curves of different components) and the followed operating curves of each equipment and device. In order to have a better understanding of the optimal control strategy, performances of the conventional control strategies widely used in China are also shown in this paper.     

Modeling of a solar-assisted HVAC system with thermal storage

A numerical model of the solar-thermal-assisted heating, ventilation and air conditioning system in a 7000 m² educational building, situated in a high-desert climate, is used to predict performance and optimize control parameters. Heating, cooling and shoulder seasons are considered in the study. It is found that the solar assist can account for over 90% of the total heating requirements if certain energy conservation strategies are adopted. The solar cooling assist can reduce the total external cooling energy requirement by between 33% and 43%, the latter result achieved, surprisingly, at lower solar array operating temperatures. In the shoulder season, it is possible to operate the building without any external contribution, by heating the building in the coldest hours of the day, and using any excess heat to produce chilled water, to be stored and used when required. Operation of the solar-assisted system within a much larger district energy system makes it possible to achieve maximum performance.     

Fuzzy and feedforward control of an hybrid thermal energy storage system

A control model for operating a system that stores simultaneously sensible heat from solar and electric energy is proposed. The hybrid thermal energy storage system accumulates solar energy during sunny days and releases it later at night or during cloudy days. It also stores heat from an electric heater during off-peak periods so as to release it later during peak periods. The control model, which makes use of 24-h weather forecasts, comprises two types of controllers: a fuzzy logic controller for estimating the daily amount of thermal electric energy to be stored and a feedforward controller for determining the electricity consumption profile of the heating element during off-peak hours. Results indicate that the proposed control system is far superior to traditional control systems. It maintains a comfortable thermal environment at all times, i.e. the temperature fluctuations are kept within the imposed margins and overheating of the room never occurs. Furthermore, compared to a traditional electric base board heating system, it reduces the electricity consumption for the winter season by 24% and 94% of this electricity is consumed during off-peak hours.     

相变和化学反应储能在建筑供暖空调领域的应用研究

以１９９７年召开的第７届国际储能会议文献为基础,综述了近年来国际上有关应用研究成果和动态,指出出近期领域中的一些值得研究的问题。     

高层建筑暖通空调防排烟施工技术与应用

分析了影响高层建筑暖通排烟雾流动的因素,从防排烟风机的设置、防排烟防火阀的设置、防排烟技术等方面入手,探讨了暖通空调防排烟施工中存在的问题,给出了一些问题的解决建议,以保证暖通空调防排烟设计的合理性。     

Development of building thermal environment emulator to evaluate the performance of the HVAC system operation

A “performance gap” arises when the actual value of building energy consumption during the operational phase deviates from the value predicted using simulation during the design phase. One cause of this performance gap is that operation is not ideal, as assumed in the simulation, and the control of the heating, ventilating, and air conditioning (HVAC) system is not optimized. These problems occur because the operator has not been trained sufficiently and/or the building automation system is not working as intended by the developer. Both problems are fundamentally caused by the fact that the quality of building operation cannot be quantitatively evaluated by comparison with other buildings because a building is a heterogenous, single-item product. To address the performance gap problem, we developed a method for quantitatively evaluating building operation using a precise simulation based on a thermal environment emulator. The emulator software was developed using the BACnet protocol as an interface to the real world and includes an occupant behavior model to enable the assessment of operation in terms of thermal comfort as well as energy performance. In this paper, we report on the program and network structure of the proposed emulator. In addition, we show the concrete results of changing the operational control, and we assess changes in energy performance and comfort from the perspective of Pareto efficiency.     

Needs and trends in integrated building and HVAC thermal design tools

Buildings are responsible for approximately 40% of the total energy consumption in developed countries. More than half of this is used to condition the indoor environment. Studies have shown that savings of between 30 and 70% may be realized through improved design and retrofit procedures for buildings and air conditioning equipment.

Designing for energy efficiency requires a system approach that includes the building, the HVAC system and the controller. Traditional design philosophy based on load calculations is inadequate. New user-friendly design tools allowing an integrated simulation of the complete system are needed.

The main features of a suitable design tool are identified. It should allow dynamic analysis of the passive performance of the building combined with pseudo-steady HVAC system simulation. HVAC component models should be based on simplified fundamental principle analysis to ensure flexibility. The tool should allow for a fully integrated simulation of the building, its HVAC system and controller.

A flexible icon-based graphical interface must be complemented be expandable databases for all components to ensure user-friendly operation. The software must run on a personal computer and should also allow standard system design calculations, life-cycle cost analysis, automatic optimization features and data exchange with CAD software. No tool could be found that provided all of these needs.

The use of such a tool will result in more energy-efficient solutions when designing, managing and retrofitting buildings. This will help to reduce the burden on the environment. The tool will make commissioning of new systems more precise and less laborious. The ability of the designer to guarantee desired comfort conditions will also be enhanced.     

办公室内空调系统对舒适度及细菌传播的影响

对上海市某办公室内的气流组织进行了实验测定,用商业软件FLUENT对室内的速度场、温度场、空气龄、人体舒适度进行了数值模拟,模拟结果与实测数据吻合较好。采用离散相模型对室内细菌传播情况进行了模拟分析。     

高大空间公共建筑暖通空调系统设计分析

在对高大空间建筑暖通空调系统特点分析的基础上,以分层空调系统、冬季辅助采暖系统、新风热回收系统等为切入点,对市场上常见的采暖通风空调系统的优缺点进行剖析,希望能对公共建筑暖通空调系统的设计有所帮助。     

暖通空调系统的热冷源节能探讨

从太阳能、热泵技术、蓄热、热回收技术、VRF多联机空调等几个方面提出了空调节能的方式,并着重探讨了几种节能方式的优缺点及其适用范围,对节能技术的进一步发展有重要意义。     

Economic evaluation of HVAC systems with ice storage designed using an optimization technique

Thermal energy storage (TES) is recognized as an important technique for energy management in heating, ventilation and air conditioning (HVAC) systems. This paper discusses the economic aspects of the optimal design for such systems. The model for optimal design so determines the sizes of the main components of the system - namely the chiller and the storage tank - that the system's life cycle cost is minimal. The model is based on linear programming and is implemented in a computer program for HVAC systems with ice storage. This paper demonstrates that the optimal sizes of chiller and storage tanks differ from those selected using traditional techniques. It emphasizes the cost-effectiveness of the optimally designed system and also includes a sensitivity analysis pertaining to the economic feasibility of such systems under different economic conditions.     

绿色建筑与暧通空调

提出绿色建筑的概念,阐述了绿色对暖通空调的要求,并从设计和运行控制的角度对HVAC系统加以分析,讨论了建筑物其他方面的HVAC系统的影响。用一具实例说明了如何实施绿色方案。     

绿色建筑与暖通空调

提出绿色建筑的概念,阐述了绿色对暖通空调的要求,并从设计和运行控制的角度对ＨＶＡＣ系统加以分析,讨论了建筑物其他方面的ＨＶＡＣ系统的影响。用一具实例说明了如何实施绿色方案。     

Needs and trends in building and HVAC system design tools

Building designers are being increasingly pressurised to design buildings with high standards of energy efficiency, performance and comfort in the shortest possible time. Computer design tools have a tremendous potential for aiding designers in achieving the above design objectives. This article provides a short overview of their application in the building and HVAC field, as well as advances made in their development.The development of applications tends towards integrated and expert design tools. This is a big step towards realising optimal, energy efficient building designs. Despite these apparent advances it was found that the potential of these tools are however largely untapped. This article further identifies the reasons for this and highlights some of the aspects that need attention. The complexity of existing tools seems to be the biggest stumbling block.     

对建筑暖通空调系统几项节能设计措施的分析

以建筑暖通空调系统节能设计为出发点,介绍了室内设计参数、冷热负荷及冷热源的选择计算原则,并阐述了采暖系统、空调水系统与风系统的设计方法,从而达到节能降耗的目的。     

建筑暖通空调系统节能设计要点

针对建筑暖通空调系统进行了分析,重点介绍了这一系统的节能设计要点。建筑暖通空调系统的节能设计,不仅能够提高居民的居住水平、改善其生活质量,而且符合当前社会低碳生活的理念。以期实现建筑暖通系统运行过程中节约能源的目标,创造出最大的环保效益。     

有关建筑暖通空调系统节能方案设计的探讨

随着社会的进步,人们对建筑节能环保的要求也越来越高,节能已成为当今建筑设计行业追求的主旋律,而暖通空调系统节能方案的设计又是整个建筑节能设计的主要环节。从分析建筑暖通空调系统耗能高的原因出发,分析了我国暖通空调节能方面存在的问题,并提出了一些节能设计方面的新技术、新方法,以供同行之间相互学习和交流。     

Co-simulation of a HVAC system-integrated phase change material thermal storage unit

A co-simulation environment, consisting of a detailed mathematical model of a thermal energy storage unit which is incorporated with an EnergyPlus simulation model of a full building HVAC system, is described. The two models are integrated using the user-defined plant component feature in EnergyPlus and the Building Controls Virtual Test Bed (BCVTB) environment. The thermal energy storage unit, which consists of encapsulated phase change material in a series of flat plates and a heat transfer working fluid (water), is modelled using a transient one-dimensional forward finite difference method. The thermal storage model is executed within MATLAB and is verified against experimental data, showing a discharging heat transfer accuracy to within 2.5%. The building model, which incorporates a retrofitted ground source heat pump system within a thermally massive building, is simulated in the EnergyPlus environment. The co-simulation arrangement allows for in-depth analysis of the integrated system under dynamic operating conditions, which is currently not possible within the EnergyPlus environment. Moreover, the overall adopted approach, based on generic integration of a detailed mathematical model, using a third party generalised programming environment, into an established building simulation environment, serves as a successful exemplar for other researchers and practitioners working in the field.     

Identifying decaying contaminant source location in building HVAC system using the adjoint probability method

Building heating, ventilation and air-conditioning (HVAC) system can be potential contaminant emission source. Released contaminants from the mechanical system are transported through the HVAC system and thus impact indoor air quality (IAQ). Effective control and improvement measures require accurate identification and prompt removal of contaminant sources from the HVAC system so as to eliminate the unfavourable influence on the IAQ. This paper studies the application of the adjoint probability method for identifying a dynamic (decaying) contaminant source in building HVAC system. A limited number of contaminant sensors are used to detect contaminant concentration variations at certain locations of the HVAC ductwork. Using the sensor inputs, the research is able to trace back and find the source location. A multi-zone airflow model, CONTAM, is employed to obtain a steady state airflow field for the studied building with detailed duct network, upon which the adjoint probability based inverse tracking method is applied. The study reveals that the adjoint probability method can effectively identify the decaying contaminant source location in building HVAC system with few properly located contaminant concentration sensors.