Development and performance evaluation of a methodology,based on distributed computing,for speeding EnergyPlus simulation

This article presents an approach for speeding EnergyPlus simulations. The computing run time of an energy simulation depends on several variables and is directly proportional to the simulation RunPeriod. In the proposed approach, data parallelization is achieved by breaking an annual simulation into several segments of smaller RunPeriod, each handled by a separate computer/processor. The speed gain achieved by running 12 one-month RunPeriod segments in parallel as compared to single simulation of 12 months is between three and six times. Segmentation of simulation has resulted in minor deviations between the results obtained through segmented simulations and annual simulations. Methods for reducing these deviations on annual and monthly basis are presented in this article using 12 benchmark models each simulated for five cities. On annual basis, a maximum deviation of 0.06% was observed in cooling, heating, and lighting consumption. In a month-to-month comparison between the segments and annual simulation, the maximum deviation was 1.7% for heating and 0.8% for cooling.     

EnergyPlus能耗模拟软件及其应用工具

在综述国内外建筑能耗模拟软件研究现状基础上,总结并评价了EnergyPlus建筑能耗模拟软件的特点和运行过程。对目前常用于EnergyPlus的界面工具、输入文件创建工具和第三方界面工具进行了详细的介绍。     

某大型公共建筑全能耗模拟和节能潜力分析

本文首先介绍全建筑能耗模拟软件EnergyPlus的性能和特点,重点说明它在模拟大型公共建筑时所具有的优势.通过比较EnergyPlus与其他能耗模拟软件的特点,讨论了如何使用EnergyPlus最大限度地反映建筑各系统如空调系统、照明系统、生活热水系统等的复杂构成及它们之间的相互耦合关系.然后采用EnergyPlus对拟申请美国LEED绿色建筑认证的某大型公共建筑进行能耗模拟并计算全年能耗费用.按照LEED标准的要求建立ASHRAE基准模型,通过比较ASHRAE基准模型和设计模型的全年能耗,讨论有效降低建筑全年能耗的途径并建立节能模型.在节能模型中,透明围护结构的遮阳性能得以加强,建筑系统中部分设备的效率得以提高,并引入日光照明、人员传感器等技术.结果表明,本文提出的节能模型与ASHRAE基准模型相比,全年耗电量减少了4.7%,全年耗气量增加了6.9%,全年电费减少了14%,全年总能耗费用减少了7.75%.     

Comparing computer run time of building simulation programs

This paper presents an approach for comparing the computer run time of building simulation programs. The computing run time of a simulation program depends on several key factors, including the calculation algorithm and modeling capabilities of the program, the run period, the simulation time step, the complexity of the energy models, the run control settings, and the software and hardware configurations of the computer used to run the simulation. To demonstrate this approach, we ran simulations for several representative DOE-2.1E and EnergyPlus energy models. We then compared and analyzed the computer run times of these energy models.     

EnergyPlus在日光温室热环境模拟中的应用验证与分析

为了寻求将现有商用能耗分析软件应用于日光温室热环境的设计、优化、建造和日常运营管理的方法,基于EnergyPlus软件,建立了日光温室模型,通过现场实验测试对所建立的模型进行了验证,并利用建立的模型对日光温室热环境进行了模拟分析。研究结果表明:提出的数值方法和建立的日光温室模型是正确可靠的,可以用于日光温室热环境的模拟分析;温室北墙夜间单位面积的供热量是东、西墙与地面总和的1.1~1.2倍,增强日光温室北墙体的蓄热和保温能力是提升日光温室调控自身热环境能力和水平最重要的途径。该研究结果可为日光温室的优化设计与热工性能分析提供参考。     

结合CFD的EnergyPlus大空间温度分层能耗模拟

本文探讨了与CFD模拟相结合的EnergyPlus大空间温度分层能耗模拟方法。首先使用Fluent软件对大空间温度分层现象进行了模拟,而后将获得的大空间温度分层数据输入到EnergyPlus Room Air模块,从而精确模拟大空间能耗。结合夏热冬冷地区火车站候车大厅实例,将采用温度分层策略的能耗与普通分层空调系统的能耗进行对比,验证了该模拟方法的可行性,同时证明了大空间采用温度分层策略的节能效果显著。     

广州市某高校图书馆能耗模拟与节能性研究

以广州市某高校图书馆为研究对象,根据建筑空间、功能布局、空调系统分布,建立图书馆的SU模型,利用能耗模拟软件Energy Plus,并针对模型进行全年能耗模拟仿真,并对模拟结果进行分析。采用改善建筑外墙、外窗隔热性能及添加遮阳设施3种不同的节能方案,分别对其进行理论节能性分析,并计算得到理论节能效率。     

风机盘管空调系统夏季节能模拟与控制研究

运用建筑能耗模拟软件EnergyPlus对北京某高层写字楼进行了能耗及节能控制策略的模拟,并根据模拟结果对该大厦的楼宇控制系统进行了设计,实现了建筑能耗模拟和楼宇控制系统节能运行的人工连接。     

Whole building energy simulation and energy saving potential analysis of a large public building

This article explores how to use EnergyPlus to construct models to accurately simulate complex building systems as well as the inter-relationships among sub-systems such as heating, ventilation and air conditioning (HVAC), lighting and service hot water systems. The energy consumption and cost of a large public building are simulated and calculated for Leadership in Energy and Environmental Design (LEED) certification using EnergyPlus. American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) baseline model is constructed according to ASHRAE 90.1 standard and the comparison of annual energy consumption between ASHRAE baseline model and proposed model is carried out. Moreover, an energy efficiency (EE) model is built based on the design model. Meanwhile, other energy conservation measures (ECMs) such as daylighting dimming and occupant sensors are considered. The simulation results show 4.7% electricity consumption decrease but 6.9% gas consumption increase of the EE model compared to ASHRAE baseline model. In summary, the annual energy cost of the EE model is reduced by 7.75%.     

Difficulties and limitations in performance simulation of a double skin façade with EnergyPlus

Currently, several whole-building simulation tools (e.g., esp-r, EnergyPlus, TRNSYS, TAS, IES VE, IDA ICE, VA114, BSim, etc.) are used to assess the energy performance of double-skin façade (DSF) buildings. The aforementioned tools are well suited to assess energy performance of conventional building systems or whole buildings; however, it is questionable whether such tools can accurately describe the transient heat and mass transfer phenomena that occur in the complex three-dimensional geometry of DSFs. This paper describes an empirical validation of the EnergyPlus simulation tool for performance simulation of a DSF. A series of experiments were conducted for cavity airflow and thermal behavior of the DSF and then compared with simulation outputs. In this paper, it is shown that there are significant differences in both thermal and airflow behavior of DSFs between the measurements and simulation predictions by EnergyPlus. This study investigates three cases causing the differences and elucidates what should be considered when modeling DSFs using EnergyPlus.     

上海某大学体育中心能耗分析

应用EnergyPlus能耗模拟软件对上海某大学体育中心进行能耗模拟。其中建筑几何使用De-signBuilder软件建立,而后利用EnergyPlus进行空调建模并计算能耗。在此基础上,由于各个场馆使用情况的不同,挑选典型日对篮球比赛、游泳比赛、羽毛球比赛这三种典型情景分别模拟,计算其能耗,并分析能耗特点,在一定程度上预估该体育中心投入使用后的耗能情况。     

A comparison of global optimization algorithms with standard benchmark functions and real-world applications using EnergyPlus

There is an increasing interest in the use of computer algorithms to identify combinations of parameters that optimize the energy performance of buildings. For such problems, the objective function can be multi-modal and needs to be approximated numerically using building energy simulation programs. As these programs contain iterative solution algorithms, they introduce discontinuities in the numerical approximation to the objective function. Metaheuristics often work well for such problems, but their convergence to a global optimum cannot be established formally. Moreover, different algorithms tend to be suited to particular classes of optimization problems.

To shed light on this issue, we compared the performance of two metaheuristics, the hybrid CMA-ES/HDE and the hybrid PSO/HJ, in minimising standard benchmark functions and real-world building energy optimization problems of varying complexity. From this, we find that the CMA-ES/HDE performs well on more complex objective functions, but that the PSO/HJ more consistently identifies the global minimum for simpler objective functions. Both identified similar values in the objective functions arising from energy simulations, but with different combinations of model parameters. This may suggest that the objective function is multi-modal. The algorithms also correctly identified some non-intuitive parameter combinations that were caused by a simplified control sequence of the building energy system that does not represent actual practice, further reinforcing their utility.     

风速时程AR模型及其快速实现

随着工程结构日趋多样化、大型化、复杂化，结构风振响应研究受到学术界、工程界的关注和重视，基于数值模拟方法得到的风速时程曲线在结构风振分析中被采用，自回归(AR)模型具有一系列优异性能，在时间系列分析中被广泛应用，本文基于自然风特性，通过考虑结构节点间的风速时程相关性，采用AR模型模拟节点随机脉动风速时程，并提出VC与Matlab混合编程模拟的快速实现方法．对模拟所得的网壳节点风速时程统计分析表明，AR模型可有效地模拟具有时间相关性、空间相关性的节点脉动风速时程，采用VC与Matlab混合编程快速实现方法，可较好解决模拟精度、模拟速度和计算稳定性的问题。     

Developing a modified typical meteorological year weather file for Hong Kong taking into account the urban heat island effect

Building energy computer simulation software is a useful tool for achieving sophisticated design and evaluation of the thermal performance of buildings. For successful thermal and energy simulation of buildings, it requires hourly weather data such as dry bulb air temperature, relative humidity, solar radiation, wind speed, etc. Nowadays, an urban city faces a problem of an urban heat island which causes the urban area to have a higher air temperature than the rural region. Since the currently available weather dataset used in building simulation software mainly comes from weather stations located in remote and rural areas, the impact of the urban heat island on thermal and energy performance of buildings may not be effectively reflected. This paper reports an approach to construct a modified typical meteorological weather file, taking into account the urban heat island effect in the summer season. Field measurements have been carried out in the summer months and the corresponding urban heat island intensities were then determined. With a morphing algorithm, an existing typical meteorological year weather file was modified. An office building and a typical residential flat were modeled with a renowned building energy simulation program EnergyPlus. Computer simulations were conducted using the existing and modified typical meteorological year weather files. It was found that there was around a 10% increase in air-conditioning demand caused by the urban heat island effect in both cases. The implications of this and further work will also be discussed in this paper.     

WM函数在风速分形特征分析中的应用

从时域角度出发研究问题,通过数值方法,利用分形理论,采用Weierstrass-Mandelbrot函数进行了风速时程重构,模拟出尽可能接近和满足自然风特性的时程样本,从而促进风速分形特征的研究。     

Development of HVAC system simulation tool for life cycle energy management Part 1: Concept of life cycle energy management and outline of the developed simulation tool

The importance of LCEM (life cycle energy management) has been recognized from the view of life cycle energy savings for sustainable buildings. The purposes of this research are the proposal of an LCEM framework and development of prototype HVAC system simulation tools for LCEM. In this paper, the necessity of energy simulation tools for LCEM is discussed, and the outline and solution method of the simulation tool are shown.     

Energy simulation and analysis of the heat recovery variable refrigerant flow system in winter

Heat recovery variable refrigerant flow (HR-VRF) system can supply cooling and heating for the building simultaneously and make good use of the indoor cooling and heating capacity efficiently. This system has a good energy performance and can meet the emerging requirements of modern buildings. In order to evaluate the energy features of the system, a new energy simulation module is developed and embedded in the dynamic energy simulation program, EnergyPlus. Using the program with the newly developed module, the dynamic energy simulation is performed for a simplified typical commercial building. The indoor thermal comfort of the building in winter and the setting temperature of the system are analyzed. Based on the simulation results, the energy characteristics of the system are investigated, and it is indicated that different methods of the temperature control and the percentage of the heat recovery have influence on the relative ratio of the energy saving. If the HR-VRF system adopts the same temperature control method as the heat pump VRF (HP-VRF) system, the HR-VRF system promises 15-17% energy-saving potential, when compared to the HP-VRF system.     

Assessment of natural and hybrid ventilation models in whole-building energy simulations

Natural ventilation is a traditional cost-effective technique to cool and ventilate buildings. Proper simulation tools are highly desired to ensure acceptable thermal performance of naturally ventilated buildings and to assist the design and optimization of such buildings. This study is to advance the use of natural and hybrid ventilation concepts in building design by assessing the accuracy and usability of current thermal-ventilation models. Because of the similarity noted among various models and tools, a prevalent airflow-thermal modeling program, EnergyPlus, was evaluated by simulating three selected real buildings that were supplied with most detailed building and measurement information. The study of these cases reveals that the current model has (1) significant functional limitations for venting and exhaust fan control schemes; (2) need for additional relationships to describe horizontal openings and fully-open connections between zones; and (3) possible over-prediction of buoyancy-driven flows in the case of multi-story buildings. The study further indicates the building and measurement data that are critical for a more accurate validation of thermal-ventilation models, including, on-site measured temperature, wind, and solar conditions; measured volume flow rate data, at critical points throughout the building; and effective area and discharge coefficients for specific vents used in building.     

Robustness of a methodology for estimating hourly energy consumption of buildings using monthly utility bills

The evaluation of building energy consumption under typical meteorological conditions requires building energy profiles on an hourly basis. Computer simulations can be used to obtain this information, but generating simulations requires a significant amount of experience, time, and effort to enter detailed building parameters. This paper considers a simple methodology for using existing EnergyPlus benchmark building energy profiles to estimate the energy profiles of buildings with similar characteristics to a given benchmark model. The method utilizes the building monthly energy bills to scale a given benchmark building energy profile to approximate the real building energy profile. In particular, this study examines the robustness of the methodology considered with respect to the parameter discrepancies between a given building and the corresponding EnergyPlus benchmark model used to estimate its profile. Test buildings are defined by perturbing several combinations of the parameters defined in the benchmark building model. The test buildings examined are similar to the EnergyPlus, medium sized office, benchmark building in Baltimore, MD, and a total of 72 distinct test building configurations are examined. The analysis reveals that the methodology can significantly reduce the errors introduced by discrepancies from the EnergyPlus benchmark model.     

中美节能标准中办公基准建筑的能耗比较

对比了中美两国节能标准,以上海地区某办公楼为例,分别建立了在中美公共建筑节能标准下的基准建筑模型,按照ASHRAE 90.1对能耗模拟的要求进行计算,得到该办公楼的空调系统能耗和总能耗.结果表明,我国标准在围护结构、机组效率方面的要求均低于ASHRAE 90.1标准,但是由于美国的空调系统因控制湿度而导致再热量增加,所以根据我国标准和ASHRAE 90.1计算出来的办公建筑的平均能耗强度基本一致.建议我国标准适当减小围护结构的传热系数,提高机组的性能,以利于节能;并且,应详细规定能耗模拟原则,以减少能耗模拟结果的人为因素.