Daylighting analysis for classrooms using DOE-2.1B

A daylighting study of classrooms in three california climates was made using the DOE-2.1B Building Energy Analysis Computer Program. The daylighting configurations studied were unilateral, clerestory, and top-lighting designs. The climates studied were Fresno, Oakland, and Mount Shasta.It was found that daylighting could produce lighting energy savings in excess of 80%, and total building energy savings in excess of 30% in all climates analyzed. It was also found that the less than optimum daylighting designs studied still used less energy than classrooms having no daylighting features.For Fresno, unilateral designs should use approximately 50% glass, with the glass oriented either north or south, provided the south is shaded. The glass should be mounted on the wall as high as possible. Clerestories should run the length of the classroom and should be 0.6 m (2 ft) high, assuming additional windows comprise 30% of the wall area. Skylights can be between 1% and 5% of the total roof area.For Oakland, unilateral designs should use approximately 70% glass, with the glass oriented in any direction, provided orientations other than north are shaded. Clerestories should be 1.2 m (4 ft) high. Skylights should be between 3% and 5% of the roof area.For Mount Shasta, unilateral designs should use approximately 50% glass, with the glass facing south with an overhang. A northern orientation performs almost identically. Clestories should also face south and have an overhang, but again northern orientations perform almost as well. Skylights should be between 3% and 5% of the roof area.Skylights save the greatest amount of energy in all three climates.     

用DOE-2程序分析建筑能耗的可靠性研究

对比我国常用的负荷计算方法，介绍了DOE—2能耗模拟程序的计算机理，并就同一建筑，用以上两种方法分别计算了其冷热负荷和全年空调、供暖耗电量，验证了DOE—2程序用于分析我国建筑物能耗的可靠性。     

DOE-2在住宅建筑能耗分析中存在的问题探讨

为了定性检验DOE-2软件对居住建筑能耗分析及节能评价的合理性,利用DOE-2软件模拟计算了两种体形系数差别较大的模型建筑在广州、重庆、杭州等8个城市围护结构改进前后单位建筑面积的全年空调和供暖能耗量。研究了围护结构性能改进、体形系数变化及换气次数增加等因素对建筑全年空调、供暖能耗相对变化率的影响规律。     

EnergyPlus: creating a new-generation building energy simulation program

Many of the popular building energy simulation programs around the world are reaching maturity — some use simulation methods (and even code) that originated in the 1960s. For more than two decades, the US government supported development of two hourly building energy simulation programs, BLAST and DOE-2. Designed in the days of mainframe computers, expanding their capabilities further has become difficult, time-consuming, and expensive. At the same time, the 30 years have seen significant advances in analysis and computational methods and power — providing an opportunity for significant improvement in these tools.In 1996, a US federal agency began developing a new building energy simulation tool, EnergyPlus, building on development experience with two existing programs: DOE-2 and BLAST. EnergyPlus includes a number of innovative simulation features — such as variable time steps, user-configurable modular systems that are integrated with a heat and mass balance-based zone simulation — and input and output data structures tailored to facilitate third party module and interface development. Other planned simulation capabilities include multizone airflow, and electric power and solar thermal and photovoltaic simulation. Beta testing of EnergyPlus began in late 1999 and the first release is scheduled for early 2001.     

EnergyPlus建筑能耗分析软件汉化用户应用界面的开发

鉴于EnergyPlus用户界面不完善,应用不便的问题,采用混合语言编程的思想,运用VB6.0开发出功能齐全、简单汉化用户应用界面,以EnergyPlus为内部计算引擎的能量^＋（汉化EnergyPlus）能耗分析软件。     

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%.     

太原市公共建筑能耗模拟分析

利用Dest软件进行建模计算分析,在太原市选取部分政府办公建筑和大型公共建筑进行了能耗统计、能源审计和能耗分析,得出了公共建筑各类能耗的比例,以及公共建筑保温节能体系存在的问题,可以为寒冷地区乃至全国的公共建筑的保温节能设计改造提供有利的依据。     

BuildOpt—a new building energy simulation program that is built on smooth models

Building energy simulation programs compute numerical approximations to physical phenomena that can be modeled by a system of differential algebraic equations (DAE). For a large class of building energy analysis problems, one can prove that the DAE system has unique solution that is once continuously differentiable in the building design parameters. Consequently, if building simulation programs are built on models that satisfy the smoothness assumptions required to prove existence of a unique smooth solution, and if their numerical solvers allow controlling the approximation error, one can use such programs with generalized pattern search optimization algorithms that adaptively control the precision of the solutions of the DAE system. Those optimization algorithms construct sequences of iterates with stationary accumulation points and have been shown to yield a significant reduction in computation time compared to algorithms that use fixed precision cost function evaluations.In this paper, we state the required smoothness assumptions and present the theorems that state existence of a unique smooth solution of the DAE system. We present BuildOpt, a detailed thermal and daylighting building energy simulation program. We discuss examples that explain the smoothing techniques used in BuildOpt. We present numerical experiments that compare the computation time for an annual simulation with the smoothing techniques applied to different parts of the models. The experiments show that high precision approximate solutions can only be computed if smooth models are used. This is significant because today's building simulation programs do not use such smoothing techniques and their solvers frequently fail to obtain a numerical solution if the solver tolerances are tight. We also present how BuildOpt's approximate solutions converge to a smooth function as the precision parameter of the numerical solver is tightened.     

建筑能耗模拟在能源审计中的应用

以某大厦为例,阐述了建筑能耗模拟时的模型校验方法,并利用经过校验的模型进行了能耗预测和节能量计算.指出在进行能源审计时,必须用实际的建筑资料和历史能耗数据对所建模型进行校验,只有经过实测能耗数据校验的模型才能对建筑能耗进行准确预测;通过能耗模拟进行能耗预测和节能量计算,可以节省大量的时间,且更加准确、直观,具有很好的应用前景.     

Ground reflectivity in the context of building energy simulation

This paper stresses the importance of a proper estimate of ground reflectivity in building energy simulation, particularly in the presence of snow. Several factors influencing ground reflectivity are reviewed. Two models for estimating ground reflectivity in the presence of snow are developed. The first one is based on the number of days with snow depth greater than 5 cm, and is appropriate for use with ‘typical’ meteorological years. The second makes use of actual records of snow depth, and takes into account snow accumulation, ageing and melting to calculate reflectivity values. The algorithms were implemented in ESP-r and tested by simulating a passive solar house for six Canadian locations. The sensible heating load calculated by the simulations is reduced by up to 10.9% on a yearly basis, and 23.3% on a monthly basis, when the ground reflectivity takes into account the presence of snow.     

Advances in building energy simulation in North America

Recent advances in building energy simulation in North America are reviewed. Six innovative programs — HVACSIM⁺, GEMS, ENET, TARP, BESA, and BEVA — are described and important new simulation techniques in the areas of functional input, moisture absorption and desorption, interzone airflow, daylighting, and automatic optimization are discussed.     

A detailed loads comparison of three building energy modeling programs: EnergyPlus, DeST and DOE-2.1E

Building energy simulation is widely used to help design energy efficient building envelopes and HVAC systems, develop and demonstrate compliance of building energy codes, and implement building energy rating programs. However, large discrepancies exist between simulation results from different building energy modeling programs (BEMPs). This leads many users and stakeholders to lack confidence in the results from BEMPs and building simulation methods. This paper compared the building thermal load modeling capabilities and simulation results of three BEMPs: EnergyPlus, DeST and DOE-2.1E. Test cases, based upon the ASHRAE Standard 140 tests, were designed to isolate and evaluate the key influencing factors responsible for the discrepancies in results between EnergyPlus and DeST. This included the load algorithms and some of the default input parameters. It was concluded that there is little difference between the results from EnergyPlus and DeST if the input values are the same or equivalent despite there being many discrepancies between the heat balance algorithms. DOE-2.1E can produce large errors for cases when adjacent zones have very different conditions, or if a zone is conditioned part-time while adjacent zones are unconditioned. This was due to the lack of a strict zonal heat balance routine in DOE-2.1E, and the steady state handling of heat flow through interior walls and partitions. This comparison study did not produce another test suite, but rather a methodology to design tests that can be used to identify and isolate key influencing factors that drive the building thermal loads, and a process with which to carry them out.     

Sensitivity analysis and application guides for integrated building energy and CFD simulation

Building energy simulation (ES) and computational fluid dynamics (CFD) programs provide complementary information essential to evaluating building thermal performance. Integration of the two programs eliminates many model assumptions in separate applications and thus improves the quality of simulation results. This paper discusses the potential building and environmental characteristics that may affect the necessity and effectiveness of applying an ES–CFD coupling simulation. These characteristics and the solution accuracy requirement determine whether a coupled simulation is needed for a specific building and which coupling method can provide the best solution with the compromise of both accuracy and efficiency. The study conducts a sensitivity analysis of the coupling simulation to the potential influential factors, based on which general suggestions on appropriate usage of the coupling simulation are provided.     

Empirical validation of building energy simulation programs

The largest-ever exercise to validate dynamic thermal simulation programs (DSPs) of buildings has recently been completed. It involved 25 program/user combinations from Europe, the USA and Australia, and included both commercial and public domain programs. Predictions were produced for three single-zone test rooms in the UK. These had either a single-glazed or double-glazed south-facing window, or no window at all. In one 10-day period the rooms were intermittently heated and in another 10-day period they were unheated. The predictions of heating energy demands and air temperatures were compared. The observed interprogram variability was highly likely to be due to inherent differences between the DSPs, rather than the way they were used. Predictions of the difference in performance of two rooms were no more consistent than predictions of the absolute performance of a single room. By comparing the predictions with the measurements and taking due account of experimental uncertainty, the DSPs that are likely to contain significant internal errors are distinguished from those which, in these tests, performed much better. The likely sources of internal error are discussed. It is recommended that empirical validation exercises should consist of an initial blind phase in which program users are unaware of the actual measured performance of the building, and then an open phase in which the measurements are made available. The work has produced five empirical validation benchmarks, which have significant practical benefits for program users, vendors and potential purchasers. There is considerable scope for improving the predictive ability of DSPs and so suggestions for further work are made.     

Contrasting the capabilities of building energy performance simulation programs

For the past 50 years, a wide variety of building energy simulation programs have been developed, enhanced and are in use throughout the building energy community. This paper is an overview of a report, which provides up-to-date comparison of the features and capabilities of twenty major building energy simulation programs. The comparison is based on information provided by the program developers in the following categories: general modeling features; zone loads; building envelope and daylighting and solar; infiltration, ventilation and multizone airflow; renewable energy systems; electrical systems and equipment; HVAC systems; HVAC equipment; environmental emissions; economic evaluation; climate data availability, results reporting; validation; and user interface, links to other programs, and availability.     

计算机模拟在建筑节能设计中的应用

依据DBJ13—62—2004《福建省居住建筑节能设计标准实施细则》,从节能率、成本、建筑热舒适性、节能方案适宜性等方面对比分析了规定性指标节能设计法与动态权衡计算设计法的优劣。得出计算机仿真模拟技术在建筑节能设计中应用的重要性。     

Simplified daylighting energy savings for non-daylighting building energy simulation programs

The California Legislature mandated the California Energy Commission (CEC) to establish and periodically update energy efficiency standards for new buildings. To this end, a sensitivity analysis was conducted by the Standards Development Office of the California Energy Commission for nonresidential buildings. The purpose of this parametric analysis was to determine which variations in building parameters actually have significant energy impacts.A “generic” building model was developed and implemented in conducting this sensitivity analysis. The generic model was used as an analytical tool in modeling the energy impact of building parameter variations, as well as architectural and mechanical energy-saving measures on the energy use of each module. It is recognized that the level of significant energy impact is equivalent to, or bounded by the accuracy of the energy analysis tools in predicting energy usage in actual buildings. For the computer program used, DOE 2.1A this accuracy is within ±5%.Since DOE 2.1A and most of the other building energy simulation programs do not have daylighting algorithms, another calculation tool was used to determine daylight availability and lighting power reduction on an hour-by-hour basis for each orientation. This is accomplished with a daylight reduction factor (DRF).Quicklite, a simplified daylighting program, calculated footcandle (lux) levels based on outdoor ambient light levels, physical room dimensions and properties. To assess the impact of the Quicklite calculated footcandle (lux) levels on artificial lighting use, a control scheme was assumed, and a DRF was calculated based on annual sky conditions by climate zone.Once the DRF values are known for each orientation, the electric lighting schedule can be modified. A new profile number, representing the proportion of installed lighting switched on at that hour, replaced the daily lighting schedules when daylighting was utilized (09:00 – 17:00). To test this methodology, a sensitivity analysis was conducted between DOE 2.1A with Quicklite modifications and DOE 2.1B which has a daylighting preprocessor. The results displayed a 3.6% variation in total energy use.We conclude that daylighting calculations for design days using simplified programs can be used to approximate daylighting energy savings in building energy simulation programs that allow zoned lighting schedules but do not calculate daylight contributions.     

Lightweight and adaptive building simulation (LABS) framework for integrated building energy and thermal comfort analysis

Coupled and distributed simulation helps in understanding the complexity arising from the combined effects of interdependent systems, by connecting and exchanging information across several software programs. In the building energy analysis domain, several tools have been created in the past to facilitate such analyses. However, the existing coupling frameworks such as Building Control Virtual Test Bed (BCVTB), MLE+, High-Level Architecture (HLA), and Functional Mockup Unit are characterized by their inherent complexity, making it a challenge for the building practitioners to widely deploy them in everyday decision-making. In addition, several of these frameworks embody tight coupling, which means they lack the flexibility to incorporate models and components of decision-makers’ choice. This study addresses these gaps by proposing a Lightweight and Adaptive Building Simulation (LABS) framework that capitalizes on Lightweight Communications and Marshalling (LCM), an inter-process communication framework widely used by the robotics community. As a case study demonstrating this new framework, a building energy simulation model is coupled with an agent-based occupant behavior model to understand the energy effects of occupants’ thermal comfort related actions (e.g., adjusting the thermostat set point). These behavioral patterns are also influenced by various interventions (e.g., peer pressure, energy-based education) that may occur in the building. Measuring these effects in a real building for a lengthy period is impractical and resource-intensive and the LABS framework can be used for understanding this system better. The results also highlight opportunities for achieving energy savings by influencing the occupants’ comfort related behavior.     

某援疆干部公寓楼基坑支护方案数值模拟分析

以喀什市某援疆干部公寓楼基坑支护为工程依托,对采用水泥土搅拌桩墙支护基坑进行数值模拟,通过模拟计算结果分析,指出采用水泥墙桩墙支护时,在基坑开挖初期坑底隆起较明显,而后期则是水平位移占主导地位。