The influence of calculation error of hourly marine meteorological parameter on building energy consumption calculation

The ocean is a crucial area for future economic development. The marine environment has high energy-efficient and ecological requirements for building construction. Meteorological parameters are the key basis for the analysis and design of building energy efficiency. The lack of meteorological parameters for energy efficiency, particularly hourly data, under oceanic climatic conditions is a universal problem. The appropriate calculation methods of hourly meteorological parameters under oceanic climatic conditions are explored in this study. The impact of the calculation errors of the hourly meteorological parameters on building energy consumption is also analyzed. Three key meteorological parameters are selected: temperature, humidity, and wind speed. Five hourly calculations methods, including linear interpolation, cubic spline interpolation, pieceated three-Hermite interpolation, Akima interpolation, and radial basis function interpolation, are selected to calculate the error of the difference method, with Xiamen, Haikou, and Sanya as the locations of meteorological research. Appropriate interpolation methods are selected for the three parameters, and the seasonal and regional characteristics of the errors of each parameter are compared. Different interpolation methods should be selected for different meteorological parameters in different seasons. The error data of the three parameters of different magnitudes are constructed. A quantitative relationship between the sum of squares due to error of the three meteorological parameters and the rate of change of cooling energy consumption is established. The hourly calculation errors of meteorological parameters have an important impact on the calculation of dynamic energy consumption. The energy consumption differences caused by the errors of different parameters are significant. Obvious regional and seasonal differences also exist. This research strengthens the research foundation of building energy consumption calculation under oceanic climate conditions.     

Comparison of HVAC system modeling in EnergyPlus, DeST and DOE-2.1E

Building energy modeling programs (BEMPs) are effective tools for evaluating the energy savings potential of building technologies and optimizing building design. However, large discrepancies in simulated results from different BEMPs have raised wide concern. Therefore, it is strongly needed to identify, understand, and quantify the main elements that contribute towards the discrepancies in simulation results. ASHRAE Standard 140 provides methods and test cases for building thermal load simulations. This article describes a new process with various methods to look inside and outside the HVAC models of three BEMPs—EnergyPlus, DeST, and DOE-2.1E—and compare them in depth to ascertain their similarities and differences. The article summarizes methodologies, processes, and the main modeling assumptions of the three BEMPs in HVAC calculations. Test cases of energy models are designed to capture and analyze the calculation process in detail. The main findings are: (1) the three BEMPs are capable of simulating conventional HVAC systems, (2) matching user inputs is key to reducing discrepancies in simulation results, (3) different HVAC models can be used and sometimes there is no way to directly map between them, and (4) different HVAC control strategies are often used in different BEMPs, which is a driving factor of some major discrepancies in simulation results from various BEMPs. The findings of this article shed some light on how to compare HVAC calculations and how to control key factors in order to obtain consistent results from various BEMPs. This directly serves building energy modelers and policy makers in selecting BEMPs for building design, retrofit, code development, code compliance, and performance ratings.     

The use of normative energy calculation beyond building performance rating

Standardized building performance assessment is best expressed with a so-called normative calculation method, such as defined in the Committee for Standardization/International Organization for Standardization (CEN/ISO) calculation standards. The normative calculation method has advantages of simplicity, transparency, robustness and reproducibility. For systematic energy performance assessment at various scales, i.e. at the unit of analysis of one building up to a large-scale collection of buildings, the authors' group developed the Energy Performance Standard Calculation Toolkit (EPSCT). This toolkit calculates objective indicators of energy performance using either the monthly or hourly calculation method as specified in the CEN/ISO standard for building energy calculation. The toolkit is the foundation for numerous single, medium-scale and large-scale building energy management applications. At the largest level, applications should be able to manage hundreds or thousands of buildings. The paper introduces two novel applications that have the normative calculation at their core: (1) network energy performance modelling and (2) agent-based building stock energy modelling.     

简述我国建筑节能设计标准

本文对国内现行的建筑节能相关法规进行分析,并据此对建筑节能设计计算方法进行说明,比较不同方法的优劣,最后对当前相关的节能计算软件进行介绍。     

Zur Genauigkeit von Heizwärme‐Bilanzverfahren. Einführung eines Heizperiodenbilanzverfahrens mit analytischen Klimafunktionen

Precision of heating energy balance methods. Introduction of annual heating energy balance with analytical climate function. By smoothing the outdoor temperature and global radiation intensities to cosine functions it is possible to obtain the length of the heating period, the mean outdoor temperature and the radiation during the heating period as functions of the base temperatures. Neglecting the time difference between radiation intensities and outdoor temperature it is also possible to represent the mean base temperature as a simple function of building parameters and outdoor climate values. With these functions the accuracy of the monthly heating energy balance method and of the annual heating energy balance method according to the European Standard EN 832 can be tested for very low heat gains. Comparisons show, that the monthly heating energy balance method and even more the annual heating energy balance method according to EN 832 tend to underestimate the annual heating energy demand. With short heating periods, this tendency is stronger. At heating periods shorter than 4 months the qualification of the monthly heating energy balance method as reference method seems to be questionable. The analytic heating energy balance method, a simple completely analytical method using energy balance over the heating period for different energetic standards is introduced. The accuracy in the calculation of annual heating energy demand is checked in comparisons with the monthly heating energy balance method. For heating periods longer than 5 months the annual heating energy demand calculated with this method differs less than 2 percent from the equivalent value of the monthly heating energy balance method in most cases. The annual method of energy balance over the heating period introduced by Loga for buildings with different energetic standards is analysed and compared with the analytic balance method.     

A pseudo dynamic analysis tool for thermal certification of dwellings

The determination of a normalised heating energy consumption of dwellings can be achieved in different ways: basic and complex calculation methods, as well as experimental procedures can be considered. This paper deals with a certification method based on a limited monitoring of the dwelling coupled with a pseudo dynamic analysis tool. Firstly, the energy performance of a monitored dwelling (a modern single family dwelling and situated in a mild climate) is estimated on the basis of previous energy bills and the application of the prEN832 calculation method; secondly, the obtained figures are compared with those resulting from the pseudo dynamic analysis of the monitoring results.One of the goals of the developed experimental method was to set-up a test procedure that would not disturb the regular life of the dwelling occupants. Therefore, extensive use was made of wireless technology and passive tracer gas techniques have been used to derive an integrated ventilation rate for the house.The background of the pseudo dynamic technique, monitoring disturbances due to building occupation and the overall accuracy of the method are presented. The impact of parameters used for normalising the consumption, such as degree-days or test reference years climatic data (TRY) is discussed. The aim of this paper is, however, not to come up with a well defined standard procedure for determining the normalised heating energy consumption of dwellings but rather to confront the developed method results with those of other procedures and to identify critical limitations routes for possible improvements.     

Basic building life cycle calculations to decrease contribution to climate change – Case study on an office building in Sweden

This study examined whether simplified life cycle-based calculations of climate change contributions can provide better decision support for building design. Contributions to climate change from a newly built office building in Gävle, Sweden, were studied from a life cycle perspective as a basis for improvements. A basic climate and energy calculation tool for buildings developed in the European project ENSLIC was used. The study also examined the relative impacts from building material production and building operation, as well as the relative importance of the impact contributions from these two life cycle stages at various conditions.     

Regulatory energy calculations versus real energy use in high-performance houses

How accurately can official energy performance calculations assess the real energy use in high-performance houses? This question was investigated by analysing 537 dwellings. Data on building characteristics and calculated performance from the Flemish Energy Performance of Buildings (EPB) database were complemented with data from energy utilities and surveys of inhabitants, their socio-demographic characteristics and user behaviours. While the real and theoretical energy uses were strongly correlated, the official calculation method overestimated the heating energy use of most houses while neglecting important electricity end uses. The prediction error varied strongly between individual cases. Two options within the calculation procedure had a significant impact on these prediction errors: the use of default values for the air tightness of the building envelope and the reported return temperature of the space heating system. The simplified calculation of net domestic hot water consumption and the real heating of the master bedrooms also affected prediction accuracy. However, extrapolations are hazardous due to the risk of selection and non-response biases implied by the approach and the need for further research into the causalities. Nonetheless, the findings stress the importance of accurate input data and realistic default values for calculation models used for high-performance buildings.     

Energetische Sanierung von Schulgebäuden in den neuen Bundesländern – Sanierungsprojekt Förderschule Rathenow

Energy efficiency improvements for school buildings in Germany's new federal states; Rathenow special school refurbishment project. Current energy saving measures for existing buildings focus on refurbishment of schools and other educational buildings. The building described in this article represents the standard type of a large‐panel construction series in the new federal states. Due to the large number of buildings (540) constructed in this way the project can act as a model for similar projects. Initial studies indicated that structural refurbishment measures for these buildings are required as a matter or urgency. The energy performance calculations for the building showed good agreement between the calculated demand values and actual heating energy consumption values and can serve as basis for predictions of energy savings through various refurbishment measures. The new DIN 18599 calculation standard enables significantly more differentiated consideration of boundary conditions such as occupied periods, occupancy levels, internal heat sources, and the effect of night setback. Based on comparative calculations, different refurbishment concepts can be developed and assessed.     

Nutzenergiebedarf für das Heizen und Kühlen einer Gebäudezone – Bilanzierung nach DIN V18599 Teil 2

Determination of the energy demand for heating and cooling of building zones. Balance calculation method according to DIN V 18599‐2. The balance calculation method of German standard DIN V18599 is using the well known and proven monthly balance calculation methods for the evaluation of the energy use for space heating. The method enables – supplemented with the energy demand for cooling, air‐conditioning and lighting – a consistently energy evaluation of a building. The method uses an integrative approach and takes the interaction of all participating crafts into consideration. Because of this integrative approach, the following boundary conditions are included in the balance calculation method: –·summer period (variable), –·variable heating period, –·division in periods of usage / no usage, –·cooling demand, –·air conditioning of supply air, –·lighting, –·variable solar protection devices, –·usage‐dependent internal sources, room conditions and air change rates. This method is consistent with the EU‐directive on the “Energy Performance Of Buildings” (EPBD) and complies the requirements of future regulations.     

Analytic calculation of degree-days for the regulated heating season

This paper describes a method for the degree-days calculation by means of the proposed cumulative air temperature duration function for the heating season by additionally setting the temperature which determines the limits of the heating season in this function. The results of calculations received under the Lithuanian climate conditions have been compared with the factual data. The results of degree-days per month calculations received without setting the limit temperatures into the function have been compared with the calculation methods of other researchers. The method proved to be acceptable and useful solving energy consumption problems in relation to of the building life cycle.     

气象参数对成都地区办公建筑能耗的影响及预测

气象参数是影响建筑热环境和供暖空调能耗的主要因素之一。基于成都地区1971—2000年共30a的历史观测数据,生成了建筑能耗模拟软件EnergyPlus所需要的逐时气象数据文件。比较分析了该地区30a干球温度、太阳辐射等各气象参数月均值的变化,模拟分析了该地区建筑的采暖、制冷及总能耗,利用多元回归建立了建筑能耗与气象参数之间的关系式,并检验了该关系式的准确性。结果表明:成都地区办公建筑能耗变化与各气象参数没有呈现明显的规律性;建筑月总能耗与各气象参数呈纯二次多项式关系,月采暖能耗、月制冷能耗与各气象参数呈交叉二项式关系;建筑月能耗回归模型能够较准确地预测建筑月能耗与各气象参数的关系,且月采暖能耗和月制冷能耗回归模型预测的准确性优于月总能耗模型。     

建筑材料环境负荷实例研究

对建筑材料环境负荷影响的评价因素进行研究,通过资料统计与计算,得出钢材、铝材、建筑玻璃、建筑卫生陶瓷等建筑材料单位生产能耗和温室气体CO2排放量,分析了它们对能源和环境负荷的量化影响,以此为基础尝试建立了比较不同住宅结构类型对温室气体环境负荷影响评价的参考方法,并通过案例计算验证。     

Quantification of safety factors for simplified heating and cooling demand calculation methods for Vienna

The method used in Austria for calculating building heating and cooling demand is a monthly quasi-steady-state calculation. This method is presented in the European draft ISO/FDIS 13790. The simplified monthly calculation method is based on utilization factors. For these factors there is no specific mathematical derivation. The factor is based on an empirical formula. For increasing the practicability of the simplified calculation methods, the precision of the method is important, as well as the prediction accuracy by modifying the building parameters. Both requirements for a simplified calculation method are verified in this investigation. A simplified investigation of the calculation method precision for the cooling demand for offices leads to a 40 percent margin of error when using the simplified method for Vienna climate. The prediction accuracy of the monthly balanced method for changing the building parameters was verified for a six zone office model. At the end, the precision of the simplified method was quantified for an office model for the heating and cooling demand. Safety factors for the simplified method resulted from the investigation of the office model. The imprecision of the simplified method is greater than the validation of the monthly calculation method, as is exposed in the draft ISO/FDIS 13790. For the cooling demand for Vienna, the safety factor is 1.25 for the one zone method and 1.15 for the multi-zone method. For the heating demand no safety factor is necessary if the simplified method is not used for low air change rates and uncoupled models.     

Identifications: inevitability of RVRs being approximately the same under different meteorological conditions when taking the same energy-saving measures in the same building

By making comparative research on hourly, daily and monthly energy consumption differences and also on energy conservation rates of heating and cooling when taking the same energy-saving measure in the same building in typical-year meteorological conditions (WDB1) and artificial meteorological conditions (WDB2), we can find from this paper that although the hourly heating and cooling load has great differences when making the same energy efficient measure in the same building under WDB1 and WDB2, the distribution laws of hourly energy efficiency rates (RVRs) of heating and cooling are very similar. It is just the similarity that determines the inevitability of approximation of annual energy conservation rates of heating and cooling. The importance of this paper is that it reveals the common rule of building efficiency. When making the same energy-saving measure on the same type of building in different regions the annual energy consumption and its reduction of the building have a great difference between the regions and the energy conservation rates (RVRs) of the same measures are approximate. After taking some energy-saving measure on the same building in the same place, within the lifetime of the building, however different the local weather conditions over the years are, the energy consumption of different years and the energy reductions of the measure must be different. However, it can be foreseen that the energy conservation rate of any year is approximate after making energy-saving measures on the building. The reason for the above is that although climate changes between years, there is nothing more impractical in artificially modifying meteorological conditions (WDB2), which provides a powerful theoretical basis for every country to lay down design standard for energy efficiency.     

Energetische Bilanzierung von Wohngebäuden nach DIN V 18599

Die energetische Bilanzierung von Wohngebäuden darf gemäß EnEV 2009 wahlweise auf Grundlage der neuen Berechnungsnorm DIN V 18599 oder auf Basis der älteren Vorschriften DIN V 4108‐6 in Verbindung mit DIN V 4701‐10 vorgenommen werden. Eine Berechnung nach DIN V 18599 führt hierbei im Regelfall zu einem höheren Primär‐ und Endenergiebedarf. Dieses ist einerseits auf den ungünstigeren Ansatz der Randbedingungen (Raumtemperatur, Interne Gewinne, Trinkwarmwasserbedarf, etc.) zurückzuführen, beruht aber im Wesentlichen auf einer im Allgemeinen deutlich ungünstigeren Bewertung der anlagentechnischen Seite bei Verwendung von Standardwerten. Auch der zulässige Primärenergiebedarf des Referenzgebäudes ist bei einer Auslegung nach DIN V 18599 im Regelfall deutlich höher und kann berechnungsabhängig sogar das Niveau der alten EnEV 2007 erreichen. Hier wäre eine zukünftige Anpassung der Rechenverfahren wünschenswert. Im Rahmen dieses Beitrags werden entsprechende Vergleichsrechnungen an idealisierten Wohngebäuden vorgenommen, die auch eine quantitative Einschätzung der Unterschiede für Regelfälle ermöglichen. Hierbei wird deutlich, dass unter Angleichung der Randbedingungen und bei genauerer Darstellung der anlagentechnischen Kenngrößen eine Annäherung der Rechenergebnisse erfolgt. Im Hinblick auf eine praxisgerechte und vereinfachte energetische Bilanzierung kann das Rechenverfahren der DIN V 4108‐6 in Verbindung mit DIN V 4701‐10 für Regelfälle im Wohnungsbau verwendet werden. Eine Berechnung von normalen Wohngebäuden nach dieser Norm gestattet eine gleichsam einfache wie zuverlässige energetische Bilanzierung. Für Gebäude mit Kühlung oder komplexer Anlagentechnik kann DIN V 18599 verwendet werden. Die Wahlfreiheit für Wohngebäude sollte auch bei zukünftigen gesetzlichen Regelungen Anwendung finden. Establishing the energy performance of residential buildings in accordance with DIN V 18599. In accordance with EnEV 2009 (Energy Conservation Regulations), it is permitted to calculate the energy performance of residential buildings on the basis of the new DIN V 18599 calculation standard or the older DIN V 4108‐6 regulations in combination with DIN V 4701‐10. As a rule, calculations carried out in accordance with DIN V 18599 lead to higher primary and final energy demand. This is in part due to less favourable input parameters (room temperature, internal gains, demand for domestic hot water, etc.) but in general, it is mostly due to a significantly less favourable evaluation of services installations when using standard values. Likewise, the permitted primary energy demand of the reference building is significantly higher in most cases when assessed under DIN V 18599, and may even reach the level of the old EnEV 2007, depending on how the calculations are carried out. For the future it would be desirable to modify the calculation methods. This article contains comparative calculations for theoretical residential buildings which also allow a quantitative assessment of the differences in standard cases. It becomes clear that when equivalent input parameters are used and the services installations parameters are defined more precisely, the calculation results are less divergent. With a view to a simplified and yet practice‐orientated method for calculating the energy performance of standard residential buildings, it is possible to use the calculation method of DIN V 4108‐6 in combination with DIN V 4701‐10. Calculating the energy performance of standard residential buildings in accordance with this standard provides a simple and yet reliable method. For buildings with cooling or more complex services installations, DIN V 18599 can be used. It is recommended that future legislation allow the option of choice for residential buildings.     

A holistic utility bill analysis method for baselining whole commercial building energy consumption in Singapore

The methodology for baseline building energy consumption is well established for energy saving calculation in the temperate zone both for performance-based energy retrofitting contracts and measurement and verification (M&V) projects. In most cases, statistical regression models based on utility bills and outdoor dry-bulb temperature have been applied to baseline monthly and annual whole building energy use. This paper presents a holistic utility bills analysis method for baseline whole building energy consumption in the tropical region. Six commercial buildings in Singapore were selected for case studies. Correlationships between the climate data, which are monthly mean outdoor dry-bulb temperature (T₀), relative humidity (RH) and global solar radiation (GSR), and whole building energy consumption are derived. A deep prediction study based monthly mean outdoor dry-bulb temperature (T₀) and whole building energy consumption is stated. The result shows that variations of the energy consumption in most of these buildings are contributed by T₀ and can be well predicted at 90% confidence level only with it. The analysis of such kind of model is especially useful for building managers, owners and ESCOs to track and baseline energy use during pre-retrofit and post-retrofit periods in the tropical condition.     

Improving direct solar shading calculations within building energy simulation tools

The calculation of the shadows that building environment, building elements or shading devices may cast on the building envelope, plays a key role in load calculations and building energy simulation. Algorithms for solar shading calculations have direct repercussions on the accuracy of the results and the computational times of building simulation tools. This paper presents an improved method for direct solar shading calculations based on the projection of every polygon on a unique receiving surface and incorporates recent and high efficient algorithms to solve polygon intersections. Firstly, the method is shortly described. Secondly, it is validated by comparisons with other methods, experimental results and European standards. Then, a comparison test between the proposed and conventional methods is presented to assess computational speed improvement. Finally, the main advantages of the proposed method are discussed.     

Optimising renovation strategies for energy conservation in housing

A method for developing an optimal energy strategy for housing refurbishment, specifically applied to high rise, multi-family blocks, is considered. The ‘BREDEM 8’ monthly calculation procedure was used to compare the effect of various refurbishment measures on a flat in a typical housing block. The performances of insulating measures, glazing options, control of ventilation and alternative heating systems were considered. A life cycle costing method was used to assess and compare their performances, to give an indication of financial benefits over the life of the measures. The ‘savings-to-investment ratio’ was used as a ranking tool, and a process for selecting measures, applying them to the building, and re-calculating the cost effectiveness of the remaining measures enabled interaction between the retrofits to be considered.     

利用统计学原理调查建筑能耗

了解建筑能耗现状,是开展建筑节能工作的基础。面对种类繁多、数量巨大的建筑物,为了使调查数据具有代表性,建议采用统计学原理进行调查。就调查方式、抽样方法和样本容量的计算进行了探讨。利用模拟结果代替试验抽样数据,得到了样本容量与建筑总量的变化关系,为样本容量的计算提供了帮助。