Calculation Of Energy Performance Research Articles

Comparative assessment of simple and detailed energy performance models for urban energy modelling based on digital twin and statistical typology database for the renovation of existing building stock

The renovation wave calls for an integrated, participatory, and neighbourhood to neighbourhood approach tailored to the local environments. This can be hindered by the lack of geometric and performance input data about the existing building stock. A parametric digital urban building energy modelling (UBEM) tool was developed for local municipalities to automate calculations for comprehensive renovation strategies utilizing public databases specifically at the neighbourhood level. This article compares the accuracy of two energy performance calculation models (seasonal heat balance method and hourly resistance–capacitance method) used within the tool to detailed energy simulation software and measured energy consumption data of existing group of residential buildings in a same neighbourhood. The accuracy for estimating the total primary energy demand was roughly below 10 % for both simplified models. The seasonal calculation method showed consistent overestimation of space heating, depending on building characteristics. Solar and internal heat gains significantly affect the accuracy of simplified heat balance calculations, particularly in well-insulated buildings, while the more detailed 5R1C lumped capacitance hourly method provides improved accuracy for space heating demand. The comparison of uniform (proportional) and project based window area distribution used in the calculation models showed only marginal difference. The study validated simple seasonal and 5R1C hourly calculation methods using data from an apartment building neighbourhood with 22 apartment buildings. Despite larger deviations in the case of individual buildings, the average deviation from measured heating demand was only around 3 %, the seasonal method slightly overestimating and the 5R1C hourly method slightly underestimating the measured values. The primary energy demand including typical values of domestic hot water and household electricity was overestimated by both simplified methods due to lower electricity and water consumption in reality although the difference was below 7 % for the entire district. This concludes that pooling the building envelope heat loss calculation on a district level improves accuracy on average allowing better assessment of comparative renovation strategies.

Reference Materials for Thermal Conductivity Measurements: European Situation

A reference material (RM), as defined by the International Vocabulary of Metrology (VIM 2012), must be homogeneous, stable, and suitable for use in measurements. Certified reference materials (CRMs) are RMs with documented property values, uncertainties, and traceability. ISO 17034:2018 outlines the requirements for RM producers, ensuring that CRMs meet standards for stability, uniformity, and reproducibility. In Europe, CE marking, from French “conformité Européenne”, which means European conformity, has been mandatory for thermal insulation products since 2002, ensuring their thermal performance is verified by accredited laboratories using RMs like IRMM440 and ERM FC440. Annually, European manufacturers produce over 200 million cubic meters of thermal insulation, necessitating thousands of thermal conductivity measurements daily to maintain CE marking compliance. Key characteristics of Reference Materials include long-term stability, thermal conductivity within specified ranges, and minimal dependence on density, thickness, and applied load. Sample thickness must conform to apparatus specifications, and homogeneity must be quantified. Reference Materials must also have appropriate dimensions, surface smoothness, and manufacturability. The Joint Research Centre (JRC) Geel has produced two Reference Materials, IRMM 440 and ERM FC 440, with specific characteristics to meet these requirements. Both are glass wool fibers with low thermal conductivity and specific density and thickness. The qualification of RMs involves inter-laboratory comparisons to ensure the accuracy and traceability of thermal conductivity measurements. The European market’s organization, including the use of Reference Materials and CE marking, has significantly improved measurement consistency and product quality. This system has led to lower uncertainties in thermal conductivity measurements compared to North America, highlighting the impact of standardized RMs on industry practices. Future needs include developing RMs with lower conductivity and increased thickness to accommodate market trends towards super insulation materials and bio-based components, enhancing energy performance calculations for buildings. This paper will present the process of defining a reference material and how it affects the uncertainty level of the calculation of building energy performance. This level depends on the characteristics of the materials used, their implementation, and external factors, such as the weather, as well as the reference material used for calibration of all European thermal conductivity measurement devices.

Life cycle environmental benchmarks for Flemish dwellings

To reduce the environmental effects caused by building construction and operation, life cycle assessment (LCA) is increasingly applied. In recent years, national building regulations have implemented LCA requirements to support building life cycle impact reduction. A key element in these regulations are environmental benchmarks which allow designers to compare their building designs with reference values. This study aims to develop bottom-up life cycle environmental benchmarks that represent the range of environmental impact results achieved with conventional construction in Flanders, Belgium. For this purpose, the study investigates the potential of using a database of building energy performance calculations. Specifically, this study considers 39 residential buildings identified as representative of the Flemish energy performance of buildings database of 2015–2016, applying modifications to establish scenarios that are still relevant in 2025. The buildings are assessed with the Belgian LCA tool TOTEM to calculate an aggregated environmental score based on the European product environmental footprint (PEF) weighting approach and including 12 main impact categories. In addition to the aggregated score, the climate change (CC) indicator is analysed individually. In view of the benchmarks, variations were applied to the 39 original buildings in terms of heating system and materialisation. The variation in heating system included changing gas boilers to electric heat pumps to comply with upcoming (2025) Flemish building regulations. The variations in building materials included three sets of conventional Flemish building element compositions that were applied to generate a wider spread of impact results as a basis for benchmarks. Benchmark values were derived through a statistical analysis of the 117 modelled variants: a best-practice value (10th percentile), reference value (median) and limit value (90th percentile). For the environmental score, the benchmark values are 86, 107 and 141 millipoints per square meter of gross heated floor area (GHFA) (mPt m−2GHFA), respectively; and for CC, the benchmark values are 844, 1015 and 1284 kg CO2-eq m−2 GHFA. Finally, the study discusses the representativeness, implications and limitations of the final benchmarks and benchmark approach.

ANALYSIS OF THE IMPACT OF LEED CERTIFICATION TECHNICAL REQUIREMENTS ON CALCULATED ENERGY PERFORMANCE OF AN OFFICE BUILDING

The article presents an analysis of the impact that meeting LEED certification criteria hason the calculated energy performance of a building based on Polish regulations regarding themethodology for determining the energy performance of a building, taking into account thetechnical modernization that affects the final result of the analysis. Calculations were carried outon the example of an office building. The analysis covered scope that combines LEED certificationand energy performance, such as water use and indoor lighting. The calculations were made ina program designed for energy performance calculations. The use of energy-saving lamps (46%lower energy use in relation to standard lamps) or fittings limiting the water flow from the tap(26% lower water use) did have a positive impact on the final calculation of post-modificationenergy performance, according to which the demand for primary energy was reduced by 36%.The static analysis was performed using commercial software for preparing energy performancecertificates and on the basis of formal guidelines set out by the LEED certification.

A simulation-based evaluation of using PCMs in buildings for energy efficiency under different climate conditions

Today, majority of energy consumed in buildings is used to provide thermal comfort conditions. Reducing heating and cooling loads to provide comfort conditions in buildings is possible by taking the right passive design decisions concerning the variables that affect these loads. The building envelope which seperates indoor environment from the outdoor environment and affects the development of indoor thermal comfort conditions is the most important determining factor for energy loads in buildings. In this study, after applying PCM on the building envelope and inner walls and inner floors annual heating, cooling and total energy consumptions and indoor environment comfort conditions in the zones were evaluated. The study was done for Istanbul representing temperate humid climatic zone and for Diyarbakir representing hot-dry climatic zone in the same degree-day region according to the TS825 standards. The residential building simulated for calculations is a 3 storey building with a rectangle floor plan and flat roof and the dimensions of these buildings are 10 m × 30 m × 9 m. The building comprises 9 zones and the building coverage is 300 m2. In order to reduce the difference in energy consumption and thermal comfort conditions among the zones due to their different locations, PCM was applied on inner walls and inner floors in addition to the building envelope to develop a range of alternatives. Annual energy performance evaluation and calculation of daily operative temperature values for January 21 which represents the heating period and July 21 which represents the cooling period were done by the EnergyPlus simulation tool. According to the calculations, the total energy load of the building in the A4.2 alternative where PCM was applied on the building envelope and on inner walls and inner floors was reduced by 11.96 % and 9.69 % in Istanbul and Diyarbakır respectively. With the alternatives, differences in energy consumption among the zones were reduced but not eliminated. Operative temperature values in the zones changed by 1.04 °C – 3.32 °C in Istanbul and by 0.87 °C – 1.16 °C in Diyarbakır with the PCM application contributing to the improvement of indoor comfort conditions.

A Comprehensive Framework for Data-Driven Building End-Use Assessment Utilizing Monitored Operational Parameters

The availability of building operational data such as energy use and indoor temperature provides opportunities to enhance the traditional building energy performance calculation. Disaggregated building energy use facilitates informed decision-making to identify cost-saving measures efficiently at the individual building and building stock levels. The existing energy performance analysis techniques with measured input data in the literature are fragmented. Moreover, they frequently approach this issue with varying degrees of complexity depending on the available input data, expertise, and time. The procedure of choosing an appropriate method is often cumbersome with limited indication of the usefulness of the outcomes. This study proposes a data-driven framework for end-use load disaggregation through techniques that exploit various kinds of building consumption data. The results demonstrate the use of different techniques for varied applications. Calibrated theoretical calculation, data-driven heat loss coefficient (HLC), and energy signature curve (ESC) are among the proposed methods in the framework that facilitate individual, and urban scale energy decomposition. It is observed that different methods yield unalike outcomes, while their performance is predictable. While the HLC methods are flexible but also highly sensitive to the input parameters, the ESC needs high-frequency time series but provides stable energy decomposition. The ESC is efficient for large-scale analysis and the HLC method for detailed case-specific applications. Calibrated theoretical energy decomposition has a simple workflow and can supplement the current energy performance assessment method, although it entails sufficient input data.

Experimental investigation of a ceramic heat regenerator for heat recovery in a decentralized reversible ventilation system

The operational characteristics of decentralized, wall–mounted, ductless, reversible heat recovery ventilation unit (HRV) with a ceramic honeycomb stone for sensible thermal energy storage and recovery were investigated in a full-scale, long-term experiment. Parametric experimental studies were carried out to obtain the operation cycles, supply air temperature, thermal effectiveness and sensible heat recovery under real working conditions of the heating season in Dfb Koepper-Geige climate. An experimental study was carried out to obtain data for determining the characteristics of supply air temperature as a base for further effectiveness and thermal sensible energy calculation. For comprehensive evaluation of the HRV the three specific effectiveness has been established as the instantaneous (from 100 to 63%–67% for the external temperature of −3 and 10 °C respectively), the air supply cycle (80–81%) and the long-term operation (62–63%), as a new approach to operation characteristics in the form of equations easy to implement in HVAC simulation programs and calculation sheets for future building energy simulation, building energy performance calculations, complex and simple engineering calculations, etc. Preserved open and universal form of research procedure and proposed equations, as a directly applicable characteristics, enable effective engineering calculations and analyzes, and allow for determining the operational characteristics of other devices with analogous operating principles.

Quality and accuracy of digital twin models for the neighbourhood level building energy performance calculations

For scaling renovation, there is a need for assessing the energy performance of buildings at the neighborhood level. Traditional methods for assessing individual buildings are manual and time-consuming – not sufficient to enable the neighborhood level assessment of the energy performance of buildings. Instead, new methods based on existing data in national registries and building typologies are required. The aim in this article is to develop for obtaining necessary initial building geometry information for energy performance calculations from the Estonian national Building Registry (EBR), including also Digital Twin (LOD) geometric models of buildings, and the quality and accuracy of this data is assessed. Altogether 417 representative buildings were used for qualitative and quantitative analysis. A sub-sample of 41 buildings were selected for more detailed analysis and development of methods. Two methods were developed to extract and enrich initial building geometry information for energy performance calculations: (a) the method combining the EBR and building reference data; and (b) the method combining the EBR and building typology data and LOD models of apartment buildings. The estimated accuracy of the first method (a) is around 98% and the second method (b) around 94%. Both methods underestimate the actual envelope area and thermal bridge lengths.

Use of energy profile indicators to determine the expected range of heating energy consumption

A small set of query variables designed to collect information about the energy-related features of residential buildings is presented. These “energy profile indicators” include information about those visible characteristics of a building which have a notable impact on its energy performance and are simple to assess. The queries are an interesting source for a rough energy performance calculation for single buildings as well as for housing portfolios or housing stocks.A method has been developed to transform the energy profile indicators into input data for a physical calculation model. It consists of procedures to estimate the envelope area, U-values, and efficiency values of the heat supply system. To all model input variables an uncertainty is assigned. If information from a query is not available, the model input is set to a state representing the average building stock and the uncertainty of this quantity is adjusted to a value reflecting the variance in the stock. The resulting uncertainty of the calculated energy use is determined.Examples of the application of the method are given to show the influence of different unknown quantities including occupant behaviour. Experiences on the coherence with metered consumption are reported.

FEM-Based Evaluation of the Point Thermal Transmittance of Various Types of Ventilated Façade Cladding Fastening Systems

The prevalence of ventilated façade systems is not only due to their aesthetic properties but also due to the fact they provide mechanical and acoustic protection for the façade and reduce the energy demand of the building. However, it is essential to mention that the point thermal bridges of the fastening system with brackets and anchors are often neglected during simplified energy performance calculations and practical design tasks. The reason practitioners do not consider the brackets in the calculation is the lack of standards for the simplified calculation of point thermal transmittances, or there being no comprehensive, manufacturer-independent thermal bridge catalogue available. This study aims to evaluate the point thermal transmittances created by the brackets and anchors of the ventilated façade claddings by using 3D numerical thermal modelling. A broad point thermal bridge catalogue was created, considering multiple factors of the ventilated facades. The FEM-based results show that thermal breaks/isolators could reduce the point thermal transmittances by only 2 to 28%, depending on the material of the brackets and the isolators. The brackets’ material and geometrical properties/parameters could cause up to 70% of difference between corrected and uncorrected thermal transmittance values, as well as significant differences between the results if the brackets were applied to different kinds of masonry walls or reinforced concrete walls.

On the assessment of the heat transfer coefficients on building components: A comparison between modeled and experimental data

The thermal performances of building components require an accurate evaluation of the heat transfer processes on the internal and external surfaces. These evaluations involve the convective and the radiative heat transfer coefficients, which in actual conditions vary dynamically. Nevertheless, international standards indicate combined and steady heat transfer coefficients, especially in building energy performance calculations. In this paper, an experimental campaign carried out on a real scale measurement station available at the University of Calabria (Italy), has allowed for comparing the actual data with those calculated by a numerical code based on the Finite Difference Method (FDM), implementing the usual equations governing the heat transfer processes. The code is generalizable for every enclosure and does not require excessive computational effort. By assuming dynamic and separated heat transfer coefficients first, and successively steady and combined values, a comparison in terms of surface temperatures and transmitted thermal fluxes was conducted using the developed code on different building components, having different dispersing and thermal mass features. Regarding the measured values, the provided results showed a large discrepancy when steady and combined heat transfer coefficients are adopted, especially for the inner surfaces. Dynamic and separated heat transfer coefficients, instead, allow for meeting experimental data quite well, independently from dispersing and thermal mass characteristics. Furthermore, in simulation tools, a large discrepancy appears both in terms of energy needs and thermal comfort conditions on the experimental set-up, when simulated with steady convective heat transfer coefficients.

A Novel Dynamic Approach to Cost-Optimal Energy Performance Calculations of a Solar Hot Water System in an nZEB Multi-Apartment Building

This paper presents the methodology for conducting a cost-optimal energy performance calculation of a solar hot water system, used for space heating and domestic hot water needs. The calculation is based on dynamic hourly methods, according to the new Energy Performance of Buildings’ (EPB) set of standards EN 15316:2017, and a revision of the standard EN 15316-5:2017 from the year 2021, dealing with storage-tank water temperature calculations. The paper provides proposals for modifications to these newly introduced standards, in order to overcome the observed ambiguities and shortcomings. The calculation of annual energy performance of a building was performed on an hourly basis over a year for the reference of an nZEB multi-apartment building, for a climate area of the city of Zagreb, taking into account water temperature change in the layers of the storage tank connected to solar collectors and hot water boilers. The cost-optimal solution was then determined by varying individual parameters of the building technical system. The influence of these parameters on the energy efficiency of the building was analyzed in detail. Furthermore, the results were compared against those obtained by the Croatian calculation algorithm based on the previous set of EPB standards, EN 15316:2008, currently used EU-wide for the energy performance certification of buildings. The results indicated that the calculation methods of the present algorithm underestimated the consumption of building primary energy by 12%. The energy delivered by solar collectors was underestimated by 18%.

Experimental observation and energy performance calculations of potential oxidants O4−/0 and O6−/0 clusters

In order to explore novel high-energy and green oxidants, oxygen-rich clusters O4−/0 and O6−/0 were investigated by laser-vaporization source, mass spectrometry and theoretical calculations. Most of the low-lying isomers of On−/0 clusters are polyline structures consisting of O2 and O3 units. With one exception, O6, which has a chair-form cyclic structure with D3d symmetry, just like cyclohexane. It has the largest HOMO-LUMO energy gap of the On−/0 (n = 4, 6) clusters. The energy performances of O6 cluster were also estimated, which the density is 2.03 g/cm3, the solid enthalpy of formation is 114.75 kcal/mol, and the theoretical specific impulse (Isp) of H2(L)/O6 cluster is calculated to be 507.78 s.

Monitoring energy performance improvement: insights from Dutch housing association dwellings

The Energy Performance of Buildings Directive (EPBD) enhanced the sustainable improvement of dwellings in the European Union. Member states formulated measurable goals to improve the housing stock, and monitoring systems were developed to give insights into the improvements. In the Netherlands, non-profit housing associations agreed to improve the quality of their housing stock to an average Dutch energy label B (energy index (EI NV) = 1.40) by 2020. Research assessing this progress over time is presented using an annual monitoring system based on 2.0 million energy performance calculations of 264 Dutch non-profit housing associations between 2017 and 2020. The assessment includes: a detailed description of the development of the state of the stock over time; the effect of changes to the stock (construction and demolition) and changes within the stock (different types of retrofit measures); and the different characteristics of non-profit housing associations. Insights from this research show which specific retrofit and other measures are adopted and have substantial impact over time. This provides a useful frame of reference for building stock analysis and accelerating the improvement of the building stock. It also creates a baseline of information for the future sustainable development of this particular stock. Practice relevance This research reveals which energy saving measures are most and least employed over time in Dutch non-profit housing associations sector. Large urban housing associations own a large share of the Dutch non-profit housing stock, and their dwellings have on average a lower energy rating. However, the improvement of their dwellings between 2017 and 2020 is higher than for smaller housing associations, which already have on average a higher energy rating. While the construction and demolition of dwellings contribute to 15.6% of the annual improvement, most of the improvement of the energy performance depends on retrofitting the existing stock. The trends are found to rely most on traditional measures (e.g. the installation of high-efficiency gas boilers and improved insulation). However, the rate of adding photovoltaic (PV) solar systems has increased rapidly in recent years, while futureproof systems (e.g. heat pumps and district heating) only have a steady adoption rate in this sector.

Multi-step building energy model calibration process based on measured data

Building energy models are a key element in regulatory compliance calculations. These energy performance calculations often do not accurately reflect actual operating conditions. Therefore, evaluation of energy performance comparing actual energy use of a building with the outcome of dynamic simulation models can be misleading, this difference is also known as the energy performance gap. The reduction of the gap is an important task aimed to provide confidence in the use of models for evaluation of energy efficiency. This paper is focused on reducing the technical issues (e.g. poorly adjusted thermal parameters in the envelope, inefficient boiler operator or lack of adjustment in parameters of heat pumps, baseboard radiators or air handling units) which are one of the main causes of the energy performance gap. The application of a multi-step, optimization-based, calibration methodology performed in a white-box simulation environment (EnergyPlus) using three months of ten minute time-step data to adjust HVAC parameter values with a genetic algorithm software (Jeplus) is validated on a real test site. Resulting in a BEM that fits the building’s hourly performance benchmark into international standards on three key levels: indoor temperature by Thermal Zone (TZ), heat production and electric consumption from heat pumps, which comprise all the components of a building energy model. A batch of 1500 h of heating operation, obtained from the building management system, has been used to calibrate the model. The results complied with the requirements of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Guideline 14–2002 at hourly interval, with NMBE ⩽±10%,Cv(RMSE) ⩽30% and R2 ⩾75% and with the International Performance Measurement and Verification Protocol (EVO) for Cv(RMSE) ⩽20% and R2 ⩾75% in the three aforementioned levels, which can be considered a step forward in the area of calibrating white box models. In addition, to prove the strength and robustness of the results, the model has been checked in a long testing and independent period of 2.500 h of heating operations with the same level of compliance. The demonstrator is the library of a school located in Denmark. The HVAC system is composed of four air–water heat pumps that deliver heating to the whole compound with the backup support of a gas boiler. The library is heated with baseboard radiators system with the support of an air handling unit used for ventilation purposes.

Evaluation of ISO 52010-1: 2017 and proposal for an alternative calculation procedure

A proper evaluation of the building energy consumption implies an accurate assessment of the solar gains and consequently an exact estimation of the direct and diffuse solar radiation on tilted and oriented surfaces.The new standard EN ISO 52016-1: 2017 introduces a new hourly methodology for the calculation of energy performance of buildings and is complemented by EN ISO 52010-1:2017, which specifies the procedure for the conversion of climate data for energy calculations. These standards represent a good compromise between the old EN ISO 13790:2008 and Trnsys, since they allow for a more accurate evaluation of energy consumption than the former, while being less onerous than the latter.In the present work, EN ISO 52010-1:2017 is analysed for the first time and an alternative calculation procedure is proposed. These two algorithms are then compared with two other irradiance splitting methods implemented in Meteonorm and Trnsys code.In order to test performance and limits of the different calculation algorithms, we make a comparison among such methods on five European cities characterized by different climatic characteristics.Results show that the model implemented in EN ISO 52010-1:2017 overestimates the diffuse solar irradiance on horizontal plane for all the considered locations, while the proposed procedure and those implemented in the Trnsys and Meteonorm softwares show similar results. Using Trnsys algorithm as a baseline, the proposed calculation algorithm gives the best approximation among the considered models for what concerns the direct, diffuse and global irradiance on vertical surfaces exposed to south, east and west.

Cost-optimal energy performance calculations of a new nZEB hotel building using dynamic simulations and optimization algorithms

This paper presents the procedure for conducting cost-optimal energy performance calculations for a new nearly zero energy hotel building in Croatia in the context of Energy Performance of Buildings Directive 2010/31/EU. For this purpose, dynamic simulation models of building and its technical systems were developed in IDA ICE simulating tool and coupled with GenOpt optimization software.Annual energy performance of the building is assessed by running hourly simulations. Energy, equipment and installation works costs were obtained by the open market analysis. After that, the global cost function was derived, and optimization performed to minimize the costs. The results show that the preferred heat source at the cost-optimal level of the building energy performance is air-to-water heat pump coupled with gas condensing boiler. Furthermore, an analysis of thermal comfort is provided to demonstrate the use of the proposed approach in preventing system oversizing, efficiency decrease and thermal comfort deterioration. At the end, energy performance calculations obtained by IDA ICE were compared to those obtained by the widely used EN 13790 and EN 15316 series of standards used for determining energy performance of buildings for legal purposes. Based on this, the recorded discrepancies in results are analysed and applicability of mentioned standards calculations on low-energy buildings is discussed.

Primary Energy Balance driven Integrated Energy Design Process of Positive Energy Building

The ISO 52000–1:2017 is the overarching Energy Performance of Buildings (EPB) standard, providing the general framework of the EPB assessment. It is applicable to the assessment of overall energy use of a building, by measurement or calculation, and the calculation of energy performance in terms of primary energy or other energy-related metrics. ISO 52000–1 provides general profound guidelines, but also gives the freedom to adapt the guidelines with national standards and regulations. This article focuses on design stage energy performance assessment in the framework of syn.ikia project, which aims to deliver a blueprint for an Integrated Design Process of sustainable plus energy buildings and neighbourhoods, leading the way to plus energy districts and cities. This project has four demonstration sites and the one being in focus of this article is located in Catalonia, Spain. Even though this project and Spanish Technical code both are based on ISO 52000–1, the criteria of calculation boundaries of those two vary in some degree, and that can cause great difference in the primary energy balance. In the calculation of the energy balance the criteria of syn.ikia considers all common energy uses in a building, including heating, cooling, ventilation, dehumidification, domestic hot water and lighting, while the Spanish Technical Code excludes lighting consumption. The main difference however is caused due to the fact that in syn.ikia hypothesis the exported energy is being considered in the calculation of how much non-renewable energy is avoided from the grid, while Spanish Technical Code excludes it. For the evaluation of these differences, a simplified monthly primary energy calculation tool is developed during the evaluation framework of key performance indicators of the project. The analysis of the calculation framework hypothesis is presented, analyzing the effects of the assessment boundaries, different primary energy balance calculation hypothesis and building design alternatives.

The level of knowledge, use and acceptance of LCA among designers in Germany: A contribution to IEA EBC Annex 72

Architects and engineers have become more concerned about the environmental consequences of their design solutions. Knowledge about Life Cycle Assessment (LCA) is crucial for the necessary building sector decarbonisation, as well as for mitigating other negative environmental impacts. In Germany, designers’ attitudes towards LCA have not been analysed since 2005. However, since then, certain developments – such as the establishment of the sustainability assessment systems BNB and DGNB – have taken place. In 2019, as part of the project IEA EBC Annex 72, a survey was conducted amongst designers in Germany. The paper presents the current status to identify the progress being made since 2005 and provides recommendations to overcome barriers to LCA dissemination. The results show that although German designers are currently doing a lot with regard to environmental performance assessment, the most critical aspects are considered in a more qualitative way, except for the mandatory operational energy performance calculations. LCA-know-how and application still lags behind expectation. To support an increased use of LCA during building design, not only the provision of related data and design/assessment tools is necessary, but also the establishment of standards and regulations. The latter will drive the also necessary client demand.

Numerical Calculation of Energy Performance and Transient Characteristics of Centrifugal Pump under Gas-Liquid Two-Phase Condition.

The unstable operation of a centrifugal pump under the gas-liquid two-phase condition seriously affects its performance and reliability. In order to study the gas phase distribution and the unsteady force in an impeller, based on the Euler-Euler heterogeneous flow model, the steady and unsteady numerical calculations of the gas-liquid two-phase full flow field in a centrifugal pump was carried out, and the simulation results were compared with the test data. The results show that the test results are in good agreement with the simulation data, which proves the accuracy of the numerical calculation method. The energy performance curve of the model pump decreases with the increase of the gas content, which illustrates a serious impact on the performance under the part-load operating condition. The results reveal that the high-efficiency-operating range become narrow, as the gas content increases. The gas phase is mainly distributed on the suction surface of the impeller blades. When the gas content reaches a certain value, the gas phase separation occurs. As the inlet gas content increases, the radial force on the impeller blades decreases. The pattern of the pressure pulsation is similar to that under pure water and low gas content conditions, and the number of peaks during the pulsation is equal to the number of the impeller blades. After the gas content reaches a certain value, the pressure fluctuates disorderly and the magnitude and the direction of radial force change frequently, which are detrimental to the operation stability of the pump. The intensity of the pressure pulsations in the impeller flow channel continues to increase in the direction of the flow under pure water conditions. The pressure pulsation intensities at the blade inlet and the volute tongue become more severe with the increase of the gas content.