•Traditional office buildings, that contain most climate-responsive design elements, consumed the least energy than Green Certified Office Buildings.•The modern office buildings with minimal and ...maximal glass façades consumed the most energy.•The buildings with single-split HVAC systems consumed less energy than those with multi/central systems.•Building classifications and HVAC type are the most significant predictors of energy use, followed by window-to-wall ratio.
The rate of energy use around the world in recent years has been alarming. In Africa, and Tanzania in particular, the energy demand for office building is increasing annually as a result of urbanisation, population growth and economic growth. Reducing office buildings’ ever-escalating energy use is a critical objective requiring scholarly attention. To contribute to achieving that objective, this study compared the energy performance of 2 green and 15 non-green office buildings in Dar es Salaam, Tanzania. The buildings were sampled purposively. The buildings’ consumption patterns were studied by examining their electricity bills over a five-year period (2015–2019). The buildings’ energy consumption data and elements of their designs were analysed using multiple regression models. The study examined four building sets (green buildings, non-green buildings with maximal glazing, non-green buildings with minimal glazing and traditional office buildings). The results indicate that the traditional office buildings, which contained the most climate-responsive design elements of the building types examined, consumed less energy than green-certified office buildings. The modern office buildings with minimal and maximal glass façades consumed the most energy. The buildings with single-split HVAC systems consumed less energy than those with multi/central systems. The study concluded that building classifications and HVAC type are the most significant predictors of energy use, followed by window-to-wall ratio. As East Africa urbanises rapidly, these findings will provide architects, engineers, property managers and policymakers with research-based, real-life data that are specific to their context. Those data can help enhance the performance of green and non-green buildings during their design and operation phases. The study recommends adopting a design strategy that considers both climatic and technical factors in order to optimise building design decisions to lower buildings’ energy use.
In the present climate, thermal insulation is crucial for reducing energy consumption for heating or cooling in buildings, increasing the lifespan of structures, and building elements, and improving ...human comfort. The wall's composition layer has advanced regularly since the building regulations and established norms. However, calculation methods have remained quite the same, governed by Fourier's law. Therefore, to address this gap, a linearization process, and a correction factor of the optimized insulation thickness for four different insulation materials (i.e., EPS Graphite, EPS, GW, and RW) and five energy carriers (i.e., electricity, diesel, natural gas, liquefied petroleum gas, and biomass) by removing the boundaries of heating degree days by using Mathcad software is proposed. Other financial parameters (i.e., inflation rate, interest rate, lifespan, and present worth factor) and heating system features that lead to the optimized insulation thickness are considered. The RETScreen Expert model was coupled with a Mathcad script to compute a standardized corrected optimized insulation thickness (COIT) value by applying sensitivity analyses at ±35% of the most influencing parameters to calculate the total overhauling cost for different building types in Albania. A correction of the existing window's heat transfer coefficient for a different glass-to-wall ratio is proposed. Our findings suggest that the overall heat transfer value (U) should be equal to or less than 0.30 (W/m2•K), leading to a range of corrected optimized insulation thickness (COIT) from 0.03 m up to 0.11 m. Moreover, results exhibited encouraging economic and environmental values concerning the unrenovated buildings leading to annual net savings of 23.50–84.50 €/m2, CO2 reduction up to 39.10 kgCO2/m2, and a simple payback period (SPP) of 0.30 maximum up to 1.20 years. The outputs of this study can bring benefits in terms of reduced energy consumption and CO2 footprint, and the proposed COIT value can be applied not only in Albania but in other regions that exhibit similar climate conditions.
•The lowest optimum insulation thickness is obtained using biomass as the energy source.•Net savings increase from zero for the uninsulated case to a maximum of 84.5 €/m2.•The CO2 level emission decreases to 82% at the optimum insulation thickness.•The simple payback period ranges from 0.303 to 1 year for the minimum insulation thickness.•The proposed U value to meet the minimum energy efficiency should be less than 0.3 W/m2.•K.
In developed countries, buildings are involved in almost 50% of total energy use and 30% of global green-house gas emissions. Buildings' operational energy is highly dependent on various building ...physical, operational, and functional characteristics, as well as meteorological and temporal properties. Besides physics-based building energy modeling, machine learning techniques can provide faster and higher accuracy estimates, given buildings' historic energy consumption data. Looking beyond individual building levels, forecasting buildings’ energy performance helps city and community managers have a better understanding of their future energy needs, and plan for satisfying them more efficiently. Focusing on an urban-scale, this study systematically reviews 70 journal articles, published in the field of building energy performance forecasting between 2015 and 2018. The recent literature have been categorized according to five criteria: 1. Learning Method, 2. Building Type, 3. Energy Type, 4. Input Data, and 5. Time-scale. The scarcity of building energy performance forecasting studies in urban-scale versus individual level is considerable. There is no study incorporating building functionality in terms of space functionality share percentages, nor assessing the effects of climate change on urban buildings energy performance using machine learning approaches and future weather scenarios. There is no optimal criteria combination for achieving the most accurate machine learning-based forecast, as there is no universal measure able to provide such global comparison. Accuracy levels are highly correlated with the characteristics of forecasting problems. The goal is to provide a comprehensive status of machine learning applications in urban building energy performance forecasting, during 2015–2018.
•Urban-level scarcity over individual level building energy performance forecasting.•No study incorporates buildings' space functionality share percentages.•No study assesses the effects of climate change using future weather scenarios.•No optimal criteria combination to provide the most accurate forecast.
•Bottom-up methodology to estimate dwellings’ theoretical final energy consumption.•High-resolution spatial scale analysis for 3092 Portuguese regions.•Energy performance gaps result from inefficient ...dwellings and low energy consumption.•The north and center inland were identified as the most vulnerable regions.•Outcomes can be used in the planning for local energy efficiency and RES policies.
An aging building stock and low-efficiency heating, ventilation and air conditioning (HVAC) systems may be preventing the adequate energy performance (EP) of Portuguese dwellings. This study aims to estimate and analyze the EP gap of the occupied main residence Portuguese residential dwelling stock, for thermal comfort attainment, at high geographical resolution scale, i.e. for every civil parish. A building typology approach was applied to estimate the heating and cooling (H&C) theoretical final energy consumption (TFEC) for thermal comfort. An energy consumption statistics-based approach was used to estimate the H&C real final energy consumption (RFEC). The EP gap is the percentual difference between the TFEC and RFEC. Three scenarios were tested, looking deeper into southern European space H&C patterns, considering varied conditioned areas and occupancy schedules. This study provides a methodological framework for zooming in the assessment of the dwelling stock EP for a whole country, allowing for a comparative analysis between regions, as the different regional EP gap drivers are identified. For nominal conditions, every civil parish has an EP gap higher than 60%, for both H&C, related to poor energy efficiency of the building stock and low H&C energy consumptions. The scenarios demonstrated a bridging of several civil parishes’ EP gap, possibly resulting from temporal space climatization patterns. High remaining EP gaps suggest the civil parishes in the north and center inland regions are the most vulnerable in the winter and summer seasons, potentially due to significant energy poverty levels.
Energy performance improvement in manufacturing is hindered by the lack of information on energy use in production and by the predominant economic vision in the assessment of energy interventions. ...This paper proposes a framework that integrates energy performance mapping with energy systems optimization. The framework introduces a new dimension to energy performance mapping by tracing energy use along processing and energy conversion steps and revisits multi-criteria assessments by assigning penalties to the energy performance gap with best practice. The suitability of food manufacturing for the application of the framework is exemplified from both a top-down and bottom-up perspective. More than 80% reductions in purchased energy carriers and non-renewable energy sources are achieved in a representative process through interventions coupling sector-specific manufacturing knowledge and energy expertise. With regard to one of the interventions, the introduction of the penalty is shown to shift the optimal solution, yielding more than 25% reductions in energy consumption compared to a purely economic assessment. The proposed framework can help industrial stakeholders identify improvement opportunities and develop more sustainable energy systems in manufacturing. Its widespread use can encourage poor performing companies to align with best practice and virtuous companies to continuous innovation to maintain their competitive advantage.
Display omitted
•A framework for energy performance improvement in manufacturing is proposed.•The framework introduces a new dimension to energy performance mapping.•The framework revisits multi-criteria assessments with an applicative orientation.•80% reductions in purchased and non-renewable energy are achieved in a case study.•The introduction of the penalty yields 25% energy reduction in the optimal solution.
•Evaluation of existing approaches of buildings energy retrofit decisions.•Generalized methodology for buildings’ energy performance knowledge base.•Key retrofit recommendations identified for urban ...scale residential buildings.•Study of reduction in energy demand and emissions at a large scale.
Urban planners face significant challenges when identifying building energy efficiency opportunities and developing strategies to achieve efficient and sustainable urban environments. A possible scalable solution to tackle this problem is through the analysis of building stock databases. Such databases can support and assist with building energy benchmarking and potential retrofit performance analysis. However, developing a building stock database is a time-intensive modeling procedure that requires extensive data (both geometric and non-geometric). Furthermore, the available data for developing a building database is sparse, inconsistent, diverse and heterogeneous in nature. The main aim of this study is to develop a generic methodology to optimize urban scale energy retrofit decisions for residential buildings using data-driven approaches. Furthermore, data-driven approaches identify the key features influencing building energy performance. The proposed methodology formulates retrofit solutions and identifies optimal features for the residential building stock of Dublin. Results signify the importance of data-driven retrofit modeling as the feature selection process reduces the number of features in Dublin’s building stock database from 203 to 56 with a building rating prediction accuracy of 86%. Amongst the 56 features, 16 are identified to be recommended as retrofit measures (such as fabric renovation values and heating system upgrade features) associated with each energy-efficiency rating. Urban planners and energy policymakers could use this methodology to optimize large-scale retrofit implementation, particularly at an urban scale with limited resources. Furthermore, stakeholders at the local authority level can estimate the required retrofit investment costs, emission reductions and energy savings using the target retrofit features of energy-efficiency ratings.
The concept of a Digital Building Logbook (DBL) was first introduced with the European strategy ‘Renovation Wave’. It is considered as one of two fundamental parts of which the Building Renovation ...Passport is composed: the DBL and a Renovation Roadmap. As the implementation of the DBL is a European priority, this paper reviews the existing literature and analyses the most developed European Digital Building Logbook models. The analysis includes iBRoad, ALDREN, X-tendo, and the Study on the Development of a European Union Framework for Buildings’ Digital Logbook, from the perspective of seven key aspects: References used as a starting point for the model definition; Identification of the relevant stakeholders in the DBL; Identified potential user needs; Proposed structure of indicators; Data sources; Potential functionalities; and Operation and use. The results show that important advancement has been made, although there is still no consensus about crucial subjects, such as the indicators to be collected or how to collect and use them. This is probably due to the fact that the final functionalities (objective and scope) that the logbook should provide are not fully clear.
Display omitted
•Energy Performance Certificates (EPCs) are being renewed across Europe.•Old and renewed EPCs for Swedish multifamily buildings are matched and compared.•A three-step method is ...developed to ensure that matched EPCs are comparable.•Novel quantitative, building-specific analyses of change in energy use are enabled.•Future applications of matched EPCs include evaluation of renovations and policies.
Energy Performance Certificates are currently one of the most extensive data sources about the energy performance of the EUs building stock and consequently provide support for researchers and policy makers in energy regulation. As Energy Performance Certificates are being renewed, there are new possibilities to study energy performance development over time and to evaluate the building-specific effect of energy policies and measures. This paper aims to explore this possibility. In Sweden, owners of multifamily buildings had to obtain their first Energy Performance Certificate no later than the end of 2008, and with a period of validity of 10 years many owners have now obtained a second Energy Performance Certificate for their building(s). This enables unprecedented quantitative, building-specific evaluations of the change in energy performance over time. However, comparability between old and new Energy Performance Certificates must be assured. This study develops a novel three-step method to attain comparability between old and renewed Energy Performance Certificates. Results show that while many pairs of Energy Performance Certificates were considered comparable, procedural changes in methods for determining heated floor area in Swedish Energy Performance Certificates caused an overestimation of energy performance improvement of approximately 7 kWh/m2 per building which had to be corrected for. The results of this paper indicate that old and renewed Energy Performance Certificates can be utilised to successfully map development of energy performance and enable evaluation of the impact on energy performance from policies and measures that have been carried out between the two points of audit.
As a way of exploitation and utilization of ocean energy, the waterjet pump is used in a wide range of high-speed marine vessels over 30 knot. This paper aims to investigate the mechanism of the ...energy loss and pressure fluctuations caused by the non-uniform inflow for a waterjet pump. Unsteady internal flows inside the waterjet pump are simulated using the Reynolds-averaged Navier-Stokes equations with the SST k-ω turbulence model. The predicted pump head and efficiency are in reasonable accordance with the experimental data. The inflow non-uniformity would decrease the hydraulic head, efficiency and increase the axial force fluctuations in the impeller, causing large pulsations in the unsteady energy performance. Based on analyses of the energy loss, the turbulent kinetic energy production and the diffusion of the Reynolds stress are major sources of the energy loss in the waterjet pump. The non-uniform inflow induces a dramatic energy loss in the intake duct and diffuser with an apparent flow separation observed near the trailing edge of the diffuser blade. Due to the inflow non-uniformity, the pressure fluctuates violently at the impeller rotating frequency (fn) in the intake duct, impeller and near the diffuser inlet, but a dominant frequency of 2fn is generated by the unsteady flow separation near the diffuser outlet.
•Inflow non-uniformity makes large pulsations to the energy performance.•Energy balance equation is introduced to clarify the mechanism of energy loss.•The non-uniform inflow induces a periodic prewhirl motion in the intake duct.•2fn is generated by an unsteady vortex evolution near the diffuser outlet.
The World Energy Council releases the Energy Trilemma Index (ETI) report annually primarily to assess the energy performance of countries worldwide. Nevertheless, the varying preferences of the ...dimensions in the ETI between the countries are debatable. The objective of this study is weight allocation therefore this study presents two-fold contribution to comprehensively formulate all possible preferences under the interval assessment outcomes by employing the interval decision matrix followed by the Principal Component Analysis (PCA) to assess the national energy performance of top ten countries for the year 2015. Unlike the conventional methods, the significant advantage of PCA for index construction is that it does not allocate ad-hoc and subjective weights to different indicators. The obtained results were demonstrated by measurement of top ten countries energy performance based on ETI of 2015. Through the development of Energy Development Index, Norway was determined as the highest performing country among the top ten countries. This does not coincide with 2015's ETI which regarded Switzerland as the best performing country. Hence, the ranks are arguable. Further results reveals that there are considerable differences in the values of indicators among all countries. The obtained outcome is expected to aid the policy makers to understand the contribution of different indicators.
PDF
