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Highlights • CFD and Global Energy Balance (GEB) to simulate a solar chimney were analyzed. • There are few calculation tools based on transient models for the dimensioning of solar chimneys. • GEB models predict the dynamic behavior in relatively short times and one can integrate them with Building Energy Simulation programs. • Results of a solar chimney using a PCM show that the airflow was available in evening and night periods. • This review paper is a reference for future research into the field of solar chimneys with a PCM and its applications. Abstract The solar chimney is one concept explored by building engineers and designers for reducing heat gain and inducing natural cooling in both commercial and residential buildings. In this sense, scientists around the world have developed significant research on solar chimneys since the 1990s. This review presents the studies related to the numerical thermal modeling of both, conventional solar chimneys and solar chimneys with phase change materials (PCM). The article focuses on two research areas: Computational Fluid Dynamics (CFD) and Global Energy Balance (GEB). Based on the literature, the CFD approach has become a powerful tool to investigate several aspects concerning the heat transfer mechanisms in a solar chimney. Additionally, the analysis of the literature showed that few calculation tools based on CFD transient state models of solar chimneys are available because the computational time required to solve these models could be excessive and impractical. Therefore, the use of high-performance computing (HPC) will be necessary to continue using CFD. On the contrary, the GEB models predict the transient behavior of these systems in short times, and one can integrate them in Building Energy Simulation programs. However, the literature about the solar chimney modeling using GEB shows that the transient mathematical model with PCM (six research papers) has been less used than the steady-state model. In general, results of a solar chimney using a PCM show that the temperature variation of PCM and air in the chimney were available for the natural ventilation in evening and night periods. Finally, this review paper is a reference for future research into the field of solar chimneys with a PCM and its applications. [ABSTRACT FROM AUTHOR]

Dynamic cooling and heating load forecasting of heating, ventilation and air conditioning (HVAC) systems is a basis for optimizing the operation of HVAC systems and can contribute to achieving the effective management for the HVAC systems. This paper proposes a load forecasting method for office buildings based on artificial intelligence and regression analysis, including wavelet transform, support vector machines (SVM), and partial least squares regression (PLS). An office building located in Tianjin, China is taken as the building case study to validate the proposed model. For selecting the input variables, the methods of sensitivity analysis and correlation analysis are used. The results of different prediction horizons, mainly including 1 h ahead, 2 h ahead, 3 h ahead and 24 h ahead forecasting, are finally provided. In order to illustrate the accuracy improvement of the proposed model, the other three models are built to compare with the proposed model. Further, the influence of weather forecast precision on the proposed model is analyzed in this paper. The results indicate that the proposed method can realize dynamic load forecasting with high accuracy for different time horizons. [ABSTRACT FROM AUTHOR]

The use of Phase Change Materials (PCM) in different building applications is a hot topic in today's R&D activities. Numerical simulations of PCM-based components are often used both for research activities and as a design tool, although present-day codes for building performance simulation (BPS) present some shortcomings that limit their reliability. One of these limitations is the limited possibility of replicating the effects given by thermal hysteresis – a characteristic of several PCMs. In this paper, an original algorithm that allows hysteresis effects to be accounted for is described and the results from simulations are compared against experimental data. The algorithm is implemented in EnergyPlus™ and makes use of the Energy Management System (EMS) group, one of the high-level control methods available in EnergyPlus™. The algorithm enables the replication of PCM's different heating/cooling enthalpy curves in this BPS tool, which just recently was equipped with an integrated module for the replication of the effects of thermal hysteresis. A comparison between numerical results from the proposed model and from other methods implemented in BPS tools, and the experimental data provided, shows the impact of the algorithm in the simulation of heat transfer in a PCM layer intent for opaque walls. In general, it is shown that the proposed method presents a better agreement with experimental data than alternative modelling approaches, but it is also seen that all the tested numerical models are not fully able to replicating the behaviour of PCM layers if the PCM does not melt or resolidify completely (i.e. it remains in the phase change) during the charge/discharge cycle. A local sensitivity analysis complements this study and highlights the most relevant parameters that influence the results of a simulation carried out with the proposed model. Finally, the paper hypothesises that the general discrepancy between simulations and experimental data seen in the case of incomplete melting of the PCM layer can be due to unsuitable data for the thermophysical behaviour of the PCM, which are obtained through conventional characterisation procedures far from the physics of the PCM layer when in real building structures. [ABSTRACT FROM AUTHOR]

This paper presents a model based on dynamic material flow analysis, general in its principles and applied to the dwelling stock of Norway for exemplification. The algorithm at the core of the model is presented in the form of a pseudo-code and is described in detail. The driving force in the model is a population’s need for housing and the necessary input are retrievable from national statistics on population, often dating back to around 1800, and its prognoses up to 2050 or beyond. Technical parameters such as the dwellings’ lifetime and the renovation cycles are expressed by probability functions. Outputs of the model are the flows of construction, demolition and renovation; analysis of the renovation activity is given particular attention. The model shows how the renovation rates are a result of the need for maintenance of an ageing stock, and provides quantitative estimates of the present and future natural renovation rates, i.e. without specific incentives. The paper shows how to validate the model against statistics and other data sources, and how to use the model’s future projections on construction, demolition and renovation activities in scenario based analyses of dwelling stocks’ energy demand and greenhouse gases emissions. [ABSTRACT FROM AUTHOR]

Developing sensitivity analysis (SA) that reliably and consistently identify sensitive variables can improve building performance design. In global SA, a linear regression model is normally applied to sampled-based solutions by stepwise manners, and the relative importance of variables is examined by sensitivity indexes. However, the robustness of stepwise regression is related to the choice of procedure options, and therefore influence the indication of variables’ sensitivities. This paper investigates the extent to which the procedure options of a stepwise regression for design objectives or constraints can affect variables global sensitivities, determined by three sensitivity indexes. Given that SA and optimization are often conducted in parallel, desiring for a combined method, the paper also investigates SA using both randomly generated samples and the biased solutions obtained from an optimization run. Main contribution is that, for each design objective or constraint, it is better to conclude the categories of variables importance, rather than ordering their sensitivities by a particular index. Importantly, the overall stepwise approach (with the use of bidirectional elimination, BIC, rank transformation and 100 sample size) is robust for global SA: the most important variables are always ranked on the top irrespective of the procedure options. [ABSTRACT FROM AUTHOR]

The goal of this paper is to identify the effects of in-pore transport of liquid water and water vapor as well as phase changes on the hygrothermal behavior of earthen buildings. Indeed, one of the main assets used to promote these constructions is their role in moisture buffering hence temperature and relative-humidity quality controlling. However, there is no clear consensus yet concerning the impact of these phenomena on the global energy performance of the buildings. A coupled model is therefore proposed in this paper, based on heat and mass balances inside the earthen walls, in order to clarify this question. This model considers separately the kinematics of each phase (e.g. liquid water, vapor, dry air and solid matrix), in interaction with each other. It also takes into account the impact of pore water confinement on the liquid-to-vapor phase change, in particular on the resulting latent heat released or absorbed. The model is successfully compared to experimental results on instrumented full-scale rammed earth wall subjected to temperature cycles. It eventually allows identifying the singular hygrothermal behavior of earth material by testing the range of applicability of the simplifying assumptions which are commonly made in function of the permeability of the tested material. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the performance and heat and mass transfer processes that occur in counter-flow indirect evaporative air coolers. Different types of counter-flow air coolers were compared: a typical counter-flow unit, the same unit operating as a heat recovery exchanger, a regenerative unit and a novel modified exchanger, proposed by authors. Additionally the paper investigated impact of location of the perforated holes in the channel plate of regenerative air cooler. The numerical model is based on a one-dimensional heat and mass transfer analysis that was validated against existing experimental data. The results obtained from the simulation reveal the high effectiveness of the presented units. It was established that selected arrangements of the presented exchangers are characterized by the different efficiency in different air-conditioning applications. [ABSTRACT FROM AUTHOR]

This paper is focused on increasing the knowledge on methods for calibrating BES models and to get more insights of different approaches for the optimization of the calibration process. The paper will be centred in the evaluation of a multistage guided search approach. It defines an iterative optimization procedure which starts with the assignment of probabilistic density functions to the unknown parameters, followed by a random sampling and running batch of simulations. It then finishes with an iterative uncertainty and sensitivity analysis combined with a re-assignment of the ranges of variation of the strong parameters. The procedure converges when no new influencing parameters are found. This method is applied to a real case study consisting of an unoccupied office building located in Lleida (Spain). The measured indoor temperature has been used to determine the uncertainty and precision of the method. The effect of the size of the sampling, the number of iterations and the parameters of the global sensitivity method are analyzed in detail. The results of this paper exemplify the degree of accuracy of multistage guided search approaches, and illustrate the reasons how these analyses can contribute to the improvement of more refined calibration methods. [ABSTRACT FROM AUTHOR]

A significant number of studies have researched into the household energy consumption and CO 2 emission (HECCE). However, little attention has been paid to model the complex interrelationships that exist among the various variables involved, especially for the effect of qualitative variables such as occupants’ behaviour. In this regard, a methodology of systems-based approach has been adopted in this research to model the complexity of the socio-technical system of household energy consumption and CO 2 emission. This paper will explore the intrinsic interrelationship between the dwellings, occupants and environment systems. The study identifies ‘cause and effect’ relationships among these systems as well as quantitatively simulates the behaviour of HECCE. A system dynamics model is proposed to utilise the hard and soft data incorporated in this system with due cognisance to the inter-dependencies of variables that are involved in addition to mental judgement of the experts and industry practitioners. The paper also discusses the validation of the proposed model. The proposed model provides policy makers with a decision making tool upon which different scenarios regarding HECCE can be tested before implementation. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model is formulated to quantify the social impact an individual has on his/her community when he/she performs any energy efficiency project and transmits that information to his/her neighbours. This model is called the expected power savings model; it combines direct and indirect expected power savings of the energy efficiency project for each individual within the network. The indirect savings are quantified through the social interactions people in the network. The example used in this paper illustrates the effectiveness of the model by identifying the households who should have free solar water heaters installed in their residential houses based on their influence through interactions in their community. Two case studies are considered in this paper, single and multiple sources case studies. In the multiple source case study, the results show that it is not necessarily the people with the highest connections who provide the maximum expected power savings. [ABSTRACT FROM AUTHOR]

Abstract: The velocity of wind in an urban location is comparatively lower than in rural or semirural locations. This paper deals with the study of a new methodology to increase the wind speed and power output of small turbines located in urban areas. The new methodology is adopted based on TRIZ (Theory of Solving Inventive Problems) principles. This idea was obtained from the different shapes adopted for the Roof Tops of Buildings at various locations. The methodology used here studies the impact of monoslide roof shape on wind speed using CFD. Majority of buildings in India have Flat Roofs. So, the paper suggests the use of adjustable roof so that the roofs could be tilted at various angles. The present study gives a diagrammatical representation of the new method and an analysis using CFD. Measuring the velocity of wind at an urban location at various altitudes and at various locations of the buildings is a complex task. Computational Fluid Dynamics (CFD) is already a necessary tool for modelling the wind over complex urban terrains. This study underlines a system to reduce the passiveness and idle time of wind turbines located in buildings. That could make the urban wind turbine more agile and active for higher power generation and resource utilization. [Copyright &y& Elsevier]

Abstract: Liquid desiccant cooling system (LDCS) is an alternative air-conditioning system with promising energy-saving potential. To further explore the potential of LDCS, it is important to reveal the mass transfer mechanism of dehumidification process. The classical mass transfer model does well in theoretical analysis, but failed to explain the dehumidification reverse phenomenon in experiments. Therefore, this paper proposes a mass transfer model based on the kinetic theory for improvement. Through theoretical and experimental research, it proves the new model clearly describes the dehumidification mechanism and did better in predicting the dehumidification reverse phenomenon. This paper also gives a method through which we can get some important parameters of the new model from the mass transfer coefficient of the classical model. [Copyright &y& Elsevier]

Abstract: This paper presents the mathematical procedure for the determination of overall sustainability index of nine options for the agglomeration of economic, environmental and social indicators. Eleven sub-indicators were selected and calculated for all chosen options. In accordance to final energy consumption (for space heating, hot water production, cooking and the household electrical appliances) the selection, defining and determining the economic, social and environmental indicators was developed. It was done for all chosen options selected by qualitative characterization of residential objects in accordance with construction period, type of heating system and type of object (buildings or family houses). Investigation of the influence of non-linear normalization on the sub-indicators’ agglomeration was the aim of this paper. Normalized sub-indicators are obtained by selection of the appropriate linear (θ =1) or non-linear function (θ ≠1). Sustainability index and its standard deviation were calculated for different value of the parameter θ and each option in six different cases. The functional dependence between the sustainability index and the associated standard deviation of the θ parameter (characterizing the way of normalization) was obtained. [Copyright &y& Elsevier]

Abstract: Although absorption cooling has been available for many years, the technology has typically been viewed as a poorly performing alternative to vapour compression refrigeration. However, rising energy prices and the requirement to improve energy-efficiency is driving renewed interest in the technology, particularly within the context of combined cooling, heat and power systems (CCHP) for buildings. In order to understand the performance of absorption cooling, numerous models are available in the literature. The complexities involved in the thermodynamics of absorption chillers have, however, so far restricted researchers to creating steady-state or dynamic models reliant on data measurements of the internal chiller state, which require difficult-to-obtain, intrusive measurements. The pragmatic, yet fully dynamic model described in this paper is designed to be easily calibrated using data obtained from the measurements of inflows and outflows to a chiller, without resorting to intrusive measurements. The model comprises a series of linked control volumes featuring both performance maps and lumped mass volumes, which reflect the underlying physical structure of the device. The paper describes the modelling approach, theory and limitations, along with an example of the implementation of the model in the ESP-r code complete with calibration and an application to a specific example. [Copyright &y& Elsevier]

Abstract: This paper presents the optimization of chillers operating using artificial neural networks and genetic algorithms. For the needs of generating chiller models, an artificial neural network was used, trained with data collected from an actual chiller. For that purpose the basic characteristics of artificial neural networks are shown as well as the process of making specific chiller models used for testing the results of application of the genetic algorithm in usage optimization. The optimal criteria with the shown steps for the use of the genetic algorithm and optimization results is also displayed in the paper. The results of use of artificial intelligence methods in optimization of chiller operation are verified through an actual office building model created in the simulation software EnergyPlus and through a series of experiments on an actual office building, equipped with a modern integrated BMS. [Copyright &y& Elsevier]

Abstract: The investigation presented in this paper has three main objectives. The first one is to study, through a case study, if it is possible to acceptably predict the energy consumption of a massive residential free-running building, when the exact behavior of the occupants is unknown or actual indoor conditions are not monitored, assuming standard use and occupation schedules, for the dry climate of the Argentinean Northwest. The second objective of the paper is to detect the possible causes of differences between actual and predicted energy consumption through an exhaustive thermal monitoring and occupant''s behavior, in order to obtain an improved model of the building giving more accurate predictions of the energy consumption. The third objective is to analyze the effect on the annual energy consumption of changing the massive envelope by a lightweight one. The comparison of real and simulated consumptions under comfort conditions defined by ASHRAE Standard 55 shows that simulations overestimated the energy consumption for heating and cooling. The main causes were detected from the experimental monitoring, indicating a lower use of the air conditioning equipment than the supposed initially. Simulations were improved to consider actual use and occupation conditions. Finally, an annual simulation of the improved model performed by changing the envelope material to a lightweight one showed that energy consumption for heating was increased, while energy consumption for cooling was decreased. In an annual balance, the massive walls are preferable over lightweight ones in arid sunny climates as in the Argentinean Northwest, giving energy savings of around 25%. [Copyright &y& Elsevier]

Abstract Building performance simulation (BPS) enables users to predict the demand reductions achieved by energy conservation measures (ECMs). Identifying an optimal set of ECMs in combination is complex due to interaction effects. This creates a combinatorial problem where every ECM combination needs be simulated to identify the optimum with certainty. To avoid the computational burden of running separate simulations for each ECM combination, approximate approaches for predicting the joint effects of ECMs based on single ECM simulations have been proposed in literature: linear-addition and log-addition of savings. These reduced-order approaches are very rapid compared to BPS, but their accuracy is not well characterized. This paper compares ECM energy savings estimated by BPS with the linear and log-additive approaches and a new reduced-order approach: log-additive decomposition. An existing library of energy models and ECMs (Hamilton, et al., 2014) representing Philadelphia medium-sized office buildings is utilized to compare the performance of each approach not only to each other but also to BPS. Overall, log-additive decomposition performs well (prediction error ∼10%) followed by log-addition (prediction error ∼20% to 30%), which outperform linear addition (prediction error often exceeding 50%). Compared to BPS, the computational cost of each is 0.018%, 0.014%, and 0.004% respectively. [ABSTRACT FROM AUTHOR]

Abstract: Due to the scientific and economic growth of recent years, the on-going innovation in electrical products has enabled people to live more comfortably and conveniently. The standby power function is one such innovation. Unfortunately, as an increasing number of products are equipped with standby power, more energy is wasted and more carbon dioxide is emitted into the atmosphere. This paper combines a two-step proportional stratified sampling technique with systematic random sampling to select representative households in Taiwan. We adopted the measurement method of the International Electro technical Commission (IEC) in measuring the overall use of standby power in Taiwanese households. We then proposed a model for the estimation of standby power consumption, before calculating annual standby power consumption among all households in Taiwan. This paper could serve as a reference for the government and relevant authorities in the establishment of corresponding standards, providing suggestions for the minimization of standby power consumption and the unnecessary waste of energy. [Copyright &y& Elsevier]

Abstract: This paper reviews existing case studies and methods for calibrating whole building energy models to measured data. This research describes a systematic, evidence-based methodology for the calibration of these models. Under this methodology, parameter values in the final calibrated model reference the source of information used to make changes to the initial model. Thus, the final model is based solely on evidence. Version control software stores a complete record of the calibration process, and the evidence on which the final model is based. Future users can review the changes made throughout the calibration process along with the supporting evidence. In addition to the evidence-based methodology, this paper also describes a new zoning process that represents the real building more closely than the typical core and four perimeter zone approach. Though the methodology is intended to apply to detailed calibration studies with high resolution measured data, the primary aspects of the methodology (evidence-based approach, version control, and zone-typing) are independent of the available measured data. [Copyright &y& Elsevier]

Abstract: The use of hygroscopic materials for moisture buffering is a passive way to moderate the variation of indoor humidity. Through absorption and desorption, surface materials in the indoor environment, such as curtains, carpets and wall paper, are able to dampen the moisture variations. The moisture buffering capacity of these materials may be used to improve the relative humidity of the indoor environment at reduced energy costs. The objectives of this paper are threefold. The first objective is to derive a theoretical model for the transient moisture transfer between a curtain system and the indoor air for the case where the curtain is placed in front of a wall. The second objective is to conduct experiments inside environmental chambers to validate the theoretical model and to test the ability of curtains to moderate indoor humidity. It is shown that the experimental results for the curtain moisture uptake and the relative humidity inside the chamber compared well with the model simulation results. The third and final objective is to test and evaluate the model under “real environment conditions” for a case study of a hygroscopic cotton curtain, placed in a “typical” office space in the city of Beirut with an area of 25m2 that uses direct expansion (DX) air conditioning system. It is found that hygroscopic curtains maintain humidity of less than 65% during part load operation compared to the upper limit of 70% relative humidity when no curtain is used. On the other hand, it is found that the energy use, as determined by the daily electrical power consumption of the DX system, is almost the same for the two cases, (with and without a curtain), where approximately 20kWh of energy input is required 13kWh of sensible energy and 7kWh of latent energy. [Copyright &y& Elsevier]

Abstract: The success of modeling the sustainable performance of the residential building envelope will be to a great extent associated to the sustainable energy performance indicators used. The sustainable energy performance indicators that these building assessment models are developed around should be chosen by taking into account the targeted objectives. However, it is very common to find building performance assessment models that do not take into account these considerations and therefore have a limited capability and scope. This leads to inadequate aggregate indicators for the actual assessment of the sustainable performance of the building envelope for a sustainable energy efficient building. The focus of this paper is to investigate the principal sustainable energy performance indicators for modeling the sustainable performance of the residential building envelope and develop an approach for determining the most appropriate sustainable energy performance indicators. In doing that, this paper provides an overview of previous research on sustainable energy performance indicators and discusses conceptual framework for developing sustainable energy performance indicators. In order to identify these indicators that influence the capability of building performance assessment models, a comprehensive survey of construction industry professionals was conducted using questionnaire survey technique while the data was analyzed using correlation analysis techniques. [Copyright &y& Elsevier]

Abstract: An experimental investigation has begun concerning the hygrothermal behaviour of wooden frame houses. The experimental set-up, consisting in a full-scale wooden frame house exposed to natural exterior climate is presented in the paper. It is located in Grenoble (South-East of France), and is equipped with over 150 sensors in order to collect a large amount of data (temperatures, relative humidity). The experimental data presented in the paper enable to get better understanding of coupled hygrothermal phenomena, and can be used to allow the validation of numerical models for heat, air and moisture transfers in wooden frame buildings. The analysed results demonstrate the importance of temperature-driven moisture diffusion from hygroscopic panelling. [Copyright &y& Elsevier]

Highlights • The accuracy of a horizontal hybrid photo-radiometer sky model is examined by comparing to the Perez all-weather sky model. • The application of the horizontal hybrid photo-radiometer sky model is extended and enriched within four office spaces. • The results indicate that both sky models generate luminance maps at the same level of accuracy. Abstract Daylight simulation results greatly rely on the accuracy of sky models. When generic CIE sky and Perez all-weather sky simulate daylighting scenes they simplify cloud distributions. The lack of cloud distributions and subtle luminance variations causes simulation result deviations. High Dynamic Range (HDR) image techniques provide a method of generating accurate and actual skies. This paper explores the accuracy of a horizontal hybrid phadiometer (HPR) sky model, which combines modeled physical descriptions of the sun and HDR sky images. The aim was to build on and enrich the findings of a previous study (Humann and McNeil, 2017). In this study, the HDR images within four office spaces were taken. Simultaneously, global horizontal illuminance and HDR sky images were recorded outside. Simulated luminance maps were generated under both the HPR and Perez skies. Daylight Glare Probability and vertical eye illuminance (E v) were calculated from 112 groups of luminance maps. The simulated E v under HPR and Perez skies presented relative RMSE of 21.3% and 23.7%, respectively. The frequencies of accurate glare prediction under HPR and Perez skies were 95.5% and 93.9%, respectively. The results indicated that both the horizontal HPR sky and the Perez sky simulate equally accurate luminance maps. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses how to optimize pre-cooling strategies for buildings in a hot California climate zone with the Demand Response Quick Assessment Tool (DRQAT), a building energy simulation tool. This paper outlines the procedure used to develop and calibrate DRQAT simulation models, and applies this procedure to eleven field test buildings. The results of a comparison between the measured demand savings during the peak period and the savings predicted by the simulation model indicate that the predicted demand shed match well with measured data for the corresponding auto-demand response (Auto-DR) days. The study shows that the accuracy of the simulation models is greatly improved after calibrating the initial models with measured data. These improved models can be used to predict load reductions for automated demand response events. The simulation results were compared with field test data to confirm the actual effect of demand response strategies. Results indicate that the optimal demand response strategies worked well for most of the buildings tested in this hot climate zone. [Copyright &y& Elsevier]

Abstract: An extended Gebhart–Block model for large space buildings is proposed in this paper, which is used to predict the vertical temperature distribution of hybrid ventilation. Natural ventilation coupled with air-conditioning is described with a mathematical model. The indoor thermal environment formed by the air-conditioning and the natural ventilation can also be conducted for the potential analysis and optimal use of the natural ventilation. Experiments were carried out in an atrium building in Shanghai Research Institute of Building Sciences. This paper describes aforementioned model, and it is found that the calculation results implying this model agree well with the measurement data. [Copyright &y& Elsevier]

Abstract: In this paper, a simplified mathematical model develops to study round the year effectiveness of photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) integrated with a greenhouse, located at IIT Delhi, India. The solar energy application through photovoltaic system and earth air heat exchanger (EAHE) for heating and cooling of a greenhouse is studied with the help of this simplified mathematical model. Calculations are done for four types of weather conditions (a, b, c and d types) in New Delhi, India. The paper compares greenhouse air temperatures when it is operated with photovoltaic/thermal (PV/T) during daytime coupled with earth air heat exchanger (EAHE) at night, with air temperatures when it is operated exclusively with photovoltaic/thermal system (PV/T) and earth air heat exchanger (EAHE), for 24h. The results reveal that air temperature inside the greenhouse can be increased by around 7–8°C during winter season, when the system is operated with photovoltaic (PV/T), coupled with earth air heat exchanger (EAHE) at night. From the results, it is seen that the hourly useful thermal energy generated, during daytime and night, when the system is operated with photovoltaic (PV/T) coupled with earth air heat exchanger (EAHE), is 33MJ and 24.5MJ, respectively. The yearly thermal energy generated by the system has been calculated to be 24728.8kWh, while the net electrical energy savings for the year is 805.9kWh and the annual thermal exergy energy generated is 1006.2kWh. [Copyright &y& Elsevier]

Abstract: Energy analysis of complex buildings is usually carried out by process analysis. The results are indices of the direct consumption by final energy carriers. This analysis, however, is not complete because the final energy carriers are generated in a system of interconnected production and transport processes, where energy is also used. The sum of the direct energy use, the energy used in intermediate stages and in transport is termed cumulative energy consumption. The analysis of cumulative energy consumption may concern either one single final energy carrier (e.g. electricity) or the global primary energy consumption. The theory of cumulative energy consumption belongs to the class of system methods. This paper applies one system method, input–output analysis, to compare different systems of supplying energy to buildings. The linear mathematical model of annual energy balance of a complex case-study building has been formulated. The paper describes the application of such a linear mathematical model for calculating the coefficients of cumulative energy consumption in buildings as well as for evaluating the effects of energy rationalisation systems and strategies. [Copyright &y& Elsevier]

In this paper we propose a novel and easily implementable model-based air balancing method for a ventilation system. The proposed method provides a well-defined form of balancing for a ventilation system, which can be effectively solved. The method follows three procedures: (i) mathematical modeling for duct system which is based on steady-state pressure balance; (ii) model parameters identification by supervised machine learning; (iii) determination of damper positions based on the model. The performance of this method is validated through testing in a duct testbed with five terminals. The results show that the final flow rates in all terminals match with the desired values with no more than 6.8% relative error. [ABSTRACT FROM AUTHOR]

It is an intuitive assumption that some activities require more energy than others. Bottom-up energy demand models therefore use time-use data to inform the timing of energy use. In this paper we present some empirical evidence to test the strength of this assumption. Using data that simultaneously captures household activities and their coinciding electricity consumption, it is possible to relate one to the other. We validate the temporal accuracy of the approach with the example of reporting hot drinks and the distinct signature of kettle usage. Despite good data accuracy, the predictive power of reported activities for electricity use is modest. At time when activities that would subjectively be associated with high energy consumption are reported, electricity use is only about 7% higher than at times with activities of low energy association. For single occupant households the link is stronger with more than 30% difference between the two activity categories. We conclude that demand models may need to take account of diversity and complexity in multi-occupant households and that more sophisticated regression techniques may be required to improve demand predictions based on time-use data. [ABSTRACT FROM AUTHOR]

This paper provides further investigation into usefulness of Aerofoil wings to enhance wind turbines energy generation integration into buildings (Architectural forms AF). It provides insight of wind follows around and beneath Aerofoils enhancing building augmented turbines, while simulating turbines as a resistance to wind flow under wings. It builds on previous work investigating factors for enhancing Aerofoil wings integration into buildings for in-site energy generation. Wind turbine simulated as a porous jump in CFD ANSYS FLUENT. Energy generated estimated as a function of pressure drop, resulting wind velocity and area per square metre. It was found that Turbine resistance has lowered wind acceleration, but the optimized case (i.e. optimized in the previous work) maintained the highest of achieved acceleration of wind speeds scoring 13.2 m/s compared with the un-optimized case 10.85 m/s. Optimized wing cases secured more pressure drop across the turbine porous surface in all the range of studied incident velocities compared to the un-optimized cases. That is 1.6–1.9 folds more energy estimated for optimized wing over un-optimized. With proper positioning of turbine an increase up to 3.38 folds secured when turbine is positioned ( 2   m behind the wing tip opposite windward ). The turbine should be placed 2 m from the tip for the highest yield. [ABSTRACT FROM AUTHOR]

Urban building energy modeling (UBEM) is a valuable tool for analyzing the building stock. Many different model approaches have been proposed in recent years suggesting various ways of dealing with the challenges of UBEM; however, central for all modeling approaches is the need for informative input data about the building stock. The availability of data for urban-scale modeling is both country-specific, time-consuming to aggregate, and data access is often limited due to privacy constraints. In this paper, we present a hierarchical bottom-up model of the Danish residential building stock using public building data for predicting the annual heating energy consumption. For more than 10,000 randomly selected single-family dwellings, the annual energy consumption is modeled and validated for the city of Aarhus, Denmark. We found that approx. 50% of the energy use is explained using only four widely available building characteristics, which enables building-scale predictions with a mean absolute error of approx. 25%. In addition, for city-scale predictions, the regression-based model enables aggregated predictions with a mean bias error of less than ±2%. Even though building-scale predictions are only somewhat accurate, the performance remains comparable to state-of-the art high-fidelity models in the literature. [ABSTRACT FROM AUTHOR]

Heat losses from a building foundation are affected by both the surrounding conditions and the surrounding soil properties. These include many factors that complicate the analysis of heat loss, such as thermal storage, snow and soil freezing. The effect of snow and soil freezing was studied with a 3D simulation model in a subarctic climate. The heat losses from the most commonly used foundation types in Sweden were studied. This paper shows that it is possible to achieve a good thermal estimation of the air temperatures in a crawl space, with an average difference of 0.4 °C compared with the validation data over a year. Snow and soil freezing reduce the annual heat losses through the different foundation types by 7–10% and the maximum heat loss rate by 13–25%. In order to describe the heat transfer correctly, snow must be included in the calculations, while soil freezing has only a minor impact. The 3D model implemented in this study shows a significant impact on the soil temperatures when these parameters are included. For a subarctic climate, the commonly used calculation methods based on the European standard ISO 13370 are not thorough enough to calculate the heat transfer through a foundation accurately. [ABSTRACT FROM AUTHOR]

In this paper our objectives are to perform a numerical and experimental study of the velocity field in the area affected by a circular exhaust duct, to define the outline of flow separation area at its inlet, to come up with a reliable mathematical simulation of the separated flow at exhaust duct inlet, and to determine the effect of the duct inclination angle its serviced area. The stationary discrete vortex method has enabled development of an adequate and reliable technique for computation of separated flows at inlet of a local exhaust hood. We have studied airflow patterns around the exhaust duct using the discrete vortex method, CFD and natural experiment. Characteristic dimensions of the flow separation area at exhaust hood inlet have been determined with relation to the length and inclination angle of the hood. Shaping the exhaust duct to fit the resulting separation zone outline will enable savings of energy that would otherwise be wasted on overcoming local drag forces; furthermore, this will prevent escape of contaminants circulating in the separation area to the environment. Determining airflow velocity distribution patterns will facilitate the choice of the most efficient exhaust duct design to minimize the cost of contaminant removal. [ABSTRACT FROM AUTHOR]

District Heating (DH) systems are commonly supplied using local heat sources. Nowadays, modern insulation materials allow for effective and economically viable heat transportation over long distances (over 20 km). The paper proposes a Decision Support System (DSS) for optimized selection of design and operating parameters of a long distance Heat Transportation System (HTS). The method allows for evaluation of feasibility and effectiveness of heat transportation from the considered heat sources to the given DH area. The optimized selection is formulated as the multicriteria decision-making problem. The constraints for this problem include a static HTS model, allowing considerations of the system life cycle, as well as time variability and spatial topology. Thereby, the variation of heat demand and ground temperature within the DH area, the insulation and pipe aging, as well as the terrain elevation profile are taken into account in the decision-making process. The HTS construction costs, the operating costs (pumping power), and the heat loss are considered as objective functions, while such parameters as: inner pipeline diameter, insulation thickness, temperature and pressure profiles, as well as pumping station locations are optimized during the decision-making process. Moreover, variants of pipe laying e.g. one pipeline with a larger diameter, or two parallel pipelines with smaller diameters might be considered during the optimization. The analyzed optimization problem is multicriteria, hybrid and nonlinear. The genetic solver has been proposed to solve it. [ABSTRACT FROM AUTHOR]

With bore fields for energy extraction and injection, it is often necessary to predict the temperature response to heat loads for many years ahead. Mathematical methods, both analytical and numerical, with different degrees of sophistication, are employed. Often the g-function concept is used, in which the borehole wall is assumed to have a uniform temperature and the heat injected is constant over time. Due to the unavoidable thermal resistance between the borehole wall and the circulating fluid and with varying heat flux along the boreholes, the concept of uniform borehole wall temperature is violated, which distorts heat flow distribution between boreholes. This aspect has often been disregarded. This paper describes improvements applied to a previous numerical model approach. Improvements aim at taking into account the effect of thermal resistance between the fluid and the borehole wall. The model employs a highly conductive material (HCM) embedded in the boreholes and connected to an HCM bar above the ground surface. The small temperature difference occurring within the HCM allows the ground to naturally control the conditions at the wall of all boreholes and the heat flow distribution to the boreholes. The thermal resistance between the fluid and the borehole wall is taken into account in the model by inserting a thermally resistive layer at the borehole wall. Also, the borehole ends are given a hemispherical shape to reduce the fluctuations in the temperature gradients there. The improvements to the HCM model are reflected in a changed distribution of the heat flow to the different boreholes. Changes increase with the number of boreholes. The improvements to the HCM model are further illustrated by predicting fluid temperatures for measured variable daily loads of two monitored GCHP installations. Predictions deviate from measured values with a mean absolute error within 1.1 and 1.6 K. [ABSTRACT FROM AUTHOR]

The main problem of previous methods for the calculation of total transmission of solar radiation through shading louvers is that they can only deal with flat slats and pure diffuse reflection. Taking the radian and specular reflection of louvers into consideration, a new model of total solar radiation transmitted through shuttle louvers was established and experimentally verified in this paper. Firstly, taking two adjacent shuttle louvers as the object of study, the new calculation model was established, and a computer program based on the model was developed in MATLAB, which can be used to study the impact of shape, size, rotation angle, and surface optical properties of shuttle louvers on the transmission of direct and diffuse radiation. Secondly, an experimental set-up equipped with integrating sphere was built and experiments were performed to verify the new model, with the results showing that the model predictions compared well with the experimental data. Finally, the calculation errors of two conventional methods, the “flat slat model” and the “pure diffuse reflection model”, were analyzed, and the results showed that the “flat slat model” can cause considerable error and the relative error increases with the rotation angle of the louvers, and the “pure diffuse reflection model” gives overestimated results when the rotation angle is positive and underestimated results when the rotation angle is negative. [ABSTRACT FROM AUTHOR]

The focus of carbon management is shifting from operational carbon to embodied carbon as a result of the improved operational energy efficiency of buildings. Measuring and managing embodied carbon right from the early stages of projects will unlock a range of opportunities to achieve the highest possible emissions reduction which could not be achieved otherwise during the latter stages. However, measuring embodied carbon during the early stages of design is challenging and highly uncertain due to the unavailability of detailed design information. Therefore, the research presented in this paper addresses this problem in a structured and an objective way. A parametric embodied carbon prediction model was developed using regression analysis to estimate embodied carbon when only minimal design information is available and with less uncertainty. The model was developed by collecting historical data of office buildings in the UK from four different data sources and estimating embodied carbon by combining several estimating techniques. Wall to floor ratio and the number of basements were identified as the model predictors with a model fit of 48.1% (R 2 ). A five-fold cross-validation ensured that the model predicts within the acceptable accuracy range for new data. The developed model had an accuracy of ±89.35% which is within the acceptable accuracy range for an early stage prediction model. In addition, the need for standardising embodied carbon measurements and to develop embodied carbon benchmarks to facilitate embodied carbon estimating throughout the project lifecycle were emphasised. [ABSTRACT FROM AUTHOR]

It is important to have practical methods for constructing and learning a good mathematical model for a building’s thermal system in the presence of unmeasured disturbances and using data from closed loop operation. With this goal in mind, this paper presents a mathematical framework that explains the asymptotic behavior of an estimated model under those conditions and that can aid in learning an accurate model. Some analytic results from the literature of system identification are extended and interpreted for building systems. A new identification approach for determining an accurate thermal network (RC) model for a multi-zone building is developed based on the analytic result, and its superior performance over a conventional grey-box modeling approach is demonstrated experimentally. [ABSTRACT FROM AUTHOR]

Experimental results of the airflow pattern for Active Chilled Beams (ACB) system are investigated in this paper, where the air velocity and turbulence intensity for the air jet near the ceiling are tested and recorded under both isothermal and non-isothermal conditions. Based on the results, the velocity profile along streamwise direction is found to be significant in analyzing air detachment from the ceiling. It is revealed that the Coandă effect can be enhanced by a high pressure drop of ACB terminal unit and impeded by the temperature difference between supply air and room air. The self-similarity for the air jet is observed to be feasible for a certain downstream distance where the vertical maximum velocity is within 1.25 slot heights. A comparison study has been conducted for two mathematical models describing the self-similarity with the experimental data. It turns out that Verhoff's model has an overall better performance than Schwarz and Cosart's model. The turbulence intensity, which tends to be larger for points with lower velocity, is higher in areas where the entrainment effect is stronger. [ABSTRACT FROM AUTHOR]

In the planning phase of district energy systems, optimization models based on mathematical programming are a widely used approach. Most optimization models determine the optimal energy system design based on a single representative year. However, this approach is unable to consider changing economic and technological boundary conditions over the system's lifetime. As a result, these one-period models fall short for districts with 5th generation district heating and cooling (5GDHC) networks, which are typically developed over long time periods and are built in multiple construction phases. In this paper, we present two multi-period optimization approaches for designing 5GDHC districts: The first approach is a forward-looking model which determines the optimal investment pathway by using a perfect foresight of future parameter developments. In the second approach, a one-period model is solved repeatedly for every investment period without knowledge of future parameter developments. Both approaches are compared to a one-period model for a real-world 5GDHC district in Germany. In comparison with a one-period design approach, the forward-looking method leads to total cost savings of up to 17 % and the sequential method of up to 11 %. By using a forward-looking model, gas-fired technologies are sized smaller while the capacity of electricity-driven technologies in the energy hub as well as photovoltaic modules and thermal energy storages in buildings increases compared to a one-period model. The case study shows that a multi-period modeling approach is an important addition to design optimization models for 5GDHC networks and can have a significant impact on the optimal design. [ABSTRACT FROM AUTHOR]

For the present paper the potential of an air- multiple phase change materials (PCMs) unit is investigated for the free cooling and ventilation of buildings. Firstly, a CFD model has been developed to determine the charging and discharging temperatures of the PCM as well as the air outlet temperature of an air-PCM unit. The effective heat capacity method is applied introducing the C p -T relationship obtained from the Differential Scanning Calorimetry (DSC) and has been validated by experimental results. Secondly, the validated model has been further extended for multiple PCMs to investigate the thermal performance enhancement incurred by using multiple PCMs for free cooling application. The model takes into account the daily temperature profile and therefore a variable temperature is coupled to the air inlet boundary condition. Thirdly, a parametric study has been conducted to investigate the effect of multiple PCMs within the panels, followed by the effect of geometry e.g. height, length and the charging and discharging air mass flow rates. The proposed best case design is a combination of RT20 and RT25 with geometric dimensions of H = 0.03 m and L = 1.5 m and an air mass flow rate of 0.25 kg/s. The unit presented a thermal energy varying from 0.4 to 1.46 kJ over 8 h, with an average thermal energy of 1.02 kJ. The average effectiveness of the unit is 0.5, remaining similar to this value for over 6 h. In order to make the proposed unit competitive in terms of energy consumption and running cost, the charging process of the PCM has to be improved during night time leading to high air mass flow rate requirement. [ABSTRACT FROM AUTHOR]

In order to coordinate and balance the demand of combined heat and power (CHP) system, a solution of optimal operation strategy of CHP system with heat recovery in a distributed energy system has been presented. This paper will discuss more deeply the suitability of the CHP system under different operation strategies. The selections of electricity determined by heat load (EDHL) and heat load determined by electricity (HLDE) are actualised by Aspen Plus and formula computing. In addition, the performance difference of the CHP system operating in EDHL and HLDE is analysed by comparing thermoelectric output and fuel consumption. The result shows that the optimal heat to power ratio (HPR) is 1.75 and is derived when the electric output is approximately equal to the electric demand and the heat output is approximately equal to the heat demand. EDHL is the optimal selection when the HPR is greater than or equal to 1 and less than 1.75, and HLDE is adopted suitably when the HPR is greater than 1.75 and less than or equal to 2.5. Additionally, the total thermal efficiency does not vary with increasing or decreasing regenerative temperature or variable HPR on CHP system, maintaining 87–88% thermal efficiency, meanwhile, the total exergy efficiency is about 24.7%–28.8% when the CHP systems operate in EDHL, and 23.1%–31.4% when the CHP systems operate in HLDE. The final research results show that, it has great significance in operation strategy and suitability analysis of the CHP system. [ABSTRACT FROM AUTHOR]

A segmented dynamic dwelling stock model is proven useful for understanding the development and changes of ageing building stocks, which is highly relevant for renovation measures and estimates of energy use and emissions in aggregated building stocks. In this paper, such a model is developed further for detailed analyses of dwelling stock energy demand and exemplified for the Norwegian dwelling stock 1960–2015. The dwelling stock model simulates the development in stock size and composition and is combined with archetype-specific energy intensities to estimate the total energy demand. After calibrating the model results with statistics, the model is used to explore the phenomena and causes of historical changes. A large-scale improvement of the energy efficiency of the Norwegian dwelling stock has taken place through renovation and construction of new dwellings. A historical shift to more efficient energy carriers and heating systems has had an effect on energy savings in the system, of the same size as the effect of the improved energy efficiency of the stock. However, the total average energy savings per m 2 are offset by changes in user heating habits. A significant decrease in average delivered energy intensity per m 2 is only observed after the introduction of heat pumps. [ABSTRACT FROM AUTHOR]

The Spanish residential building stock built between 1940 and 1980 period presents a high energy saving potential as it represents a significant percentage of the total housing stock and it was built without any regulation regarding energy efficiency. Accordingly, the first aim of this paper was to quantify the energy saving potential and the related reduction in CO 2 emissions of the housing stock in those years. The work focuses on the Mediterranean climate of the Comunitat Valenciana Region, therefore the energy efficiency strategies proposed are passive and deal with the envelope of buildings. On the basis of the results obtained, several scenarios with intervention periods of 10, 20 and 30 years were calculated. The conclusion was that with the current rate of annual building renovation, it will be nearly impossible to reach the goals established by the EPBD. Only a deep transformation of the building fabric within this sector could help in achieving them. Finally, it should be noted that the proposed methodology can be applied to other areas with different climates, particularly in Spain. [ABSTRACT FROM AUTHOR]

Residential buildings are currently equipped with energy production facilities, e.g., solar rooftops and batteries, which in conjunction with smart meters, can function as smart energy hubs coordinating the loads and the resources in an optimal manner. This paper presents a mathematical model for the optimal energy management of a residential building and proposes a centralized energy management system (CEMS) framework for off-grid operation. The model of each component of the hub is integrated within the CEMS. The optimal decisions are determined in real-time by considering these models with realistic parameter settings and customer preferences. Model predictive control (MPC) is used to adapt the optimal decisions on a receding horizon to account for the deviations in the system inputs. Simulation results are presented to demonstrate the feasibility and effectiveness of the proposed CEMS framework. Results show that the proposed CEMS can reduce the energy cost and energy consumption of the customers by approximately 17% and 8%, respectively, over a day. Using the proposed CEMS, the total charging cycles of the ESS were reduced by more than 50% in a day. [ABSTRACT FROM AUTHOR]

A series of numerical investigations of a fire induced airflow in a compartment are carried out using the Fluent 6.3CFD code, in order to examine the effect of the source location on the thermal flow field and the mass flow rate at the exit doorway. The Fire is modeled by a volumetric heat source and the induced transport flow phenomena is considered as a buoyancy-induced turbulent flow so Boussinesq approximations are applied. Resolution of the governing equations comprises the Reynolds averaged Navier-Stokes (RANS) equations using the k-ε turbulence model combined with an enhanced wall treatment. The research results show that the height position of the heat source has a significant impact on the temperature field and the stratification interface of the buoyant layer, comparing to the transversal or the longitudinal position. For the highest positions tested, the fire room becomes more stratified and essentially divided into two layers: an upper layer corresponding to the hot exhaust gases and a lower layer for the fresh air entrance. The second part of this paper was devoted to the establishment of a mathematical correlation linking firstly, the ventilation mass flow rate at the doorway exit, as a critical parameter in fire induced flow studies, and the three-dimensional coordinates of the fire source location within the room. The validity and accuracy of this mathematical correlation have been proven by comparing the results with available experimental data in the configuration studied and a good agreement was recorded. [ABSTRACT FROM AUTHOR]

Several building-stock modelling techniques have been employed to investigate the impact of energy efficiency measures (EEM), where the description of the building-stock generally consists of an age-type classification to specify building characteristics for groups of buildings. Such descriptions lack the appropriate level of detail to differentiate the potential for EEM within age groups. This paper proposes a methodology for building-stock description using building-specific data and measured energy use to augment an age-type building-stock classification. By integrating building characteristics from energy performance certificates, measured energy use and envelope areas from a 2.5D GIS model, the building-stock description reflects the heterogeneity of the building-stock. The proposed method is validated using a local building portfolio (N = 433) in the city of Gothenburg, where modelled results for space heating and domestic hot water are compared to data from measurements, both on an individual building level and for the entire portfolio. Calculated energy use based on the building-stock description of the portfolio differ less than 3% from measured values, with 42% of the individual buildings being within a 20% margin of measured energy use indicating further work is needed to reduce or quantify the uncertainty on a building level. [ABSTRACT FROM AUTHOR]

Most of the state-of-the-art building simulation programs implement models in imperative programming languages. This complicates modeling and excludes the use of certain efficient methods for simulation and optimization. In contrast, equation-based modeling languages declare relations among variables, thereby allowing the use of computer algebra to enable much simpler schematic modeling and to generate efficient code for simulation and optimization. We contrast the two approaches in this paper. We explain how such manipulations support new use cases. In the first of two examples, we couple models of the electrical grid, multiple buildings, HVAC systems and controllers to test a controller that adjusts building room temperatures and PV inverter reactive power to maintain power quality. In the second example, we contrast the computing time for solving an optimal control problem for a room-level model predictive controller with and without symbolic manipulations. Exploiting the equation-based language led to 2200 times faster solution. [ABSTRACT FROM AUTHOR]

Traditionally, in building energy modeling (BEM) programs, occupant behavior (OB) inputs are deterministic and less indicative of real world scenarios, contributing to discrepancies between simulated and actual energy use in buildings. This paper presents a new OB modeling tool, with an occupant behavior functional mock-up unit (obFMU) that enables co-simulation with BEM programs implementing functional mock-up interface (FMI). The components detailed in the development of the obFMU include an overview of the DNAS (drivers-needs-actions-systems) ontology and the occupant behavior eXtensible Markup Language (obXML) schema, in addition to details on the creation of the obFMU that contains the co-simulation interface, the data model and solvers. To demonstrate functionality of the tool, three examples of occupant behaviors were simulated, including: (1) turning on and off lights, (2) opening and closing windows, and (3) turning on and off the air conditioners. The obFMU can be used via co-simulation with all building simulation programs that implement the FMI, thus users are not limited to a particular tool. Another advantage is the use of obXML schema to represent occupant behavior, standardize the description of occupant behavior enabling information exchange. [ABSTRACT FROM AUTHOR]

The OpenStudio software development kit has played a significant role in the adoption of the EnergyPlus whole building energy modeling engine and in the development and launch of new applications that use EnergyPlus for a variety of purposes, from design to auditing to code compliance and management of large portfolios. One of the most powerful features of the OpenStudio platform is Measure, a scripting facility similar to Excel's Visual Basic macros. Measures can be used to apply energy conservation measures to models—hence the name—to create reports and visualizations, and even to sew together custom workflows. Measures automate tedious tasks increasing modeler productivity and reducing error. Measures have also become a currency in the OpenStudio tools ecosystem, a way to codify knowledge and protocol and transfer it from one modeler to another, either within an organization or within the global modeling community. This paper describes some of the many applications of Measures. [ABSTRACT FROM AUTHOR]