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Highlights • Development of a heat exchanger semi-empirical model accounting for frost formation. • Experimental validation of the HX model in partially frost regime. • Frost control strategies numerically implemented and compared. • Strategies lead to trade-offs between ventilation quality and energy consumption. Abstract This paper tackles the issue of frost formation in air-to-air heat recovery devices dedicated to single room ventilation by means of both numerical simulations and experimental approaches. In such heat exchangers, it is commonly known that the formation of a frost layer on the surface generates an additional thermal resistance and a flow section reduction, which leads to an overall degradation of the overall unit performance. This paper proposes a three-zone model, considering a dry, a wet and a frost zone, by determining the location of moving boundaries. Each zone is handled independently and the relative proportion of each zone is determined by means of the exchanger wall temperature. Besides this frost model, a defrost model is also envisaged. Once validated with experimental data collected on a U-flow-type heat exchanger, the developed model is used to implement different strategies to reduce or prevent frost formation in the exchanger. Based on three different criteria, these strategies are compared with each other to evaluate their benefits and drawbacks. The criteria give information on the energy efficiency of the ventilation, on the air renewal quality and on the pressure balance between the inside and the outside of the building. [ABSTRACT FROM AUTHOR]

Highlights: [•] The paper reports stochastic comparison between ISO 13790 and EnergyPlus. [•] The paper delivers the audience the need of stochastic calibration for ISO 13790. [•] The calibrated ISO model can predict similarly to dynamic simulation. [ABSTRACT FROM AUTHOR]

Abstract: A lecture theatre with dimension 16m×8.4m×3.6m located at Roorkee (28.58°N, 77.20°E) in the northern region of India, is selected to calculate the monthly and annual cooling load (kWh) and cooling capacity of air conditioning system by a computer simulation. The paper also presents the results of a study investigating the effect of different glazing systems on windows and the reduction in building cooling load. DesignBuilder software has been used for the computer simulation for calculating the cooling load. The paper aims to investigate the reduction in thermal gains and cooling load requirements by varying the U-values of different glazing types, insulating the ceiling, providing cool roofs, interior and exterior insulation on walls, and replacing the conventional fluorescent tube lamp (FTL) by energy efficient compact fluorescent lamp (CFL). Installation of false ceiling, wall insulation, different glazing types and lighting systems are cost effective with normalized annual saving ranging from 17% to 19.8% from this retrofitting project. Furthermore, the study also highlights the potential of reducing the emission of CO2 and equivalent carbon credit. Retrofitting techniques strongly influence the level of energy saving, although the payback period is generally quite long of order 8years. [Copyright &y& Elsevier]

Abstract: In this paper, an attempt is made to evaluate the exergetic performance of a solar photovoltaic thermal (PV/T) air collector. A detailed energy and exergy analysis is carried out to calculate the thermal and electrical parameters, exergy components and exergy efficiency of a typical PV/T air collector. Some corrections are done on related heat loss coefficients. An improved electrical model is used to estimate the electrical parameters of a PV/T air collector. Further, a modified equation for the exergy efficiency of a PV/T air collector is derived in terms of design and climatic parameters. A computer simulation program is also developed to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. It is observed that the modified exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency, overall energy efficiency and exergy efficiency of PV/T air collector is about 17.18%, 10.01%, 45% and 10.75% respectively for a sample climatic, operating and design parameters. [ABSTRACT FROM AUTHOR]

This paper presents a practical case study using the computational fluid dynamics (CFD) technique in retrofitting the large cabinet fans and airflow channels in malt processing air-conditioning systems in order to get uniform airflow field, to increase fan capacity and reduce energy consumption.Site measurements were used to validate the models before they were used. CFD simulation results were used to evaluate and optimise the design and construction of splitter vanes in the airflow channels and scrolls of the fans. Simulation tests showed that the fan capacity (maximum total air flow rate delivered at full fan speed) could be increased by 8.3–20% using different shapes of scroll, and 30–34% by adding splitter vanes further in the airflow channels. After retrofitting the fans and airflow channels, site measurements showed that the fan capacity increased 21–24 and 28–29%, respectively in the two buildings validated. The approach of using the CFD technique in the retrofitting, the simulation results, and the site measurements before and after fan retrofitting are presented and compared in this paper. [Copyright &y& Elsevier]

• A review of simulation-aided occupant-centric building design studies is presented. • Covered themes include occupant-centric metrics, models and design practices. • Most studies focus on energy-related metrics with a lack of implementation. • Metrics related to occupant comfort, wellbeing and space planning are understudied. • Improved data collection, modeling and communication methods are recommended. Occupants are active participants in their built environment, affecting its performance while simultaneously being affected by its design and indoor environmental conditions. With recent advances in computer modeling, simulation tools, and analysis techniques, topics such as human-building interactions and occupant behavior have gained significant interest in the literature given their premise of improving building design processes and operating strategies. In practice, the focus of occupant-centric literature has been mostly geared towards the latter (i.e., operation), leaving the implications on building design practices underexplored. This paper fills the gap by providing a critical review of existing studies applying computer-based modeling and simulation to guide occupant-centric building design. The reviewed papers are organized along four main themes, namely occupant-centric: (i) metrics of building performance, (ii) modeling and simulation approaches, (iii) design methods and applications, and (iv) supporting practices and mechanisms. Important barriers are identified for a more effective application of occupant-centric building design practices, including the limited consideration of metrics beyond energy efficiency (e.g., occupant well-being and space planning), the limited implementation and validation of the proposed methods, and the lack of integration of occupant behavior modeling in existing building performance simulation tools. Future research directions are discussed, covering large-scale international data collection efforts to move from generic assumptions about occupant behavior to specific/localized knowledge, improved metrics of measuring building performance, and improved industry practices, such as building codes, to promote an occupant-in-the-loop approach to the building design process. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the interactions of users with air conditioning systems, lighting, natural ventilation, internal shading devices, and costs related to automation of a teaching building. Three behavior patterns (proactive, intermediate and careless) were created. The proactive user seeks to use natural light, uses passive solar shading and integration of natural and artificial ventilation. The intermediate user does not seek integration of natural and artificial lighting, they use hybrid ventilation as a ventilation strategy. The careless user does not use any passive strategy, predominantly uses artificial conditioning and adjusts cooling and heating setpoint to values out of the norms. In addition to the users' behaviors, the automated building was modeled. Computer simulations were performed in the EnergyPlus program, in order to measure the influence of behavior patterns on the building's energy consumption. Based on the analysis of the building's energy consumption profile, results indicate users are between the intermediate and the careless user classification, with a tendency to the intermediate user profile. The paper also presents an analysis of the payback time with the building automation in face of the user profiles. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we outline a framework and the algorithms that will enable a home controller to accomplish occupancy-moderated multi-zone, multi-inhabitant space-conditioning under a demand-driven pricing scheme for electricity. We investigated the effects that influencing factors such as the number of zones and inhabitants, randomness of occupancy patterns and thermal mass of the residence can have on the efficacy of occupancy-moderated zonal space-conditioning (OZS) under different scenarios. Simulations driven by real data and highly realistic proxy data reveal that OZS can achieve improvements averaging 23% over the case without under certain settings. Our investigations also revealed that a house with heavier thermal mass stands to gain as much as 15% from OZS with pre-conditioning than a lighter one. We further offer a few pointers on reducing the cost of space-conditioning using OZS under a demand-driven pricing scheme to the average homeowner based on our findings. [Copyright &y& Elsevier]

Abstract: This paper describes field experiments and numerical simulations on hybrid utilization of renewable energy and fuel cells for a residential energy system. It presents results of empirical testing and evaluation of hybrid utilization involving solar energy. First, field experiments were conducted on an electric power and domestic hot water supply system that uses both solar energy and fuel cells. The system achieved a large amount of reduction in primary energy consumption compared with conventional systems. Secondly, a simulation was performed on the optimum scale and effect of introduction of the system. The simulation results proposed the optimum capacities of the solar energy utilization and fuel cells to minimize primary energy consumption of the system. [Copyright &y& Elsevier]

Abstract: It becomes popular to use computer simulation technique to evaluate the performance of energy utilizations in buildings. The hourly weather data as simulation input is a crucial factor for the successful energy system simulation, and obtaining an accurate set of weather data is necessary to represent the long-term typical weather conditions throughout a year. This paper introduces a stochastic approach, which is called the first order multivariate Markov chain model, to generate the annual weather data for better evaluating and sizing different energy systems. The process for generating the weather data time series from the multivariate Markov transition probability matrices is described using 15-years actual hourly weather data of Hong Kong. The ability of this new model for retaining the statistical properties of the generated weather data series is examined and compared with the current existing TMY and TRY data. The main statistical properties used for this purpose are mean value, standard deviation, maximum value, minimum value, frequency distribution probability and persistency probability of the weather data sequence. The comparison between the observed weather data and the synthetically generated ones shows that the statistical characteristics of the developed set of weather data are satisfactorily preserved and the developed set of weather data can predict and evaluate different energy systems more accurately. [Copyright &y& Elsevier]

Abstract: To streamline the design of the energy efficient buildings, appropriate tools are needed to assess their energy performance taking into account the microclimatic context. Numerical simulation seems to be the most suitable issue, but none tool is dedicate to the direct evaluation of the microclimate influence on the building energy consumption. A complete solution could be to use both CFD and thermoradiative simulation tools complementary with the coupling technique perspective. This paper presents both a developed CFD–thermoradiative coupled simulation tool and a typical application on an urban fragment. The results lead to two kind of observations: [•] Integration of the thermal model of a building in the microclimatic simulation platform enable a quantitative evaluation of the building energy demand regarding different urban design scenarii (e.g. mineralized vs vegetated). [•] Different physical phenomena do not contribute as much in the energy balance and it is important to compute precisely each one to obtain the small scale microclimatic influence. [Copyright &y& Elsevier]

Abstract: Efforts have been devoted to the identification of the impacts of occupant behavior on building energy consumption. Various factors influence building energy consumption at the same time, leading to the lack of precision when identifying the individual effects of occupant behavior. This paper reports the development of a new methodology for examining the influences of occupant behavior on building energy consumption; the method is based on a basic data mining technique (cluster analysis). To deal with data inconsistencies, min–max normalization is performed as a data preprocessing step before clustering. Grey relational grades, a measure of relevancy between two factors, are used as weighted coefficients of different attributes in cluster analysis. To demonstrate the applicability of the proposed method, the method was applied to a set of residential buildings’ measurement data. The results show that the method facilitates the evaluation of building energy-saving potential by improving the behavior of building occupants, and provides multifaceted insights into building energy end-use patterns associated with the occupant behavior. The results obtained could help prioritize efforts at modification of occupant behavior in order to reduce building energy consumption, and help improve modeling of occupant behavior in numerical simulation. [Copyright &y& Elsevier]

Abstract: Active transparent façades constitute a building envelope component that is becoming more and more common in high-rise office buildings. Many designers have opted for a ventilated façade, claiming that this technology is sustainable, reduces energy consumption and enhances indoor comfort conditions, but these claims have often proved to be wrong. From the thermofluid-dynamic analysis point of view, few design procedures or sufficiently detailed, reliable and easy to use simulation software are available for ventilated façades. A numerical model that has been developed to simulate the thermal behaviour of mechanically ventilated active transparent façades is presented in this paper. The model, developed in the Simulink/Matlab® environment, simulates the façade in both steady-state and transient conditions and provides the temperature of the different layers of the façade structure and the corresponding heat fluxes as output data. The model has been validated by comparing the simulation results with experimental data obtained in the laboratory. A test has also been performed on a real façade under actual operating conditions. The model performance has resulted to be quite promising. The accuracy of the prediction of the temperature is good, while the simulations of the heat fluxes are slightly less reliable for some operative conditions. [Copyright &y& Elsevier]

Abstract: This paper explores the potential of reducing the annual energy consumption of a central air-conditioned building through advanced evaporative cooling systems. The building considered is a typical three floor library building of a University. The regenerative evaporative cooling technology is coupled with the liquid cooled water chiller system to accomplish the energy conservation objective. Comparisons of the regenerative evaporative cooling are made with simple evaporative cooling to bring out the importance such a system. The well-known building simulation software, TRNSYS is used to carry out the heat load calculations and the dynamic simulations of the building. Annual energy consumptions of different components of the air-conditioning system are estimated for the existing water chiller system as well as for both coupled evaporative cooling systems (simple and regenerative). The annual energy consumptions, the indoor temperature, the relative humidity and the thermal comfort index ‘PMV’ are compared for all the three different air-conditioning systems. The coupling of direct and regenerative evaporative cooling technologies with water chiller system has shown, respectively, 12.09% and 15.69% savings in annual energy consumption of the building, while maintaining PMV between −1 and +1 for most of the hours in the year. [ABSTRACT FROM AUTHOR]

Abstract: A traditional Chinese heating system, the Chinese Kang, is used by 175 million people in detached houses in the rural regions of China, especially in Northeast China. This system utilizes biomass such as corn stalks, straw, corncob and energy plants as the heat sources. The objective of this paper is to establish a set of models to simulate the energy performance of the Kang heating system in one Chinese detached house. An experimental field study was carried out to collect practical parameters in a newly constructed Chinese detached house. The dynamic performance of the Kang heating system was simulated by using IDA-ICE 4.0 embedded with an empirical model built in the field study. The results show that the simulation can obtain good overall agreement with the field measurement results. It was confirmed that the Kang model created by IDA-ICE 4.0 is capable of simulating the performance of the Kang system and of calculating energy consumption in the detached house. Moreover, the result reveals that the thermal environment in the present Chinese detached house is still poor during the severe cold season if only the Kang system is used to heat the whole house. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of building energy consumption usually requires building energy profiles on an hourly basis. Computer simulations can be used to obtain this information but generating simulations requires a significant amount of experience, time, and effort to enter detailed building parameters. This paper presents a simple methodology to estimate hourly electrical and fuel energy consumption of a building by applying a series of predetermined coefficients to the monthly energy consumption data from electrical and fuel utility bills. The advantage of having predetermined coefficients is that it relieves the user from the burden of performing a detailed dynamic simulation of the building. The coefficients provided to the user are obtained by running EnergyPlus Benchmark Models simulations; thus, the simulation process is transparent to the user. The methodology has been applied to a hypothetical building placed both in Atlanta, GA, and in Meridian, MS, and in both cases, errors obtained for the estimated hourly energy consumption are mainly within 10%. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the energy performance of a central atrium is investigated and compared with the energy performance of a courtyard with the same geometric proportions. The atrium and the courtyard design used for the analysis are square in plan and surrounded by the building on all four sides. The glazing type and percentage for the courtyard walls and atrium skylight are varied in the analysis. Weather data from four cities representative of climatic conditions of cold, temperate, hot-humid and hot-dry were used. The results show that, in general, the open courtyard building exhibits a better energy performance for the shorter buildings. As the building height increases, however, at some point the enclosed atrium exhibits a better energy performance. This “break even” point for the number of stories depends on different factors like glazing and climate parameters discussed above. [Copyright &y& Elsevier]

Abstract: Through a case study, this research explores an approach, which uses computer simulation technology, to evaluate different energy conservation alternatives and to assist facility managers to select reliable and feasible solutions. The subject facility is located in the Southeast region of the United States. One of the major challenges and operation goals of the General Services Administration, who manages the facility, is for that facility to achieve the Energy Star designation. However, due to the complexity of the facility, the requirements from building occupants, as well as other difficulties, finding a path for optimizing the operation of the facility in order to achieve the Energy Star designation is not always easy. This project uses eQuest, a simulation software tool, to create a “virtual environment”, in which the operations of the HVAC (heating ventilation air-conditioning) system and the lighting of the facility are studied. Subsequently, recommendations initially made by experts through traditional energy audit approaches are evaluated in the “virtual environment” in order to determine the best solution to achieve the goal of the facility managers. This paper discusses major aspects of the project, including the challenges, the values and the limitations of applying computer simulation techniques in such a facility with complicated structural, occupancy and operation features. [Copyright &y& Elsevier]

Abstract: Glass façades, particularly in high-rise buildings, increase in energy consumption for heating, cooling and ventilation. This causes too high running cost of mechanical systems. Double skin glass façade is a system that decreases these disadvantages, by providing natural ventilation, preventing solar heat gain, controlling daylight, etc. This paper aims to investigate the appropriateness of double skin glass façades in moderate climate, such as Istanbul, in terms of the energy and cost efficiency when compared to single skin glass façades. For this purpose, an approach is proposed to determine the efficient alternatives. It comprises to generate standard façade alternatives by considering the objectives, constraints and performance criteria, and to evaluate their energy and cost efficiency for both single and double skin glass façades. In conclusion, the most energy efficient double skin glass façade is about 22.84% more efficient than the most energy efficient single skin glass façade is. Additionally, the most cost efficient single skin glass façade is about 24.68% more efficient than the most cost efficient double skin glass façade is. [Copyright &y& Elsevier]