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Abstract In order to reduce the energy consumption for cooling in our buildings, the use of passive cooling solutions is necessary. One of these solutions is natural ventilative cooling, where airflows generated by single-sided natural ventilation, until today have mainly been calculated from the De Gids & Phaff equation in the European Standard EN 15242:2007. In the revised standard EN 16798-7:2017, a new version of the equation for single-sided natural ventilation is released. The work in this paper will compare the results from the new equation with earlier equations for single-sided ventilation and hold them up against wind-tunnel measurements, full-scale measurements and CONTAM calculations to clarify whether and why the new equation is to be preferred for future design solutions for single-sided natural ventilation and ventilative cooling. Due to the implementation in calculation standards and regulations, the new calculation model should underestimate rather than overestimate the airflow rates, so as to remain on the safe side when estimating ventilative cooling potential. The work in this paper concludes that the new simple direct calculation model in EN 16798-7:2017 predicts the airflows through windows in a more conservative way than earlier equations, by representing an average of the airflow rate in the building that is generally on the safe side. The accuracy of the EN 16798-7:2017 equation was found by comparison to wind tunnel measurements to be 29% but with underestimations in 88% of the cases investigated. For the CONTAM calculations, it was found that the use of the new EN 16798-7:2017 equation (with room based height for the stack effect) slightly underestimates the airflow rate as desired, as soon as the temperature difference across the opening is above 0°C. Based on the comparisons presented in this paper, the authors consider the new calculation model in EN 16798-7:2017 well suited for the use in calculation standards to integrate natural ventilative cooling effects from single-sided ventilation. [ABSTRACT FROM AUTHOR]

Highlights • This paper uses building structural attributes such as shapes of buildings, relative compactness(RC), glazing area(GA), roof area(RA), surface area(SA), wall area(WA), orientation(OR), overall height(OH) and glazing area distribution(GAD) for prediction of heating and cooling load. • The paper explores the data set and features to get insights with feature correlation, mutual information their association strengths etc and their relation with heating and cooling load. • The paper proposes novel group of methods based on emerging machine learning method extreme learning machine(ELM) which has shallows architecture. • The paper proposes novel method based on ELM variant online sequential extreme learning machine(OSELM) for heating and cooling load prediction in online and adaptive environment. This model also helps when data is trained in chunk by chunk fashion. • The paper demonstrates several models based on combination of learning mode, activation function and features sets and compare their results with existing work extensively. Abstract In the present day environment, smart buildings require optimization of energy consumption through monitoring, consumption prediction and making policy decisions accordingly. Attributes related to building design and structure play a vital role in heating load(HL) and cooling load(CL) of the building which directly affects the energy performance of the buildings. For prediction of HL and CL, emerging machine learning approaches can help in improving accuracy and efficiency in real time. This paper provides improvements in energy load assessment of the buildings. It is the first is the in-depth study and analysis of design and structural attributes and their correlation with HL and CL, the novel methods based on ELM and its variants online sequential ELM(OSELM) to predict HL and CL. This study also proposes OSELM based online/real-time prediction when data is coming in stream The total 24 models have been developed including 12 models based on ELM and 12 models based on OSELM with different feature sets and activation functions. Models have been compared on the basis of accuracy, computational performance and efficiency with few existing models. The experimental results show that the proposed models learn better and outperform other popular machine learning approaches such as the artificial neural network(ANNs), support vector machine(SVM), radial basis function network(RBFN), random forest(RF) and existing work in the energy and building domain. [ABSTRACT FROM AUTHOR]

Occupant behaviour on air conditioning directly influences building energy consumption. Current building energy simulation typically assumes that occupants operate air conditioners ideally ignoring the stochastic characteristic of occupant behaviour, which leads to a large deviation of predicted energy performance from real consumption. This paper proposed a methodology framework for modelling occupants’ stochastic behaviour on air conditioning. This method combined measured data, statistical analysis and logistic regression to derive stochastic behaviour models that give the probability of when and above which temperature occupants may turn on air conditioning, at what temperature they may set and when they may turn off air conditioning. The behaviour models developed in this paper were further incorporated in widely used building simulation engine—EnergyPlus. The accuracy of the developed simulation model was validated against field measurement. Using this model, the cooling energy performance was simulated and compared with results from building energy standard based settings. The result shows that simulation using settings according to building energy standard over-predicts cooling load and total cooling energy requirements by 113% and 5.6 times respectively, which are very large discrepancies and may lead to a misunderstanding of energy savings potential of energy efficiency measures. The methodology developed in this paper has generality and can be extended and applied in other buildings for constructing behaviour models of air conditioning. The limitations of the current research as well as future research works were also discussed. [ABSTRACT FROM AUTHOR]

This paper investigates a novel terminal unit that integrates a radiant cooling floor (RCF) with an underfloor air distribution system (UFAD). The unit consists of rectangular modules that are installed above the standard structural floor of the building, creating a raised floor. The upper face of these modules incorporates a grid for easy installation of the pipes of the RCF, while the space between the raised floor and the structural slab is used as the air supply plenum of the UFAD system. The proposed system presents some advantages over the standard air systems: (1) it allows increasing production and zone set point temperatures, which improve the efficiency of the chiller plant, (2) improved comfort, and (3) improved air quality due to reduced mixing within the occupied zone. The proposed system can also solve or mitigate some of the drawbacks of cooling floors: (1) prevent water condensation over the surface of the floor, (2) increase the cooling capacity of the floor, and (3) reduce the response time to changes in the space thermal loads. The interactions between the RCF and the UFAD are not evident. In this paper, the thermal behavior of the combined unit is investigated by means of a numerical model implemented in COMSOL Multiphysics. The accuracy of this model is checked against three experiments undertaken in laboratory using a scale model of the system. In the first experiment, the air above the floor is kept quiescent and the cooling capacity is measured. The maximum relative error between the predicted and measured capacities is 19.5%. The numerical model is then used to study how the air movement within the plenum modifies the transient thermal response of the unit. The second and third experiments are designed to quantify the temperature change of the air circulating within the plenum (thermal decay or TD). In nominal operating conditions, TD is about 2.7 °C. In short, the new terminal unit is like a radiant cooling floor and a UFAD system working separately, but integrated in the same terminal unit. [ABSTRACT FROM AUTHOR]

A novel solar cooling system, i.e., the solar absorption-subcooled compression hybrid cooling system (SASCHCS), is a better solution for large-scale buildings with many floors, but the thermodynamic characteristics of the system are not adequately realized. The thermodynamic model of the hybrid system is absent, and the design of the nominal cooling capacity of the absorption subsystem and the volume of the storage tank are not known. Consequently, this paper primarily examined the thermodynamics of SASCHCS. A thermodynamic model of the hybrid system was developed, and the working process and performance of the hybrid system for different nominal cooling capacities of the absorption subsystem and the volumes of storage tanks were analysed in detail. The influence of selected parameters on the performance was discussed. It was found that the performance of the system first increases and subsequently decreases gradually with improvement in the nominal cooling capacity of the absorption subsystem. The appropriate ratio of the nominal cooling capacity of the absorption subsystem to the area of the collector should be 0.148 kW/m 2 to 0.222 kW/m 2 . Additionally, the performance of the hybrid system increases first but subsequently decreases gradually with the decrease in volume of the storage tank. An appropriate decrease in the volume of the storage tank is recommended. This paper contributes to a deeper understanding of SASCHCS. [ABSTRACT FROM AUTHOR]

This paper aims to provide the current state of the art of solar sorption systems. Through comprehensive literature review of solar sorption systems, it was concluded that these technologies have several limitations and drawbacks. The low performance and the high cost are the main disadvantages of these technologies. However, solar cooling is considered attractive because solar radiation is in phase with the demand for cooling. Due to its attractiveness, the research is still going and focusing on solving the technical, economical, environmental problems, to achieve high performance and low cost of solar sorption systems. Improvements through investigating geometrical, system configurations, physical parameters, and operational modes on the performance of solar thermal sorption cooling systems are presented. A survey of the new configurations, novel additions, new techniques, new methodologies are also presented in this paper. Several cases studies in different climatic conditions are summarized. Economic feasibility for absorption and adsorption systems is discussed. It can be concluded that cost and energy effective solar sorption systems can be developed if suitable combinations of system components with operating conditions are selected. Finally, there is still the need for more research on solar sorption systems to make them both cost and energy competitive with the conventional cooling technologies. [ABSTRACT FROM AUTHOR]

Many post-occupancy comfort studies of energy renovated residential buildings have documented elevated temperatures above comfort levels, not only during the summer period but also during the shoulder months. The main focus in renovation projects is on heat savings while the risk of overheating is not considered. This paper analyze in which situations overheating and cooling need to be addressed in building energy renovation projects and which renovation measures are causing this need. The analysis contains four reference single family houses from central and northern Europe. Both dynamic and static methods were used to assess the overheating risk. In terms of overheating occurrences, the most critical renovation measures are the insulation of the floor and the increase of the airtightness. The contribution of decreasing the g value of the window glazing is positive. The way to energy efficiency improvements also results in an extension of the overheating period and higher average and maximum building temperatures. The increase of the ventilation rates and the use of shading systems are useful measures for preventing overheating increase. The paper will highlight the inconsistencies which arise from the use of different criteria and also propose suggestions for future work. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a case of an office building and show how different concepts of envelope construction affect the energy efficiency of building. Assessment of energy performances of different scenarios of the hypothetical models of the office building in the central zone of Belgrade is the aim of this research. A few scenarios are created for each hypothetical model: basic scenario and scenarios of two shading devices types in order contribution to reduction of cooling demands to be estimated. The office building scenarios are modelled and analysed by using PHPP ’ 2007 software to estimate heat and cooling energy demands. Also, CO 2 emissions are discussed. Comparative analysis of the results highlights the advantages and disadvantages of the treated models and scenarios of office building envelope construction. Findings indicate the preferable solutions and highlight methodological approach in the office building envelope design, which has not yet been adopted extensively in practice in our country. Methodological approach and findings can generally be applicable for new office building design, both in Belgrade and in the similar climatic conditions. The paper demonstrates various feasible solutions of office building envelope construction that might help comply with the regulation. [ABSTRACT FROM AUTHOR]

The design and deployment of DG systems requires an integrated assessment of the building and generator dynamics including the time-variant energy costs and emission factors. Static design optimizations are unable to consider the physical generator operating constraints, seasonal variability and non-coincidence in electric, heating, and cooling demands. This paper introduces the Distributed Generation Build-out Economic Assessment Tool (DG-BEAT) which combines building, utilities, and emissions databases with a library of simplified generator and building models in a user-friendly interface. Five control strategies are presented for the dynamic dispatch of distributed generation technologies at commercial buildings. The control approaches stem from the physical limitations of different generator types. Methods are also outlined for the dispatch of complementary technologies (e.g. energy storage) and accommodation of on-site renewables (e.g. solar PV) which could further improve the economic or environmental benefits of distributed generation. This paper details the methodology of sizing and dispatching distributed generation components, outlines eight databases that are employed to capture regional variations in pricing and building dynamics, and discusses the myriad of customizations available to provide a tailored analysis for a single building or national impact studies. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally the cooling performance of a concept, where the radiant ceiling is suspended from the hollow-core concrete slab and by ventilation supply in the plenum and the perforations of the ceiling tiles, ventilation air is distributed without ducts and air terminals to the occupied zone. Literature has proven that this concept allows for more streamlined installation procedures and excellent performance in terms of thermal comfort and draught. The paper reports experimental results from a climate chamber, where the concept was tested under both steady-state and quasi-steady conditions. The steady-state conditions were chosen to map the cooling performance with different air change rates, and different ventilation and water supply temperatures. The results showed that for air change rates of 3 h−1 in the occupied zone and water supply temperature of 17 °C, the cooling output from the ceiling increased by 10 %. The concept was also tested under quasi-steady conditions in a 48 h cycle to quantify the thermal buffering effect of the exposed upper concrete slab when subjected to ventilation supply air. The effect amounted to 11–12 % increased cooling capacity at the end of the working day when the driving temperatures between air, water and thermal zones were at their maximum. [ABSTRACT FROM AUTHOR]

Conceptually, many energy poverty studies to date have been narrowly focused on inadequate indoor heating, paying little attention to other domestic energy services. Yet there are indications that a growing number of households in Europe are struggling to achieve adequate levels of indoor cooling, with adverse consequences for their health, well-being and productivity. This situation is exacerbated by changing global weather patterns, with many countries facing increases in the frequency and intensity of extreme heatwaves. There is limited understanding of the ways in which households respond to extreme heat, and consequently how this might create greater demand for indoor space cooling and air conditioning, and the consequences for increased stress on power grids and conflicts with carbon reduction goals. Using custom-built survey data collected from 2337 households in Gdańsk (Poland), Prague (Czech Republic), Budapest (Hungary) and Skopje (North Macedonia), along with in-depth qualitative fieldwork with 55 households in the same cities, this paper presents novel evidence on the issue of summertime energy poverty and space cooling difficulties. We identify the driving forces of household vulnerability to excessive indoor heat, in terms of risk of exposure, adaptive capacity, and sensitivity, and explore the implications for addressing energy poverty. [ABSTRACT FROM AUTHOR]

• A model-based optimization strategy is developed for energy saving in LDCD system. • An improved self-adaptive firefly algorithm is proposed to the presented optimization problem. • 12.49% energy savings can be realized by utilizing the proposed optimization strategy. • The energy reduction of chiller system contributes significantly to energy efficiency of the whole LDCD system. In this paper, a model-based optimization strategy for a liquid desiccant cooling and dehumidification (LDCD) system is proposed to improve system energy efficiency. The energy models of the LDCD system are established to predict system energy consumption under different operating conditions. To minimize the system energy consumption while maintaining the system thermal performance, the system energy consumption and thermal performance indicators are normalized by introducing a weight factor in cost function, then an optimization problem considering the interactions between components and system constraints is formulated. An improved self-adaptive firefly algorithm with fast convergence rate is proposed to solve the optimization problem and obtain the optimal set-points for control settings. Tests on an experimental apparatus are carried out to verify the energy saving potential of optimal control strategy under different weight factors and operating conditions. The results indicate that the energy consumption of LDCD system in the proposed optimization strategy is reduced by 12.49% over the conventional strategy. Meanwhile, the energy saving potential of the optimal control strategy is more remarkable for high cooling and dehumidification load. The proposed optimal control strategy can work well for applications in control and energy efficiency improvement of the existing dehumidification systems. [ABSTRACT FROM AUTHOR]

In recent years, water-side free cooling has been broadly applied in data centers to lessen the high cost of energy consumption. The energy-saving opportunities of free cooling have been recognized by numerous studies across the world. In this paper, the field test and energy performance evaluation were performed in an operational data center with water-side free cooling, located in Chongqing, China. Existing problems were found during tests, including the insufficient cooling capacity of towers in wintertime and the inability to activate partial-free cooling. The results of the tests show that the reduction in Power Usage Effectiveness (PUE) is much lower than the expected. To understand the marked discrepancies, the performance of the cooling tower was discussed in terms of the approach temperature and actual cooling capacity. The maximum cooling capacity in winter is only about 50 % of the rated. With the consideration of the cooling tower configuration performance in different climate conditions, the conservative energy effects were calculated in 34 provincial cities of China. To prolong the hours available, optimized operation schemes of cooling towers are presented. The available hours for free cooling could be increased from 730 h to 1300 h when operating at 67 % of rated flow rate, resulting in a decrease in the energy saving of chillers between 8.44 % and 21.05 %. [ABSTRACT FROM AUTHOR]

Cooling demands of commercial buildings present a relevant challenge for a sustainable future. They account for over half of the overall energy needs for the operation of an average office building in warm climates, and this situation is expected to become more pressing due to increasing temperatures in cities worldwide. To tackle this issue, it is widely agreed that the application of passive strategies should be the first step in the design of energy efficient buildings, only using active equipment if it is truly necessary. Nonetheless, there is still further need for information regarding the potential limits derived from their application. This paper explores the effectiveness of selected passive cooling strategies in commercial buildings from warm climates, defining performance ranges based on the assessment of multiple scenarios and climate contexts. This task was conducted through the statistical analysis of results from documented research experiences, to define overall ranges and boundary conditions; and through software simulation of selected parameters to isolate their impact under a controlled experimental setup. General findings showed that the mere application of passive strategies is not enough to guarantee relevant savings. Their effectiveness was conditioned to both the harshness of a given climate and different building parameters. Specific recommendations were also discussed for the selected passive strategies considered in the evaluation. [ABSTRACT FROM AUTHOR]

Actual national and international energy strategies generally encourage the use of renewable energy sources. Thermal energy storage (TES) offers various opportunities in the design of renewable energy systems. Thermochemical heat storage has gained popularity among researches because of higher energy density and lower heat loss compared to sensible and latent heat storage. On the other side solar energy has been recognized as one of the renewable energy sources with the most potential. This paper reviews thermochemical heat storage technologies and systems with emphasis on systems involving solar energy utilization in buildings. The studies are reviewed based on used storage materials, system configuration as well as models to predict and optimize system performance. [ABSTRACT FROM AUTHOR]

Latent Thermal Energy Storage (LTES) is a promising solution to reduce cooling energy consumption in buildings. Laboratory and computational studies have demonstrated its capabilities while commercial passive and active systems are available. This paper presents data and analysis of the performance of an active LTES ventilation system in two case-studies, a seminar room and an open plan office in the UK. Analysis using environmental data from the system’s control as well as additional space monitoring indicates that (a) internal temperature is maintained within adaptive thermal comfort limits, (b) acceptable Indoor Air Quality is also maintained (using metabolic CO 2 as indicator) and (c) energy costs are low compared to air-conditioned buildings. Thermal and CFD computational studies indicate that purging and charging duration and associated set-points for room temperature as well as air flow rate are the important parameters for optimised performance for a given LTES design. These parameters should be optimised according to the use of the space and prevailing external conditions to maintain internal thermal comfort within upper (usually in the afternoon) and lower (usually in the morning) limits. [ABSTRACT FROM AUTHOR]

The relationship between Urban Heat Island (UHI) and energy consumption in buildings has been widely observed and studied. The aim of this paper is to investigate the impact of large-scale deployment of indirect Vertical Greenery Systems (VGS) on the cooling demand of buildings and on the urban microclimate. VGS significantly reduces air temperature and wind speed near the walls. In doing so, it also positively impacts the UHI intensity. This is achieved mainly through the conversion of sensible heat to latent heat mediated by evaporation and transpiration from the VGS foliage. Evapotranspiration is a physically complex phenomenon and its interaction with the building and the urban climate is difficult to model accurately. We propose to use a dynamic nonlinear lumped parameter thermal network model to determine the thermal interactions between the prototypical building, the VGS, the paved road, the urban canopy air and the atmosphere. The model accounts for both sensible and latent exchanges within and outside the building. Solar (short-wave) radiation on building façade and road accounts for shading and unlimited diffuse reflections. Long-wave radiation among surfaces and between surfaces and the sky are estimated using view factors and the fully nonlinear Stefan-Bolzmann law. Building envelope infiltration rate and convective heat transfer coefficient vary with wind speed so as to properly reflect the energetic impact of wind speed attenuation near the wall due to the foliage. The thermal and aerodynamic characterization of the vegetation is based on the formulations proposed by Deardorff (1978). The evapotranspiration rate is estimated based on the Penman formula and is driven by the ‘vapor pressure deficit’ between actual vapor pressure in the ambient air and the saturation vapor pressure assumed to prevail on the surface of leaves. The calculation of sensible and latent heat fluxes between the urban canopy and the first level of the atmosphere considers buoyancy effects, using the coefficients introduced by Mascart et al. (1995). First, a base case model (no VGS) is created and validated using both building energy consumption data and urban air temperature measurements. The validated model is then used to investigate the impact of a large-scale deployment of VGS in the urban context. The weather data and the typical building thermo-physical properties are from the UAE. Comparison of the urban base case to the rural base case (both without VGS) shows a cooling load penalty, due to the UHI, of about 7 % . Retrofitting VGS to all buildings in the urban domain of study results in a 5 − 8 % reduction of the cooling load and a dramatic drop of the urban air temperature of about 0.7 − 0.9 °C, reducing the UHI intensity by almost half. [ABSTRACT FROM AUTHOR]

This paper gives practical information related to the use of simplified EnergyPlus models and its impact on estimates of the cooling demand, especially when EnergyPlus models are coupled with an urban canopy model. By simplified models, it is referred to shoebox as well as multi-floor models. For the interest of climatologists, their influence on estimates of urban temperature and specific humidity is also studied. To explore divergences between the use of detailed and simplified EnergyPlus models, a typical office area in Singapore is selected as a case study. As a result, it is observed that the use of multi-floor models provides estimates of the cooling demand and urban microclimatic conditions which achieve the best agreement with these assessed from detailed models. On the other hand, less time is required to run a shoebox than a multi-floor model. Although these outcomes are inferred from an excellent case study, further research must be conducted on several types of urban areas to elaborate a general theory. [ABSTRACT FROM AUTHOR]

• We review sixteen models for Variable Refrigerant Flow System (VRF). • We develop three data-driven models for VRF. • Physics-based and data-driven models are compared on a real-world dataset. • The impacts of different input features on VRF efficiency are analyzed. Variable Refrigerant Flow (VRF) systems are gradually gaining popularity in small and medium-sized commercial and residential buildings owing to their high part-load performance, flexible control, and ease of installation and maintenance. Developing models of VRF systems to predict their performance are important for model-based control, fault diagnostic and detection. There are VRF models published in existing literatures, however those models were developed and validated in different datasets. As a result, the model accuracy cannot be directly compared. To fill this gap, this paper presents a comprehensive review of the existing VRF models, and summarizes the input/output parameters and mathematical formulas of 16 VRF models from literature (referred to as physics-based model). Next, we validate and compare the model accuracy of existing models using the same dataset. Additionally, we develop data-driven models using the state-of-art machine learning algorithms, and compare the model accuracy between existing physics-based models with data-driven models. We find the model proposed by Hu et al. in 2019, which regresses the VRF cooling capacity and COP as a linear combination of indoor and outdoor temperatures times a cubed polynomial function of compressor frequency, is the most accurate physics-based model, with a prediction error of 22.19% in the training dataset and 22.44% in the validation dataset. XGBoost is the most accurate data-driven model, with a prediction error of 19.29% in the training dataset and 22.02% in the validation dataset. The data-driven model is more accurate while the physics-based model is more generalizable. The findings of this study can help researchers to select the proper VRF model for building energy prediction, model-based optimization, and fault diagnostic and detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • 90 papers are reviewed and focus group discussions with resilence experts took place. • A definition of resilient cooling for buildings is developed and discussed. • Different disruption types and events are proposed. • Four resilience stages are proposed: vulnerability, resistance, robustness, recovery. • The influencing factors of resilient cooling of buildings are presented. The concept of climate resilience has gained extensive international attention during the last few years and is now seen as the future target for building cooling design. However, before being fully implemented in building design, the concept requires a clear and consistent definition and a commonly agreed framework of key concepts. The most critical issues that should be given special attention before developing a new definition for resilient cooling of buildings are (1) the disruptions or the associated climatic shocks to protect against, (2) the scale of the built domain, (3) the timeline of resilience, (4) the events of disruption, (5) the stages of resilience, (6) the indoor climate limits and critical comfort conditions, and (7) the influencing factors of resilient cooling of buildings. This paper focuses on a scoping review of the most of the existing resilience definitions and the various approaches, found in 90 documents, towards possible resilient buildings. In conclusion, the paper suggests a definition and a set of criteria —vulnerability, resistance, robustness, and recoverability— that can help to develop intrinsic performance-driven indicators and functions of passive and active cooling solutions in buildings against two disruptors of indoor thermal environmental quality—heat waves and power outages. [ABSTRACT FROM AUTHOR]

• That aim is to quantify the impact of urban context on building cooling loads. • Building energy modeling is used to test 108 urban context configurations. • The configurations combine different context heights, distances, and orientations. • Savings of 26% and 24% were observed for total and peak cooling, respectively. • Implications on cooling system sizing and urban planning practices are discussed. This paper presents a systematic evaluation of the impact of the built urban context on the cooling energy performance of buildings subjected to extreme hot weather conditions. The proposed approach combines building energy modeling with an extensive parametric variation and statistical analysis scheme. It provides a direct quantification of inter-building shading on energy performance, with an emphasis on the cooling demand patterns for buildings of different types and sizes. Results show that the combined effects of urban context height, distance, and orientation can lead to significant reductions in cooling demand, reaching up to 26% for total cooling loads and 24% for peak cooling loads. The observed savings are particularly notable for residential buildings, making them an ideal target for urban development strategies that aim to leverage inter-building shading effects for energy conservation purposes. Moreover, an in-depth analysis of peak loads illustrates how the density and compactness of the urban form can be used as passive design strategies to reduce the load, and hence, the size of air conditioning systems. Finally, the paper explores how to translate the gained knowledge to design guidelines, bridging the gap between theory and practice. [ABSTRACT FROM AUTHOR]

Thermally activated building system (TABS) is a hydronic cooling system, in which cold water is circulated through pipes embedded in the building structure to remove the heat from the indoor space. This paper proposes a hybrid passive cooling system, in which TABS is integrated with a cooling tower. The performance of this integrated system greatly depends on the climatic conditions of the geographical area. Hence, the feasibility of the proposed system to provide thermal comfort in twelve Indian cities spread over five different climatic regions is investigated using COMSOL Multiphysics. Different cooling scenarios like Roof and Floor cooled TABS (RF) and All Surfaces cooled TABS (AS) are compared. The proposed system performs well in arid and semi-arid regions, and the RF scenario is sufficient to achieve thermal comfort. The system is able to reduce the indoor operative temperature by 14 °C for the arid climatic conditions of Jaipur. In the other three regions, i.e., humid subtropical, tropical wet and dry and tropical wet regions, the performance of the proposed system is relatively low and the AS scenario is required to achieve thermal comfort. [ABSTRACT FROM AUTHOR]

Heat output and uniformity of surface temperature distribution are primarily concerned by designers and users of radiant floor heating. The testing approach, testing conditions and calculation of the heat output at each stage of program are different among the test standards. In this paper, a mathematical model to calculate surface temperature and heat output of radiant floor heating system was proposed. Measured data from experiments was used to validate the proposed model. Based on this simulation model, four current test standards in China, Europe, America and Japan were simulated. The simulation results show that the heat output of the same sample is different under the four test standards. Meanwhile, simulations were carried out at various non-heating surface temperatures. The results indicate that the non-heating surface temperature has a significant impact on the heat output of the radiant floor. The differences in the simulations of heating capacity vary from 2% to 7%. Hence, a parameter, the temperature difference between average water temperature of test sample and area weighted average temperature of non-heating surfaces, is introduced to revise the heat output characteristic equation based on the Chinese test standard. [ABSTRACT FROM AUTHOR]

Indoor air humidity is an important parameter for building up a thermally appropriate artificial indoor environment. However, introducing air humidity as a controlled parameter in addition to air temperature would significantly increase the difficulty to develop a control-oriented model for building air conditioning systems. This is particularly true for direct expansion (DX) air conditioning (A/C) systems, whose operational parameters are highly coupled and behave non-linearly and influenced by the controlled parameters. Neither physical modeling approach nor artificial neural network (ANN) modeling approach could solely satisfy the requirement, in terms of accuracy and sensitivity, for simultaneous control of air temperature and humidity using a DX A/C system. In this paper, a hybrid modeling approach is proposed and validated, which uses the physical modeling approach to simulate the performance of evaporator for accurately catching the cooling and dehumidification processes under various working conditions and uses ANN to simulate all other components of a DX A/C system for reduced calculation efforts. By such a hybrid modeling approach, the advantage of simplicity of an ANN-based sub-model could be utilized and the disadvantage of it that do not allow to accurately extrapolate beyond the range of the data used for training/estimating the model parameters could be avoided. [ABSTRACT FROM AUTHOR]

This paper focuses on influences of a “green-buffer-space” (GB) on the photovoltaic-module (PV) temperatures. The described results correspond to the first year of research. They are part of an ongoing project-development: “Multifunctional System: Building Greening and Photovoltaic” (MFS). The MFS combines two well-known systems: photovoltaics and green façades. The aim is to evaluate the synergies and benefits of the system on its components − the PV, buffer space (BS) and green facade (GF) − on the building façade (BF). The presented outcome shows the effects of the GB layer on the PV layer. The analysis focusses on two PV systems of the same technology and power output, but with different buffer spaces: one with a GF and the other one without a GF. The first two assumptions were confirmed: the plants can growth behind PV mounted on a façade, and the GB acts as a temperature regulation tool. The GB reduces the PV operating temperatures in increasing ranges, about 1 °C up to 4 °C. Temperature differences increase by outdoor temperatures above 20 °C, i.e. the GB benefits are higher under higher outdoor temperatures. The third one, GB benefits on the PV performance were positive for specific time intervals: when the PV module was operating under extreme conditions, what requires further research. [ABSTRACT FROM AUTHOR]

This paper presents a parametric study on the effect of four green-roof types on outdoor/indoor temperature and cooling demand under four different climates and three urban densities using co-simulation approach with ENVI-met and EnergyPlus. Results reveal an outdoor nighttime warming effect of not more than 0.2 °C which is most obvious with the semi-extensive while the outdoor and indoor cooling effect ranges between 0.05–0.6 °C and 0.4–1.4 °C, respectively depending on the green-roof type, urban density and time of the day. These daytime temperature reductions also vary per prevailing climates and follow this order: hot-dry, hot (or warm)-humid, and temperate which can be explained by the interplay between solar intensity/air temperature and relative humidity between the regions. In a hot-humid region, the evaporative cooling potential of greenery is dampened when compared to hot-dry region. This is also true for region with low solar intensity and humidity like the temperate region. In terms of cooling demand reduction, 5.2% was observed in hot-dry climate on the hottest day of the year with full-intensive green-roof while the least saving of 0.1% was found with semi-extensive green-roof in temperate climate. In general, for both outdoor temperature and cooling demand reduction, semi-intensive green-roof was found more effective than its full-extensive counterpart while the higher spatial green-roof is most important for indoor temperature reduction irrespective of the leaf density of the greenery. Therefore, the intent of green-roof installation should be a determining factor for the type and spatial extent to be implemented. [ABSTRACT FROM AUTHOR]

This paper analyses the performance of an air/water chiller typically used for residential air conditioning when a minichannel condenser is used in replacement of a conventional fin-and-tube condenser. The experimental facility, the data reduction process and the uncertainty analysis are briefly described and then the experimental results are presented and discussed, comparing the results obtained with both, the minichannel and the fin-and-tube condenser. Additionally, the chiller is numerically modelled using a commercial refrigeration system modelling software (IMST-ART). The good agreement between experimental and numerical results allows validating the model that is then used to calculate the mass of refrigerant contained in all the components of the system, as well as other operational parameters of interest not measured experimentally. The analysis of the results shows that replacing a conventional fin-and-tube condenser by a minichannel condenser allows, under almost any operating condition, reducing the mass of refrigerant increasing efficiency and cooling capacity. [ABSTRACT FROM AUTHOR]

Seasonal variation of thermal comfort demands directly affects the energy needs for heating or cooling purpose. In previous studies, the differences of neutral temperatures between summer and winter were revealed, but the studies on the difference of human thermal adaption in transitional seasons are insufficient. To clarify this, this paper presents a year-long survey which was carried out in 505 residential buildings in six cities located in the Hot Summer and Cold Winter (HSCW) zone of China involving 11,524 subjects. Results show a significant difference of adaptive responses in different seasons, and a lag of behavioral responses behind climate change in transitional seasons is observed. Occupants not only adjust clothing insulation according to air temperature in different seasons, but also actively control indoor air movement, including closing/opening windows and using fans. The seasonal, monthly and daily neutral temperatures are studied, implying that occupants’ thermal experience has significant effect on their thermal comfort by behavioral, physiological and psychological paths. According to the comparative study, the running mean air temperature method and aPMV model are recommended in free-running space. The findings provide scientific evidence to the concept that dynamic thermal comfort temperature range should be considered in evaluation of indoor thermal environment. [ABSTRACT FROM AUTHOR]

Modelling, simulation and optimization of an isolated building separated from the district in which they operate is no longer of interest as a view point of improved efficiency, economic benefits and exploitation of renewable energy resources. Instead, district energy systems have the capacity to obtain several benefits, regarding the practical, environmental and safety by taking advantage of large poly-generation energy conversion technologies. The use of optimization techniques to design such high-efficient systems is strongly motivated by minimizing of the cost for the required infrastructures, minimizing emission, and maximizing the generation or efficiency but is particularly challenging because of the technical characteristics and the size of the real world applications. In this paper, different types of optimization problems, constraints and techniques as well as the optimization tools used in district energy systems are discussed. [ABSTRACT FROM AUTHOR]

The air diffusion performance index (ADPI) concept and its implementation in the diffuser selection guideline ( ASHRAE Handbook-Fundamentals, 2009 ) provide designers a simple method to design overhead-air-distribution systems. However, the current guideline considers only five diffuser types and the range of sensible cooling loads used to develop the guideline (65 W/m 2 –250 W/m 2 ) is high for current buildings. Applying this outdated guideline may cause draft discomfort and/or unnecessary fan-energy waste. This paper presents new experimental results to update the ADPI-based guideline to include 15 diffuser types at low cooling loads of 25 W/m 2 and 50 W/m 2 . Compared to the high loads in the current guideline, the ADPI values generated in this work are greater due to the lower loads used. Most ceiling-mounted diffusers produce higher ADPI at a large range of airflow than do sidewall and other diffuser types. ADPI for ceiling diffusers has the least variation with changes in loads or airflow rates. The results show that the minimum airflow set-point for a variable air volume system varies with diffuser type. For ceiling diffusers other than round and perforated diffusers, the minimum set-point can be reduced to lower than 30% of the peak flow rate without significantly reducing ADPI. [ABSTRACT FROM AUTHOR]

As problems of meeting energy demand and promoting sustainable development become more serious, saving energy and reducing consumption in the building industry has gained increasing attention. In building air-conditioning (AC) design, the AC equipment is usually selected depending on the design weather data. Therefore, appropriate design weather data to determine the kind of AC equipment and design for building energy conservation is necessary. Compared to the existing Technical Activities Committee (TAC) method for creating weather data for AC design, a method to create the design weather data using two weather indices for Osaka, Japan with consideration of the simultaneous occurrence and continuous occurrence of each weather element is shown in this paper. In addition, peak hourly thermal loads of a simulation building were evaluated through these created weather data and weather data created using the TAC method. It showed that the weather data created using the TAC method and the mean daily enthalpy as the first index may lead to an overestimation in heating design. The weather data created using the TAC method and the mean daily dry-bulb temperature as the first index may lead to an overestimation in cooling design. [ABSTRACT FROM AUTHOR]

This paper analyzes the performance of a novel two-pipe system that operates one water loop to simultaneously provide space heating and cooling with a water supply temperature of around 22 °C. To analyze the energy performance of the system, a simulation-based research was conducted. The two-pipe system was modelled using the equation-based Modelica modeling language in Dymola. A typical office building model was considered as the case study. Simulations were run for two construction sets of the building envelope and two conditions related to inter-zone air flows. To calculate energy savings, a conventional four-pipe system was modelled and used for comparison. The conventional system presented two separated water loops for heating and cooling with supply temperatures of 45 °C and 14 °C, respectively. Simulation results showed that the two-pipe system was able to use less energy than the four-pipe system thanks to three effects: useful heat transfer from warm to cold zones, higher free cooling potential and higher efficiency of the heat pump. In particular, the two-pipe system used approximately between 12% and 18% less total annual primary energy than the four-pipe system, depending on the simulation case considered. [ABSTRACT FROM AUTHOR]

• Thermal performance of ceiling panels under natural convection was studied. • A validated CFD model considering conjugate heat transfer was established. • CFD model was used to investigate the influencing factors on melting. • The pyramidal panel is advantageous than the tetrahedral panel. • Tweaking the geometric features can affect the thermal performance. To relieve the upsurge of the energy demand associated to building indoor cooling, passive cooling employing phase change materials (PCMs) has been proposed as a promising technique to stabilise indoor air temperature fluctuation and reduce building energy demand. PCMs can exchange a large amount of latent heat during the melting and solidification processes, which can be utilised in line with the discharging and charging processes of a cooling system. The use of encapsulated PCM ceiling panels in buildings has immense application potential for passive cooling, which has attracted investigations in recent years. The geometry selection of the PCM ceiling panel is vital as it determines the exposed surface area to the surrounding air and the natural convection, and therefore the heat transfer rate to/from the PCM, which generally suffers from low thermal conductivity. This paper builds on the geometric optimisation of enclosed PCM capsules driven by natural convection, aiming to investigate the phase change behaviour and thermal performance of encapsulated PCM ceiling panels of different geometries. Here, the presented study focuses on the conjugate heat transfer phenomena through the surrounding air, panel shell, and PCM. A mixture of lauric, capric, and oleic acids was selected as PCM encapsulated in a thin-shell enclosure made of acrylonitrile butadiene styrene plastic, which forms the aesthetic panels attached to the ceiling. A computational fluid dynamics model was validated using full-scale experimental data and further employed to analyse the discharging process and design considerations of the PCM ceiling panels. The effects of various influencing factors were explored, such as panel volume, the initial temperature difference between PCMs and surrounding air, shell thickness, and geometrical features. The results indicate that the panel comprised of a pyramid array is more advantageous than the tetrahedral-based panel in terms of thermal performance, where the average melting rate is 20.8 % higher when the panel volume is 250 mL. In addition, tweaking the geometric features of the panel will largely impact its thermal performance as the effective heat transfer area and natural convection conditions are varied. Finally, it was found that hanging the panel to the ceiling will effectively enhance the heat transfer compared to directly attaching it to the ceiling. The results complement the knowledge body of macro-encapsulated PCM ceiling panels in terms of thermal performance and geometric optimisation. The effects of geometric features on the thermal performance of the PCM ceiling panels are studied in a more holistic manner. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study and compare the temperature profile and energy performance of traditional and Vegetative Roofs (VRs) during winter season in Lebanon, a country in the Middle East. Three roof mockups were installed on the rooftop of the Chemical Engineering Department at the University of Balamand: a Traditional Gravel Ballasted Roof (TGBR) and two Extensive Green Roofs (EGRs) with different substrate depth and composition. Each minute, the temperature of air, on TGBR surface, and at different depths of EGR was recorded. The daily cooling and heating demands were also calculated. Results confirmed that VRs protect the roof membrane from high temperature fluctuations and decrease air temperature by a factor of one and a half during sunny winter days ( T airmax = 32 ° C ). Findings of this study also showed that the total cooling demand of EGR decreased by 90% compared to TGBR. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on a bilinear temperature control of a ground source heat pump (GSHP) integrated variable air volume (VAV) air-conditioning system, which may experience significant variations in the supply air temperature due to the frequent on/off switch of the ground source heat pump and the low thermal capacity at the air side. The bilinear control was realized in a building automation system (BAS) and applied to a test rig. The experimental results show that with an online estimation of the cooling load the bilinear control was able to maintain the space temperature at its set-point well and the control performance was superior to that of a conventional PI control. Therefore, the bilinear control has the potential to be used in GSHP integrated air-conditioning systems to improve the robustness and accuracy of the space temperature control. [ABSTRACT FROM AUTHOR]

• An energy model of condensing water systems is developed using an ε -NTU cooling tower model. • The optimal fan speed is developed using COP of actual chiller and calibrated models of cooling tower. • The operation with less connected chillers to cooling towers is considered. • The open-loop fan speed control strategy still can achieve the best control and energy performance. • The optimal fan speed significantly decreases as the number of connected chillers decreases. Open-loop fan speed control and closed-loop approach temperature control of cooling towers were recommended by different researchers. With the further consideration of the coefficient of performance (COP) change of chillers over 30 years and the potential turndown operation of cooling towers, the paper is to reinvestigate different cooling tower fan control strategies. First a total power model of condensing water systems is developed to calculate the total system power and obtain the optimal fan speed, leaving water temperature and approach temperature of cooling towers. Then a studied condensing water system with the cooling tower turndown ratio of 50 % is selected and calibrated. Finally, the developed model is applied on the studied system to evaluate different optimal and conventional controls and give the recommendations. The evaluation reveals that the optimal fan speed is significantly impacted by the chiller load and the total system power is less sensitive to the fan speed near the optimal speed. Thus, the simplified optimal speed control by resetting the setpoint with the chiller load is recommended. When physical models are not available, the conventional fixed fan speed control with the setpoint equal to the cooling tower turndown ratio is recommended with the energy penalty of 1.1 %. [ABSTRACT FROM AUTHOR]

Space heating and cooling appliances consume a significant amount of energy in buildings. In recent decades, ground source heat pump (GSHP) systems have become popular for space heating applications in many countries. However, countries like India need both space heating and cooling and hence its performance needs to be evaluated in both heating and cooling functions for economical operation. The experimental results obtained for both modes of operation are discussed in detail in this paper. Details of the experimental setup used, measurements, performance of ground heat exchanger (GHX) used and calculation of COP, effectiveness and extraction/injection are explained. Using the experimental data the coefficient of performance (COP) of heat pump and GSHP are obtained. The average COP of the GSHP system obtained during space cooling was found to be 21% less than the value obtained for heating mode operation and also heat extraction by the GHX fluid is observed to be high at the starting of the operation. In heat injection mode, as the operational time increases, the surrounding soil temperature also increased thus creating more resistance for heat flow. The average effectiveness of GHX was found to be 0.29 and 0.33 in heating and cooling mode operations respectively. [ABSTRACT FROM AUTHOR]

Accurately modeling thermal storage and discharge play a pivotal role in predicting the peak savings of demand response buildings. Considerable studies have been conducted on the transient thermal behavior of building envelopes, much of which has focused on the thermal mass effects of building envelopes and floors. However, it is unclear how to precisely describe the cooling storage effects of irregular internal mass such as furniture. EnergyPlus and other simulation tools have internal mass models, but these models require ambiguous inputs such as internal mass surface area, thickness, volume and thermal properties. These inputs are impossible to obtain due to the irregular shapes and random spatial distributions of internal mass. In this paper, the novel “Effective Area” method is proposed that improves the theory of the conventional “Equivalent Slab” method. The new method establishes a relationship between the actual furniture and the equivalent furniture through a converted coefficient in the dynamic heat transfer equations. Experiments are conducted to test and verify the accuracy of the new method and to calculate common parameters, such as the converted coefficient and the distribution density of the irregular internal mass in some typical office setups. [ABSTRACT FROM AUTHOR]

There is a growing trend for the use of thermo-active building systems (TABS) for the heating and cooling of buildings, because these systems are known to be very economical and efficient. However, their control is complicated due to the large thermal inertia, and their parameterization is time-consuming. With conventional TABS-control strategies, the required thermal comfort in buildings can often not be maintained, particularly if the internal heat sources are suddenly changed. This paper shows measurement results and evaluations of the operation of a novel adaptive and predictive calculation method, based on a multiple linear regression (AMLR) for the control of TABS. The measurement results are compared with the standard TABS strategy. The results show that the electrical pump energy could be reduced by more than 86%. Including the weather adjustment, it could be demonstrated that thermal energy savings of over 41% could be reached. In addition, the thermal comfort could be improved due to the possibility to specify mean room set-point temperatures. With the AMLR, comfort category I of the comfort norms ISO 7730 and DIN EN 15251 are observed in about 95% of occasions. With the standard TABS strategy, only about 24% are within category I. [ABSTRACT FROM AUTHOR]

In active chilled beams, primary air from the air handling unit induces room air which passes a cooling coil before it mixes with the primary air and discharges into the room. The ratio of induced room air flow to the primary air flow is the induction ratio (IR). Knowledge about the IR is important when modelling cooling capacity as well as temperature and velocity of the air discharged from the beam. Most previous studies of the behavior of IR are focusing on the influence of primary air flow. The purpose of the work presented in this paper is to investigate whether other operating conditions also influence the IR. Three methods of determining the IR are compared in order to strengthen the conclusions. The results indicate that the IR is influenced by the chilled water temperature due to buoyant forces. Novel methods of determining the IR are presented and it is concluded that current methods may lead to overestimation. [ABSTRACT FROM AUTHOR]

In this study, we propose a novel cooling and dehumidification strategy, in which a condensing panel can be hydronically connected in series with the radiant cooling system to overcome condensation risks. According to the concept, the sensible load is primarily treated by radiant cooling panels and the latent load and some amount of sensible load can be accomplished by the condensing panel. This paper evaluates the heat transfer and dehumidifying performance of the proposed condensing panel. For these purposes, a new experimental set-up was developed and condensation heat transfer of water vapor in the presence of air, on a vertical surface with different sub-cooling temperatures studied experimentally. However, the new test set-up allowed the measurement of the heat transfer coefficient from the measurement of the total sensible, radiation and condensation heat flux densities and the characteristic temperature differences. To investigate the heat transfer coefficient, tests were conducted using surface temperatures of 10.6, 10.9, 11.4, 12.2, 13 and 14 °C with the same initial conditions of mixture (mixture temperature 25 °C and relative humidity 75%). The average heat transfer coefficients were determined using the characteristic temperatures. The approximate average values 2.21, 4.45, 3.24 and 6.69 W m −2 K −1 were found respectively for the radiation, convection, condensation and total sensible heat transfer coefficients. The present experimental data provide a new database for the natural convective steam condensation in the presence of non-condensable gas over the vertical plate for the full scale atmospheric condition in a closed room. [ABSTRACT FROM AUTHOR]

Building energy consumption used for internal heating and cooling purposes is one of the most viral research topics. Retrofitting and renovation activities in building applications aim towards utilizing modern construction materials, with improved thermal and insulation characteristics. It is more than evident that such an approach leads to an improved thermal shield for the building (improving passive building elements). In addition well calibrated rule based control designs are also being adopted in the last decades as a way to improve the energy efficiency in buildings (improving active elements management). Both of the above approaches though are considered as time static since disturbances with high uncertainty (weather conditions, human presence and activity) along with the unavoidable construction material aging phenomena affect building behavior and HVAC dynamics. As a result control recalibration activities seem more than necessary to maintain energy efficiency. Followed by the rapid evolution in the computing machines sector and simulation software kits, research effort has been focused on model-assisted and co-simulation based control strategies which utilize the available computational power of modern machines towards improving energy efficiency and comfort levels through appropriate design Building Optimization and Control (BOC) systems, utilizing available system models. However the main drawback in model-assisted strategies is the fact that they heavily rely on the available building model which requires a tedious offline pre-application period including many simulation tests and/or field experiments so as to fine tune and tailor manually the model and consequently the control logic implemented. Moreover, no matter how elaborate the building model is, aging characteristics and uncertain disturbances are factors which call for re-designing (periodically) the available simulation model and the respective control strategies. This paper considers an alternative approach to BOC system design. The main attribute of the proposed methodology is that it can provide automated fine-tuning of the BOC system: no human intervention or a simulation model are required for the initial deployment of the controller as well as for the continuously applied fine-tuning procedure. Real-life experiments performed in a highly energy demanding building in Tel Aviv Israel, during spring time, demonstrate that the proposed approach can effectively provide intelligent decisions that none of the currently employed rule/event-based strategy can replicate. [ABSTRACT FROM AUTHOR]

Current indoor thermal environment is usually automatically controlled based on a temperature set-point given by room occupants or building managers. However, investigation shows that many temperature set-points are far from the comfortable temperature range recommended by design handbooks. Such unreasonable temperature set-points will result in not only uncomfortable indoor thermal environment, but also waste of cooling or heating energy. The authors have proposed a methodology of satisfaction based control to take place of the traditional set-point based control. This paper describes the experimental comparison results between satisfaction based indoor thermal environment control and set-point based control. Two test-beds were set up and a series of experiments was conducted to compare control performances, user acceptances, user work performances and system energy consumptions of the set-point based and satisfaction based control. The comparison results show that the satisfaction based control can achieve more stable thermal environment. Both of the two control methods can get relatively high scores regarding user acceptance and work performance. There are no statistically significant differences for user acceptance and work performance between two control methods. However, satisfaction based control consumed 15.3% and 11.9% less energy at two test-beds respectively than set-point based control due to more reasonable temperature settings given by the satisfaction based control. [ABSTRACT FROM AUTHOR]

Cooling of buildings currently represents a considerable fraction of the total energy consumption in the world. Global and local climate change in combination with the projected population increase and economic development is expected to increase tremendously the future cooling energy demand of buildings and make it the dominant energy component. The present paper aims to present and discuss the details of the framework which defines the present and future cooling energy consumption of the building sector. The more recent quantitative and qualitative data concerning the penetration of air conditioning around the world are presented and analyzed. The main technological, economic, environmental and social drivers that determine the market penetration of air conditioning are identified and their impact is investigated. The potential future evolution of the main parameters that define the cooling energy consumption and in particular climate change, the population increase, income growth, potential technological improvements and the main socioeconomic drivers are investigated and existing forecasts are presented. Proposed methodologies to predict the future cooling energy consumption of the building sector are reported and discussed, while existing estimates and predictions regarding the future cooling energy consumption of individual buildings as well as of the total building sector are documented, evaluated and analyzed. Based on the explored inputs and forecasts, a model to predict the future cooling energy consumption of both the residential and commercial sector is developed. Three scenarios based on low, average and high future development, compared to the current development, are created and the range of the expected cooling energy demand in 2050 is predicted under various boundary assumptions. It is calculated that the average cooling energy demand of the residential and commercial buildings in 2050, will increase up to 750% and 275% respectively. [ABSTRACT FROM AUTHOR]

Although it is widely acknowledged that occupants play a critical role in building energy consumption, the characteristics of occupants are not well-represented in building simulation. Many statistic and data-mining technologies have been applied to develop a reliable occupant model. In contrast, rather than attempting to develop the occupant model, this study aims to investigate the correlation between the occupant behavior and energy consumption based on a series of experiments. First, this paper discusses the randomness of the occupants’ presence and behavior. The degree of randomness was verified using a Normalized Cumulative Periodogram (NCP) based on a random walk hypothesis. In addition, the correlation between occupant and energy consumption was investigated using the wavelet coherence. This study shows that, while the occupants’ presence has a randomness, it is not strongly correlated to the energy consumption. The occupants’ active action to control a heating/cooling system (turn on/off) is correlated to the energy consumption. In contrast to the occupant's presence, the occupants’ active action does not follow the random walk, and it has no particular frequency. This means that it is difficult to predict the control action of occupants with a specific time interval. [ABSTRACT FROM AUTHOR]

Ground heat exchangers (GHEs) present declining performance during continuous running. The purpose of this paper is to study the effects of intermittent operations on improving the heat transfer of GHEs in a ground sink direct cooling system (GSDCS), and then optimize the on-time and off-time durations of the intermittent cycles. A numerical model of a GHE was developed with experimental validation. The influences of different flow rates and ground temperatures on the GHE performance were studied in direct cooling mode. Different operation modes were adopted to investigate the intermittent performance of the GHE and analyze the recovery mechanism of the surrounding ground temperature. The results reveal that lower flow rate of the GHE is preferred to decrease the outlet water temperature in direct cooling. Intermittent operations can effectively raise the heat transfer rate of the GHE and slower the increase of its outlet water temperature. The length of on-time and off-time shows significant influence on the ground temperature recovery. Shorter on-time contributes to quicker recovery for next off period. Prolonging off-time enables ground temperature to recover more sufficiently, however, overlong time leads to inefficient process. The proper length of intermittent durations is provided in the study for better utilization of the system. [ABSTRACT FROM AUTHOR]

The total energy demand of data centres has experienced an important increase in the last years. This is why data centres industry and researchers are working on implementing energy efficiency measures in data centre portfolio. The cooling system of these unique infrastructures can account for 40% of the total energy consumption. Therefore, air management plays an important role to reduce operating costs and to increase overall cooling system efficiency. In order to improve and optimize the energy consumption and thermal management in data centres, appropriate metrics are imperative to evaluate their efficiency and performance. The present paper examines the air management of a real data centre by the use of the most promising air metrics. Noticeable air recirculation and hot spots were observed in the facility. Dynamic modelling was used to evaluate the benefit of air inefficiency mitigation. The combination of air management improvement with increasing the supply air temperature and reducing the air flow rate would allow important energy reduction in the cooling system. [ABSTRACT FROM AUTHOR]

Although numerous technologies – such as double skin façade (DSF), double glazing window (DGW), etc. – have been applied in the glass envelope, the heat transfer of the glass envelope is still considerable. Cooling pipes embedded in the venetian blinds of a double-skin envelope are presented in this study as a system for reducing the heat transfer of the glass envelope in summer. Solar radiation is taken away directly by pipes through which cooling water is circulated, and the water can be produced from natural cooling. CFD software is employed in this paper to simulate the conjugated heat transfer in the double-skin envelope and the numerical model has been validated. The effect of embedded pipes is numerically investigated based on DGW. Different DGW structure and glass assemblies are taken into consideration. The results show that the cooling pipes can significantly reduce the temperature of the venetian blinds and air cavity, which will in turn lower heat transfer and improve thermal comfort. With pipe embedded, cooling water averagely takes away about 60% of the solar radiation directly and the average solar energy transmittance is only 13%. In addition, cheap glass can be employed to the pipe-embedded DGW with only small negative influence. [ABSTRACT FROM AUTHOR]

This paper presents a cooperative fuzzy model predictive control (CFMPC) for heating and cooling of buildings. Because of different supply zones, the large time constants and the non-linear building dynamics with respect to the different seasons, a CFMPC concept is proposed. The overall non-linear building is split into different zones, which are consisting of input-coupled Takagi-Sugeno (TS)-fuzzy models. Each such TS-fuzzy model is constituted by a local linear model network (LLMN). The LLMN consists of local linear models (LLM), which are representing the different seasons: winter, transition season (fall and spring), and summer. The control of each LLM is realized by model predictive control (MPC). For each building zone the associated MPCs are output-blended by the fuzzy membership functions, which leads to fuzzy model predictive control (FMPC). In addition to the FMPCs a global MPC is controlling the thermally activated building systems, which affect all other zones. To coordinate the different controllers a cooperative iteration-loop is assumed, which leads to cooperative fuzzy model predictive control (CFMPC). The concept is developed for a specific demonstration building and can be easily adapted for other complex buildings. A simulation example demonstrates that the proposed CFMPC achieves a performance increase with less energy consumption, as compared to FMPC controllers and historical measured data of the demonstration building. [ABSTRACT FROM AUTHOR]

Ground source heat pump systems have been proved to be one of the most efficient systems for heating and cooling in buildings. However, an optimal energy performance depends on a good control of the auxiliaries, which stand for an important part of the total energy consumption. The authors previously developed an experimental in situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems when single stage and multi-stage ON/OFF regulation is employed. However, the user comfort was not completely met under extreme weather conditions during summer. This paper presents the upgrading of this energy optimization strategy combining circulation pumps frequency variation and building supply temperature compensation in order to ensure the user comfort while keeping high energy savings. Experimental results show that the user comfort is met by means of this new methodology and the energy savings (33%) are even higher than those obtained with the previous methodology. [ABSTRACT FROM AUTHOR]