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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]

Green roofs have been proposed for energy saving purposes in many countries with different climatic conditions. However, their cooling and heating potential strongly depends on the climate and building characteristics. In particular, the increase of the thermal capacity of green roofs compared to traditional roofs, if not controlled with insulation, may lead to higher cooling and heating loads. This paper discusses the energy saving potential of green roofs adopting a variable insulation strategy. A system consisting of a plenum located between a green roof and the room underneath and a sensor-operated fan that couples (or decouples) the green roof mass with the indoor environment was developed. The fan is activated and stopped using temperature based rules; the plenum is ventilated only when the fan works, creating a variable insulation system. Four cells with an insulated traditional roof, a non-insulated green roof, an insulated green roof, and a green roof with the variable insulation system have been tested in a hot and dry climate with mild winters over several years. This paper compares and discusses different plenum control algorithms. Results are particularly promising because the variable insulating system proved to adjust the thermal capacity of the roof effectively. In summer, the non-insulated green roof and the green roof with variable insulation system achieved the lowest indoor temperature; in winter, the insulated traditional roof and the variable insulation green roof system achieved the highest indoor temperatures. Measurements are hence compared with simulations. Finally, the energy saving potential of the new green roof system is evaluated. [ABSTRACT FROM AUTHOR]

Global warming has drawn great attention in recent years because of its large impact on many aspects of the environment and human activities in buildings. One area directly affected by climate change is the energy consumption for heating and cooling. To quantify the impact, this study used the HadCM3 Global Circulation Model (GCM) to generate weather data for future typical meteorological years, such as 2020, 2050, and 2080, for 15 cities in the U.S. based on three CO 2 emission scenarios. The method was validated by comparing the projected TMY3 data using HadCM3 with the actual TMY3 data. By morphing method, the weather data was downscaled to hourly data for use in building energy simulations by EnergyPlus. Two types of residential buildings and seven types of commercial buildings were simulated for each of the 15 cities. This paper is the first to systematically study the climate change impact on various types of residential and commercial buildings in all seven climate zones in the U.S. through EnergyPlus simulations and provide weighted averaged results for national-wide building stock. We also identified geographical dependency of the impact of climate change on future energy uses. There would be a net increase in source energy consumption by the 2080s for climate zones 1–4 and net decrease in climate zones 6–7 based on the HadCM3 weather projection. Furthermore, this paper investigated natural ventilation performance in San Francisco, San Diego, and Seattle with improved natural ventilation model. We found that by the 2080s passive cooling would not be suitable for San Diego because of global warming, but it would still be acceptable for San Francisco and Seattle. [ABSTRACT FROM AUTHOR]

To study the dynamic thermal response performance of concrete radiant cooling slab, this paper introduces the concept of core temperature layer. Heat transfer process in the concrete slab is divided into three sub-processes, correspondingly, and three heat transfer models are built by reaction coefficient method. Two-dimensional unsteady heat transfer model of concrete cooling slab is established ultimately. Experiments are conducted to test the slab thermal performance in steady and unsteady conditions. Error analysis and consistency verification are presented between the experimental value and calculated results of the model. The relative error between calculation and experimental value is within 2% in steady conditions and within 7% in unsteady conditions. The application scope of the heat transfer model for practical engineering is defined in this paper. [ABSTRACT FROM AUTHOR]

Energy consumption presents increasing trends during last decades, presenting a great challenge. The building sector contributes to a high proportion of the energy consumed and therefore efforts should be focused to improve energy efficiency of buildings. For such purpose, the use of phase change materials in building envelopes has been extensively studied and its benefits were demonstrated. However, there is a lack of simple evaluation tools to assess these benefits. In this paper a previously proposed methodology based on four indicators, which were tested through simulation only are experimentally validated using brick, concrete and timber constructions, incorporating PCM. Results show that the methodology is successful for buildings with heat gains and having low thermal inertia or insulation. However, for highly insulated buildings with significant inertia and low heat gains the method fails to assess the potential benefit of the PCM. Moreover, the ITD indicator is found to be the most accurate in assessing PCM benefits compared to other parameters studied. In this paper the ITD indicator will be modified to take into account an upper and lower comfort temperature levels rather than single set temperature. [ABSTRACT FROM AUTHOR]

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

Abstract: Reducing the energy consumption of air-conditioning systems is becoming increasingly important. This paper focuses on the air-conditioning system in Terminal 3 in Xi’an Xianyang International Airport, the first airport terminal to adopt radiant cooling in China. In the large spaces of this airport terminal, a temperature and humidity independent control (THIC) system has been adopted instead of a conventional nozzle air supply method, which significantly reduces the energy consumption of the air supply. The radiant floor is the main mechanism for indoor temperature control, while a liquid desiccant outdoor air processor combined with displacement ventilation is responsible for humidity control. Ice storage is adopted to reduce operating costs, and the supplied chilled water temperature can be as low as 3°C. This paper examines the performance of the THIC system in detail. The indoor environment is determined through measurements to be comfortable, and the on-site performances of key components in both the airport terminal and the cooling plant are investigated. The outdoor air processor supplies air of appropriate temperature and humidity ratio; two kinds of radiant floors are used for temperature control, both with measured cooling capacities of about 30–40W/m2; and the energy efficiency ratio (EER) of the cooling plant is 2.62. [Copyright &y& Elsevier]

Abstract: It is not feasible to apply the traditional prediction method to predict hourly building cooling load at the urban energy planning stage because of the limited building information and complexity of energy prediction. This paper presents a simplified prediction model: Hourly Cooling Load Factor Method (HCLFM) that can provide quick and fair estimate of building cooling load for large-scale urban energy planning. The paper introduces the assumptions and principles of the proposed method, as well as discussing the implication and limitation of the approach. As a verification and demonstration, the method is applied to an office building in Beijing. The predicted results show that the dynamical trend of the cooling load is reasonable. The study further analyzes the potential causes of prediction errors and the significance of various cooling load influence factors. [Copyright &y& Elsevier]

Abstract: This paper presents a heat storage and cooling concept that utilizes a phase change material (PCM) and a thermally activated building system (TABS) implemented in a hollow core concrete deck. Numerical calculations of the dynamic heat storage capacity of the hollow core concrete deck element with and without microencapsulated PCM are presented. The new concrete deck with microencapsulated PCM is the standard deck on which an additional layer of the PCM concrete was added and, at the same time, the latent heat storage was introduced to the construction. The challenge of numerically simulating the performance of the new deck with PCM concrete is the thermal properties of such a new material, as the PCM concrete is yet to be well defined. The results presented in the paper include models in which the PCM concrete material properties, such as thermal conductivity, and specific heat capacity were first calculated theoretically and subsequently the models were updated with the experimentally determined thermal properties of the PCM concrete. Then, the heat storage of the decks with theoretically and experimentally determined thermal properties were compared with each other. Finally, the results presented in the article highlight the potential of using TABS and PCM in a prefabricated concrete deck element. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a computational study on the energy consumption and related CO2 emissions for heating and cooling of an office building within the Urban Heat Island of London, currently and in the future. The study developed twenty weather files in an East-West axis through London; the weather files were constructed according to future climate change scenario for 2050 suitable for the UK which have been modified to represent specific locations within the London UHI based on measurements and predictions from a program developed for this purpose (LSSAT). The study simulated an office with typical construction, heat gains and operational patterns with an advanced thermal simulation program (IESVE). The predictions confirm that heating load decreases, cooling load and overheating hours increase as the office location moves from rural to urban sites and from present to future years. It is shown that internal heat gains are an important factor affecting energy performance and that night cooling using natural ventilation will have a beneficial effect at rural and city locations. As overheating will increase in the future, more buildings will use cooling; it is shown that this might lead to a five-fold increase of CO2 emission for city centre offices in London in 2050. The paper presents detailed results of the typical office placed on the East-West axis of the city, arguing the necessity to consider using weather files based on climate projections and urban heat island for the design of current buildings to safeguard their efficiency in the future. [Copyright &y& Elsevier]

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]

Abstract: An experimental system was developed and tested in order to investigate the exergetic performance of a solar photovoltaic system (PV) assisted earth-to-air heat exchanger (under ground air tunnel) that is used for greenhouse cooling at the Solar Energy Institute, Ege University, Izmir, Turkey. This system was under operational conditions successfully during the 2010 summer cooling season. This paper provides the experimental results obtained between 18th of August and 26th of August of in 2010. Exergy destruction in the system was calculated and presented in this paper using a reference temperature of 15°C. Results are discussed and interpreted in the paper for various performance metrics, such as the effect of climatic conditions and operating conditions on the system performance. Results show that the system may be satisfactorily used for greenhouse cooling in the Mediterranean and Aegean regions of Turkey. [Copyright &y& Elsevier]

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: Design engineers commonly oversize HVAC systems with the justification of needing a reasonable safety factor to manage periods more extreme than the specific design conditions. Unfortunately, the safety factor easily becomes excessive. The design engineers minimize their professional risk, and by doing so they are actually asking the building owner to pay an immediate penalty due to increased first cost of equipment and an ongoing penalty due to maintenance and energy use implications. The penalties associated with excessive safety factors are often not communicated to the client. This paper presents the results of a study of “rightsizing” rooftop HVAC systems. The study included intensive interviews with HVAC designers investigating the design process and extensive field measurement of rooftop units (RTUs) during peak cooling conditions. This paper focuses on defining the signature of oversizing, i.e. how to use the physical measurements to quantify the degree of oversizing of an RTU and how to estimate the penalty of oversizing in terms of energy consumption and peak electricity demand. Utility companies incentive programs have not yet identified mechanisms for incentivizing rightsizing of HVAC system. The methodology described in this paper can be used as the basis for such programs. [ABSTRACT FROM AUTHOR]

Abstract: Combined cooling, heating, and power (CCHP) system models have been used by many researchers to compare their performance with conventional systems. However, decisions based on the results of computer simulations need to take into account the uncertainty of these results to get insight into the level of confidence in the predictions. This paper presents an analysis of a CCHP system model under different operating strategies with input and model data uncertainty. However, the uncertainties that underlie the variation in input parameters such as the thermal load, natural gas prices and electricity prices are not readily available. Additionally, engine performance uncertainty can be difficult to characterize because of the nonlinearity of engine efficiency curves. This paper presents practical and novel approaches to estimating the uncertainty in these and other input parameters. A case study using a small office building located in Atlanta, GA, is described to illustrate the importance of the use of uncertainty and sensitivity analysis in CCHP system performance predictions, and how the primary energy consumption, operational cost, and carbon dioxide emissions are affected by the uncertainty associated with the model input parameters. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a calculation method for the floor surface temperature in radiant floor heating/cooling system is proposed, a new formula is derived to estimate the floor surface temperature. The floor is divided into two layers. The correlation for the thermal conductivity of the lower layer is developed based on the numerical model of the radiant floor system built in this paper. The results show that the floor surface temperature values from the proposed method are in agreement with the experimental and numerical values. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to study the various parameters that affect the energy performance of commercial buildings in Singapore. The parameters are diverse, ranging from characteristics of construction of the walls and windows, to the various system settings and types within the building. Building energy performance is measured via two key indexes, namely, the Envelope Thermal Transfer Value (ETTV) and the annual cooling energy requirement (E c). Parameters related to these two indexes are identified. An additional parameter, the solar absorptance of the wall, is further incorporated to calibrate the ETTV equation. A relative ranking on the functional parameters of ETTV has been performed to evaluate their effectiveness in lowering the ETTV of buildings. In addition, the impact of using cladding on ETTV is also studied. A correlation for E c, expressed in the form of a simple linear equation, has been developed. This correlation accounts for the internal building loads, envelope loads, operating schedules and efficiency of the cooling equipment. Finally, ETTV and E c have been employed to study the effects of chiller over-sizing and ventilation rates on building cooling energy. In the pursuit for better energy-efficient buildings, the approach presented in this paper contributes to the construct of sustainable energy-efficient built-environment. [Copyright &y& Elsevier]

Abstract: This paper presents general guidelines for the required cooling capacity of an entire office building using thermally activated building systems (TABS). By activating the thermal mass of the building using pipes embedded in the floor, peak loads can be reduced. On-site measurements were performed to obtain the required cooling power of an entire building as well as individual zones. Beside this, the internal climate conditions of rooms and surface temperatures of the TABS were measured. The measured data were used to analyze the predictive performance of a simulation model. In order to acquire general guidelines for the required cooling capacity of a standard office building, simulations of an entire building were used to determine the impact of variable internal heat gains and different sized windows. The required cooling capacity was compared to the cooling capacity of a system without energy buffering (e.g. chilled ceiling panels). It was found that reductions up to 50% of the cooling capacity for a chiller can be achieved using TABS. The presented results within this paper can be used as design guidelines in the first stage of a design process. The results focus on temperate climates and were derived using Dutch climate conditions. [Copyright &y& Elsevier]

Abstract: The paper deals with an innovative natural gas combined heat, cooling and power (CHCP) system with electrical, heating and cooling capacities of 126/220/210kW, respectively. The trigeneration plant is composed of a cogenerator which uses an automotive derived gas fired internal combustion engine (ICE), coupled to a liquid LiCl–water desiccant cooling system which recovers heat from the flue gases and from the ICE cooling water. The paper describes the energetic and economic analyses of the plant and it makes some evaluations of the effects of fuel and electric prices and of the subsides and plant costs on the economic indices of the system. [Copyright &y& Elsevier]

Abstract: This paper investigates the development of a low cost air cooling system used for small scale applications. Its operation is based on the rational and efficient use of energy available in conventional freezers, used for other purposes than air conditioning, to cool small areas. In this paper, the proposed air cooling system is applied to small kiosk prototype (called “periptero”), found very often in the streets of Greek cities and villages, used to sell goods to people. The proposed air cooling system is using the low temperature air inside the freezers to cool the air inside the kiosk and provide a better living environment for the owner, particularly during summer period. The basic principle of the system operation and the experimental installation will be described and the experimental results will be presented and discussed. [Copyright &y& Elsevier]

Abstract: This paper studies air flow in an air-conditioned room containing a distributed heat source and a localised heat source, into which cool air is supplied at low momentum through openings at a low level, and from which old air is extracted from a high level. This situation may be analogous to an auditorium containing a distributed audience and a localised group of actors and lighting on a stage, into which cool air is distributed from underneath the seating, and from which old air is removed through a ceiling, for example. Using a combination of a theoretical model and laboratory experiments, the paper shows that, in such conditions, if the localised heating is sufficiently strong compared to the distributed heating, the room will become stratified into two layers at steady state. A layer of warm air lies atop a cooler layer that attains a temperature above that of the supply air. This temperature structure depends primarily on the supply air flow rate and the ratio of the distributed heating to the total heat flux. For a room with fixed heating, increasing the supply air flow rate raises the interface between the upper and lower layers, while cooling both layers. The temperature in the upper layer depends on the total heat flux, but the temperature in the lower layer depends on the flux of distributed heating. For a room with a fixed supply air flow rate and a fixed total heat flux, increasing the strength of distributed heating warms the lower layer, but does not affect the temperature in the upper layer. Such increase in the strength of distributed heating also raises the interface. To achieve sufficient ventilation and thermal comfort in an occupied lower zone while keeping any pocket of uncomfortably warm air well above it, cool air needs to be supplied within an appropriate range of flow rates, which depends on the ratio of the distributed heating to the total heat flux. The paper shows how to determine such appropriate ranges of flow rates for different heating ratios, using the model. [Copyright &y& Elsevier]

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]

• 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]

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]

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]

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]

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]

• 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]

• 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]

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]

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]

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]

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]