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Abstract: This paper deals with the development of a low cost and low energy consumption air conditioning system based on the conventional central heating installations. It is aimed to convert, with minimal cost and work intervention in the interior of the buildings, the classic central heating systems into a new type system which can cool during summer and heat during winter period. In general, the above mentioned heating–cooling system constitutes an integrated new technology in building air conditioning, with good prospects in replacing eventually the conventional air conditioning systems. The experimental installation is described in detail and the experimental results are presented and analysed. The achieved energy saving is also calculated. The advantages and disadvantages of the proposed system are discussed and useful conclusions are drawn. [Copyright &y& Elsevier]

Abstract: In this paper are presented the results of experimental analysis of the influence of ventilation systems and related energy consumption on inhalable and respirable dust concentrations in fattening pigs confinement buildings. The application of different under pressure ventilation systems in reducing and controlling dust concentrations was analyzed. Optimal ventilation systems designs and the ranges of airflow velocities were defined and discussed. Airflow velocities in the finishing room, under floor, roof and both ventilations, ranged from: 0.01 to 0.10, 0.01 to 0.10 and 0.02 to 0.10m/s, respectively. The average inhalable dust concentrations during the reference regime (no ventilation), as well as second (floor-), third (roof-) and fourth (both ventilations) regime were: 20, 20, 25 and 17particles/cm3, respectively. The average respirable dust concentrations during the reference regime, as well as second, third and fourth regime were: 18, 19, 23 and 16particles/cm3, respectively. Significant decrements of inhalable (F =44.35, P ≪0.01) and respirable (F =43.82, P ≪0.01) dust concentration, in the finishing fattening pig house, were achieved only with the fourth regime (both ventilations). [Copyright &y& Elsevier]

Abstract: Variable air volume (VAV) air conditioning control system has the feature of multi-control loops. While all the control loops are working together, they interfere and influence each other. This paper designs the decoupling unit in VAV air conditioning system in the method of diagonal matrix decoupling. Lonworks technology is adopted in VAV air conditioning decoupling control system so that data could be exchanged among multi-loops. It is suitable that decoupling compensation coefficients among multi-loops are handled as network variables of Lonworks technology. Experimental results demonstrate that the combination of the diagonal matrix decoupling and Lonworks technology can improve the performance of the VAV air conditioning control system. [Copyright &y& Elsevier]

Abstract: Internal air flows due to ventilation through large openings is an integral part of the ventilation and energy design of buildings and should be taken into account among other thinks in the simulation of occupants’ behavior. In this paper, the effect of the arrangement and use of the internal openings in a two-storey house on the interzonal flows inside the building''s rooms is examined, with the aid of nodal ventilation modeling. Validation experiments are also performed for a series of arrangements of internal and external openings, by conducting tracer gas measurements. A parametrical investigation is carried out for selected parameters, including the effect of the percentages of the windward and leeward openings on the interzonal flows, monitoring magnitude and direction changes, for specific climatic conditions. Conclusions about interzonal flows and ventilation design are drawn. [Copyright &y& Elsevier]

Abstract: The Mediterranean climate is characterized by a high level of the solar resource in winter and some coolness of the nights in summer, which offer a good opportunity for thermal comfort achievement at low energy cost and reduced CO2 emissions, provided that an appropriate design of the building envelope is adopted. It has thus been decided to implement some regulations in three countries of North-Africa for controlling the heating and cooling loads. The study described in this paper has been conducted in the frame of this project. It has two objectives: to define adequate indicators for the thermal performance of buildings during both the cold season and the hot one, and to develop a standard calculation procedure for these indicators. The developed procedure, CHEOPS, is fast and requires minimum input data; it is very easy to use, the steps for calculating the cooling and heating coefficients being almost the same. The transmission losses and the solar gains are clearly identified; this fact can contribute to a better understanding by the designer of the effect of each parameter, leading him towards the appropriate trade-offs between summer and winter considerations. [Copyright &y& Elsevier]

Abstract: A liquid desiccant total heat exchanger and small capacity refrigeration cycle combined fresh air processor is proposed here in this paper, in order to improve indoor air quality and decrease the energy consumption of the air-conditioning system. Operating principles of both the total heat recovery device and fresh air processor using liquid desiccant are presented in details. Experimental tests of the fresh air processor installed in a hospital show that energy efficiency ratio (EER) is around 6.3–7.3 in the summer experimental conditions and 4.7–5.0 in the winter experimental conditions. Hour-by-hour simulation, which is based on the climate data in Beijing, shows that the average EER is 5.3 and 4.3 in summer and winter period, respectively. Liquid desiccant has the potential to remove a number of pollutants, avoiding cross contamination. Furthermore, in summer fresh air is dehumidified by contacting liquid desiccant instead of 7°C chilled water, which avoids wet surfaces in the air-conditioning system and much higher indoor air quality can be achieved. [Copyright &y& Elsevier]

Abstract: Near-extreme outside dry- and wet-bulb temperatures are essential for the design of building HVAC systems. Coincident design temperatures currently defined by ASHRAE and CIBSE may not fully allow engineers to design an HVAC system that can match a risk level desired for the problem at hand. A rational method is therefore presented in this paper for the proper selection of coincident climate design conditions, which is based on the theory of probability. An average statistic risk level has been proved to be approximately equal to the annual percentile of coincident dry- and wet-bulb temperatures for HVAC systems whose thermal time constant is less than 1h. An algorithm is also developed to determine the contours of equal risk. Representative coincident design dry- and wet-bulb temperatures are obtained through statistic analysis of the 15 years of weather records in Hong Kong. These rationally derived outside design temperatures are compared with the coincident dry- and wet-bulb temperatures currently defined by ASHRAE and CIBSE. [Copyright &y& Elsevier]

Abstract: Thermal driven desiccant assisted air conditioning systems make use of waste heat to dehumidify humid outside air in a desiccant wheel. Within the scope of a research project, an investigation of a desiccant assisted air conditioning system was carried out, and a demonstration plant was built in an office building in Hamburg, Germany. The HVAC system consists of a small CHP-plant, a desiccant assisted ventilation system and an earth energy system (borehole heat exchangers) for cooling instead of an electric driven compression chiller. The radiant floor heating system of the building is used for cooling. In this paper, measurement results and investigations of performance, energy demand and operating costs will be presented. It was found that considerable primary energy savings can be achieved (70%) using desiccant air conditioning with borehole heat exchangers. But even if electric chiller is used, savings of 30% in primary energy can be accomplished. Starting costs for the demonstration plant were not higher than for a conventional system, but running costs could be reduced drastically. [Copyright &y& Elsevier]

Abstract: This paper evaluates the performance of a personalized air-conditioning system, namely an innovative partition-type fan-coil unit (PFCU), against that of a central air-conditioning system, in terms of their thermal comfort provided and cooling energy consumed. For a cooling load given, it is found that the thermal comfort index (PMV) resulted from the personalized system is always lower than that from a central system. Also, the PMV-curve of the personalized system responds to the loads faster. The experimental results indicate that the personalized system, as compared to the central system, can shorten the operation time for the same level of thermal comfort required and save up to 45% of the energy consumed by the central system. As regards thermal comfort, the experiment with a thermal manikin substrates the PFCU design for its considerable reduction of the cold draft. [Copyright &y& Elsevier]

Abstract: Double-skin façade is getting more and more attention as it provides many possibilities for energy conservation and at the same time creates good indoor environment. In this paper, natural ventilation performance of a double-skin façade is highlighted. A prototype building is proposed, which is thought to be an eight-storey office building with an atrium space in the north side. The south façade of the building is a double-skin façade and a thermal storage space called solar chimney is considered above the double-skin space. Actually, the double-skin space is connected with the chimney channel. Reduced scale model experiments and computational fluid dynamics (CFD) analysis are carried out in this research to evaluate the natural ventilation performance of the prototype building. [Copyright &y& Elsevier]

Abstract: Solar air collectors are important components for solar energy utilization in green houses. In this paper, experimental studies were carried out regarding to a solar air collector (SAC), for which the length of air channel is 1500mm, the width is 500mm, and a variable air channel gap ranges from 100 to 500mm. In the experiment, the uniform heat flux along the air channel is effected by three electric heating plates, which play a role as solar radiation. It is found that the temperature distribution of air and the induced natural air-flow rate are highly dependent on heat input, inclination angle, channel gap, etc. Experimental results indicate that the optimum inclination angle for the SAC is 45°, under which a maximum natural ventilation rate can be created. Also found is that there exists an appropriate channel length, about 1m in this study, beyond which the obtained heat and the natural ventilation rate cannot be increased drastically. Higher the volume of air-flow rate through the SAC, lower the temperature difference between inlet and outlet, consequently, it should be balanced between the air temperature rise and a suitable mechanical air-flow rate in order to obtain maximum heat. Additionally, theoretical analysis based on heat balance equations is testified to agree well with experimental results. [Copyright &y& Elsevier]

Abstract: The integration of building energy simulation (ES) and computational fluid dynamics (CFD) programs can provide more accurate prediction of building energy use and indoor environment due to the complementary information provided by the two programs. This paper outlines briefly a coupled energy simulation and computational fluid dynamics program with different coupling methods and validates the coupled program by using four sets of experimental data from literature. The comparison of the simulated results with the experimental/empirical data reveals the advantages of the integrated building simulation over the separated energy simulation and computational-fluid-dynamics applications. The program was then used to calculate the cooling load of a large-scale indoor auto-racing complex. [Copyright &y& Elsevier]

This paper presents figures for the small power equipment loads encountered by the Welsh School of Architecture in UK offices while undertaking a programme of research and monitoring into the energy efficiency of air-conditioning systems in use. The findings are based on surveys undertaken in 30 air-conditioned offices between April 2000 and October 2002. Peak small power equipment loads were calculated using the CIBSE nameplate-ratio method. The results show that the small power loads averaged 17.5 W/m2 with a range between 6 and 34 W/m2 of treated floor area. When normalised for occupancy the calculated peak small power equipment loads averaged 158 W per person, with a range between 124 and 229 W per person. Current industry guidance could lead to the overestimation of small power equipment loads by as much as 650%, ultimately resulting in increased capital and running costs of air-conditioning plant and reduced thermal comfort. A more accurate method of estimating peak small power equipment loads in UK office buildings is suggested based on occupant density. [Copyright &y& Elsevier]

Commenting on some negative effects of traditional conditioning strategies of indoor thermal environment in warm climates, the authors present a fundamental concept of thermal comfort and acceptability, new air-conditioning strategies by using fluctuating air movement based on the findings of human responses to transient thermal environment, and a prediction of energy saving caused by elevated indoor temperature settings. In addition, how to meet the requirement of providing human-beings a healthy, comfortable and affordable indoor air temperature, and to achieve a goal of sustainable development are also discussed in this paper. [Copyright &y& Elsevier]

Almost in all the major cities in Asian countries, residential buildings are characterized with high-rise and high density. Under this circumstance, achieving comfortable and healthy indoor environment with minimized energy consumption becomes a very challenging engineering and societal issue. While the wide use of air-conditioning helped to improve thermal comfort, health problems associated with poor indoor air qualities have appeared more frequently. The increased energy consumption is also a great concern in view of its impact on the energy economics of the region. Drawn from some of the onsite measurements and survey, and also the author’s personal observation, some of the key issues are discussed in this paper. [Copyright &y& Elsevier]

The purpose of this study is to propose a residential building model with voids which is appropriate for hot and humid regions of Asia with high population densities that also reduces the environmental load of buildings. This paper will explain an outline of a porous-type residential building model in Hanoi and the design process for introducing voids in buildings in order to improve natural cross ventilation effectively. Furthermore, the effects of natural ventilation, solar shading, and some devices for air conditioning systems for reduction the cooling and environmental load are estimated. [Copyright &y& Elsevier]

This paper investigates a hybrid cooling system, utilizing wind-driven cross ventilation and radiational panel cooling in an office setting. The characteristics of the indoor environment are examined using computational fluid dynamics (CFD) simulation, which is coupled with a radiation heat transfer simulation, and HVAC control in which the PMV value for a human model in the center of the room is controlled to attain the target value. The system is devised with an energy-saving strategy, which utilizes stratified room air with a vertical temperature gradient. The cooled air settles down within the lower part of the room, while the hot and humid air passes through the upper region of the room, sweeping out the heat and contaminants generated indoors. This strategy is found to be quite energy-efficient in the intermediate seasons of spring and autumn in Japan. Even under hot and humid outdoor conditions, the hybrid system coupled with radiational cooling would bring significant energy savings are possible compared with a hybrid system coupled with underfloor air-conditioning. [Copyright &y& Elsevier]

The paper describes the calibration of a simulation model of double-skin façade systems with controlled rotating louvers and ventilation openings. The approach is based on a parameter estimation technique and in situ monitoring of a full-scale element mounted on the south facing façade of an existing building. Contrary to similar work that attempts to derive the behavior from detailed modeling of the physical transport phenomena, the new approach is based on a postulated “minimalistic” lumped model, which is calibrated on in-situ measurements. It is found that the calibrated model is surprisingly accurate and ideally suited for use in the ensuing optimal control and performance studies. [Copyright &y& Elsevier]

The aim of the work accounted for in this paper has been to investigate a demand controlled ventilation (DCV) system for a typical Swedish multifamily building with exhaust ventilation. Another aim has been to apply and evaluate the IDA Indoor Climate and Energy (ICE) simulation software in this application. The work has been related to a renovation project of a large number of apartments with exhaust ventilation systems recently carried out by a Swedish municipal housing association.A typical apartment, chosen among 1000 existing apartments, has been modelled using IDA Climate and Energy simulation software. Four exhaust ventilation system concepts have been evaluated:The simulations show that it would be possible to achieve energy savings using occupancy and/or humidity controlled ventilation to reduce the average ventilation flow rate while keeping an acceptable indoor climate. Based on the simulation results a demand controlled ventilation system is developed and implemented in occupied apartments in order to investigate the performance.A measurement based validation of the simulation program indicates that it can be applied reliably. [Copyright &y& Elsevier]

This paper outlines a methodology for the reduction of a complex computational fluid dynamics (CFD) model using data-based mechanistic (DBM) modelling technique. For this study a full scale, adiabatic walled ventilated installation was used. Primarily, a CFD model that is three dimensional, transient and turbulent was proposed and solved by a commercial package CFX 4.3 in order to obtain informative data that will be used to build a DBM model. At the inlet a step rise in temperature was applied and the ventilation rate is kept steady. Turbulence is modelled by the widely used standard k–ε model. Temperature responses at 36 monitoring positions inside the installation were extracted out of the simulation. In the second stage of the work, for the same ventilation system, a DBM model was formulated from an energy balance equation. The simplified refined instrumental variable (SRIV) algorithm is employed as model parameter identification tool. The obtained highly accurate model parameters for all monitoring positions demonstrate the possibility of reducing complex CFD models using identification technique. [Copyright &y& Elsevier]

An indoor climate is mainly influenced by factors including heating, ventilation and air-conditioning, building envelope and materials, occupants, furniture, and service life of the building components. These last few years, the usual porous medium provided in wall and flooring constructions have been pointed out as possible passive systems capable of buffering the indoor climate variations in terms of temperature and humidity. The objective for the ongoing project is, therefore, to evaluate the possibility of ensuring an indoor climate within an acceptable range making use of large exposed massive wood surfaces. An experimental study, being performed in four occupied apartments of a multi-storey residential building in Sweden, is described in this paper. A brief analysis of the in situ recordings is also included. The temperature and relative humidity recordings show fairly well-agreement with the ASHRAE recommended values for a good indoor climate excepted during the cold periods revealing low indoor relative humidity. The first results show evidences that a large area of exposed massive wood contributes to buffer the indoor temperature variations. Furthermore, this far it does not shows evidences that a large area of exposed massive wood is able to damp the daily fluctuations in relative humidity. [Copyright &y& Elsevier]

The design of ventilation performance of air-conditioning systems in large commercial and office buildings is quite established. However, it is not the same with the designs of air-conditioning systems in most residential buildings. Split system air-conditioning units are commonly employed in residential buildings in the tropics due to their convenience in terms of energy conservation, aesthetics, flexibility, acoustic performance and ease of operation. Such units are also popular among small offices, shopping complex and even as supplementary air-conditioning units beyond normal office-hours in large commercial and office buildings. This paper presents findings from a recent study of the ventilation performance and indoor air quality (IAQ) in a master bed room of a condominium unit in Singapore, employed with a split system air-conditioning unit. The attached bathroom is equipped with an exhaust fan, whose operation and its impact on the resulting ventilation characteristics was also studied. Four adults occupied the room throughout the course of the experiments. It was observed that the carbon dioxide level in the bed room can exceed 2000 ppm without the exhaust fan in about 2 h. The operation of the exhaust fan quickly lowered the level of carbon dioxide to about 1000 ppm. The findings suggest the need to design for ventilation provision in split system air-conditioning units. [Copyright &y& Elsevier]

A 9-month study of four relocatable school buildings, each retro-fitted with small reverse cycle air conditioners (ACs), was conducted to investigate their effectiveness in heating and cooling the classrooms. A comparison with data from previous studies found the energy used by the ACs for heating these temporary classrooms was only 19–20% of the energy used by individual gas heaters installed in permanent classrooms. When equipment efficiencies were considered, the AC units supplied 20–27% less energy to heat the classrooms. The possible reasons for this reduction in supplied energy are explored in this paper. CO2 emissions for the AC units in heating mode, however, were calculated to be 16% greater than for individual gas heaters. The AC units were also used for cooling and on an average the total annual energy consumption for heating and cooling was found to be 11.6 kWh m−2. Responses to a small survey of staff and students about the use and operation of the conditioners are presented. Their responses were more favourable than the predictions of comfort levels in the classrooms using the Predicted Mean Vote–Predicted Percentage of Dissatisfaction (PMV–PPD) model, which indicated “uncomfortable” conditions on average summer days at 3:00 p.m. and average winter days at 10:00 a.m. Background noise levels in the classrooms with the air conditioners in use were above the recommended maximum design level of 45 dB(A); levels of up to 65 dB(A) were measured. [Copyright &y& Elsevier]

Building automation systems (BASs) are extensively utilized in fault detection and isolation (FDI) of heating, ventilating and air-conditioning (HVAC) processes. Usually a BAS, which is directly interfaced to the process only monitors or collects data for the FDI algorithm. Rarely both control and monitoring actions of the automation system are harnessed for FDI. However, in buildings such a diagnostic approach is possible and illustrated in this paper. The fault detection is based on an on-line diagnostic test (ODT), which is a series of control and monitoring actions applied to a process. Performing an ODT means exciting the automated process by using prescribed input signals, supervising responses and comparing results with a process model. All operations are performed on-line, during normal up state of the process and controlled by the automation system. The fault detection method is outlined for an air-handling unit (AHU) and implemented for its preheating process. The approach is demonstrated in a real building by programming the diagnostic algorithms in a BEMS, installed in a college building and further performing test runs. Faults are detected by comparing gathered data with a statistical model. Due to the difficulties in generating natural faults, a few artificial faults were introduced. The test runs show that the ODT is an uncomplicated diagnostic method for finding distinct and abrupt changes in a process but not for detection of slow degradations and gradual faults. Moreover, the ODT seems to be generic over faults and processes, requires no additional instrumentation and no more than domain knowledge for initiation. [Copyright &y& Elsevier]

The design of buildings is a multi-criterion optimization problem, there always being a trade-off to be made between capital expenditure, operating cost, and occupant thermal comfort. This paper investigates the application of a multi-objective genetic algorithm (MOGA) search method in the identification of the optimum pay-off characteristic between the energy cost of a building and the the occupant thermal discomfort. Results are presented for the pay-off characteristics between energy cost and zone thermal comfort, for three design days and three building weights. Inspection of the solutions indicates that the MOGA is able to find the optimum pay-off characteristic between the daily energy cost and zone thermal comfort. It can be concluded that multi-criterion genetic algorithm search methods offer great potential for the identification of the pay-off between the elements of building thermal design, and as such can help inform the building design process. [Copyright &y& Elsevier]

CEN TC247 has prepared draft standards for main types of room controllers. These standards include a performance testing procedure that was designed to facilitate the introduction on the market of innovative controllers (adaptive controllers, fuzzy controllers …). The test procedure is based on the connection of the real controller to be tested to a virtual building and technical plants. The objective of the study which is part of the European SIMTEST project is the development of a testing method by emulation for control systems for heating ventilating and air conditioning applications. This study was focused on the development of numerical models of building and HVAC systems, which are the core of the test facility. The models developed are adapted to the needs of HVAC controller design and test. They take into account static and dynamic phenomena, which are necessary to assess, control functions in terms of comfort and energy consumption. These models are adapted to the test of all controllers, which are in the scope of the three draft standards CEN TC247, in particular to controllers for heating systems, fan coils, variable air volume systems and chilled ceilings. We present in this paper:(1)The testing method developed including the simulated environment with its models, the interfaces and the test procedure.(2)The validation of the testing method by inspection and comparison of the results obtained by emulation to the results obtained by real tests in a cell. Each application is tested with two different controllers: a high performance and low performance controllers. The same controllers are used in the two different testing methods. [Copyright &y& Elsevier]

This paper reports thermal comfort and indoor air quality (IAQ) studies of an under-floor air-conditioning (UFAC) system in hot and humid climate. Thermal comfort parameters were measured at predetermined grid points within an imaginary plane to predict the airflow pattern of the supply air jet as well as to determine the occurrence of thermal stratification in the office space. Fanger’s [Thermal Comfort Analysis and Applications in Environmental Engineering, McGraw-Hill, New York, 1970] thermal comfort index was also computed to detect the occupants’ thermal sensation. Besides, the concentration levels of dust and carbon dioxide were recorded with the intention to examine the quality of the indoor air. Statistical methods were applied to derive the relationship between air velocity and the other parameters as mentioned earlier. The main findings from the study revealed reasonable level of acceptability of IAQ associated with the UFAC system. However, occupants are likely to experience localised thermal discomfort near the supply diffusers due to the existence of large temperature gradients. In addition, a stagnant zone is discovered at sedentary level, which is caused by the parabolic airflow nature of the primary air jet. [Copyright &y& Elsevier]

[Display omitted] Thermoelectric (TE) air cooling is a solid-state technology that has the potential to replace conventional vapor compression-based air conditioning. In this paper, we present a detailed system-level modeling for thermoelectric air conditioning system with position-dependent (graded) and constant material properties. Strategies for design optimization of the system are provided in terms of cost-performance trade-off. Realistic convection heat transfer at both sides of the system are taken into account in our modeling. Effects of convection heat transfer coefficients, air flowrate, and thermoelectric material properties are investigated with varying key parameters such as TE leg thickness, module fill factor, and input current. Both constant material properties and graded properties are considered for the TE materials, and they are compared in terms of the degree of cooling, coefficient of performance (COP), and power consumption. For graded materials, we employ one-dimensional finite element methods to solve the coupled electrical and thermal current equations with arbitrary profile of material properties varying with position along the TE legs. We find that graded materials can enhance the degree of cooling, but only at the expense of COP , compared to the case of constant property materials. With constant material properties of ZT = 1 and relatively low electric current, the power consumption of TE coolers can be lower than those of conventional air conditioners at an equivalent cooling capacity. Considering additional advantages such as demand-flexible operation, low noise, and high scalability, thermoelectric cooling could be a competitive technology for future air conditioning applications.. [ABSTRACT FROM AUTHOR]

This paper describes a new tool developed for the detection of operating faults in ventilation units with heat recovery. In principle, the tool is based on the APAR (Air Handling Unit Performance Assessment Rules) method. By following the semantic data description in accordance with the BrickSchema and Project Haystack initiatives, the tool is portable. The executive part of the fault detection system consists of several dozen detection rules, which simultaneously seeks to estimate wasted energy, the threat to user comfort, or the risk of reduced device lifespan, so that the detected faults can be sorted according to their severity. The developed detection tool was validated on real devices incorporated in a pilot plant. For validation purposes, the method of fault induction on real HVAC (Heating, Ventilation and Air Conditioning system) units was used, with subsequent inspection of whether the faults were revealed or not. The results revealed a 90% detection rate. The data set created as a result of this pilot plant is published as an annex to this article. In addition, the ability of the detection tool to reveal faults was also verified on the basis of data sets of measurements taken during the standard operation of several dozen HVAC units. The elimination of the identified operating faults generated energy savings of several thousands of dollars per year. [ABSTRACT FROM AUTHOR]

[Display omitted] • Residential fault detection with room thermostat, and local weather station data. • 3R2C modeling using extended Kalman filter when air-conditioning system cycled off. • Indoor air-flow, refrigerant undercharge, and duct-leak fault identification algorithm. • Modeling and fault detection algorithm verified with EnergyPlus simulations. Residential air conditioning equipment comprises a significant portion of the total energy consumption of a home. Unfortunately, air-conditioning systems can be susceptible to faulty operation either from installation errors or faults that accrue over the equipment's lifetime. This paper presents a novel automated fault detection algorithm for residential air-conditioning systems that can alert the homeowner of the presence of these faults. The proposed algorithm utilizes only the home's thermostat and outside air temperature to perform automated fault detection over the course of the equipment's lifetime, including immediately after installation. The algorithm uses an extended Kalman filter approach to identify a three-resistor, two-capacitor (3R2C) electrical equivalent thermodynamic model. The identified 3R2C model is used to predict cooling times during a testing period comprising of a series of thermostat drive-cycle experiments. We tested the algorithm on an EnergyPlus™ model of a typical residential building in Orlando, Florida. Duct faults, indoor airflow faults, and refrigerant undercharge faults were introduced into the building model one at a time. The algorithm was able to accurately determine duct-leak faults, 40% airflow faults, 40% undercharge faults, and no-fault cases with an accuracy of 70%, 77%, 82%, and 87%, respectively. [ABSTRACT FROM AUTHOR]

A novel dynamic overhang system is evaluated in this paper when applied to control solar heat gains through windows of US residential buildings. In particular, the energy performance of the dynamic overhangs is compared to static systems using various operation scenarios. The main objective for the control strategies evaluated in the analysis is to minimize annual heating and cooling energy consumption when dynamic instead of static overhangs are applied to US residential buildings. The operation of the dynamic overhangs is adjusted to account for the range of positions allowed as well as the setting frequencies. In particular, the dynamic overhangs can be set on hourly, daily, and monthly basis depending on the window orientation and the time of the year. The analysis has indicated that the performance of the dynamic overhangs depend on their design specifications as well as on the window glazing type. However, the energy saving potential for the dynamic overhangs compared to static devices depend largely on the window size and the climate with significant reduction in cooling energy use achieved in hot and mild US climatic zones. Indeed, the dynamic overhangs can save over 45% of the air conditioning needs for US homes with window-to-wall ratio of 30% located in Phoenix, AZ, and San Francisco, CA, when automatically operated on hourly basis. [ABSTRACT FROM AUTHOR]

• Cooling operation of the multi-energy system (SAAC and GSHP) was discussed, three different operation configurations and their best working condition in a NZEB was analyzed. • Real energy consumption of three working modes wad analyzed and discussed. A 4025 m2 office building was built in Beijing, China, in 2014 as a living laboratory and prototype to explore the technical energy systems of nearly zero energy buildings (NZEBs) in China. Not only the building itself but also the heating, ventilation and air conditioning (HVAC) systems were designed with flexibility to explore their performance. Solar-assisted air conditioning (SAAC) and ground source heat pump (GSHP) systems with different terminal units were designed as HVAC systems for either experimental, comparison, or measurement purposes. In this paper, the cooling operation of multienergy systems is discussed on the basis of actual measurement data. HVAC systems have three possible types of operation configuration types, namely, SAAC priority, GSHP only and multimode. Operation scenarios for these configurations are presented first, and the small-scale simulation was carried out to analyze the performance of SAAC priority and GSHP#1 only mode. It indicates that SAAC could save about 47% of energy than that of GSHP#1. Then, the actual operation performance in 2018 was analyzed by reference to the operation data. Through this study, it is found that 1) multienergy systems of SAAC and GSHP operated well in this NZEBs during the summer season; 2) a 10 RT absorption chiller can work well for an NZEB building of approximately 1000 m2 when outdoor enthalpy is low and the solar radiation is stronger than 400 W/m2 as a result of high building thermal performance and air tightness; 3) SAAC can save about 40 to 50% of energy compared to that of GSHP system when providing services for the same terminal system under the same outdoor weather conditions and 4) The GSHP system is a good complement to the SAAC system which works well in June, September and early July when outdoor enthalpy is low. This study indicates that a combination of GSHP and SAAC systems is highly promising for NZEBs in cold climate zones such as Beijing, where the solar radiation is sound. [ABSTRACT FROM AUTHOR]

• A novel ventilation method, i.e. attachment ventilation is proposed and studied experimentally and numerically by authors. • Velocity profiles of wall/column-based attachment ventilation show similarity. • Semi-theoretical equations characterizing centerline velocity of different attached jets are obtained and compared. • Unified expressions of centerline velocity decay for different attachment ventilation methods are proposed. Ventilation and air distribution methods play an important role in indoor air quality and thermal environments. Effective airflow distribution within indoor environments has always been a great cause of concern. Attachment ventilation has drawn considerable interest since it is more energy efficient and space saving than traditional mixing or displacement ventilation methods. As a newly developed and applied attachment ventilation method, vertical wall-based attachment ventilation (WAV) was first proposed in the 1990's by the authors. Later, the concepts of square column-based attachment ventilation (SAV) and circular column-based attachment ventilation (CAV) were also presented to meet the needs of more industrial applications. In this paper, three attachment ventilation methods— i.e., WAV, SAV and CAV are compared based on experimental studies and numerical simulations. For the vertical attachment region, semi-theoretical equations characterizing the dimensionless centerline velocity of WAV, SAV and CAV are proposed. The velocity profiles of all three types of attachment ventilation methods are similar. Of the three attachment ventilation methods, for the same distance y * along the attached wall measured from the slot inlet, the dimensionless centerline velocity of WAV is the largest, while those of SAV and CAV remain almost identical. In the horizontal air reservoir region (air lake zone), the semi-theoretical equations to predict dimensionless centerline velocity also are presented. The results show that for the same distance x normal to the wall/column, the dimensionless centerline velocity of WAV is the largest, followed by SAV and CAV. Additionally, unified semi-theoretical equations are presented for predicting the jet centerline velocity decay of attachment ventilation, which is helpful for the design of air distribution systems in heating, ventilation and air conditioning (HVAC) engineering applications. [ABSTRACT FROM AUTHOR]

• Comprehensive review of mixed-mode buildings studies since 2010. • Assessment of weather-dependent potential for cooling demand reduction. • Analysis of key factors such as simulations inputs, comfort standards and schedules. • Analysis of the control methods used for managing mixed mode buildings. Ventilative cooling technologies have the potential to be an effective measure to reduce buildings energy consumption, by meeting some or all of the cooling requirement of a building without the need for mechanical cooling. Mixed-Mode (MM) buildings utilise both natural and mechanical cooling systems to meet their thermal energy demand. These buildings are able to guarantee that thermal comfort conditions are maintained, whilst exploiting the cooling potential provided by the climate. Effective management of the cooling systems in MM buildings is important to ensure that comfort is maintained and free cooling is exploited when available. While the implementation of hybrid ventilation systems is becoming more common, the current industrial and academic research state-of-the-art provide different and sometimes contrasting approaches to the management and evaluation of MM buildings. The current review provides an overview of studies into MM buildings performed in the last 10 years, analyzing in detail key factors that determine the potential of a building to save energy, including simulations inputs assumption, comfort standard used for evaluation, building and Heating, Ventilation and Air Conditioning (HVAC) systems typologies and control strategy employed. A detailed analysis of the papers which had a focus on methods for control of hybrid ventilation system was undertaken. This highlighted the importance of coordination between systems to ensure operational effectiveness and showing that while the majority of the studies employed classical control techniques, predictive control methods were the most investigated approaches to fully exploit the potential efficiency of MM buildings. [ABSTRACT FROM AUTHOR]

• Temporal and seasonal variations of window opening in residences are explored. • Cross-sectional survey, photography and longitudinal monitoring are combined. • Window operation habits of residents are driven by natural ventilation and fresh air. • Logistic models for window opening are developed and differentiated by seasons. • Outcomes provides evidence for window operation strategies and accurate building simulation. Window operation behavior has been recognized as one of the pivotal factors affecting building energy efficiency and indoor environments. Such behavior could vary from one region to another. A holistic understanding of the temporal and seasonal variations in the operation of residential windows in the Yangtze River region remains insufficiently explored. This paper presents a multi-scale approach by combining cross-sectional surveys, photographic image observations, and longitudinal onsite measurements to investigate the window opening characteristics of residents. The advantage is being able to perform qualitative and quantitative analyses systematically upon the completion of each step. The methodology has been applied to a case study in Chongqing, China. A year-long study revealed the window operation habits of residents in this region who rely greatly on windows for natural ventilation in transient seasons and for fresh air in summer/winter, especially when heating and cooling systems are in operation. Logistic models were developed and differentiated by seasons: transient, winter, summer with natural ventilation, and summer with air conditioning. The models quantified the driving factors and their corresponding variations affecting window opening probabilities in different periods of a year. It can be integrated into building simulations with realistic profiles for more accurate prediction of energy consumption in buildings. The proposed research methodology is applicable to other regions. The gained knowledge of residents' window operation characteristics in this region provides evidence for window operations and building designs/retrofit strategies. [ABSTRACT FROM AUTHOR]

An aggregate model is a single-zone equivalent of a multi-zone building, and is useful for many purposes, including model based control of large heating, ventilation and air conditioning (HVAC) equipment. This paper deals with the problem of simultaneously identifying an aggregate thermal dynamic model and unknown disturbances from input–output data of multi-zone buildings. The unknown disturbance is a key challenge since it is not measurable but non-negligible. We first present a principled method to aggregate a multi-zone building model into a single zone model, and show the aggregation is not as trivial as it has been assumed in the prior art. We then provide a method to identify the parameters of the model and the unknown disturbance for this aggregate (single-zone) model. Finally, we test our proposed identification algorithm to data collected from a multi-zone building testbed in Oak Ridge National Laboratory. A key insight provided by the aggregation method allows us to recognize under what conditions the estimation of the disturbance signal will be necessarily poor and uncertain, even in the case of a specially designed test in which the disturbances affecting each zone are known (as the case of our experimental testbed). This insight is used to provide a heuristic that can be used to assess when the identification results are likely to have high or low accuracy. [ABSTRACT FROM AUTHOR]

Polymer heat exchangers are gaining increasing attention in the field of air cooling applications. This paper aims to present a parametrical analysis on a membrane-based semi-direct evaporative cooler (MSDEC) with internal baffles. A mathematical model has been established to achieve an in-depth understanding of the heat and mass transfer process of the proposed MSDEC. An experimental system has been employed to study the evaporative cooling performance of the hollow fiber module and validate the mathematical process. Simulation results demonstrated that the installation of baffles can improve the wet-bulb effectiveness by up to 32%. In addition, the developed model is adopted to study the air treatment performance of the MSDEC with baffles by evaluating the influence of various essential parameters including the fiber length, the number of fiber rows, the fiber row spacing, the geometrical dimension of baffles, and the inlet air velocity. [ABSTRACT FROM AUTHOR]

• Innovative micro CAES – TES trigeneration system powered by the extra-production of green energy. • Compressed air energy storage instead of electrochemical batteries for small and residential use. • No typical electrochemical battery recovery and disposal problems. • Energy storage with extremely long lifetime, absence of hysteresis cycles. • Micro CAES – TES trigeneration system coupled with HVAC system. This paper proposes the application on microscale of an innovative trigeneration system with micro CAES (Compressed Air Energy Storage) – TES (Thermal Energy Storage) and the integration of renewable energy production, focusing on the potential use for air conditioning and domestic hot water systems. The system allows storing mechanical energy in the form of elastic and thermal potential of compressed air through two thermal storage units, HTTES (High Temperature Thermal Energy Storage) and LTTES (Low Temperature Thermal Energy Storage). The proposed system is tested on a single-family building in a warm climate. The analysis is carried out for integrated and independent operating modes. In integrated mode, the LTTES refrigerant charge and the vapor compression chiller operate simultaneously to cover the building's thermal load. In this case the energy expenditure is only related to the power supply of the chiller. In independent mode, the cold storage and the chiller work alternately during evening operation to limit the absorption of energy from the distribution network. The results show that, in integrated operating mode with partial recirculation and internal temperature conditions of 26 °C and 50% of relative humidity, the system reaches, in relation to the peak thermal load, a maximum operating time of 236 min. The minimum operating time of 26 min is reached using the full external air operating mode with an internal temperature of 26 °C and relative humidity of 40%. In independent operation mode, it is possible to sustain the evening thermal load for up to a maximum of 5 h without electricity absorption from the distribution network. [ABSTRACT FROM AUTHOR]

• Conducted a state-of-the-art review on self-tuned thermal environments. • Focused on learning approaches for individual occupants' thermal comfort and the integration with HVAC control. • Elaborated on data collection, input variable selection, and performance evaluation, considering the data efficiency. Previous studies show differences in thermal comfort among individual occupants and suggest solutions that incorporate building occupants in sensing and control frameworks (a.k.a., human-in-the-loop) and tune heating, ventilation, and air conditioning (HVAC) systems based on their preferences to enable self-tuned thermal environments. The objective of the review presented in this paper is to discuss two key aspects of self-tuned thermal environments: (i) learning individual occupants' thermal comfort; (ii) HVAC control based on the learned comfort profiles. The review is conducted considering practical issues associated with the implementation of such modeling and control approaches in real buildings. We found that research on learning personalized comfort profiles has rather focused on developing and testing the adopted methods assuming that it is feasible to collect a large amount of training data in real buildings. In addition, previous research has given less attention to the validity of methods for collecting occupants' feedback responses. Hence, we focus our discussion on data collection, input variable selection, and performance evaluation considering the data efficiency. Regarding HVAC systems control, we found that arbitrary rules have been used to operate the systems with the learned occupant comfort profiles, and we discuss their validity and consistency for different occupants and buildings. [ABSTRACT FROM AUTHOR]

• 1-D CNN is an innovative approach utilized for fault diagnosis in VRF system. • 1-D CNN models achieves good accuracy and is capable of fault diagnosis. • Enhanced the method to an ensemble model by using parallel 1-D CNNs. • The ensemble model's performance is improved and archived state-of-the-art accuracy. Variable refrigerant flow (VRF) systems are widely-adopted air conditioning systems. When system faults occur in VRF systems, the efficiency of VRF system will drop drastically. This paper presents a single 1-D CNN model and an ensemble model with parallel 1-D CNNs for diagnosing VRF system refrigerant charge faults under heating condition. From the cleaned experiment data of a commercial VRF system, 15 features are selected as the input for the proposed model with ReliefF algorithm. After training, the diagnosis accuracy of the single 1-D CNN model and ensemble 1-D CNN models is evaluated and compared with that of BPNN model and DT model. The result shows that both single 1-D CNN and ensemble 1-D CNN model can diagnose VRF system refrigerant charge fault effectively. The fault detection is also achieved in proposed models. The average diagnosis accuracy of 9-level refrigerant charge faults of the ensemble 1-D CNN model is up to 97.4%, surpassing that of BPNN model, SVM model, DT mode and DBN model. 1-D CNN based model is utilized for VRF system fault diagnosis for the first time, which lays a foundation for the expansion of the related researches. [ABSTRACT FROM AUTHOR]

Current methods for energy diagnosis in heating, ventilation and air conditioning (HVAC) systems are not consistent with process and instrumentation diagrams (P&IDs) as used by engineers to design and operate these systems, leading to very limited application of energy performance diagnosis in practice. In a previous paper, a generic reference architecture – hereafter referred to as the 4S3F (four symptoms and three faults) framework – was developed. Because it is closely related to the way HVAC experts diagnose problems in HVAC installations, 4S3F largely overcomes the problem of limited application. The present article addresses the fault diagnosis process using automated fault identification (AFI) based on symptoms detected with a diagnostic Bayesian network (DBN). It demonstrates that possible faults can be extracted from P&IDs at different levels and that P&IDs form the basis for setting up effective DBNs. The process was applied to real sensor data for a whole year. In a case study for a thermal energy plant, control faults were successfully isolated using balance, energy performance and operational state symptoms. Correction of the isolated faults led to annual primary energy savings of 25%. An analysis showed that the values of set probabilities in the DBN model are not outcome-sensitive. [ABSTRACT FROM AUTHOR]

This paper presents the findings of a field research on occupant comfort with radiant ceiling cooling and overhead dedicated outdoor air system (RCF). This extends a previous thermal comfort study with radiant cooling and intended to investigate the actual occupant thermal comfort with radiant ceiling cooling and overhead air distribution system. The research is based on a revised ASHRAE RP-921 project protocol with a combination of field measurements and questionnaires. A total of 135 sets of data from 44 participants were collected in summer. The results show that occupant whole-body thermal sensations with the radiant ceiling and overhead air system had deviated from the PMV model at the 23.6~28.6 °C operative temperature (OPT) range in the summer. The main advantage of the RCF system for thermal comfort was found to be better comfort conditions than with conventional air conditioning at the same operative temperature range. The results of this study showed that the neutral temperature with the RCF is around 26 °C; the preferred temperature by occupants was around 25.3 °C with the RCF. The calculated Predicted Percentage Dissatisfied (PPD) rate is 13.9%, but the actual thermal environment dissatisfaction rate was 8.3% with an unacceptability rate of only 1.5%, which is substantially better than the calculated PPD rate. The study results were compared to earlier findings and validated against some important results, providing benchmarks for future work. [ABSTRACT FROM AUTHOR]

Existing pre-cooling strategies provide a means of shifting or reducing the peak demand and/or energy cost in residential buildings. However, majority of them are rule-based and therefore may not be optimal in terms of cost saving, leaving room for improvement. In this paper, an integer linear programming problem that accounts for the thermal properties of a specific home, HVAC system capacity, utility rate structure, and weather conditions and makes use of a home thermal model is formulated. This problem determines the HVAC on/off control signal that minimizes the 24-h energy cost while maintaining thermal comfort and calculates the corresponding optimal indoor air temperature. The model is constructed using home thermal properties identified via data training in real-time. Through simulation, the energy performance of the proposed optimal pre-cooling strategy is investigated and compared with three rule-based operation strategies from the literature. It is found that the optimal strategy requires the least energy consumption without sacrificing thermal comfort. The superb energy performance of the optimal strategy is attributed to a longer runtime of the HVAC system in cool outdoor air conditions and to the elimination of deadband in HVAC operation, which is required by the rule-based strategies, to allow the indoor air temperature to stay near the thermal comfort upper bound as much as possible. In terms of energy cost, the rule-based operation strategies require $3.52, $1.90, and $2.79, respectively, while the optimal strategy only requires $1.52. These figures represent a saving of 56.82%, 20.00%, and 45.52%, respectively. The results suggest that the optimal strategy is indeed significantly more effective than the existing rule-based operation strategies. [ABSTRACT FROM AUTHOR]

This work concerns performance enhancement of phase change material (PCM) based thermal energy storage (TES) devices for air-conditioning applications. Such devices have numerous potential applications in the building environment. The TES device often uses air as the heat transfer fluid and, as a result, its performance is often limited by heat transfer in either or both of the PCM and the air sides. This paper aims to overcome the heat transfer limitations through intensifying heat transfer using two methods of extending heat transfer surfaces (fins) in both the PCM and air sides and adding heat transfer enhancement materials in the PCM. First, a TES device with different configurations (no fins; offset strip fins on the air side only; straight fins on the PCM side only; offset strip fins on air side and straight fins on PCM side) and PCM with different thermal conductivities were modelled and compared. The comparison leads to an advantageous utilization of fins instead of adding thermal conductive particles. The results also indicated a significant extent of performance enhancement of the TES device due to the use of fins with the charging and discharging times reduced respectively by ~85% and ~74%. The airside fins were found to be more effective than the PCM side fins. The results also showed that the heat transfer enhancement due to the PCM side fins could be achieved by increasing PCM thermal conductivity. The modelling results were then validated by experimental data. Finally, a PCM-based TES device was designed and manufactured based on the above results. The device was integrated into an air-conditioning system and experimentally tested. The results showed that, for both charge and discharge processes, the stabilization of the outlet temperature of the air conditioning system was significantly improved, leading to an increased extent of thermal comfort and decreased outlet temperature fluctuations. The obtained results can be used as the design guideline of the compact TES device for air conditioning. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• We applied support vector machine algorithms to predict thermal sensation vote. • The new model can distinguish thermal comfort response in different contexts. • It produces high prediction accuracy in both air conditioning and natural ventilation cases. • Comfort zones determined by the new model are similar to the existing ones. Many models can predict building occupants' thermal comfort, but their accuracies were not always perfect due to the limited self-learning and self-correction capability when varying the application contexts. Advances in machine learning algorithms allow us to reveal the "hidden insights" behind a large amount of data, offering a great opportunity to understand more nuanced aspects of thermal comfort in buildings. This study applied the support vector machine (SVM) algorithm to the RP-884 thermal comfort database and developed a new model with self-learning and self-correction ability. We identified its application range according to the features of the SVM algorithm and the sample distribution characteristics of RP-884. With variables of indoor air temperature, clothing insulation, metabolic rate, air velocity and so forth, the model can largely reduce the previous models' inaccuracy. Compared to the PMV model, the new model's sum of squares for residuals (SSE) reduced by 96.4%, and the fitting degree (R new) increased by 83.7%. It can also quantify the effects of each input variable on building occupants' thermal sensation. Instead of using two separate models, the data-driven model can automatically distinguish occupants' thermal comfort responses in natural ventilation (NV) and air-conditioning (AC) buildings. Using the new model, we determined thermally comfortable zones on the psychrometric chart for NV and AC buildings. Moreover, an open-access platform has been developed to help apply machine learning algorithms in thermal comfort data analysis. The work introduced in this paper can be a reference for a more comprehensive comfort model development. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A ceiling-sidewall composite air carrying energy radiant air-conditioning system (ACERS) is presented, and the heating performance of the ceiling-sidewall composite ACERS combined with air source heat pump is investigated by field experiment. The results show that the combined system can meet the heating requirement for office buildings in south-central China, and also have the energy-saving potential. Moreover, the indoor thermal environment under three different installation types, namely the ceiling, the sidewall, and the ceiling-sidewall composite type, is analyzed by using computational fluid dynamic (CFD) simulation. The comparisons of three types indicate that all of them can meet the temperature requirement, but the temperature is more uniform and higher in the composite ACERS. Meanwhile, the temperature gradient in the ceiling ACERS is smaller than that of the sidewall ACERS due to the further heat transfer caused by air penetration. Both the experimental and CFD simulated temperature distribution demonstrates that the shelter of furniture has an impact on the indoor thermal environment, and it should not be ignored in practical engineering. This research shows the feasibility of winter heating by using the ACERS in office buildings, and is helpful for HVAC engineers to design and apply different ACERS types and realize the integration of air conditioning in winter and summer in this area. [ABSTRACT FROM AUTHOR]