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Abstract: HVAC (Heating, Ventilation and Air Conditioning) systems used for heating or cooling buildings, consume a considerable amount of energy. To optimize the energy consumption, the behavior of occupants must be changed. This can be achieved by providing information and suggestions to occupants. A first step is developing of a less expensive and non-invasive measurement system and metering of the electricity and heat consumed. Based on collected experimental data, it can identify the parameters of a thermal model of the house. The model obtained will be used to simulate different aspects that can help to reduce the energy consumption. This paper presents a simple solution for thermal modeling of a house which includes experimental identification of the model''s parameters. Such data are used to simulate the thermal behavior of the house and to obtain solutions to reduce energy consumption. In simulation, the control of the thermal system is performed using a model based predictive control algorithm. [Copyright &y& Elsevier]

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

Abstract: Numerous computer programs are available to calculate the energy efficiency of buildings. Many are based on the use of a reference building to determine the degree of efficiency. However, this methodology presents a major constraint when assessing a building after construction and during the use stage. To assess the energy efficiency of buildings, this paper proposes new indices based on energy consumption during different periods; as well as other parameters of the buildings such as construction area, number of users, and air-conditioned volume. Results are presented as an application for various buildings on the campus of the Universidad Politécnica de Valencia. [ABSTRACT FROM AUTHOR]

Abstract: In conventional air-conditioning system, fresh air volume is always restricted to save energy, which sacrifices indoor air quality (IAQ) to some extent. However, removing the latent load of air by liquid desiccant rather than by cooling is an alternative way of reducing energy consumption. Therefore, IAQ can be improved by increasing the volume of fresh air introduced into an air-conditioning system. In this paper, a liquid desiccant based air-conditioning system is studied, with the system performance under various fresh air ratios analyzed using simulation tests. In addition, the proposed system and a conventional system are compared. In the proposed system, with the increase in fresh air ratio, the heating load for solution regeneration rises, the dehumidification efficiency increases and the regeneration efficiency drops. The coefficient of performance (COP) of the liquid desiccant based system decreases sharply when the fresh air ratio exceeds 60%. The results also show that the proposed system can save power notably. The maximum power saving ratio is 58.9% when the fresh air ratio is 20%; however, the ratio drops when the fresh air ratio increases. These findings will be beneficial in the selection of fresh air ventilation strategies for liquid desiccant based air-conditioning systems. [ABSTRACT FROM AUTHOR]

Abstract: Desiccant based air conditioning systems are a suitable way to improve indoor air quality due to its superior humidity control. In this study, a novel desiccant based air conditioning system is designed and tested experimentally to improve the indoor air quality and reduce energy consumption. In the system studied, a heat exchanger, which is not used in this type of systems, for pre-heating the regeneration air with exhaust air is used. This paper reports results of initial operation and operational procedures. The performance of the system and its components is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Physically based load modelling methodologies have been widely developed and used because of their ability to predict the energy load dynamic response. Most building energy programs predict energy consumption and energy system performance through a whole building energy simulation as well as a global analysis of building thermal processes and heating, ventilation and air-conditioning (HVAC) system performance. A different approach is presented in this paper by introducing a new method for modelling the daily load profile of a group of air-conditioning systems. This method is based on the simulation of a single HVAC system, a set of end-use electrical measurements, and a detailed walk-through and energy audit. The basic methodology allows deducing the aggregated load of a group of space conditioning devices by the addition of the daily simulation of each individual physical system. As an application, the space conditioning daily demand curve of a university building is studied and results are presented. [Copyright &y& Elsevier]

Abstract: The general methodology for estimating energy consumption in buildings, in accordance with the EN ISO 13790, needs the use of constants that are valid for each set of climatic conditions. Furthermore, there are variables other than building structure and weather conditions that have an influence. In this sense, recent research works showed the real effect of permeable coverings on indoor environmental conditions, by controlling indoor moisture. The effect of the associated heat and mass transfer on heating or cooling energy consumption is evident during the initial hours of building occupation. In the present paper, the general methodology of building heat demand calculation is modified to consider different levels of permeability of internal coverings, in order to obtain a more accurate model. Results showed that permeable coverings are related with a higher building utilisation factor, and that the value of this factor is higher in summer than in winter season. Consequently, despite the fact that the sensibility of energy consumption to internal coverings may be lower than to building envelope, new constants are proposed to express a relationship between building permeability and energy consumption, in order to apply the certification equation. [Copyright &y& Elsevier]

Abstract: A water-cooled chiller system in an air-conditioned hotel can take up about one-quarter of the total electricity consumption and considerable amounts of water in the heat rejection process. This paper evaluates operating cost savings of a chiller system integrated with optimal control of cooling towers and condenser water pumps. A sophisticated chiller system model was used to ascertain how different control methods influence the annual electricity and water consumption of chillers operating for the cooling load profile of a reference hotel. It is estimated that applying load-based speed control to the cooling tower fans and condenser water pumps could reduce the annual system electricity use by 8.6% and operating cost by 9.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point of 29.4°C for cooling water temperature control. The ways to implement this advanced control for system optimization are discussed. [Copyright &y& Elsevier]

Abstract: The large thermal time constant of thermally activated building systems (TABS) hampers communication between the system''s production and emission. Therefore, conventional building control strategies, typically using room temperature feedback, are unadapted to control thermal comfort efficiently. In this paper, measurement data and simulation results reveal that unadapted TABS control has a dramatic impact on overall energy performance. Measurements in a TABS building with room temperature feedback show the HVAC system switching between heating and cooling in a very short time frame. A simplified, generic room model is used to simulate, understand and evaluate this behaviour. For room temperature feedback control, only 45% of the cold and 15% of the heat produced actually controls room temperature. The remainder is stored in the TABS and exchanged between the heating and cooling system. Enlarging the heating-to-cooling set point band improves this ratio, while maintaining thermal comfort. On the other hand, night time operation control of the circulation pump, adapted to the TABS thermal time constant, eliminates this ‘unused’ energy completely. In this case, however, even with perfect heat gain forecasts, it is difficult to avoid room temperatures dropping below thermal comfort limits during initial office hours. Hence, a supplementary air-conditioning system seems inevitable. [Copyright &y& Elsevier]

Abstract: In harsh climatic regions, buildings require air-conditioning in order to provide an acceptable level of thermal comfort. In many situations buildings are over cooled or the HVAC system is kept running for a much longer time than needed. In some other situations thermal comfort is not achieved due to improper operation practices coupled with poor maintenance and even lack it, and consequently inefficient air-conditioning systems. Mosques represent one type of building that is characterized by their unique intermittent operating schedule determined by prayer times, which vary continuously according to the local solar time. This paper presents the results of a study designed to monitor energy use and thermal comfort conditions of a number of mosques in a hot-humid climate so that both energy efficiency and the quality of thermal comfort conditions especially during occupancy periods in such intermittently operated buildings can be assessed accurately. [Copyright &y& Elsevier]

Abstract: Axiomatic design (AD) is a theory that helps to develop new design objects and allows one to evaluate the quality of designs. The aim of this paper is to apply this theory to the design of heat ventilation and air-conditioning (HVAC) systems and to come to conclusions about the design quality of some specific applications. The focus is the comfort and energy consumption in commercial buildings in South European climates. The discussion contains a brief description of variable air volume (VAV) systems and dedicated outdoor air systems (DOAS) with terminal units, such as fan-coils, induction units and chilled ceilings. Occasionally, the DOAS design should include over-cooled outdoor air in order to ensure an extra cooling means. According to the AD''s first axiom, ideal systems are independent or decoupled. Our conclusion is that VAV and DOAS with induction units are coupled designs, and on the other end, DOAS with fan-coils or chilled ceilings are decoupled designs. In addition, over-cooling outdoor air (OA) flow couples the OA flow with the indoor heat removable needs. [Copyright &y& Elsevier]

Abstract: There are many reports about faulty status in building air-conditioning systems recently. It becomes difficult to keep indoor air temperature appropriately as faults occur, and the faults cause waste of building energy consumption. The model-based fault detection and diagnosis (FDD) methods have been researched for specific parts of air-conditioning system such as chillers, coils, variable air volume units (VAV units), etc. It needs, however, much time and labor to monitor and check every single part because we cannot predict where and when the faults occur. The purpose of this study is to examine indoor air temperature changes and energy consumption increase when faults occur and to develop an easy-to-use FDD tool that helps to find out the faulty place through the whole building air-conditioning system. And then, we treat the reliability of the proposed FDD tool and effectiveness to control of indoor environment deterioration and energy consumption increase by the tool is evaluated based on building air-conditioning system simulation in this paper. [Copyright &y& Elsevier]

Abstract: This paper treats energy and cost performance of a cooling source system with indirect seawater utilization for air conditioning in a commercial complex. Seawater utilization has merits as a cooling source, because seawater temperature is lower than outdoor air in summer and it is cost effective because there is no water monetary cost. Actual operating data has been measured for about 2 years and the chiller and system co-efficient of performance (COP) have indicated about 4.77 and 2.93, respectively, even in summer season and the mean efficiency of the thermal storage system was about 89.9% taking into account heat loss of pumps. In addition, we have constructed simulation models for cooling tower systems, air cooling chiller systems and direct seawater utilization systems then compared them to this system. The electric power consumption of the indirect seawater utilization system was almost the same as the other systems except the air cooling chiller system, because using lower seawater temperature made the chiller efficiency higher. In conclusion, our results showed the indirect seawater utilization system was able to improve the system COP compared to air cooling chiller system, and cancel water consumption compared with the cooling tower system, and cut down an initial and maintenance costs compared with the direct seawater utilization system. [Copyright &y& Elsevier]

Abstract: In the air conditioning (AC) industry chilled water storage (CWS) systems are one form of cool thermal storage technology that can be used to time shift the electrical load of the system from the peak day periods to off peak night time periods. In this paper the data for the actual exported and generated electrical energy obtained for the power stations in Kuwait has been used to estimate the electrical energy consumption and the peak electrical load of AC systems. Since the chiller in an air cooled AC system represent more than 75% of the total electrical power consumed by an AC system during the peak demand period, the impact of using CWS systems with alternative operating strategies including partial (load levelling), partial (demand limiting) and full load has been investigated. In our conclusions we estimate that approximately 45% of the total annual exported electrical energy is consumed solely by AC systems as a result of the very high ambient temperatures occurring between March and October. Furthermore, it is estimated AC systems represent about 62% of the peak electrical load. The results demonstrate that CWS can reduce the peak electrical load of a chiller in an air cooled AC system by up to 100% and reduce the nominal chiller size by up to 33% depending upon the operating strategy adopted. This is achieved with only a 4% increase in power consumption of the chiller for all CWS strategies except for full storage where the energy consumption actually decreases by approximately 4%. [Copyright &y& Elsevier]

Abstract: The methods used to assess the energy performance of buildings are static or dynamic. A paradigm shift is to estimate the energy consumption by using a probabilistic approach and a single concept for the whole range of operation of the building (heating, ventilation and cooling) and to decouple the thermal behavior of the building, the thermal comfort range and the climate data. These requirements can be achieved by using the free-running temperature to characterize the building behavior and the frequency distribution of the outdoor temperature to describe the climate. This paper demonstrates that the dynamic values can be used to estimate the energy load curve, that this curve may be applied to calculate the energy consumption and that the free-running temperature is an equivalent form of the heating/cooling curve. The main advantages of using the concept of free-running temperature are that: (1) the dynamic behavior may be described by steady-state concepts, (2) the whole range of building operation (heating, ventilation and cooling) is described by a single concept and (3) the thermal behavior of the building, the comfort and the climate are decoupled. The mathematical formalism uses matrix notation. [Copyright &y& Elsevier]

Abstract: Chillers are widely used for cooling buildings in the subtropical regions at the expense of considerable energy. This paper discusses how the number and size of air-cooled chillers in a chiller plant should be designed to improve their energy performance. Using an experimentally verified chiller model, four design options were studied for a chiller plant handling the cooling load profile of an office building. Using chillers of different sizes is desirable to increase the number of steps of total cooling capacity. This enables the chillers to operate frequently at or near full load to save chiller power. Pumping energy can also be saved because of the improved control of chilled water flow whereby the chilled water supplied by the staged chillers can match with that required by air side equipment for most of the operating time. It is estimated that the annual electricity consumption of chiller plants could drop by 9.4% with the use of unequally sized chillers. The findings of this research will offer guidance on how to select chillers of different sizes for a low-energy chiller plant. [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: 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]

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]

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]

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]

[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]