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In this paper the results of a wide investigation on a geothermal-integrated air HVAC system are reported: in the first part, the energy performances of an Earth to Air Heat eXchanger (EAHX) operating in Pomezia (a locality of the area of Rome, Italy) are carried out through a comprehensive numerical two-dimensional model based on the finite element method and the system is forced under real time-changing weather conditions over 1 year. The model is able to reproduce the time- and space- dependent thermo-fluid-dynamic behavior of the EAHX system, the humid air flux and the surrounding soil, as well as to account for the mass of condensed water in the tubes. In the second part of the investigation, the EAHX is coupled to an air handling unit of a company building for office use and tested while operating both in cooling and heating mode. The hourly results, in terms of power savings and energy consumption were reported for representative days of all the months belonging to the cooling or the heating working seasons, monthly and seasonal assessment. The convenience in terms of seasonal energy savings is +40.8% in cooling mode and +44.1% in heating mode. Then, the economic impact in terms of payback time and net present value was investigated through a cost analysis to examine the return of the economic investment under two possible soil morphologies and different prices of electrical energy in Italy. The simple payback with the real price of energy in Italy (0.50 €/kWh) is 3.3 years for the tufa-soil and 5.8 years for soft rock-soil; the economic return in terms of net present value is around 500 k€ for both the morphologies (560 k€ for the tufa; 446 k€ for the soft rock), per effect of the energy saving and, consequently, for a reduced expense of electrical energy. Therefore, in all the considered cases the installation of EAHX systems in support of traditional systems would generate both energy and economic advantages. [ABSTRACT FROM AUTHOR]

Air conditioning and mechanical ventilation systems may be oversized in commercial buildings in the Tropics. Oversized cooling coils may lead to reduced dehumidifying performance, indoor air quality and thermal comfort and increased energy consumption. In this paper, an adaptable cooling coil design is assessed with a general-purpose coil selection software tool, in which the number of active rows changes as a function of the load. For a 100% oversized coil, it is shown that the adaptable cooling coil is able to provide small but relevant improved humidity control down to 25% of the design load. This was obtained without affecting energy performance in typical variable air volume design and control. For specific applications, where variable air volume systems mainly control space humidity, there are also energy savings. The adaptable cooling coil could be seen as providing additional flexibility in the operation of HVAC systems, particularly in the tropics. [ABSTRACT FROM AUTHOR]

Due to the increased expectations on human thermal comfort in sleeping environments at a low energy consumption, task/ambient air condition system (TAC) can be the best air conditioning method when considering the immobility of a sleeping person. Previously, convection-based TAC systems for sleeping environments were developed, with an obvious inadequacy of cold-draft problem. Therefore, a new radiation-based TAC system (R-TAC) was previously developed and experimentally studied at a set of fixed design parameter for its radiant panel. Therefore, a follow-up numerical study on the effects of varying design/operating parameters of the radiant panel on indoor thermal comfort and energy saving performances has been carried out, and the study results reported in this paper. Firstly, a geometry model based on the experimental bedroom used in the previous experimental study, boundary conditions and numerical study cases are detailed. Secondly, the results of validating the numerical method using the previous experimental data are reported. Thirdly, the numerical results on indoor thermal comfort, energy saving and draft risk at different surface temperature and emissivity, area of the radiant panel, and the distance between the radiant panel and a bed are presented. The numerical results demonstrated that all the four design/operating parameters of the radiant panel can significantly affect thermal comfort and energy saving performances in the bedroom when using the R-TAC system: increasing surface temperature can lead to a higher PMV value and a higher EUC value; increasing surface emissivity and area of the radiant panel a lower PMV value and a lower EUC value; reducing the distance between the bed and the panel a lower PMV value and a higher EUC value. Finally, the DR values were at a very low level in all the study cases, indicating the cold draft problem encountered when using a convective heat transfer based TAC system for a sleeping environment can be effectively resolved when using the R-TAC system. [ABSTRACT FROM AUTHOR]

• An improved system is proposed based on multi-fans with frequency conversion. • The improved system meets pressure control requirement in non-working modes. • The energy saving and cleanliness can be achieved by switching operation modes. Pressure control for cleanrooms in the pharmaceutical industry is a necessary means to avoid the cross-contamination. The pressure control of traditional air conditioning can only handle the working stage. In the non-working stage, the system cannot reduce the air change rate per hour (ACH) in order to alleviate the problem of high energy consumption. This paper proposes an improved air conditioning system, which focuses on the ability to control pressure gradient of the system in working and non-working mode. By theoretical derivation of the combined fan frequency conversion, when the impedance and volume of the infiltration air satisfy S i G Z , i = S j G Z , j = S k G Z , k = c o n s t a n t , the pressure gradient in multi-zone cleanrooms can remain stable. A mathematical model of the system has been established, which includes five modules: air pipe network, fan characteristic curve, fan operating point solution, variable volume damper characteristic curve and multi-zone network pressure gradient solution. The correctness of the model is verified by field measurements. Taking a clean workshop as case study, the room pressure can be stabilized in the range of ± 3 Pa by switching the working and non-working mode, which can save 39.8% of the energy consumption in non-working mode, while ensuring cleanliness. This paper demonstrates the process of the air pipe network's influence on cleanrooms pressure and proves the effectiveness of improved purification air conditioning system in pressure gradient control and energy saving potential. [ABSTRACT FROM AUTHOR]

In this paper, measures such as planting urban greenery and using high-albedo paint to mitigate the urban heat-island effect, conserve energy, and reduce CO 2 emissions were assessed. As a typical energy-saving method for buildings, reducing the internal heat sources and increasing the insulation are also assessed. We used a coupled urban canopy and building energy model to predict the heat loads of buildings in city districts, the effects of air-conditioning on energy consumption, and air temperature changes. In this model, a vertical one-dimensional local atmospheric model is coupled with an air-conditioning load calculation model for buildings, making it possible to assess the interaction between anthropogenic heat release due to air-conditioning usage and the outside thermal environment. In this study, we selected a target study region in the city of Kawasaki, Japan. When typical city districts were assessed, planting greenery or increasing albedo achieved temperature reductions of 0.6–1.0 °C and 0.1–0.5 °C, respectively, and energy savings of 40–80 and 70–90 kJ/m 2 /day (per unit floor area) on a typical summer day. The results from the large-scale assessment show that urban greening or albedo increases achieved the highest energy savings, of up to 400 t-CO 2 /day, in the entire target study region. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the effect of operating water mist system to enhance the energy efficiency of air-cooled chillers under various operating conditions. A thermodynamic model for an air-cooled chiller with twin refrigeration circuits coupled with a water mist system was developed and validated by measured operating data. The validated model was used to investigate how the thermal properties of the entering condenser air and the performance of the air-cooled chiller varied under different operating schemes with water mist pre-cooling. Under the conventional head pressure control (HPC) with a designed water mist generation rate, the coefficient of performance (COP) increased by up to 21.3%. The chiller performance could be improved further under variable condensing temperature control (CTC). Under CTC, chiller COP was increased up to 51.5% with optimal water mist generation rate. The potential energy savings of these chillers serving a representative office building in subtropical climate was evaluated, and CTC coupling with optimal water mist generation rate would reduce the annual total electricity consumption for cooling by 14.1%. The water consumption of the water mist system was comparatively small, comparing with the total water losses for an open-loop cooling tower system with equivalent heat rejection capacity. [Copyright &y& Elsevier]

Abstract: This paper presents a study of an ejector expansion CO2 air conditioner system. A comprehensive analytical model for 3-ton air-to-air controllable ejector expansion transcritical CO2 air conditioners was developed and validated. The ejector component efficiencies were estimated using empirical correlations, instead of being simply assumed to be fixed values as done in other literature studies. Parametric studies of the ejector expansion CO2 systems show that the coefficient of performance (COP) and the cooling capacity reach maximum levels when the motive nozzle throat diameter becomes 2.8mm; the maximum cooling COP and cooling capacity occurred for a mixing section constant-area diameter of between 4.1 and 4.2mm; COP and cooling capacity are affected by the outdoor air temperature. At particular ejector geometries and an outdoor temperature of 37.8°C, the transcritical CO2 system using an ejector as the expansion device outperformed a conventional expansion-valve transcritical CO2 system in COP and cooling capacity by approximately 30.7% and 32.1%, respectively. A careful selection of ejector geometry, such as motive nozzle throat diameter and mixing section constant-area diameter, is critical in order to improve the performance of an ejector expansion CO2 air conditioning system. [Copyright &y& Elsevier]

Abstract: Energy-efficient retrofitting of existing building is a huge contribution to the sustainability of the society since building energy consumption takes more than one fourth of total energy consumption. The application of external shading system could block out unwanted radiant heat gain, thus reduces the cooling load of the air-conditioning system. During the assessment of energy-efficient retrofitting projects, apart from annual saving figures and economic payback time, energy and CO2 emission payback periods should also be taken as indispensable references. In this paper, a methodology is described for analyzing the energy and CO2 emission payback periods of external overhang shading in a university campus in Hong Kong. Result shows that due to requirements of structural strength under typhoon situation, although introducing overhang shading system could reduce almost half of the cooling load in the related area, the energy and CO2 emission payback periods of the project are still unrealistically long. This case study presents an example of multi-disciplinary approach being not only important to the energy-efficient retrofitting but also necessary for policy making in different climatic and geographic regions. [Copyright &y& Elsevier]

Abstract: Because of their excellent performance in local thermal environmental control, task/ambient conditioning (TAC) systems have attracted increasingly more research attention. However, the current applications of TAC systems are mainly for daytime activities, but seldom for nighttime. In fact, TAC systems may be best applied to a sleeping environment, since the subjects to be served by a TAC system are immobile during sleep. Therefore, there is a strong need for studying the operational and energy saving performance of TAC systems when applied to sleeping environments. This paper reports on an experimental study on evaluating the operational and energy saving performance of a novel bed-based TAC system. The experimental results and their analysis demonstrated that the use of the novel bed-based TAC system can help achieve energy saving, compared with the use of a full volume air conditioning (FAC) system. Considering the experimental limitations, the energy saving potential of the novel bed-based TAC system if used in an actual bedroom was studied through a theoretical analysis. It demonstrated that the novel bed-based TAC system would help achieve significant energy saving when used in real buildings. [Copyright &y& Elsevier]

• The potential of energy saving by using adaptive setpoint temperatures. • The influence of thermostats according to their accuracy: 0.1, 0.5, and 1 °C. • The analysis of two case studies in the current scenarios, 2050 and 2100. • The 0.5 and 1 °C thermostats achieved energy savings of more than 40%. Building energy performance should be improved to reduce the impact of climate change. The energy saving potential has been recently proved with adaptive setpoint temperatures. However, the accuracy of thermostats hinders the achievement of the energy saving obtained in previous studies. For this reason, this paper studies the influence of three types of thermostats according to their configuration accuracy: 0.1, 0.5, and 1 °C. Two case studies (with and without retrofitting) were analysed in three cities in the current scenario, in 2050, and in 2100. The results showed that the implementation of adaptive setpoint temperatures in thermostats of 0.1 °C virtually obtains the same savings as the direct application of thermal comfort limits. Nevertheless, obtaining considerable energy savings in the other two thermostats depends on the type of energy consumption, climate, and the category of the thermal comfort model. The application of adaptive setpoint temperatures in air conditioning systems obtains energy savings greater than 40%, regardless of the type of thermostat and category, whereas in heating systems, only the category III obtains energy savings with old thermostats. [ABSTRACT FROM AUTHOR]

Abstract: Suitable conditioning plant design is only one aspect of a wide problem that concerns thermo-physical building performance and then building envelope characteristics quality. This is really very important when a building is a museum and work of art at the same time, like the Hall of the Five Hundred that is the object of our study. Its need for conditioning is due to its prestige utilization for public meetings; but it must be seen as connected to different interventions for energy saving and rational energy use. Because of the architectural structure of the Hall and lack of space for plant allocation, the solution proposed in this paper is based on the minimum impact and reversibility concept. A movable platform on the existing floor that can hold all plants was proposed. This thin radiant panel solution was studied by a CFD simulation based on the finite volume method in transient conditions. In order to obtain reliable information concerning the fluid dynamic and thermal fields, the simulations were performed by using experimental data carried out by the Opificio delle Pietre Dure as comparison. [Copyright &y& Elsevier]

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: 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]