This paper examines the impact of upstream merger and acquisition(M&A)activities driven by supply chain integration motives on firm energy performance.By developing a microlevel theoretical framework,we examine th...This paper examines the impact of upstream merger and acquisition(M&A)activities driven by supply chain integration motives on firm energy performance.By developing a microlevel theoretical framework,we examine the intricate relationship between firms’upstream M&A strategies geared toward supply chain integration and their energy efficiency.We examine the impact of upstream M&A activities on energy performance using data from Chinese listed companies from 2007 to 2021.Our findings reveal that upstream M&A initiatives can enhance firms’energy efficiency,although there are discernible variations in the effects observed for M&A activities targeted downstream or within the same industry.By examining mechanisms,we elucidate the pivotal roles of input substitution effects and productivity enhancements through which upstream M&As boost energy performance.Furthermore,our analysis underscores the catalyzing impact of M&A activities in fostering collaborative innovation in green technologies among firms and suppliers,thus improving productivity and energy efficiency.We provide new microlevel evidence of the relationship between M&A transactions and corporate energy efficiency from upstream and downstream perspectives.展开更多
Water-using operations in the process industry have demands for water usually both on water quality and temperature, and the existing mathematical models of heat exchange networks cannot guarantee the energy performan...Water-using operations in the process industry have demands for water usually both on water quality and temperature, and the existing mathematical models of heat exchange networks cannot guarantee the energy performance of a water network optimal. In this paper, the effects of non-isothermal merging on energy performance of water allocation networks are analyzed, which include utility consumption, total heat exchange load, and number of heat exchange matches. Three principles are proposed to express the effects of non-isothermal merging on energy performance of water allocation networks. A rule of non-isothermal merging without increasing utility consumption is deduced. And an approach to improve energy performance of water allocation network is presented. A case study is given to demonstrate the method.展开更多
This study uses a building energy performance simulation to investigate the impact of predicted climate warming and the additional issue of building ageing on the energy performance for a library in Turin,Italy.The cl...This study uses a building energy performance simulation to investigate the impact of predicted climate warming and the additional issue of building ageing on the energy performance for a library in Turin,Italy.The climate and ageing factors were modelled individually and then integrated together for several decades.Results from the climate-only simulation showed a decrease in thebuilding heating energy usage which outweighed the increase in the on-site cooling energy demand occurring in a warming scenario.The study revealed a high sensitivity of energy performance to building ageing,in particular due to HVAC(Heating,Ventilation and Air Conditioning) equipment efficiency degradation.Building ageing was seen to negatively affect the energy performance as it induced a further increase of the cooling energy usage in a warming climate,while it also counteracted the reduction of the heating energy usage resulting from warming.Simulations on the combination of mitigation techniques showed a number of potentially retrofit measures that would be beneficial for buildings to avoid an increase in the cooling energy usage due to climate warming.The combination of these retrofit techniques showed a potential decrease of 87.3% in the final cooling energy usage for the considered building.展开更多
Energy Performance Contracting was introduced into China in the mid 1990s. Since western energy service companies came to China, their management pattern has undergone major changes. Why did such changes occur? Mainly...Energy Performance Contracting was introduced into China in the mid 1990s. Since western energy service companies came to China, their management pattern has undergone major changes. Why did such changes occur? Mainly because these companies encountered two difficulties in China: tax and financing.展开更多
Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipmen...Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A "holistic" approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP(coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.展开更多
The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this stud...The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.展开更多
The commitment to improve energy and environmental performance in public administration is essential for the success of development models geared towards lasting sustainability. The Public Administration （PA） in Ita...The commitment to improve energy and environmental performance in public administration is essential for the success of development models geared towards lasting sustainability. The Public Administration （PA） in Italy, in particular, plays a key role to affn-m models of development oriented towards energy and environmental sustainability, thanks to a wider and more innovative vision. The PA has a dual consumer/user role, public heritage and decision maker/planner, in promoting energy efficiency at local level, in the light of specific problems and peculiarities. For several decades, initiatives have been launched at various levels to improve energy and environmental performance in the public administration. The aim of this study is to outline from a critical perspective, the state of the art of policy makers in Italy concerning energy efficiency measures in public administration. There are however many cultural, value-related, financial, technological, institutional, and operational issues in the PA sector that limit investments in energy efficiency. It should be noted that if on one hand the PA shows a lack of knowledge and is unwilling to adopt practices and systemic tools for monitoring and control, on the other, in terms of bureaucracy, the system appears to be far too complicated and costly. The multiple benefits linked to improved energy performance would therefore require that the PA rethink their organizational and functional models, put in place more flexible and less bureaucratic forms of management and a more dynamic, pervasive, and proactive approach towards initiatives that promote energy efficiency. The research is a contribution towards identifying the driving forces behind potential systems and tools for energy efficiency in the PA, highlighting both critical elements and opportunities and, in particular, the limits deriving from the technological, managerial, and organizational options available for energy eff^ciency enhancement in the sector of the Italian PA.展开更多
The reliable assessment of the annual energy demand has become necessary in view of building energy performance certification. Accurate models must be used to simulate the behaviour of HVAC （heating, ventilation and ...The reliable assessment of the annual energy demand has become necessary in view of building energy performance certification. Accurate models must be used to simulate the behaviour of HVAC （heating, ventilation and air conditioning） components in real operation, usually characterized by a wide variation of building loads. In this context, this paper deals with the development and validation of an algorithm aimed at the assessment of part load performance of various kinds of controls for vapour compresion based heat pumps and chillers, in particular referring to on-off, inverter-driven and multi-stage vapour compression. The reliability of this algorithm in the calculation of seasonal performances is checked against monitoring of heat pumps and chillers operating under real conditions.展开更多
A simple calculator for early stage energy performance assessment in residential buildings was developed and partially validated in this study. The calculator is based on the correlation of heat loss and energy need f...A simple calculator for early stage energy performance assessment in residential buildings was developed and partially validated in this study. The calculator is based on the correlation of heat loss and energy need for heating and has fixed internal heat gains as intended for compliance assessment. With the calculator, the effect of any parameter implemented can be immediately seen on delivered and primary energy. Because of simple equations, it is suitable for implementation into CAD （computer aided design） design tools including basic BIM （building information modeling） data. Results showed that the accuracy of the correlation for the cases with practical relevance was not worse than 14% of the energy need of space heating. This applies for passive house insulation level; for less insulated building envelopes, the deviations were smaller. This 14% equals to only 3 kWh/（m2.a）, i.e., the percentage difference in the total delivered and primary energy was much lower because of other components in the energy balance. The deviations determined were implemented in the calculator as safety margin. Results prove that simple energy performance assessment based on specific heat loss coefficient is well justified for early stage energy analyses as well as for compliance assessment implemented in Estonian regulation.展开更多
The content of contribution is to analyse suggested renovation of school building in term of energy performance and indoor environment quality. There were three selected variants of possible reno ration of school buil...The content of contribution is to analyse suggested renovation of school building in term of energy performance and indoor environment quality. There were three selected variants of possible reno ration of school building. At first, it was installation of equipment for heat recovery into existing mechanical ventilation system. There were further evaluated possibilities how to use glass atrium or ground air-heat exchanger in mechanical ventilation system. These suggested variants were analysed in field of energy performance, namely in term of impacts on heat demand for space heating in order to keep required parameters of indoor environment quality according to standard STN EN 15251 （operative temperature, relative air humidity, air change rate）. The analysis was elaborated by using energy simulation tool Design Builder in order to evaluate yearlong operation of buildings.展开更多
In the quest to minimize energy waste,the energy performance of buildings(EPB)has been a focus because building appliances,such as heating,ventilation,and air conditioning,consume the highest energy.Therefore,effectiv...In the quest to minimize energy waste,the energy performance of buildings(EPB)has been a focus because building appliances,such as heating,ventilation,and air conditioning,consume the highest energy.Therefore,effective design and planning for estimating heating load(HL)and cooling load(CL)for energy saving have become paramount.In this vein,efforts have been made to predict the HL and CL using a univariate approach.However,this approach necessitates two models for learning HL and CL,requiring more computational time.Moreover,the one-dimensional(1D)convolutional neural network(CNN)has gained popularity due to its nominal computa-tional complexity,high performance,and low-cost hardware requirement.In this paper,we formulate the prediction as a multivariate regression problem in which the HL and CL are simultaneously predicted using the 1D CNN.Considering the building shape characteristics,one kernel size is adopted to create the receptive fields of the 1D CNN to extract the feature maps,a dense layer to interpret the maps,and an output layer with two neurons to predict the two real-valued responses,HL and CL.As the 1D data are not affected by excessive parameters,the pooling layer is not applied in this implementation.Besides,the use of pooling has been questioned by recent studies.The performance of the proposed model displays a comparative advantage over existing models in terms of the mean squared error(MSE).Thus,the proposed model is effective for EPB prediction because it reduces computational time and significantly lowers the MSE.展开更多
In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of...In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of pure aluminum particles to mitigate agglomeration and enhance the combustion efficiency of solid propellants(Combustion efficiency herein refers to the completeness of metallic fuel oxidation,quantified as the ratio of actual-to-theoretical energy released during combustion)with high Al content and low burning rates.The impact of Al-Li alloy with different Li contents on combustion and agglomeration of solid propellant was investigated using explosion heat,combustion heat,differential thermal analysis(DTA),thermos-gravimetric analysis(TG),dynamic high-pressure combustion test,ignition experiment of small solid rocket motor(SRM)tests,condensation combustion product collection,and X-ray diffraction techniques(XRD).Compared with pure Al,Al-Li alloys exhibit higher combustion heat,which contributes to improved combustion efficiency in Al-Li alloy-containing propellants.DTA and TG analyses demonstrated higher reactivity and lower ignition temperatures for Al-Li alloys.High-pressure combustion experiments at 5 MPa showed that Al-Li alloy fuel significantly decreases combustion agglomeration.The results from theφ75 mm andφ165 mm SRM and XRD tests further support this finding.This study provides novel insights into the combustion and agglomeration behaviors of high-Al,low-burning-rate composite solid propellants and supports the potential application of Al-Li alloys in advanced propellant formulations.展开更多
NaNbO_(3)-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors.However,their development is hindered by low recoverable energy storage density(W_(rec))and...NaNbO_(3)-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors.However,their development is hindered by low recoverable energy storage density(W_(rec))and energy storage efficiency(η).Herein,novel NaNbO_(3)-based ceramics,(1-x)[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–xCaTiO_(3),were created by adding CaTiO_(3) linear dielectric,aiming to improve their energy storage performance(ESP).The phase structure,microstructure,dielectric properties,energy storage and charge–discharge performances of the ceramics were methodically analyzed.All components of the ceramics exhibit a perovskite structure consisting of two phases:antiferroelectric P-phase(AFE P)and antiferroelectric R-phase(AFE R),with the AFE R phase increasing as x rises.All ceramic surfaces exhibit clear grain morphology.The resultant ceramics have an appropriate dielectric constant and a small dielectric loss,which are beneficial for improving breakdown field strength(E_(b)).Finally,at an E_(b) of 470 kV/cm,0.85[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–0.15CaTiO_(3) ceramic achieves optimal ESP:W_(rec)=3.9 J/cm^(3),η=72.49%.In addition,it has remarkable stability with temperature and frequency in energy storage and displays ultrafast speed in the charge–discharge process(t_(0.9)=27 ns).展开更多
Thermal bridges may represent up to 50%of the building’s envelope area and may increase the energy consumption of buildings by up to 30%,however their impact is often not taken into account adequately in China.In thi...Thermal bridges may represent up to 50%of the building’s envelope area and may increase the energy consumption of buildings by up to 30%,however their impact is often not taken into account adequately in China.In this study,the energy performance of a typical two-story residential building under four different Chinese climate zones is investigated using WUFI Plus program in terms of annual heating and cooling energy demands.Several typical thermal bridges were taken into consideration.Two methods were used to evaluate the effect of thermal bridges on the building energy performance,the simplified method commonly used in China and the dynamic 3D modelling method,and were compared to do not consider thermal bridge.Also,two different types of building envelope,brick wall and aerated concrete wall,were used to evaluate the effect.The results show that by taking into account the thermal bridges,the annual heating energy demands of residential building increase 21.2%,24.8%,27.8%,and 16.6%under the four Chinese climate zones.Therefore,attention should be paid in the building envelope design to reduce thermal bridges.Compared to the dynamic 3D modelling method,the simplified method underestimates annual heating and cooling energy demands.展开更多
In this paper,a multi-objective optimization strategy for a volute mixed flow pump is implemented based on inverse design theory.The controllable velocity moment(CVM)design parameters are defined based on the impeller...In this paper,a multi-objective optimization strategy for a volute mixed flow pump is implemented based on inverse design theory.The controllable velocity moment(CVM)design parameters are defined based on the impeller outlet velocity moment and its partial derivative in the streamline direction,and flow control is further realized by directly adjusting the velocity moment distribution inside the impeller.The significance order of the effect of the CVM parameters on the efficiency and NPHSc at the best operation points is first investigated,and the elliptical basis function(EBF)approximation model and MOPS optimization algorithm are combined to carry out multi-objective optimization.Compared with the baseline model,an improvement in the efficiency and head at the best operation points of 0.48%,1.07 m is obtained for the optimal model,with a widened and efficient operation range,and NPHSc is reduced from 4.545 m-4.235 m,with a slowed cavitation development.The proposed CVM method effectively realizes flow control under multiple conditions,optimizing the pressure distribution on the blade pressure side and suppressing the reverse jet in the cavity closure area.展开更多
Re-entrant honeycombs are widely used in safeguard structures due to their geometric simplicity and excellent energy absorption capacities.However,traditional re-entrant honeycombs exhibit insufficient stiffness and s...Re-entrant honeycombs are widely used in safeguard structures due to their geometric simplicity and excellent energy absorption capacities.However,traditional re-entrant honeycombs exhibit insufficient stiffness and stability owing to the lack of internal support.This paper proposes a new hybrid honeycomb by integrating a chiral component inside the re-entrant honeycomb.Since Young's modulus is a key parameter to evaluate the energy absorption performance and stiffness,an analytical model is given to predict the effective Young's modulus of the proposed hybrid honeycomb.It is found that the optimal design scheme is to directly insert a circular ring inside the re-entrant honeycomb.The normalized specific energy absorption(SEA)of the hybrid honeycomb is 95%larger than that of the traditional re-entrant honeycomb.The normalized SEA first increases to a peak value and then decreases with the cell wall thickness.The optimal thickness of the cell wall for the maximum SEA is derived in terms of the geometric configuration of the unit cell.The normalized SEA first decreases to a valley value and then increases with the re-entrant angle.A longer horizontal cell wall results in a smaller normalized SEA.This paper provides a new design method for safeguard structures with high stiffness and energy absorption performance.展开更多
The integration of phase change material(PCM)with building-integrated photovoltaic(BIPV)presents a compelling approach to enhance solar energy utilization and mitigate indoor thermal loads,contributing to energy-effic...The integration of phase change material(PCM)with building-integrated photovoltaic(BIPV)presents a compelling approach to enhance solar energy utilization and mitigate indoor thermal loads,contributing to energy-efficient and low-carbon building development.Traditional BIPV-PCM structures,however,struggle to balance PV efficiency and thermal insulation,particularly with varying PCM wall positions.To address this situation,this study introduces a novel double-PCM BIPV composite envelope(BIPV-dPCM).An experimentally validated dynamic heat transfer model was developed and used to perform a comparative simulation analysis with three reference systems to quantify the energy-saving potential of the BIPV-dPCM,focusing on PV output and wall insulation effectiveness metrics.Further dimensionless parametric analysis were carried out to investigate the systematic performance of the two PCMs at different relativities.In addition,the coupled working mechanism of the BIPV-dPCM system concerning the power generation performance and thermal insulation performance under transient variations is explored.It was found that the BIPV-dPCM showcases superior thermoelectric coupling performance compared to three alternative enclosures.Incorporating two PCMs significantly enhances electrical exergy efficiency by 11.66%and thermal exergy efficiency by 1.54%,surpassing other reference systems.The increase in PCM latent heat ratio has a limited effect on performance gain.Notably,as the PCM thickness ratio exceeds 1,the decline in P value decelerates,for every 0.5 increment in the g,the P value diminishes by merely 0.2%.The ideal h is identified between 1 and 1.5,with 1.5 being optimal for energy conservation objectives.Additionally,the self-sufficiency coefficient(SSC)of the BIPV-dPCM remains robust,sustaining a range of 55%to 65%over prolonged periods.This study offers novel perspectives and serves as a design reference for optimizing building energy systems and enhancing cooling efficiencies in subtropical climates.展开更多
Many efforts have been detected to investigate thermochromic(TC)glazing for improving building energy saving,while only a few approaches for daylight performance analysis.In this study,the performance of TC glazing is...Many efforts have been detected to investigate thermochromic(TC)glazing for improving building energy saving,while only a few approaches for daylight performance analysis.In this study,the performance of TC glazing is investigated based on multi-objective optimization for minimizing energy demand while maximizing daylight availability.The effects of five parameters including transition temperature,solar transmittance in clear state,solar transmittance modulation ability,luminous transmittance in clear state,and luminous modulation ability on the building energy consumption and useful daylighting illuminance(UDI_(300-3000))are examined.Linear Programming Technique for Multi-dimensional Analysis of Preference(LINMAP)is used for the decision-making of Pareto frontier.This research aims to explore the ideal thermochromic glazing by considering the daylight and energy performance of a typical office room,taking the weather condition of Xiamen,China as an example.Although it is impossible to achieve both optimal values of energy consumption and UDI_(300-3000)simultaneously,the proposed multi-objective optimization method could still provide low energy consumption with sufficient daylight.The non-dominated sorting of Pareto optimal solution(POS)demonstrated that the optimum building energy consumption and UDI_(300-3000)for single glazed windows are 46.64 kWh/m^(2)and 70.92%,respectively,while the values for double glazed windows are 44.40 kWh/m^(2)and 71.88%,respectively.The selected hypothetical TC windows can improve the building energy and daylighting performance simultaneously when compared with traditional clear single and double glazed windows.The presented framework provides a multi-objective optimization method to determine the most suitable TC glazing technologies for designers and architects during the design and retrofit procedure.展开更多
Simulation is recognized as an effective tool for building energy performance assessment during design or retrofit processes. Nevertheless, simulation models yield deviating outcomes from the actual building performan...Simulation is recognized as an effective tool for building energy performance assessment during design or retrofit processes. Nevertheless, simulation models yield deviating outcomes from the actual building performance and a significant portion of this deviation originates from the dynamic nature of occupant behavior. Literature on occupant behavior indicates that occupant behavior is not integrated into building energy performance assessment procedures with appropriate resolution, instead they are accepted as assumed and fixed data sets that usually represent the presence of occupants. This study attempts to evaluate the effect of diverse patterns of occupant behavior on energy performance simulation for office buildings. Diverse levels of sensitivity of occupant behavior on control-based activities such as using lighting apparatus, adjusting thermostat settings, and presence in space are employed through three diverse occupant behavior patterns. These occupancy patterns are correlated with three identical office spaces simulated within a conceptual office building. EDSL Tas is used to run building energy performance simulations. Effects of occupant behavior patterns on simulation outcomes are compared for five sample winter and summer workdays, with respect to heating and cooling loads. Results present findings on how diversity of occupancy profiles influences the consumption outcomes.展开更多
Sustainable building has become a future development trend in the building sector.Building Energy Efficiency Retrofit(BEER)provides excellent opportunities to reduce energy consumption in existing buildings,and to pro...Sustainable building has become a future development trend in the building sector.Building Energy Efficiency Retrofit(BEER)provides excellent opportunities to reduce energy consumption in existing buildings,and to promote environmental protection,the rational use of resources,occupants’health,all of which helps to improve the sustainability of existing buildings.Energy Performance Contracting(EPC)provided by Energy Service Companies(ESCOs)is a market mechanism to provide financial and technological support for energy efficiency projects.This paper aims to develop a sustainability promotion framework for BEER projects under the EPC mechanism to link the sustainable performance of BEER with the success factors of this EPC mechanism.Different types of building have different energy consumption characteristics.This research focuses on hotel buildings in China.The paper develops a framework for sustainable BEER through an EPC mechanism in hotel buildings based on the EFQM Excellence Model for business quality management.Interviews were conducted with experts from the hotel industry,from energy service companies and with academics.Based on the developed framework,the study has identified 11 performance indicators for sustainable BEER and 28 success factors of an EPC mechanism.This provides significant groundwork for future study in developing an assessment model to evaluate the sustainability of BEER projects.展开更多
基金supported by the following:the Fundamental Research Funds for the Central Universities of China[Grant No.JBK2406055]the 2024 Annual General Project of Humanities and Social Sciences Research by the Ministry of Education[Grant No.24XJA790005]the Cultivation Program of High-level Scholarly Representative Achievements for Graduate Students of Southwestern University of Finance and Economics[Grant No.JGS2024055].
文摘This paper examines the impact of upstream merger and acquisition(M&A)activities driven by supply chain integration motives on firm energy performance.By developing a microlevel theoretical framework,we examine the intricate relationship between firms’upstream M&A strategies geared toward supply chain integration and their energy efficiency.We examine the impact of upstream M&A activities on energy performance using data from Chinese listed companies from 2007 to 2021.Our findings reveal that upstream M&A initiatives can enhance firms’energy efficiency,although there are discernible variations in the effects observed for M&A activities targeted downstream or within the same industry.By examining mechanisms,we elucidate the pivotal roles of input substitution effects and productivity enhancements through which upstream M&As boost energy performance.Furthermore,our analysis underscores the catalyzing impact of M&A activities in fostering collaborative innovation in green technologies among firms and suppliers,thus improving productivity and energy efficiency.We provide new microlevel evidence of the relationship between M&A transactions and corporate energy efficiency from upstream and downstream perspectives.
基金Supported by the National Natural Science Foundation of China （20436040）.
文摘Water-using operations in the process industry have demands for water usually both on water quality and temperature, and the existing mathematical models of heat exchange networks cannot guarantee the energy performance of a water network optimal. In this paper, the effects of non-isothermal merging on energy performance of water allocation networks are analyzed, which include utility consumption, total heat exchange load, and number of heat exchange matches. Three principles are proposed to express the effects of non-isothermal merging on energy performance of water allocation networks. A rule of non-isothermal merging without increasing utility consumption is deduced. And an approach to improve energy performance of water allocation network is presented. A case study is given to demonstrate the method.
文摘This study uses a building energy performance simulation to investigate the impact of predicted climate warming and the additional issue of building ageing on the energy performance for a library in Turin,Italy.The climate and ageing factors were modelled individually and then integrated together for several decades.Results from the climate-only simulation showed a decrease in thebuilding heating energy usage which outweighed the increase in the on-site cooling energy demand occurring in a warming scenario.The study revealed a high sensitivity of energy performance to building ageing,in particular due to HVAC(Heating,Ventilation and Air Conditioning) equipment efficiency degradation.Building ageing was seen to negatively affect the energy performance as it induced a further increase of the cooling energy usage in a warming climate,while it also counteracted the reduction of the heating energy usage resulting from warming.Simulations on the combination of mitigation techniques showed a number of potentially retrofit measures that would be beneficial for buildings to avoid an increase in the cooling energy usage due to climate warming.The combination of these retrofit techniques showed a potential decrease of 87.3% in the final cooling energy usage for the considered building.
文摘Energy Performance Contracting was introduced into China in the mid 1990s. Since western energy service companies came to China, their management pattern has undergone major changes. Why did such changes occur? Mainly because these companies encountered two difficulties in China: tax and financing.
基金Project(2011B061200043)supported by the Guangdong Provincial Department of Science and Technology,China
文摘Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A "holistic" approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP(coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.
基金Supported by Competitive Earmarked Research Grant of Hong Kong Government(CERG No.522709)
文摘The combined use of dry cooling(DC) system and dedicated ventilation(DV) system to decouple cooling and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its application in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment performance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54% in comparison with the conventional system(constant air volume with reheat system). In respect of condensation risk, it was found that the annual frequency of occurrence of condensation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parameters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed.
文摘The commitment to improve energy and environmental performance in public administration is essential for the success of development models geared towards lasting sustainability. The Public Administration （PA） in Italy, in particular, plays a key role to affn-m models of development oriented towards energy and environmental sustainability, thanks to a wider and more innovative vision. The PA has a dual consumer/user role, public heritage and decision maker/planner, in promoting energy efficiency at local level, in the light of specific problems and peculiarities. For several decades, initiatives have been launched at various levels to improve energy and environmental performance in the public administration. The aim of this study is to outline from a critical perspective, the state of the art of policy makers in Italy concerning energy efficiency measures in public administration. There are however many cultural, value-related, financial, technological, institutional, and operational issues in the PA sector that limit investments in energy efficiency. It should be noted that if on one hand the PA shows a lack of knowledge and is unwilling to adopt practices and systemic tools for monitoring and control, on the other, in terms of bureaucracy, the system appears to be far too complicated and costly. The multiple benefits linked to improved energy performance would therefore require that the PA rethink their organizational and functional models, put in place more flexible and less bureaucratic forms of management and a more dynamic, pervasive, and proactive approach towards initiatives that promote energy efficiency. The research is a contribution towards identifying the driving forces behind potential systems and tools for energy efficiency in the PA, highlighting both critical elements and opportunities and, in particular, the limits deriving from the technological, managerial, and organizational options available for energy eff^ciency enhancement in the sector of the Italian PA.
文摘The reliable assessment of the annual energy demand has become necessary in view of building energy performance certification. Accurate models must be used to simulate the behaviour of HVAC （heating, ventilation and air conditioning） components in real operation, usually characterized by a wide variation of building loads. In this context, this paper deals with the development and validation of an algorithm aimed at the assessment of part load performance of various kinds of controls for vapour compresion based heat pumps and chillers, in particular referring to on-off, inverter-driven and multi-stage vapour compression. The reliability of this algorithm in the calculation of seasonal performances is checked against monitoring of heat pumps and chillers operating under real conditions.
文摘A simple calculator for early stage energy performance assessment in residential buildings was developed and partially validated in this study. The calculator is based on the correlation of heat loss and energy need for heating and has fixed internal heat gains as intended for compliance assessment. With the calculator, the effect of any parameter implemented can be immediately seen on delivered and primary energy. Because of simple equations, it is suitable for implementation into CAD （computer aided design） design tools including basic BIM （building information modeling） data. Results showed that the accuracy of the correlation for the cases with practical relevance was not worse than 14% of the energy need of space heating. This applies for passive house insulation level; for less insulated building envelopes, the deviations were smaller. This 14% equals to only 3 kWh/（m2.a）, i.e., the percentage difference in the total delivered and primary energy was much lower because of other components in the energy balance. The deviations determined were implemented in the calculator as safety margin. Results prove that simple energy performance assessment based on specific heat loss coefficient is well justified for early stage energy analyses as well as for compliance assessment implemented in Estonian regulation.
文摘The content of contribution is to analyse suggested renovation of school building in term of energy performance and indoor environment quality. There were three selected variants of possible reno ration of school building. At first, it was installation of equipment for heat recovery into existing mechanical ventilation system. There were further evaluated possibilities how to use glass atrium or ground air-heat exchanger in mechanical ventilation system. These suggested variants were analysed in field of energy performance, namely in term of impacts on heat demand for space heating in order to keep required parameters of indoor environment quality according to standard STN EN 15251 （operative temperature, relative air humidity, air change rate）. The analysis was elaborated by using energy simulation tool Design Builder in order to evaluate yearlong operation of buildings.
基金supported in part by the Institute of Information and Communications Technology Planning and Evaluation(IITP)Grant by the Korean Government Ministry of Science and ICT(MSITArtificial Intelligence Innovation Hub)under Grant 2021-0-02068in part by the NationalResearch Foundation of Korea(NRF)Grant by theKorean Government(MSIT)under Grant NRF-2021R1I1A3060565.
文摘In the quest to minimize energy waste,the energy performance of buildings(EPB)has been a focus because building appliances,such as heating,ventilation,and air conditioning,consume the highest energy.Therefore,effective design and planning for estimating heating load(HL)and cooling load(CL)for energy saving have become paramount.In this vein,efforts have been made to predict the HL and CL using a univariate approach.However,this approach necessitates two models for learning HL and CL,requiring more computational time.Moreover,the one-dimensional(1D)convolutional neural network(CNN)has gained popularity due to its nominal computa-tional complexity,high performance,and low-cost hardware requirement.In this paper,we formulate the prediction as a multivariate regression problem in which the HL and CL are simultaneously predicted using the 1D CNN.Considering the building shape characteristics,one kernel size is adopted to create the receptive fields of the 1D CNN to extract the feature maps,a dense layer to interpret the maps,and an output layer with two neurons to predict the two real-valued responses,HL and CL.As the 1D data are not affected by excessive parameters,the pooling layer is not applied in this implementation.Besides,the use of pooling has been questioned by recent studies.The performance of the proposed model displays a comparative advantage over existing models in terms of the mean squared error(MSE).Thus,the proposed model is effective for EPB prediction because it reduces computational time and significantly lowers the MSE.
基金the National Natural Science Foundation of China(Grant No.U2441263)for financial support of this work。
文摘In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of pure aluminum particles to mitigate agglomeration and enhance the combustion efficiency of solid propellants(Combustion efficiency herein refers to the completeness of metallic fuel oxidation,quantified as the ratio of actual-to-theoretical energy released during combustion)with high Al content and low burning rates.The impact of Al-Li alloy with different Li contents on combustion and agglomeration of solid propellant was investigated using explosion heat,combustion heat,differential thermal analysis(DTA),thermos-gravimetric analysis(TG),dynamic high-pressure combustion test,ignition experiment of small solid rocket motor(SRM)tests,condensation combustion product collection,and X-ray diffraction techniques(XRD).Compared with pure Al,Al-Li alloys exhibit higher combustion heat,which contributes to improved combustion efficiency in Al-Li alloy-containing propellants.DTA and TG analyses demonstrated higher reactivity and lower ignition temperatures for Al-Li alloys.High-pressure combustion experiments at 5 MPa showed that Al-Li alloy fuel significantly decreases combustion agglomeration.The results from theφ75 mm andφ165 mm SRM and XRD tests further support this finding.This study provides novel insights into the combustion and agglomeration behaviors of high-Al,low-burning-rate composite solid propellants and supports the potential application of Al-Li alloys in advanced propellant formulations.
基金Project supported by the Natural Science Foundation of Anhui Provincial Education Department(Grant No.KJ2019A0054)。
文摘NaNbO_(3)-based lead-free dielectric ceramics possess significant application prospects in the field of dielectric capacitors.However,their development is hindered by low recoverable energy storage density(W_(rec))and energy storage efficiency(η).Herein,novel NaNbO_(3)-based ceramics,(1-x)[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–xCaTiO_(3),were created by adding CaTiO_(3) linear dielectric,aiming to improve their energy storage performance(ESP).The phase structure,microstructure,dielectric properties,energy storage and charge–discharge performances of the ceramics were methodically analyzed.All components of the ceramics exhibit a perovskite structure consisting of two phases:antiferroelectric P-phase(AFE P)and antiferroelectric R-phase(AFE R),with the AFE R phase increasing as x rises.All ceramic surfaces exhibit clear grain morphology.The resultant ceramics have an appropriate dielectric constant and a small dielectric loss,which are beneficial for improving breakdown field strength(E_(b)).Finally,at an E_(b) of 470 kV/cm,0.85[0.7Na_(0.97)Sm_(0.01)NbO_(3)–0.3(Sr_(0.7)Bi_(0.2))(Ti_(0.8)Zr_(0.2))O_(3)]–0.15CaTiO_(3) ceramic achieves optimal ESP:W_(rec)=3.9 J/cm^(3),η=72.49%.In addition,it has remarkable stability with temperature and frequency in energy storage and displays ultrafast speed in the charge–discharge process(t_(0.9)=27 ns).
基金supported by Natural Science Foundation of China(Grant no.51876087,51708271)Hunan Provincial Natural Science Foundation of China(Grant no.2021JJ50089)+1 种基金Scientific Research Project of Education Department of Hunan Province(Grant no.22A0301)China Scholarship Council(Grant No.2018020505002).
文摘Thermal bridges may represent up to 50%of the building’s envelope area and may increase the energy consumption of buildings by up to 30%,however their impact is often not taken into account adequately in China.In this study,the energy performance of a typical two-story residential building under four different Chinese climate zones is investigated using WUFI Plus program in terms of annual heating and cooling energy demands.Several typical thermal bridges were taken into consideration.Two methods were used to evaluate the effect of thermal bridges on the building energy performance,the simplified method commonly used in China and the dynamic 3D modelling method,and were compared to do not consider thermal bridge.Also,two different types of building envelope,brick wall and aerated concrete wall,were used to evaluate the effect.The results show that by taking into account the thermal bridges,the annual heating energy demands of residential building increase 21.2%,24.8%,27.8%,and 16.6%under the four Chinese climate zones.Therefore,attention should be paid in the building envelope design to reduce thermal bridges.Compared to the dynamic 3D modelling method,the simplified method underestimates annual heating and cooling energy demands.
基金supported by the Ranking the Top of the List for Science and Technology Projects of Yunnan Province(Grant No.202204BW050001)the Graduate Science and Technology Innovation Projects of Jiangsu Province(Grant No.KYCX23_3703).
文摘In this paper,a multi-objective optimization strategy for a volute mixed flow pump is implemented based on inverse design theory.The controllable velocity moment(CVM)design parameters are defined based on the impeller outlet velocity moment and its partial derivative in the streamline direction,and flow control is further realized by directly adjusting the velocity moment distribution inside the impeller.The significance order of the effect of the CVM parameters on the efficiency and NPHSc at the best operation points is first investigated,and the elliptical basis function(EBF)approximation model and MOPS optimization algorithm are combined to carry out multi-objective optimization.Compared with the baseline model,an improvement in the efficiency and head at the best operation points of 0.48%,1.07 m is obtained for the optimal model,with a widened and efficient operation range,and NPHSc is reduced from 4.545 m-4.235 m,with a slowed cavitation development.The proposed CVM method effectively realizes flow control under multiple conditions,optimizing the pressure distribution on the blade pressure side and suppressing the reverse jet in the cavity closure area.
基金Project supported by Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515240072,2023A1515240053,2022B1515020099,and 2023A1515012641)Shenzhen Science and Technology Program(No.JCYJ20220818102409020)the National Natural Science Foundation of China(Nos.12102104 and 12002180)。
文摘Re-entrant honeycombs are widely used in safeguard structures due to their geometric simplicity and excellent energy absorption capacities.However,traditional re-entrant honeycombs exhibit insufficient stiffness and stability owing to the lack of internal support.This paper proposes a new hybrid honeycomb by integrating a chiral component inside the re-entrant honeycomb.Since Young's modulus is a key parameter to evaluate the energy absorption performance and stiffness,an analytical model is given to predict the effective Young's modulus of the proposed hybrid honeycomb.It is found that the optimal design scheme is to directly insert a circular ring inside the re-entrant honeycomb.The normalized specific energy absorption(SEA)of the hybrid honeycomb is 95%larger than that of the traditional re-entrant honeycomb.The normalized SEA first increases to a peak value and then decreases with the cell wall thickness.The optimal thickness of the cell wall for the maximum SEA is derived in terms of the geometric configuration of the unit cell.The normalized SEA first decreases to a valley value and then increases with the re-entrant angle.A longer horizontal cell wall results in a smaller normalized SEA.This paper provides a new design method for safeguard structures with high stiffness and energy absorption performance.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515010681)Fundamental Research Funds for the Central Universities(Grant No.21622417)Special Projects in Key Fields of Guangdong Universities(2022ZDZX1005).
文摘The integration of phase change material(PCM)with building-integrated photovoltaic(BIPV)presents a compelling approach to enhance solar energy utilization and mitigate indoor thermal loads,contributing to energy-efficient and low-carbon building development.Traditional BIPV-PCM structures,however,struggle to balance PV efficiency and thermal insulation,particularly with varying PCM wall positions.To address this situation,this study introduces a novel double-PCM BIPV composite envelope(BIPV-dPCM).An experimentally validated dynamic heat transfer model was developed and used to perform a comparative simulation analysis with three reference systems to quantify the energy-saving potential of the BIPV-dPCM,focusing on PV output and wall insulation effectiveness metrics.Further dimensionless parametric analysis were carried out to investigate the systematic performance of the two PCMs at different relativities.In addition,the coupled working mechanism of the BIPV-dPCM system concerning the power generation performance and thermal insulation performance under transient variations is explored.It was found that the BIPV-dPCM showcases superior thermoelectric coupling performance compared to three alternative enclosures.Incorporating two PCMs significantly enhances electrical exergy efficiency by 11.66%and thermal exergy efficiency by 1.54%,surpassing other reference systems.The increase in PCM latent heat ratio has a limited effect on performance gain.Notably,as the PCM thickness ratio exceeds 1,the decline in P value decelerates,for every 0.5 increment in the g,the P value diminishes by merely 0.2%.The ideal h is identified between 1 and 1.5,with 1.5 being optimal for energy conservation objectives.Additionally,the self-sufficiency coefficient(SSC)of the BIPV-dPCM remains robust,sustaining a range of 55%to 65%over prolonged periods.This study offers novel perspectives and serves as a design reference for optimizing building energy systems and enhancing cooling efficiencies in subtropical climates.
基金This work was supported by the National Natural Science Foundation of China(No.51878581 and No.51778549)the Fundamental Research Funds for the Central Universities(No.20720200087).
文摘Many efforts have been detected to investigate thermochromic(TC)glazing for improving building energy saving,while only a few approaches for daylight performance analysis.In this study,the performance of TC glazing is investigated based on multi-objective optimization for minimizing energy demand while maximizing daylight availability.The effects of five parameters including transition temperature,solar transmittance in clear state,solar transmittance modulation ability,luminous transmittance in clear state,and luminous modulation ability on the building energy consumption and useful daylighting illuminance(UDI_(300-3000))are examined.Linear Programming Technique for Multi-dimensional Analysis of Preference(LINMAP)is used for the decision-making of Pareto frontier.This research aims to explore the ideal thermochromic glazing by considering the daylight and energy performance of a typical office room,taking the weather condition of Xiamen,China as an example.Although it is impossible to achieve both optimal values of energy consumption and UDI_(300-3000)simultaneously,the proposed multi-objective optimization method could still provide low energy consumption with sufficient daylight.The non-dominated sorting of Pareto optimal solution(POS)demonstrated that the optimum building energy consumption and UDI_(300-3000)for single glazed windows are 46.64 kWh/m^(2)and 70.92%,respectively,while the values for double glazed windows are 44.40 kWh/m^(2)and 71.88%,respectively.The selected hypothetical TC windows can improve the building energy and daylighting performance simultaneously when compared with traditional clear single and double glazed windows.The presented framework provides a multi-objective optimization method to determine the most suitable TC glazing technologies for designers and architects during the design and retrofit procedure.
文摘Simulation is recognized as an effective tool for building energy performance assessment during design or retrofit processes. Nevertheless, simulation models yield deviating outcomes from the actual building performance and a significant portion of this deviation originates from the dynamic nature of occupant behavior. Literature on occupant behavior indicates that occupant behavior is not integrated into building energy performance assessment procedures with appropriate resolution, instead they are accepted as assumed and fixed data sets that usually represent the presence of occupants. This study attempts to evaluate the effect of diverse patterns of occupant behavior on energy performance simulation for office buildings. Diverse levels of sensitivity of occupant behavior on control-based activities such as using lighting apparatus, adjusting thermostat settings, and presence in space are employed through three diverse occupant behavior patterns. These occupancy patterns are correlated with three identical office spaces simulated within a conceptual office building. EDSL Tas is used to run building energy performance simulations. Effects of occupant behavior patterns on simulation outcomes are compared for five sample winter and summer workdays, with respect to heating and cooling loads. Results present findings on how diversity of occupancy profiles influences the consumption outcomes.
基金supported by a research grant from Hong Kong Polytechnic University.
文摘Sustainable building has become a future development trend in the building sector.Building Energy Efficiency Retrofit(BEER)provides excellent opportunities to reduce energy consumption in existing buildings,and to promote environmental protection,the rational use of resources,occupants’health,all of which helps to improve the sustainability of existing buildings.Energy Performance Contracting(EPC)provided by Energy Service Companies(ESCOs)is a market mechanism to provide financial and technological support for energy efficiency projects.This paper aims to develop a sustainability promotion framework for BEER projects under the EPC mechanism to link the sustainable performance of BEER with the success factors of this EPC mechanism.Different types of building have different energy consumption characteristics.This research focuses on hotel buildings in China.The paper develops a framework for sustainable BEER through an EPC mechanism in hotel buildings based on the EFQM Excellence Model for business quality management.Interviews were conducted with experts from the hotel industry,from energy service companies and with academics.Based on the developed framework,the study has identified 11 performance indicators for sustainable BEER and 28 success factors of an EPC mechanism.This provides significant groundwork for future study in developing an assessment model to evaluate the sustainability of BEER projects.
