As the ubiquitous electric power internet of things(UEPIoT)evolves and IoT data increases,traditional scheduling modes for load dispatch centers have yielded a variety of chal-lenges such as calculation of real-time o...As the ubiquitous electric power internet of things(UEPIoT)evolves and IoT data increases,traditional scheduling modes for load dispatch centers have yielded a variety of chal-lenges such as calculation of real-time optimization,extraction of time-varying characteristics and formulation of coordinated scheduling strategy for capacity optimization of electric heating and cooling loads.In this paper,a deep neural network coor-dination model for electric heating and cooling loads based on the situation awareness(SA)of thermostatically controlled loads(TCLs)is proposed.First,a sliding window is used to adaptively preprocess the IoT node data with uncertainty.According to personal thermal comfort(PTC)and peak shaving contribution(PSC),a dynamic model for loads is proposed;meanwhile,personalized behavior and consumer psychology are integrated into a flexible regulation model of TCLs.Then,a deep Q-network(DQN)-based approach,using the thermal comfort and electricity cost as the comprehensive reward function,is proposed to solve the sequential decision problem.Finally,the simulation model is designed to support the validity of the deep neural network coordination model for electric heating and cooling loads,by using UEPIoT intelligent dispatching system data.The case study demonstrates that the proposed method can efficiently manage coordination with large-scale electric heating and cooling loads.展开更多
Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The...Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The laboratory uniaxial compression experiments were also conducted.Then,a coupled thermo-mechanical ordinary state-based peridynamic(OSB-PD)model and corresponding numerical scheme were developed to simulate the damage of rocks after the heating and cooling processes,and the change of crack evolution process was predicted.The results demonstrate that elevated heating temperatures exacerbate the thermal damage to the specimens,resulting in a decrease in peak strength and an increase in ductility of granite.The escalating occurrence of thermal-induced cracks significantly affects the crack evolution process during the loading phase.The numerical results accurately reproduce the damage and fracture characteristics of the granite under different final heating temperatures(FHTs),which are consistent with the test results in terms of strength,crack evolution process,and failure mode.展开更多
The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to...The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to peak temperature has yet to be thoroughly investigated.It is crucial for determining confined concrete structures’post-fire performance and burnout resistance.The paper presents the fundamental behavior of the confined concrete constitutive parameters and stress-strain curve at subsequent cooling temperatures after being heated to peak temperature.The study includes the stress-stress relationship of a 200 mm diameter cylinder with two distinct confinement spacings of 60 mm and 120 mm.The constitutive parameters for confined concrete were initially determined for a peak heating temperature of 750℃ and then modified to establish the stress-strain relationship for successive cooling temperatures of 500℃,250℃,and ambient temperature.The study results show that confinement has a considerable impact on compressive strength,stiffness,and ductility at ambient and fire conditions.After being heated to peak temperature,the confined concrete compressive strength recovers during successive cooling temperatures,with the recovery dependent on confinement spacing.The established stress-strain relationship can assist in better comprehending structural performance and capacity degradation for different tie spacings,and is useful for the analysis and design of confined RC(reinforced concrete)elements during and after a fire.展开更多
The prediction of the heating and cooling loads of a building is an essential aspect in studies involving the analysis of energy consumption in buildings. An accurate estimation of heating and cooling load leads to be...The prediction of the heating and cooling loads of a building is an essential aspect in studies involving the analysis of energy consumption in buildings. An accurate estimation of heating and cooling load leads to better management of energy related tasks and progressing towards an energy efficient building. With increasing global energy demands and buildings being major energy consuming entities, there is renewed interest in studying the energy performance of buildings. Alternative technologies like Artificial Intelligence (AI) techniques are being widely used in energy studies involving buildings. This paper presents a review of research in the area of forecasting the heating and cooling load of buildings using AI techniques. The results discussed in this paper demonstrate the use of AI techniques in the estimation of the thermal loads of buildings. An accurate prediction of the heating and cooling loads of buildings is necessary for forecasting the energy expenditure in buildings. It can also help in the design and construction of energy efficient buildings.展开更多
Internal thermal mass,such as furniture and partitions,plays a crucial role in enhancing building energy efficiency and indoor thermal comfort by passively regulating temperature fluctuations.However,the irregular geo...Internal thermal mass,such as furniture and partitions,plays a crucial role in enhancing building energy efficiency and indoor thermal comfort by passively regulating temperature fluctuations.However,the irregular geometry of these elements poses a significant challenge for accurate modeling in building energy simulations.This study addresses this gap by developing a rigorous analytical model that idealizes internal thermal mass as a sphere,thereby capturing multi-directional heat conduction effects that are neglected in simpler one-dimensional slab models.The transient heat conduction within the sphere is solved analytically using Duhamel’s theorem for three representative indoor air temperature scenarios:(1)constant,simulating a space with active HVAC;(2)exponentially decaying,representing a free-floating space after HVAC shutdown;and(3)periodically varying,corresponding to a naturally ventilated environment.Closed-form solutions are derived for the sphere’s internal temperature field,surface heat flux,and cumulative heat absorbed.The results demonstrate that a material’s Biot number governs its transient thermal response,with high-Biot-number materials(e.g.,plywood)exhibiting a faster surface temperature rise but a steeper internal temperature gradient compared to low-Biot-number materials(e.g.,concrete).The analysis of exponentially decaying and periodic scenarios reveals that sphere radius is the dominant factor determining total heat storage capacity;larger spheres absorb and release significantly more energy per cycle,despite having a lower heat flux density.Furthermore,a quantitative comparison of the decrement factor and time lag shows that while different materials may similarly dampen temperature amplitudes,a material with lower thermal diffusivity(like reinforced concrete)provides a substantially longer time lag,making it more effective for shifting thermal loads.This work provides a versatile and physically insightful analytical framework that advances the modeling accuracy of internal thermal mass beyond existing lumped-parameter methods.展开更多
Thermal shock,a phenomenon known to cause rock fracturing,has gained increasing significance with advancements in enhanced geothermal systems.In this comprehensive review,we delve into the intricacies of thermal shock...Thermal shock,a phenomenon known to cause rock fracturing,has gained increasing significance with advancements in enhanced geothermal systems.In this comprehensive review,we delve into the intricacies of thermal shock in rocks,exploring its mechanisms,mechanical interpretations,impacts,and applications.Despite generations of researchers'attempts to identify the conditions that trigger thermal shock and propose various thresholds for heating rates,temperatures,and durations,establishing a universal threshold remains elusive.Commonly adopted heating rate threshold of 2℃/min and critical temperature around 75℃still require further experimental data and theoretical model support.This study scrutinizes the typical thermal shock process in rocks during heating and cooling,employing both microscopic and macroscopic approaches.To examine the effects of thermal shock,we compile and analyze published experimental findings on rock physico-mechanical properties under rapid heating,cooling,and cyclic conditions.Our review reveals that both external and internal conditions significantly impact a rock's response to thermal shock.We assess several analytical equations related to rock thermal shock;nevertheless,a thorough and strong mechanical model is still required.Thermal shock can be harnessed to support underground rock engineering project design and construction,ranging from thermal spallation drilling to cryogenic fracturing.This review examines the evolution of thermal spallation drilling regarding mechanical models and experimental investigations,and discusses cryogenic fracturing in terms of mechanisms,advantages,application cases,and future developments.Serving as a crucial resource,this review paper consolidates the current understanding of thermal shock in rocks,enabling researchers and engineers to develop improved,sustainable solutions for underground engineering projects that cater to the growing demand for underground space and energy.展开更多
The surge in demand for renewable energy to combat the ever-escalating climate crisis promotes development of the energy-saving,carbon saving and reduction technologies.Shallow ground-source heat pump(GSHP)system is a...The surge in demand for renewable energy to combat the ever-escalating climate crisis promotes development of the energy-saving,carbon saving and reduction technologies.Shallow ground-source heat pump(GSHP)system is a promising carbon reduction technology that can stably and effectively exploit subsurface geothermal energy by taking advantage of load-bearing structural elements as heat transfer medium.However,the transformation of conventional geo-structures(e.g.piles)into heat exchangers between the ground and superstructures can potentially induce variable thermal axial stresses and displacements in piles.Traditional energy pile analysis methods often rely on deterministic and homogeneous soil parameter profiles for investigating thermo-mechanical soil-structure interaction,without consideration of soil spatial variability,model uncertainty or statistical uncertainty associated with interpolation of soil parameter profiles from limited site-specific measurements.In this study,a random finite difference model(FDM)is proposed to investigate the thermo-mechanical load-transfer mechanism of energy piles in granular soils.Spatially varying soil parameter profile is interpreted from limited site-specific measurements using Bayesian compressive sensing(BCS)with proper considering of soil spatial variability and other uncertainties in the framework of Monte Carlo simulation(MCS).Performance of the proposed method is demonstrated using an illustrative example.Results indicate that the proposed method enables an accurate evaluation of thermally induced axial stress/displacement and variation in null point(NP)location with quantified uncertainty.A series of sensitivity analyses are also carried out to assess effects of the pile-superstructure stiffness and measurement data number on the performance of the proposed method,leading to useful insights.展开更多
In this study,a model of combined cooling,heating and power system with municipal solid waste(MSW)and liquefied natural gas(LNG)as energy sources was proposed and developed based on the energy demand of a large commun...In this study,a model of combined cooling,heating and power system with municipal solid waste(MSW)and liquefied natural gas(LNG)as energy sources was proposed and developed based on the energy demand of a large community,andMSW was classified and utilized.The systemoperated by determining power by heating load,and measures were taken to reduce operating costs by purchasing and selling LNG,natural gas(NG),cooling,heating,and power.Based on this system model,three operation strategies were proposed based on whether MSW was classified and the length of kitchen waste fermentation time,and each strategy was simulated hourly throughout the year.The results showed that the strategy of MSW classified and centralized fermentation of kitchen waste in summer(i.e.,strategy 3)required the least total amount of LNG for the whole year,which was 47701.77 t.In terms of total annual cost expenditure,strategy 3 had the best overall economy,with the lowest total annual expenditure of 2.7730×108 RMB at LNG and NG unit prices of 4 and 4.2 RMB/kg,respectively.The lower heating value of biogas produced by fermentation of kitchen waste from MSW being classified was higher than that of MSW before being classified,so the average annual thermal economy of the operating strategy of MSW being classified was better than that of MSW not being classified.Among the strategies in which MSW was classified and utilized,strategy 3 could better meet the load demand of users in the corresponding season,and thus this strategy had better thermal economy than the strategy of year-round fermentation of kitchen waste(i.e.,strategy 2).The hourly analysis data showed that the net electrical efficiency of the system varies in the same trend as the cooling,heating and power loads in all seasons,while the relationship between the energy utilization efficiency and load varied from season to season.This study can provide guidance for the practical application of MSW being classified in the system.展开更多
Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance fo...Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance for heating and cooling between passive houses in different climate zones.Therefore,this research develops a comparative analysis on the energy saving potential of passive houses with the conventional around China.A sensitivity analysis of thermal characteristics of building envelope(insulation of exterior walls and windows,and airtightness)on energy consumption is further carried out to improve the climate adaptability of passive house.Moreover,the variation of energy consumption under different heat gain intensity is also compared,to evaluate the effects of envelope thermal characteristics comprehensively.Results suggest that the decrease of exterior wall insulation leads to the greatest increase in energy consumption,especially in severe cold zone in China.However,the optimal insulation may change with the internal heat gain intensity,for instance,the decrease of insulation(from 0.4 to 1.0 W/(m^(2)·K))could reduce the energy consumption by 4.65 kW·h/(m^(2)·a)when the heat gain increases to 20 W/m^(2)for buildings in Hot Summer and Cold Winter zone in China.展开更多
The goal of this study is to determine specific guidelines for Iraqi architects to contribute to the design and composition of energy-efficient housing units within the limits of a normal budget, locally available mat...The goal of this study is to determine specific guidelines for Iraqi architects to contribute to the design and composition of energy-efficient housing units within the limits of a normal budget, locally available materials and technologies. These units can provide comfort despite the current energy situation in Iraq. The study is based on a computer simulation for a reference building in Baghdad, which has been selected according to the urban conditions, building legislations, housing market and statistics. The final results displayed the main recommendations and the possibility to achieve up to 50% energy reduction with a pay-back period not exceeding two years in some cases. There are some measures that have big energy saving potential. Yet, some of the measures may require big investment or have some bad environmental impacts. Some other good measures are already being implemented.展开更多
Geotechnical structures are increasingly employed as energy geostructures in Europe and worldwide.Besides being constructed for their primary structural role,they are equipped to exchange heat with the ground and supp...Geotechnical structures are increasingly employed as energy geostructures in Europe and worldwide.Besides being constructed for their primary structural role,they are equipped to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructures.This technology can play a fundamental role in the current challenge of addressing the increasing need for clean and renewable sources of energy.This study investigates the possibility of thermal activation of tunnel linings.Particularly,attention will be paid on a new energy segment,which can be used together with tunnel boring machine tunneling to create so-called energy tunnels.Thermal and mechanical designs need to be developed by making effective use of computational methods to quantify the exploitable heat and assess the possible consequences on the surrounding ground and the structure itself.Guidance on how to proceed in this direction will be provided in this study,showing how thermo-hydro and thermo-mechanical numerical analyses can be used to achieve a proper and effective design of energy tunnels.Two examples of possible applications will also be presented.展开更多
Phase change materials(PCMs) designate materials able to store latent heat.PCMs change state from solid to liquid over a defined temperature range.This process is reversible and can be used for thermo-technical purpos...Phase change materials(PCMs) designate materials able to store latent heat.PCMs change state from solid to liquid over a defined temperature range.This process is reversible and can be used for thermo-technical purposes.The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management.The experiment is conducted in two test rooms in Antofagasta(Chile) during summer,fall,and winter.The PCM is integrated into the rooftop of the first test room,while the roof panel of the second room is a sealed air cavity.The work introduces a numerical model,which is built using the finite difference method and used to simulate the rooms' thermal behavior.Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates.Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1℃±10.6℃,while the one of the air-panel room varies 28.3℃±18.5℃.Under the experiment's conditions,the PCM room's indoor temperature observes smoother diurnal fluctuations,with lower maximum and higher minimum indoor temperatures than that of the air-panel room.Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter,as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures.This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs,and improve indoor thermal comfort in different climates of Chile.展开更多
In this paper,a novel cooling control strategy as part of the smart energy system that can balance thermal comfort against building energy consumption by using the sensing and machine programming technology was invest...In this paper,a novel cooling control strategy as part of the smart energy system that can balance thermal comfort against building energy consumption by using the sensing and machine programming technology was investigated.For this goal,a general form of a building was coupled by the smart cooling system(SCS)and the consumption of energy with thermal comfort cooling of persons simulated by using the EnergyPlus software and compared with similar buildings without SCS.At the beginning of the research,using the data from a survey in a randomly selected group of hundreds and by analyzing and verifying the results of the specific relationship between the different groups of people in the statistical society,the body mass index(BMI)and their thermal comfort temperature were obtained,and the sample building was modeled using the EnergyPlus software.The result show that if an intelligent ventilation system that can calculate the thermal comfort temperature was used in accordance with the BMI of persons,it can save up to 35%of the cooling load of the building yearly.展开更多
Building simulation is a powerful way to evaluate the performance of a building.The quality of simulation results however strongly depends on the accuracy of simulation input data.Especially for weather data files and...Building simulation is a powerful way to evaluate the performance of a building.The quality of simulation results however strongly depends on the accuracy of simulation input data.Especially for weather data files and occupant behaviour it is difficult to obtain accurate data.This paper evaluates the variability of building simulation results with regards to different weather data sets as well as different heating and cooling set points for a residential building in Victoria,Australia.Thermal comfort accord-ing to ASHRAE Standard 55,final energy consumption and peak cooling and heating loads are assessed.Simulations have been performed with Energy-Plus,and weather data for a multi-year approach have been generated with the software Meteonorm.The results show that different weather files for the same location as well as different conditioning set points can influence the results by approximately a factor of 2.展开更多
The building sector is facing a challenge in achieving carbon neutrality due to climate change and urbanization.Urban building energy modeling(UBEM)is an effective method to understand the energy use of building stock...The building sector is facing a challenge in achieving carbon neutrality due to climate change and urbanization.Urban building energy modeling(UBEM)is an effective method to understand the energy use of building stocks at an urban scale and evaluate retrofit scenarios against future weather variations,supporting the implementation of carbon emission reduction policies.Currently,most studies focus on the energy performance of archetype buildings under climate change,which is hard to obtain refined results for individual buildings when scaling up to an urban area.Therefore,this study integrates future weather data with an UBEM approach to assess the impacts of climate change on the energy performance of urban areas,by taking two urban neighborhoods comprising 483 buildings in Geneva,Switzerland as case studies.In this regard,GIS datasets and Swiss building norms were collected to develop an archetype library.The building heating energy consumption was calculated by the UBEM tool—AutoBPS,which was then calibrated against annual metered data.A rapid UBEM calibration method was applied to achieve a percentage error of 2.7%.The calibrated models were then used to assess the impacts of climate change using four future weather datasets out of Shared Socioeconomic Pathways(SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).The results showed a decrease of 22%–31%and 21%–29%for heating energy consumption,an increase of 113%–173%and 95%–144%for cooling energy consumption in the two neighborhoods by 2050.The average annual heating intensity dropped from 81 kWh/m^(2) in the current typical climate to 57 kWh/m^(2) in the SSP5-8.5,while the cooling intensity rose from 12 kWh/m^(2) to 32 kWh/m^(2).The overall envelope system upgrade reduced the average heating and cooling energy consumption by 41.7%and 18.6%,respectively,in the SSP scenarios.The spatial and temporal distribution of energy consumption change can provide valuable information for future urban energy planning against climate change.展开更多
Metal nanoparticles of multi-principal element alloys(MPEA)with a single crystalline phase have been synthesized by flash heating/cooling of nanosized metals encapsulated in micelle vesicles dispersed in an oil phase(...Metal nanoparticles of multi-principal element alloys(MPEA)with a single crystalline phase have been synthesized by flash heating/cooling of nanosized metals encapsulated in micelle vesicles dispersed in an oil phase(e.g.,cyclohexane).Flash heating is realized by selective absorption of a microwave pulse in metals to rapidly heat metals into uniform melts.The oil phase barely absorbs microwave and maintains the low temperature,which can rapidly quench the high-temperature metal melts to enable the flash cooling process.The precursor ions of four metals,including Au,Pt,Pd,and Cu,can be simultaneously reduced by hydrazine in the aqueous solution encapsulated in the micelle vesicles.The resulting metals efficiently absorb microwave energy to locally reach a temperature high enough to melt themselves into a uniform mixture.The duration of microwave pulse is crucial to ensure the reduced metals mix uniformly,while the temperature of oil phase is still low to rapidly quench the metals and freeze the single-phase crystalline lattices in alloy nanoparticles.The microwave-enabled flash heating/cooling provides a new method to synthesize single-phase MPEA nanoparticles of many metal combinations when the appropriate water-in-oil micelle systems and the appropriate reduction reactions of metal precursors are available.展开更多
In this paper we present a stochastic model for daily average temperature to calculate the temperature indices upon which temperature-based derivatives are written. We propose a seasonal mean and volatility model that...In this paper we present a stochastic model for daily average temperature to calculate the temperature indices upon which temperature-based derivatives are written. We propose a seasonal mean and volatility model that describes the daily average temperature behavior using the mean-reverting Ornstein-Uhlenbeck process. We also use higher order continuous-time autoregressive process with lag 3 for modeling the time evolution of the temperatures after removing trend and seasonality. Our model is fitted to 11 years of data recorded, in the period 1 January 2005 to 31 December 2015, Bahir Dar, Ethiopia, obtained from Ethiopia National Meteorological Services Agency. The analytical approximation formulas are used to price heating degree days(HDD) and cooling degree days(CDD) futures. The suggested model is analytically tractable for derivation of explicit prices for CDD and HDD futures and option. The price of the CDD future is calculated, using analytical approximation formulas. Numerical examples are presented to indicate the accuracy of the method. The results show that our model performs better to predict CDD indices.展开更多
This paper discusses the design and building process of a net-zero energy solar-powered house developed for the 2013 Solar Decathlon competition to promote high-performance design while using traditional passive strat...This paper discusses the design and building process of a net-zero energy solar-powered house developed for the 2013 Solar Decathlon competition to promote high-performance design while using traditional passive strategies.This project,sponsored by the Department of Energy,brought together students from architecture,engineering,and marketing departments to design and build the house of the future.The challenge was to design a net-zero energy completely solar-powered house that is economically viable,aesthetically pleasant,and completely functional as well.Given that a net-zero energy building will rely on the functional interdependency of a building’s passive and active elements,the UNC Charlotte entry-the UrbanEden house-tried to effectively integrate those elements and deliver a best practice.To that end,the building envelope embraced passive strategies to minimize the annual heating and cooling loads and to optimize natural lighting.Several design ideas were tested via energy simulation to optimize energy and comfort performance.The estimated energy demand led into the design of the photovoltaic system,which has the dual function of producing energy and acting as a shading device.The modular configuration of the house accommodated the transportation of the house across the country while enhancing the future expansion of the house for bigger size applications.Daylighting simulation was performed to finalize the building openings and address the lighting needs.This paper reports a way of effectively designing and constructing a net-zero energy,comfortable,and affordable solar house.展开更多
Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the p...Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the precise design and operation of BTES systems.This study conducts a sensitivity analysis of BTES modeling by employing a comparative investigation of five distinct parameters on a wedge-shaped model,with implications extendable to a cylindrical configuration.The parameters examined included two design factors(well spacing and grout thermal conductivity),two operational variables(charging and discharging rates),and one geological attribute(soil thermal conductivity).Finite element simulations were carried out for the sensitivity analysis to evaluate the round-trip efficiency,both on a per-cycle basis and cumulatively over three years of operation,serving as performance metrics.The results showed varying degrees of sensitivity across different models to changes in these parameters.In particular,the round-trip efficiency exhibited a greater sensitivity to changes in spacing and volumetric flow rate.Furthermore,this study underscores the importance of considering the impact of the soil and grout-material thermal conductivities on the BTES-system performance over time.An optimized scenario is modelled and compared with the base case,over a comparative assessment based on a 10-year simulation.The analysis revealed that,at the end of the 10-year period,the optimized BTES model achieved a cycle efficiency of 83.4%.This sensitivity analysis provides valuable insights into the merits and constraints of diverse BTES modeling methodologies,aiding in the selection of appropriate modeling tools for BTES system design and operation.展开更多
New trigeneration system consists of an internal combustion engine,a power and cooling cogeneration system and an absorption heat transformer system.The exhaust gas is recovered by the power and cooling cogeneration s...New trigeneration system consists of an internal combustion engine,a power and cooling cogeneration system and an absorption heat transformer system.The exhaust gas is recovered by the power and cooling cogeneration subsystem producing the cooling and power.The jacket water is recovered by the absorption heat transformer subsystem producing lowpressure steam.The exergy performance and the energy saving performance which is evaluated by the primary energy saving ratio of the new distributed energy system are analyzed.The effects of the ratio of the output power and cooling of the power and cooling cogeneration subsystem and the generator outlet temperature of the absorption heat transformer subsystem to the primary energy saving ratio are considered.The contributions of the subsystems to the primary energy saving ratio are quantified.The maximum primary energy saving ratio of the new distributed energy system is 15.8%,which is 3.9 percentage points higher than that of the conventional distributed energy system due to the cascade utilization of the waste heat from the internal combustion engine.展开更多
基金This project was supported by National Key Research and Development Plan(2017YFB0902100)Key Project of Liaoning Natural Science Foundation under Grant(20170520292).
文摘As the ubiquitous electric power internet of things(UEPIoT)evolves and IoT data increases,traditional scheduling modes for load dispatch centers have yielded a variety of chal-lenges such as calculation of real-time optimization,extraction of time-varying characteristics and formulation of coordinated scheduling strategy for capacity optimization of electric heating and cooling loads.In this paper,a deep neural network coor-dination model for electric heating and cooling loads based on the situation awareness(SA)of thermostatically controlled loads(TCLs)is proposed.First,a sliding window is used to adaptively preprocess the IoT node data with uncertainty.According to personal thermal comfort(PTC)and peak shaving contribution(PSC),a dynamic model for loads is proposed;meanwhile,personalized behavior and consumer psychology are integrated into a flexible regulation model of TCLs.Then,a deep Q-network(DQN)-based approach,using the thermal comfort and electricity cost as the comprehensive reward function,is proposed to solve the sequential decision problem.Finally,the simulation model is designed to support the validity of the deep neural network coordination model for electric heating and cooling loads,by using UEPIoT intelligent dispatching system data.The case study demonstrates that the proposed method can efficiently manage coordination with large-scale electric heating and cooling loads.
基金funded by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_0613)the National Natural Science Foundation of China(Grant Nos.41831278 and 51878249).
文摘Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The laboratory uniaxial compression experiments were also conducted.Then,a coupled thermo-mechanical ordinary state-based peridynamic(OSB-PD)model and corresponding numerical scheme were developed to simulate the damage of rocks after the heating and cooling processes,and the change of crack evolution process was predicted.The results demonstrate that elevated heating temperatures exacerbate the thermal damage to the specimens,resulting in a decrease in peak strength and an increase in ductility of granite.The escalating occurrence of thermal-induced cracks significantly affects the crack evolution process during the loading phase.The numerical results accurately reproduce the damage and fracture characteristics of the granite under different final heating temperatures(FHTs),which are consistent with the test results in terms of strength,crack evolution process,and failure mode.
文摘The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to peak temperature has yet to be thoroughly investigated.It is crucial for determining confined concrete structures’post-fire performance and burnout resistance.The paper presents the fundamental behavior of the confined concrete constitutive parameters and stress-strain curve at subsequent cooling temperatures after being heated to peak temperature.The study includes the stress-stress relationship of a 200 mm diameter cylinder with two distinct confinement spacings of 60 mm and 120 mm.The constitutive parameters for confined concrete were initially determined for a peak heating temperature of 750℃ and then modified to establish the stress-strain relationship for successive cooling temperatures of 500℃,250℃,and ambient temperature.The study results show that confinement has a considerable impact on compressive strength,stiffness,and ductility at ambient and fire conditions.After being heated to peak temperature,the confined concrete compressive strength recovers during successive cooling temperatures,with the recovery dependent on confinement spacing.The established stress-strain relationship can assist in better comprehending structural performance and capacity degradation for different tie spacings,and is useful for the analysis and design of confined RC(reinforced concrete)elements during and after a fire.
文摘The prediction of the heating and cooling loads of a building is an essential aspect in studies involving the analysis of energy consumption in buildings. An accurate estimation of heating and cooling load leads to better management of energy related tasks and progressing towards an energy efficient building. With increasing global energy demands and buildings being major energy consuming entities, there is renewed interest in studying the energy performance of buildings. Alternative technologies like Artificial Intelligence (AI) techniques are being widely used in energy studies involving buildings. This paper presents a review of research in the area of forecasting the heating and cooling load of buildings using AI techniques. The results discussed in this paper demonstrate the use of AI techniques in the estimation of the thermal loads of buildings. An accurate prediction of the heating and cooling loads of buildings is necessary for forecasting the energy expenditure in buildings. It can also help in the design and construction of energy efficient buildings.
基金supported by the Nanxu Scholars Program for Young Scholars of ZJWEU(RC2024021184).
文摘Internal thermal mass,such as furniture and partitions,plays a crucial role in enhancing building energy efficiency and indoor thermal comfort by passively regulating temperature fluctuations.However,the irregular geometry of these elements poses a significant challenge for accurate modeling in building energy simulations.This study addresses this gap by developing a rigorous analytical model that idealizes internal thermal mass as a sphere,thereby capturing multi-directional heat conduction effects that are neglected in simpler one-dimensional slab models.The transient heat conduction within the sphere is solved analytically using Duhamel’s theorem for three representative indoor air temperature scenarios:(1)constant,simulating a space with active HVAC;(2)exponentially decaying,representing a free-floating space after HVAC shutdown;and(3)periodically varying,corresponding to a naturally ventilated environment.Closed-form solutions are derived for the sphere’s internal temperature field,surface heat flux,and cumulative heat absorbed.The results demonstrate that a material’s Biot number governs its transient thermal response,with high-Biot-number materials(e.g.,plywood)exhibiting a faster surface temperature rise but a steeper internal temperature gradient compared to low-Biot-number materials(e.g.,concrete).The analysis of exponentially decaying and periodic scenarios reveals that sphere radius is the dominant factor determining total heat storage capacity;larger spheres absorb and release significantly more energy per cycle,despite having a lower heat flux density.Furthermore,a quantitative comparison of the decrement factor and time lag shows that while different materials may similarly dampen temperature amplitudes,a material with lower thermal diffusivity(like reinforced concrete)provides a substantially longer time lag,making it more effective for shifting thermal loads.This work provides a versatile and physically insightful analytical framework that advances the modeling accuracy of internal thermal mass beyond existing lumped-parameter methods.
基金supported by the National Natural Science Foundation of China(Grant No.42377149)the Research Grants Council of Hong Kong,China(General Research Fund Project Nos.17200721 and 17202423)。
文摘Thermal shock,a phenomenon known to cause rock fracturing,has gained increasing significance with advancements in enhanced geothermal systems.In this comprehensive review,we delve into the intricacies of thermal shock in rocks,exploring its mechanisms,mechanical interpretations,impacts,and applications.Despite generations of researchers'attempts to identify the conditions that trigger thermal shock and propose various thresholds for heating rates,temperatures,and durations,establishing a universal threshold remains elusive.Commonly adopted heating rate threshold of 2℃/min and critical temperature around 75℃still require further experimental data and theoretical model support.This study scrutinizes the typical thermal shock process in rocks during heating and cooling,employing both microscopic and macroscopic approaches.To examine the effects of thermal shock,we compile and analyze published experimental findings on rock physico-mechanical properties under rapid heating,cooling,and cyclic conditions.Our review reveals that both external and internal conditions significantly impact a rock's response to thermal shock.We assess several analytical equations related to rock thermal shock;nevertheless,a thorough and strong mechanical model is still required.Thermal shock can be harnessed to support underground rock engineering project design and construction,ranging from thermal spallation drilling to cryogenic fracturing.This review examines the evolution of thermal spallation drilling regarding mechanical models and experimental investigations,and discusses cryogenic fracturing in terms of mechanisms,advantages,application cases,and future developments.Serving as a crucial resource,this review paper consolidates the current understanding of thermal shock in rocks,enabling researchers and engineers to develop improved,sustainable solutions for underground engineering projects that cater to the growing demand for underground space and energy.
基金The work described in this paper was supported by grants from the Research Grant Council of Hong Kong Special Administrative Region,China(Grants Nos.CityU 11213119 and CityU 11202121).The financial support is gratefully acknowledged.
文摘The surge in demand for renewable energy to combat the ever-escalating climate crisis promotes development of the energy-saving,carbon saving and reduction technologies.Shallow ground-source heat pump(GSHP)system is a promising carbon reduction technology that can stably and effectively exploit subsurface geothermal energy by taking advantage of load-bearing structural elements as heat transfer medium.However,the transformation of conventional geo-structures(e.g.piles)into heat exchangers between the ground and superstructures can potentially induce variable thermal axial stresses and displacements in piles.Traditional energy pile analysis methods often rely on deterministic and homogeneous soil parameter profiles for investigating thermo-mechanical soil-structure interaction,without consideration of soil spatial variability,model uncertainty or statistical uncertainty associated with interpolation of soil parameter profiles from limited site-specific measurements.In this study,a random finite difference model(FDM)is proposed to investigate the thermo-mechanical load-transfer mechanism of energy piles in granular soils.Spatially varying soil parameter profile is interpreted from limited site-specific measurements using Bayesian compressive sensing(BCS)with proper considering of soil spatial variability and other uncertainties in the framework of Monte Carlo simulation(MCS).Performance of the proposed method is demonstrated using an illustrative example.Results indicate that the proposed method enables an accurate evaluation of thermally induced axial stress/displacement and variation in null point(NP)location with quantified uncertainty.A series of sensitivity analyses are also carried out to assess effects of the pile-superstructure stiffness and measurement data number on the performance of the proposed method,leading to useful insights.
基金support provided by the Nature Science Foundation of Shandong Province(ZR201709180049)the Shandong Key Research and Development Program(2019GSF109023).
文摘In this study,a model of combined cooling,heating and power system with municipal solid waste(MSW)and liquefied natural gas(LNG)as energy sources was proposed and developed based on the energy demand of a large community,andMSW was classified and utilized.The systemoperated by determining power by heating load,and measures were taken to reduce operating costs by purchasing and selling LNG,natural gas(NG),cooling,heating,and power.Based on this system model,three operation strategies were proposed based on whether MSW was classified and the length of kitchen waste fermentation time,and each strategy was simulated hourly throughout the year.The results showed that the strategy of MSW classified and centralized fermentation of kitchen waste in summer(i.e.,strategy 3)required the least total amount of LNG for the whole year,which was 47701.77 t.In terms of total annual cost expenditure,strategy 3 had the best overall economy,with the lowest total annual expenditure of 2.7730×108 RMB at LNG and NG unit prices of 4 and 4.2 RMB/kg,respectively.The lower heating value of biogas produced by fermentation of kitchen waste from MSW being classified was higher than that of MSW before being classified,so the average annual thermal economy of the operating strategy of MSW being classified was better than that of MSW not being classified.Among the strategies in which MSW was classified and utilized,strategy 3 could better meet the load demand of users in the corresponding season,and thus this strategy had better thermal economy than the strategy of year-round fermentation of kitchen waste(i.e.,strategy 2).The hourly analysis data showed that the net electrical efficiency of the system varies in the same trend as the cooling,heating and power loads in all seasons,while the relationship between the energy utilization efficiency and load varied from season to season.This study can provide guidance for the practical application of MSW being classified in the system.
基金Project(51825802)supported by the National Science Foundation for Distinguished Young Scholars of ChinaProject(2018YFE0106100)supported by the National Key R&D Program of China。
文摘Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance for heating and cooling between passive houses in different climate zones.Therefore,this research develops a comparative analysis on the energy saving potential of passive houses with the conventional around China.A sensitivity analysis of thermal characteristics of building envelope(insulation of exterior walls and windows,and airtightness)on energy consumption is further carried out to improve the climate adaptability of passive house.Moreover,the variation of energy consumption under different heat gain intensity is also compared,to evaluate the effects of envelope thermal characteristics comprehensively.Results suggest that the decrease of exterior wall insulation leads to the greatest increase in energy consumption,especially in severe cold zone in China.However,the optimal insulation may change with the internal heat gain intensity,for instance,the decrease of insulation(from 0.4 to 1.0 W/(m^(2)·K))could reduce the energy consumption by 4.65 kW·h/(m^(2)·a)when the heat gain increases to 20 W/m^(2)for buildings in Hot Summer and Cold Winter zone in China.
文摘The goal of this study is to determine specific guidelines for Iraqi architects to contribute to the design and composition of energy-efficient housing units within the limits of a normal budget, locally available materials and technologies. These units can provide comfort despite the current energy situation in Iraq. The study is based on a computer simulation for a reference building in Baghdad, which has been selected according to the urban conditions, building legislations, housing market and statistics. The final results displayed the main recommendations and the possibility to achieve up to 50% energy reduction with a pay-back period not exceeding two years in some cases. There are some measures that have big energy saving potential. Yet, some of the measures may require big investment or have some bad environmental impacts. Some other good measures are already being implemented.
文摘Geotechnical structures are increasingly employed as energy geostructures in Europe and worldwide.Besides being constructed for their primary structural role,they are equipped to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructures.This technology can play a fundamental role in the current challenge of addressing the increasing need for clean and renewable sources of energy.This study investigates the possibility of thermal activation of tunnel linings.Particularly,attention will be paid on a new energy segment,which can be used together with tunnel boring machine tunneling to create so-called energy tunnels.Thermal and mechanical designs need to be developed by making effective use of computational methods to quantify the exploitable heat and assess the possible consequences on the surrounding ground and the structure itself.Guidance on how to proceed in this direction will be provided in this study,showing how thermo-hydro and thermo-mechanical numerical analyses can be used to achieve a proper and effective design of energy tunnels.Two examples of possible applications will also be presented.
基金supported by ANID/FONDAP 1522A0002,ANID/FONDAP 1522A0006,ANID/FONDECYT 3210690,MESCyT/FONDOCyT 2018-2019-3C1-069the UAI Earth Research Center。
文摘Phase change materials(PCMs) designate materials able to store latent heat.PCMs change state from solid to liquid over a defined temperature range.This process is reversible and can be used for thermo-technical purposes.The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management.The experiment is conducted in two test rooms in Antofagasta(Chile) during summer,fall,and winter.The PCM is integrated into the rooftop of the first test room,while the roof panel of the second room is a sealed air cavity.The work introduces a numerical model,which is built using the finite difference method and used to simulate the rooms' thermal behavior.Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates.Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1℃±10.6℃,while the one of the air-panel room varies 28.3℃±18.5℃.Under the experiment's conditions,the PCM room's indoor temperature observes smoother diurnal fluctuations,with lower maximum and higher minimum indoor temperatures than that of the air-panel room.Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter,as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures.This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs,and improve indoor thermal comfort in different climates of Chile.
文摘In this paper,a novel cooling control strategy as part of the smart energy system that can balance thermal comfort against building energy consumption by using the sensing and machine programming technology was investigated.For this goal,a general form of a building was coupled by the smart cooling system(SCS)and the consumption of energy with thermal comfort cooling of persons simulated by using the EnergyPlus software and compared with similar buildings without SCS.At the beginning of the research,using the data from a survey in a randomly selected group of hundreds and by analyzing and verifying the results of the specific relationship between the different groups of people in the statistical society,the body mass index(BMI)and their thermal comfort temperature were obtained,and the sample building was modeled using the EnergyPlus software.The result show that if an intelligent ventilation system that can calculate the thermal comfort temperature was used in accordance with the BMI of persons,it can save up to 35%of the cooling load of the building yearly.
文摘Building simulation is a powerful way to evaluate the performance of a building.The quality of simulation results however strongly depends on the accuracy of simulation input data.Especially for weather data files and occupant behaviour it is difficult to obtain accurate data.This paper evaluates the variability of building simulation results with regards to different weather data sets as well as different heating and cooling set points for a residential building in Victoria,Australia.Thermal comfort accord-ing to ASHRAE Standard 55,final energy consumption and peak cooling and heating loads are assessed.Simulations have been performed with Energy-Plus,and weather data for a multi-year approach have been generated with the software Meteonorm.The results show that different weather files for the same location as well as different conditioning set points can influence the results by approximately a factor of 2.
基金This paper is supported by the National Natural Science Foundation of China(NSFC)through Grant No.51908204the Natural Science Foundation of Hunan Province of China through Grant No.2020JJ3008Supports of the Sweden’s innovation agency(VINNOVA-MIRAI)and the Crafoord Foundation are acknowledged.
文摘The building sector is facing a challenge in achieving carbon neutrality due to climate change and urbanization.Urban building energy modeling(UBEM)is an effective method to understand the energy use of building stocks at an urban scale and evaluate retrofit scenarios against future weather variations,supporting the implementation of carbon emission reduction policies.Currently,most studies focus on the energy performance of archetype buildings under climate change,which is hard to obtain refined results for individual buildings when scaling up to an urban area.Therefore,this study integrates future weather data with an UBEM approach to assess the impacts of climate change on the energy performance of urban areas,by taking two urban neighborhoods comprising 483 buildings in Geneva,Switzerland as case studies.In this regard,GIS datasets and Swiss building norms were collected to develop an archetype library.The building heating energy consumption was calculated by the UBEM tool—AutoBPS,which was then calibrated against annual metered data.A rapid UBEM calibration method was applied to achieve a percentage error of 2.7%.The calibrated models were then used to assess the impacts of climate change using four future weather datasets out of Shared Socioeconomic Pathways(SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5).The results showed a decrease of 22%–31%and 21%–29%for heating energy consumption,an increase of 113%–173%and 95%–144%for cooling energy consumption in the two neighborhoods by 2050.The average annual heating intensity dropped from 81 kWh/m^(2) in the current typical climate to 57 kWh/m^(2) in the SSP5-8.5,while the cooling intensity rose from 12 kWh/m^(2) to 32 kWh/m^(2).The overall envelope system upgrade reduced the average heating and cooling energy consumption by 41.7%and 18.6%,respectively,in the SSP scenarios.The spatial and temporal distribution of energy consumption change can provide valuable information for future urban energy planning against climate change.
基金supported by the National Science Foundation(NSF)of United States under NSF award(No.1946912)Materials characterizations were partially performed at Temple Materials Institute(TMI).Use of the Center for Nanoscale Materials,an Office of Science user facility+1 种基金was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357This research used resources of the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of Science User Facility,operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357.
文摘Metal nanoparticles of multi-principal element alloys(MPEA)with a single crystalline phase have been synthesized by flash heating/cooling of nanosized metals encapsulated in micelle vesicles dispersed in an oil phase(e.g.,cyclohexane).Flash heating is realized by selective absorption of a microwave pulse in metals to rapidly heat metals into uniform melts.The oil phase barely absorbs microwave and maintains the low temperature,which can rapidly quench the high-temperature metal melts to enable the flash cooling process.The precursor ions of four metals,including Au,Pt,Pd,and Cu,can be simultaneously reduced by hydrazine in the aqueous solution encapsulated in the micelle vesicles.The resulting metals efficiently absorb microwave energy to locally reach a temperature high enough to melt themselves into a uniform mixture.The duration of microwave pulse is crucial to ensure the reduced metals mix uniformly,while the temperature of oil phase is still low to rapidly quench the metals and freeze the single-phase crystalline lattices in alloy nanoparticles.The microwave-enabled flash heating/cooling provides a new method to synthesize single-phase MPEA nanoparticles of many metal combinations when the appropriate water-in-oil micelle systems and the appropriate reduction reactions of metal precursors are available.
文摘In this paper we present a stochastic model for daily average temperature to calculate the temperature indices upon which temperature-based derivatives are written. We propose a seasonal mean and volatility model that describes the daily average temperature behavior using the mean-reverting Ornstein-Uhlenbeck process. We also use higher order continuous-time autoregressive process with lag 3 for modeling the time evolution of the temperatures after removing trend and seasonality. Our model is fitted to 11 years of data recorded, in the period 1 January 2005 to 31 December 2015, Bahir Dar, Ethiopia, obtained from Ethiopia National Meteorological Services Agency. The analytical approximation formulas are used to price heating degree days(HDD) and cooling degree days(CDD) futures. The suggested model is analytically tractable for derivation of explicit prices for CDD and HDD futures and option. The price of the CDD future is calculated, using analytical approximation formulas. Numerical examples are presented to indicate the accuracy of the method. The results show that our model performs better to predict CDD indices.
文摘This paper discusses the design and building process of a net-zero energy solar-powered house developed for the 2013 Solar Decathlon competition to promote high-performance design while using traditional passive strategies.This project,sponsored by the Department of Energy,brought together students from architecture,engineering,and marketing departments to design and build the house of the future.The challenge was to design a net-zero energy completely solar-powered house that is economically viable,aesthetically pleasant,and completely functional as well.Given that a net-zero energy building will rely on the functional interdependency of a building’s passive and active elements,the UNC Charlotte entry-the UrbanEden house-tried to effectively integrate those elements and deliver a best practice.To that end,the building envelope embraced passive strategies to minimize the annual heating and cooling loads and to optimize natural lighting.Several design ideas were tested via energy simulation to optimize energy and comfort performance.The estimated energy demand led into the design of the photovoltaic system,which has the dual function of producing energy and acting as a shading device.The modular configuration of the house accommodated the transportation of the house across the country while enhancing the future expansion of the house for bigger size applications.Daylighting simulation was performed to finalize the building openings and address the lighting needs.This paper reports a way of effectively designing and constructing a net-zero energy,comfortable,and affordable solar house.
文摘Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the precise design and operation of BTES systems.This study conducts a sensitivity analysis of BTES modeling by employing a comparative investigation of five distinct parameters on a wedge-shaped model,with implications extendable to a cylindrical configuration.The parameters examined included two design factors(well spacing and grout thermal conductivity),two operational variables(charging and discharging rates),and one geological attribute(soil thermal conductivity).Finite element simulations were carried out for the sensitivity analysis to evaluate the round-trip efficiency,both on a per-cycle basis and cumulatively over three years of operation,serving as performance metrics.The results showed varying degrees of sensitivity across different models to changes in these parameters.In particular,the round-trip efficiency exhibited a greater sensitivity to changes in spacing and volumetric flow rate.Furthermore,this study underscores the importance of considering the impact of the soil and grout-material thermal conductivities on the BTES-system performance over time.An optimized scenario is modelled and compared with the base case,over a comparative assessment based on a 10-year simulation.The analysis revealed that,at the end of the 10-year period,the optimized BTES model achieved a cycle efficiency of 83.4%.This sensitivity analysis provides valuable insights into the merits and constraints of diverse BTES modeling methodologies,aiding in the selection of appropriate modeling tools for BTES system design and operation.
基金This work was supported in part by the National Basic Research Program of China(No.2014CB249202)International Science&Technology Cooperation Program of China(No.S2014GR03880).
文摘New trigeneration system consists of an internal combustion engine,a power and cooling cogeneration system and an absorption heat transformer system.The exhaust gas is recovered by the power and cooling cogeneration subsystem producing the cooling and power.The jacket water is recovered by the absorption heat transformer subsystem producing lowpressure steam.The exergy performance and the energy saving performance which is evaluated by the primary energy saving ratio of the new distributed energy system are analyzed.The effects of the ratio of the output power and cooling of the power and cooling cogeneration subsystem and the generator outlet temperature of the absorption heat transformer subsystem to the primary energy saving ratio are considered.The contributions of the subsystems to the primary energy saving ratio are quantified.The maximum primary energy saving ratio of the new distributed energy system is 15.8%,which is 3.9 percentage points higher than that of the conventional distributed energy system due to the cascade utilization of the waste heat from the internal combustion engine.
