Search

Measuring greenhouse gas (GHG) emissions across different types of land is essential for urban planning during the transition to low-carbon cities. Urban land identification, based on remote sensing images and points of interest (POIs), has the potential to narrow down the statistical unit, helping achieve spatial visualization of GHG emissions below the city level and distinguish emission characteristics of different land-use types. Considering land type as a classification standard for GHG emissions, we constructed the modified STRIPAT-PLS model by identifying land-use types, reconstructing land-use GHG emissions (LUGEs) inventory, and extracting driving indexes, which calculated driving force and LUGEs that were missed in historical years. It deepened the depth and precision of GHG emissions research and provided a reference for LUGE reduction and land management below the city level where missing historical data on GHG inventories. The results showed that: 1) the modified STRIPAT-PLS model achieved a simulation accuracy of 94.9%, demonstrating the effectiveness of our research approach in depicting GHG emissions across different land-use types. 2) Land scale, socio-economic development, and industrial development were key factors that impacted agricultural land, residential land, and airport respectively. 3) Airport was the most significant carbon contributor, while industrial witnessed the highest growth in emission intensity; 4) the spatial analysis indicated decreasing differences in GHG emissions and an overall increase in emission intensity. In addition, the research proposed emission reduction priorities and strategies for each land type to promote low-carbon goals in airport cities. • More detailed land-use data improved the accuracy of LUGEs prediction. • The characteristics and drivers of different LUGEs vary greatly, influencing the focus of low-carbon development for each land type. • During the transformation of a city airport into an airport city, spatial disparities in GHG emissions decreased due to industrial development. [ABSTRACT FROM AUTHOR]

• Simulated effects of vegetation on microclimate of different urban blocks in winter. • Simulated effects of vegetation on building heating energy in different urban blocks. • Vegetation brought a building heating load increase of 7.16 % in a sunny day at most. • Vegetation brought a building heating load decrease of 2.80 % in a cloudy day at most. • Offered evergreen urban vegetation strategies for high-density cities in cold region. As an important landscape, the evergreen vegetation is prevailing, even in cold region cities. However, the impacts of promoting vegetation on microclimate and building heating load (BHL) are still inexplicit. This study validated the feasibility of a new-developed coupled model that linked ENVI-met and EnergyPlus, for predicting the microclimate and BHL in winter. The impacts of vegetation configuration changes on the performances of three typical urban blocks in Xi'an, a high-density city in the cold region of China, were then evaluated. When the leaf area index of green lands increased from 0.79 to 4.77 m2/m2, a decrease of 3.27 °C on mean radiant temperature, a decrease of 0.48 m/s on wind speed, and an increase of 0.47 °C on air temperature at the block scale could be observed. To the three blocks, the BHL of thermal zones in the height range of tree canopy increased by 7.16 %, 1.52 % and 3.57 % during a sunny day, and decreased by 2.80 %, 0.55 %, and 0.06 % during a cloudy day maximally. Overall, the evergreen vegetation produced negative impacts on the building energy efficiency of cold region cities. For urban planners, it's advisable to concentrate evergreen plants in high-rise blocks to mitigate such disadvantages. [ABSTRACT FROM AUTHOR]

High-rise buildings have been promoted in high-density cities. The impact degree of urban high-rises on the building energy demand at the urban block scale is determined by many factors, including the effects of the vertical meteorological pattern (VMP), which have been discussed insufficiently. In this study, the VMP of urban areas in Xi'an, China was observed, and a building energy simulation model that revealed the "urban block form–outdoor climate–building energy" nexus was developed with the URBANopt plugin on the Grasshopper platform. The impacts of the VMP on the building heating and cooling energy demands of different urban blocks were then predicted. In January, the VMP led to building heating load increases of 0.7–1.6 kWh/m2 (16–52%) and 0.0–1.1 kWh/m2 (0–35%) in the residential and mixed-use blocks, respectively. In July, the ranges of the building cooling load changes produced by the effects of the VMP were 0.0–0.1 kWh/m2 (0–1%) and −0.3–0.2 kWh/m2 (−2%) in the residential and mixed-use blocks, respectively. Furthermore, the VMP affected the relationship between the urban block form and the building energy demand. Based on the relationship, we provided form-optimization advice for different functional urban blocks. The urban high-rise mechanisms in high-density cities and their impacts on the building energy demand were discovered in this study. This can help decision-makers to optimize urban planning while promoting urban sustainability. • A vertical meteorological pattern (VMP) for building energy simulations is developed. • Effects of VMP increase the building heating loads of urban blocks by 52% maximally. • Effects of VMP decrease the building cooling loads of urban blocks by 2% maximally. • Impacts of VMP on the block form – building energy demand relationship are evaluated. [ABSTRACT FROM AUTHOR]

Abstract A liquid desiccant-indirect evaporative cooling (LD-IEC) system has been proposed. The design is able to dehumidify and cool the product air simultaneously in one unit. A computational model has been developed to determine the performance of the heat and mass transfer process. The validation of the model demonstrated good agreement with the experimental data to within 10%. The detailed air treatment process has been theoretically studied. The thermal performance of the LD-IEC has been evaluated. Simulation results showed that the outlet temperature and humidity ratio were influenced by the liquid desiccant film length, intake air temperature, and intake air humidity ratio. For a specific inlet temperature and humidity ratio condition, a desired outlet condition can be obtained by adjusting the length of the liquid desiccant film. [ABSTRACT FROM AUTHOR]

Abstract A hybrid evaporative pre-cooled air-conditioning system is introduced for tropical climate applications. The indirect evaporative heat exchanger is employed to pre-cool the ambient humid air before passing through the vapor compression system. A computational model has been developed for the evaporative pre-cooling process. We validated the model by comparing the simulated outlet air temperature against experimental data. The validated model is then used to investigate the performance of the indirect evaporative heat exchanger in terms of the air temperature and humidity profiles. The pre-cooling process is able to reduce the product air temperature and condense water in the product channel. Consequently, the hybrid evaporative pre-cooled air-conditioning system is able to achieve a potential energy saving due the pre-cooling effect and the improvement of the chiller's efficiency. [ABSTRACT FROM AUTHOR]

Abstract Outdoor thermal comfort has been receiving more and more attentions due to the increased demand of outdoor activities during last decades. People require good thermal comfort when they are exposed to the outdoor thermal environment. However, the natural environment is severely suffering from the pollution of air, water as well as the extremely hot weather. Therefore, construction of ecological living environment is of great importance. To evaluate and improve the built environment, a campus area located in Northwest China was selected. Numerical simulations based on the software ENVI-met V4.0 were conducted and the effect of growing plants upon the outdoor thermal comfort was analyzed. Numerical results were compared using different thermal Indexes: Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI). Results demonstrated that UTCI gave a lower prediction than that of PET and was more suitable for evaluating the outdoor thermal comfort. Growing trees can significantly reduce the uncomfortable hours during hot summer but the improvement will reach the limitation after growing amount of trees. [ABSTRACT FROM AUTHOR]

With the construction of new villages in China, energy-saving technologies for rural buildings have been attracted extensive attention. According to the characteristic of severe cold climate in Hailar, Inner Mongolia, and the structure of rural residential buildings in Taohai Pasture and the energy use customs in these houses, the energy efficiencies of passive energy-saving technologies which are applied to demonstration houses in Taohai Pasture are analyzed. Based on BIM, the calculation models of three types of houses, including the demonstration house applied passive energy-saving technologies, the traditional house and the energy-saving standard model based on local rural residential energy-saving design standard, are established. Then energy simulation software is used to calculate dynamic heating loads of these houses. Furthermore some indexes such as heating load and annual energy consumption per unit building area are compared. The calculated results show that the heating load of the demonstration house in Taohai Pasture is decreased obviously through the passive energy-saving strategies of the thermal insulation of building envelopes, the effective setting of a solar room and the reasonable distribution of indoor functional zones. Compared to the annual heating loads of the traditional house and the energy-saving standard model, that of the demonstration house is reduced about 74.8 % and 28.9%, respectively. The investment increase of the envelope of the demonstration house can be recovered within 11.4 years through the reduction of annual energy use for heating. [ABSTRACT FROM AUTHOR]

Urban vegetation is an important factor for urban heat island mitigation, which also contributes to indoor cooling energy reduction. In this study, a one-way coupled simulation method which linked the ENVI-met and Energyplus models was developed to evaluate the impacts of urban vegetation on micro-climate parameters and the building cooling energy consumptions. The simulation results from 27 cases (three typical scenarios with nine vegetation configurations) under extreme hot weather in the summer of Xi'an city, China were compared and analyzed. Compared to that in high-rise blocks, the vegetation in low-rise blocks showed a larger potential at cooling-energy saving. The maximum air temperature reduction around the buildings reached to 0.40 °C, the maximum mean radiant temperature reduction reached to 1.78 °C, and the sensible cooling load of some thermal zones dropped by 2.13%. Although the overall effect of vegetation on decreasing the district cooling load is positive, the evaporation effect and the limited area of vegetation cooling may induce a limited rate on the cooling energy saving, especially in the high-rise blocks. This study provides a method for evaluating the potential of environmental and energy-saving benefits of vegetation planting in different urban blocks, and the result is valuable for planners to balance the costs and benefits of green configurations. • A coupled model was developed to evaluate microclimate impact on building energy. • The cooling mechanisms and benefits of planting in different scenarios were analyzed. • Planting brought a 2.13% (1.81%) sensible (latent) cooling load change in maximum. • The overall energy saving potential by planting in different districts were evaluated. [ABSTRACT FROM AUTHOR]

Latent thermal energy storage (LTES) is widely used in excess energy reservation. The performance of a LTES unit is critical for its application. In this study, the spiral tube embedded LTES tank is investigated experimentally, with a composite of paraffin as the phase change material (PCM). Temperature distribution of PCM in the tank was obtained, for both charging and discharging processes. The results showed that during the charging process, the temperature of upper part of PCM increases faster than that in the lower part, which is considered as the effect of natural convection of PCM that dominates the charging process. Inlet water temperature has a greater influence rather than flow rate on heat transfer performance since the increase of temperature difference between HTF and PCM reduces all thermal resistance in the heat transfer, however it could not be increased infinitely to enhance heat transfer performance. [ABSTRACT FROM AUTHOR]

This study presented a pore-scaled numerical simulation on the melting phase change heat transfer of a phase change material (PCM) impregnated in open-cell metal foam. Idealized tetrakaidecahedron was selected as the representing unit cell (UC) to mimic the real foam microstructure and an assembly of tetrakaidecahedron UCs with six lines and three rows was built for computation. Phase change heat transfer in PCM and coupled heat transfer between PCM and metallic ligaments were directly simulated. To address the contribution of natural convection in the melting phase to the overall melting time and pore-scaled melting interface, natural convection in the interstitial fluid was modeled and compared with the conduction-dominated case. Results demonstrated that micro-foam can significantly accelerate the melting phase change rate and further enhancement was observed at pore scale when natural convection in the melting phase was triggered on. [ABSTRACT FROM AUTHOR]

The construction of eco-city is a hot spot nowadays, aiming to build harmony between human and nature. Ecological city is able to deal with the relationship between human and the environment, whose key point is to establish a comfortable outdoor thermal environment. To evaluate the built microclimate environment, a campus area located in Northwest China was selected. Different scenarios with extra greening, high albedo pavement materials, water body and their combinations were numerically analyzed through Universal Thermal Climate Index (UTCI) incorporated in the software ENVI-met V4.0. Results demonstrated that the scenarios with water body or high albedo materials was found to have little contribution to reduce UTCI, while the green scenario significantly reduced the UTCI peak (6.9 ̊ C) and also the duration (4.5 hours) of heat stress. The present study may be used as a guide for urban planning and construction for ecological city. [ABSTRACT FROM AUTHOR]

• Results from 33 measurement points in 5 selected urban districts were analyzed. • Urban morphology explains 34% of the variation in air temperature. • Suggested morphological indices are proposed to mitigate the high temperature. • 20m buffer zone is proper to analyze microclimate in high anthropogenic heat areas. • The microclimatic prediction models were established for sustainable development. The negative impacts of urban heat island (UHI) have attracted more and more academic attention. Currently, few studies have considered the effects of anthropogenic heat emission (AHE) in different urban districts. To explore the spatial and temporal differences in microclimate in high-AHE areas, five high-anthropogenic-heat-emission blocks in Xi'an, China were selected, and the microclimatic indices of air temperature (AT) and relative humidity (RH) were measured in 33 urban points in the five typical urban blocks. Meanwhile, the urban morphological indices of 33 points were calculated in the 20 m and 50 m buffer areas (BAs). Results show that the green cover ratio (GCR), the impervious surface area ratio (ISAR), sky view factor (SVF) and reflectivity (REF) were important variables affecting microclimate. These indices explained up to 35% and 31% of the changes in AT and RH, respectively. In addition, the ISAR should be controlled within 44% and the REF should be controlled above 21.5%, in order to ensure that the maximum AT remained less than 37°C (high-temperature orange warning) inside the block on a typical summer day. This study improves the prediction method of high summer temperatures in high-AHE blocks and provides hints for developing UHI mitigation strategies. [ABSTRACT FROM AUTHOR]

This paper proposes a gravity heat pipe exchanger used for cooling the communication base station to replace the air conditioning in winter and transition seasons. Tests were made on the gravity heat pipe exchanger of DHHP 3000 produced by Harbin Dawnhappy Heat Pipe Technology Incorporated. The experiment was performed in order to study the effects of the inlet air flow rate, temperature and the exchanger inclination angle on cooling capacity and efficiency of the heat pipe exchanger. As the indoor and outdoor air flow rate are equal, the cooling capacity of heat pipe exchanger increases with the air flow rate and it also increases with the increase of indoor air temperature and with the decrease of outdoor air temperature; The cooling efficiency decreases with the increase of air flow rate and it gradually reduces with the outdoor air temperature increases from 2 °C to 18 °C. Among the ratios of indoor to outdoor air flow rate of 0.4 kg/s:0.5 kg/s, 0.4 kg/s:0.6 kg/s and 0.5 kg/s:0.6 kg/s, the cooling efficiency of 0.4 kg/s:0.6 kg/s achieves the highest value. In addition, as the inclination angle varies from 5° to 50°, the maximum cooling efficiency can be obtained at angle of 20°. [ABSTRACT FROM AUTHOR]

• Temporal and spatial distribution characteristics of urban climate in Xi'an were assessed. • The assignment method was proposed for drawing single meteorological factor distribution map. • The divided climate zones were classified by applying the k-means clustering analysis in winter and summer. • A method of drawing the UC-Map based on the spatial statistical analysis of multivariate data was developed. • Multivariate data were converted into the urban planning management unit to facilitate the urban management work. Rapid urbanization have increased the sensitivity of urban environment to extreme weather. To improve the deteriorating urban environment, the current situation of urban climate should be evaluated systematically and applied to the planning process. This study reports on the temporal and spatial variability of urban climate and introduces a method for constructing an urban climate map based on spatial statistical analysis of field measurement data. Taking Xi'an, a metropolis in northern China, as the case study, we first conducted a 3-year meteorological investigation, including air temperature, relative humidity, and wind speed in both summer and winter. Meanwhile, five indicators with potential impacts on urban climate were selected to describe the urban characteristics. Then, the geographic information system was applied to integrate the meteorological data and urban characteristic data in order to assign more meteorological data. Next, three types of meteorological single-factor and thermal comfort spatial distribution maps were derived. The k-means clustering analysis method was then employed to classify three types of meteorological factors into seven zones in horizontal spatial dimension. Finally, urban climate maps were generated. This study can help planners quickly distinguish urban climate-sensitive and valuable zones in order to make better strategies for future development. [ABSTRACT FROM AUTHOR]