Cold Winter Area Research Articles

Research on indoor thermal comfort of traditional dwellings in Northeast Sichuan based on the thermal comfort evaluation model and EnergyPlus

Northeast Sichuan is in the hot summer and cold winter area (HSCW), making its traditional dwellings highly valuable for study. Due to the lack of an appropriate indoor thermal comfort evaluation model, this study developed a suitable model by combining field measurement, questionnaire, and dynamic simulation. The study also investigated the indoor thermal environment of traditional dwellings in the area. The results indicate that in summer, the average indoor air temperature in the bedroom is 25.3°C, and for 81.4% of the summer period, the bedroom operative temperature (top) is below the highest acceptable top of 29.2°C. In contrast, in winter, the average indoor air temperatures in both the bedroom and the hall are below 9.0°C, with only 9.6% of the winter period having bedroom top exceeding the minimum acceptable top of 12.2°C. These findings suggest that there is significant room for improvement in the winter indoor thermal environment. Additionally, the summer neutral top for occupants is 27.0°C, which is higher than the predicted value of 25.4°C, while the winter neutral top is 14.2°C, which is lower than the predicted value of 19.3°C. This indicates that both the traditional dwellings and their occupants have adapted to the local climate to some extent. This study aims to provide a theoretical framework and research basis for optimizing the indoor thermal environment of traditional dwellings in this area.

Research on assessing and enhancing indoor thermal and air conditions within typical elementary school classrooms in southern China

The thermal design of buildings in hot summer and cold winter regions must meet the requirements of thermal insulation in summer and heat preservation in winter. As a vital component of national compulsory education, primary schools must create a good indoor thermal environment for classrooms, which is particularly important for students. Due to the lack of construction standards and limited research on Chinese regions with hot summers and cold winters, policymakers have no comprehensive and efficient approach to creating optimal indoor thermal conditions in primary school classrooms. Therefore, based on the climate conditions of hot summer and cold winter areas, this study conducted field surveys in primary and secondary schools in hot summer and cold winter areas, summarized and analyzed the current situation of the surveyed classrooms and users' subjective evaluation of the indoor thermal environment of classrooms, and summarized the current hot summer and cold winter conditions. Problems in classrooms in primary and secondary schools in the region are clarified, and the research direction of construction strategies is clarified. The study found that most of the school hours in summer and winter were in a poor indoor thermal environment without refrigeration equipment. This study adjusted the school leaving time to 17:20 in summer and 17:00 in winter by adjusting the school leaving time to reduce the time of adverse thermal environment.

The Impact of Different Types of Trees on Annual Thermal Comfort in Hot Summer and Cold Winter Areas

Trees positively improve the annual thermal comfort of the built environment in tropical areas, where climate change is slight throughout the year. However, for areas with high changes in climate all year, the current studies have only explored the summer cooling performance of trees without the impact of different types of trees on annual thermal comfort, especially in cold seasons. Therefore, to quantify the impacts and scientifically guide the optimization of green space layout in hot summer and cold winter areas, this study selected Changsha City as the study area and analyzed how the annual thermal comfort is affected by evergreen trees and deciduous trees, which are two common types of trees in hot summer and cold winter areas. The analytical results indicated that the difference in the effect of deciduous and evergreen trees on outdoor thermal comfort was insignificant in summer, where the difference in the monthly mean PET for the three summer months was slight, being 0.28 °C, 0.14 °C, and 0.29 °C, respectively. However, evergreen trees greatly exacerbated winter cold compared to deciduous trees, with a monthly mean PET decrease by nearly 1.0 °C and an hourly PET reduced by up to 3.57 °C. The difference is mainly attributed to the absorption and reflection of solar radiation by the tree canopy, as well as the cooling and humidifying effect of the tree leaf. In hot summer and cold winter areas, outdoor thermal comfort is still in the “comfortable” and “slightly warm” acceptable stage despite the warming effect of deciduous trees in the spring and autumn seasons. Planting evergreen trees is an inevitable thermal mitigation choice for tropical areas. However, for the areas with high annual climate change, such as hot summer and cold winter areas in China, a change in empirical tree planting patterns and selecting deciduous trees where appropriate will improve year-round outdoor thermal comfort.

Research on Summer Environmental Thermal Comfort Model of Buildings in Hot Summer and Cold Winter Area

Research on Summer Environmental Thermal Comfort Model of Buildings in Hot Summer and Cold Winter Area

Development of a doubly-fed compound control for hybrid ground source heat pump systems in hot summer and cold winter areas

In hot summer and cold winter areas, the impact of soil thermal accumulation is significant even for hybrid ground source heat pump systems (HGSHPs), especially after a long-term operation. To alleviate the energy performance degradation caused by soil temperature rise, a detailed temperature field heat transfer model of ground heat exchangers (GHXs) has been established and a doubly-fed compound control for HGSHPs is developed and integrated into a central controller module. The central controller can automatically control the loop flow distribution of units and achieve group activation of GHXs based on the load sequences forecasting feedforward and system variables feedback processes. Five control modes are included in the central controller, and the energy performances and soil temperature rise distribution of the HGSHPs with different control modes for fifteen years are compared. The results indicated that the HGSHPs performs best in terms of energy performance and soil thermal alleviation with Control Unit 13. Compared to the Normal control mode, the mean water temperature of GHXs, energy consumption of the chiller and heat pump decreased by 1.6 °C, 5.9 %, and 15.5 %, respectively, and the units COP increased by 11.3 %.

Seismic behavior and failure analysis of prefabricated foamed concrete composite walls for passive houses

In view of the lack of research on the failure mode and seismic behavior of high-performance insulation walls utilizing lightweight concrete as the structural material, this study presents experimental findings from a seismic behavior investigation of prefabricate foamed concrete composite walls (PFCCWs) for passive house in China. The PFCCWs incorporate low thermal conductivity and high-strength foamed concrete, polyurethane, decorative magnesium straw slabs to provide excellent thermal and mechanical properties for prefabricated passive houses in hot summer and cold winter area. The seismic behavior of PFCCWs under different influence factors were elaborated using quasi-static test data and observation of external damage. The lightweight and porous nature of foamed concrete leads to significant crack formation during failure. The findings suggest that the skin effect of magnesium straw slabs and polyurethane impedes crack development and improve the load-bearing capacity with ductility enhancement. Additionally, reducing the aspect ratio and substituting post-cast column concrete with common concrete are effective to improve the seismic behavior. The window opening changes the worst damage area of the wall and notably weakens the seismic behavior. The enhanced integrity of cast-in-place wall leads to the difference in the failure mechanism and increases in load-bearing and deformation capacities. Meanwhile, design suggestions for the foamed concrete insulation walls are also proposed by comparing the failure mode and hysteretic response of various wall types.

Research on the energy saving behaviors of university students based on TPB in a hot summer–cold winter area in China

Energy saving in higher education institutions holds significant importance in the establishment of environmentally friendly and low-carbon societies, with the energy-saving behaviors of university students playing a pivotal role in the development of sustainable campuses. However, there is a clear need for customized strategies to encourage energy-saving habits among university students in areas of China with extreme weather conditions, such as hot summers and cold winters. This study offers a thorough examination of the literature regarding energy-saving behaviors among college students and presents a new theoretical framework based on the Theory of Planned Behavior (TPB). A survey questionnaire is conducted at universities in regions with hot summers and cold winters across China, with the goal of identifying the main factors that influence students' intentions and actions regarding campus energy conservation. From July to August 2022, we collected 512 survey responses from different university campuses in China's hot summer-cold winter weather zone. The survey asked about subjective norms, understanding of energy conservation, and the importance of saving energy. Utilizing the Structural Equation Model (SEM), we examined how influencing factors are associated with energy conservation behaviors. Our findings indicate that (1) both the significance of energy conservation and subjective norms significantly drive energy-saving actions; (2) distinct factors impact different forms of energy-saving practices; and (3) the inclination to save energy partially mediates the relationship between comfort choices and the significance of energy conservation. This study presents a validated behavioral model tailored for regions experiencing hot summers and cold winters, offering valuable insights for college administrators in managing energy usage while also serving as a theoretical reference for establishing environmentally sustainable campuses.

Experimental investigation of the cooling effect of topology-optimized structure on photovoltaic wall

Nowadays, photovoltaic walls have been widely used, which will generate heat behind the PV panel and cause overheating, making the lower efficiency of the PV panel and higher temperature of the exterior wall. Topology optimization structures have been explored in many fields for heat dissipation, but few are applied in heat dissipation of the PV wall systems. The purpose of this paper is to experimentally investigate the effect of topological optimized structure of the copper sheet on electricity generation efficiency of the PV panel and cooling effect of the exterior wall. The topology optimization method is used to numerically find the optimal geometric configuration of high thermal conductivity material of copper sheet on the back of the photovoltaic panel. And the topology-optimized copper sheet is fabricated by 3D printing and experimented with four different cases. The experimental results show that under natural convection, compared with the reference photovoltaic wall, the largest reduction of temperature of the photovoltaic panel (ΔTpv) and the largest output power increment rate (ΔE/E) of the photovoltaic wall with topology-optimized copper in the 5 test days are 2.7℃and 1.30 % respectively, and the largest reduction of temperature of the exterior wall (ΔTw) is 1.6℃. Under forced convection, the temperature reduction (ΔTpv) and the increment of output power (ΔE) of the photovoltaic panel and the temperature reduction of the exterior wall (ΔTw) increase significantly under wind speed of 1 m/s compared with natural convection. But when the wind speed is increased from 1.5 m/s to 2 m/s, the increment is less obvious. Therefore, the optimal wind speed in the air gap of the photovoltaic wall with topology-optimized copper is 1 ∼ 1.5 m/s. At last, based on the results of our previous study, the optimal-constructed photovoltaic wall in hot summer and cold winter area is discussed. The results of this research can provide some technical guidance for engineering application of the photovoltaic panel integrated with walls in similar climate regions.

Numerical simulation of layout and landscape elements on the thermal environment of urban squares

Extreme urban heat poses significant challenges to the resilience and livability of cities. Urban squares are important open public spaces in cities, serving as main locations for residents' leisure and recreational activities and reflect the identity and cultural background of the cities. Improvement in thermal comfort in urban squares can improve the quality of the urban environment and help mitigate the urban heat island effect. This study developed 18 layout and landscape combination scenarios based on statistical analysis of data from 100 urban squares in regions with hot summers and cold winters. Further, the effectiveness of the proposed design solutions in improving the thermal environment was comprehensively analyzed. The results show that: 1) The block array layout with vegetation, water bodies, and permeable tiles is the most effective scenario, with a PET of 31.84 °C, approaching a comfortable level of heat stress; 2) Among the three layouts, the block array layout optimizes thermal comfort better than the main view entrance layout and main view center layout, and reduces physiological equivalent temperature by 10.51–10.77 °C compared with that of the other two layouts; 3) Scenarios incorporating water bodies provide better optimization effects than those with only trees, even when the total area covered by greenery remains unchanged; and 4) Permeable paving materials with high albedo more effectively improve the thermal comfort. Our results highlight a great potential of comprehensively using multiple landscape strategies to improve outdoor thermal comfort, and provides design basis for enhancing thermal comfort in similar sized urban squares in hot summer and cold winter areas.

Single-nucleotide polymorphisms and copy number variations drive adaptive evolution to freezing stress in a subtropical evergreen broad-leaved tree: Hexaploid wild Camellia oleifera

Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress, while hexaploid wild Camellia oleifera shows strong freezing tolerance. As a valuable genetic resource of woody oil crop C. oleifera, wild C. oleifera can serve as a case for studying the molecular bases of adaptive evolution to freezing stress. Here, 47 wild C. oleifera from 11 natural distribution sites in China and 4 relative species of C. oleifera were selected for genome sequencing. “Min Temperature of Coldest Month” (BIO6) had the highest comprehensive contribution to wild C. oleifera distribution. The population genetic structure of wild C. oleifera could be divided into two groups: in cold winter (BIO6 ≤ 0 °C) and warm winter (BIO6 > 0 °C) areas. Wild C. oleifera in cold winter areas might have experienced stronger selection pressures and population bottlenecks with lower Ne than those in warm winter areas. 155 single-nucleotide polymorphisms (SNPs) were significantly correlated with the key bioclimatic variables (106 SNPs significantly correlated with BIO6). Twenty key SNPs and 15 key copy number variation regions (CNVRs) were found with genotype differentiation > 50% between the two groups of wild C. oleifera. Key SNPs in cis-regulatory elements might affect the expression of key genes associated with freezing tolerance, and they were also found within a CNVR suggesting interactions between them. Some key CNVRs in the exon regions were closely related to the differentially expressed genes under freezing stress. The findings suggest that rich SNPs and CNVRs in polyploid trees may contribute to the adaptive evolution to freezing stress.

A simplified modeling method for studying the thermal performance of buildings with vertical greening systems

Vertical greening systems (VGS) are considered an effective strategy to enhance the insulation performance of the building envelope. Existing methods predicting the performance of this strategy usually require a combination of mathematical modeling and building performance simulation, hence difficult for practical use. To simplify this work, this study has proposed a prediction method requiring building simulation only, by considering VGS as a shading component in the simulation work. To compare its performance, a model using conventional methods has also been proposed. A further simplification by neglecting the impact of transpiration has been investigated as well. To justify the implementation of the new method, it has been used to optimize the design of VGS for buildings located in the hot summer and cold winter areas in China. The validation result confirmed the accuracies of both methods, with the simpler method giving an insignificant lower accuracy than the conventional method, which can be compensated by its simpler prediction procedure. The implementation justification showed that for buildings in the HSCW area, VGS is suggested to be installed on the west facade, with a leaf area index of 4. This can help to reduce the heat transfer of the wall by 56.6%.

Design Parameters Affecting Energy Consumption of University Educational Buildings in Hot Summer and Cold Winter Area of China

Design Parameters Affecting Energy Consumption of University Educational Buildings in Hot Summer and Cold Winter Area of China

Analysis of the indoor thermal environment of traditional residents in the South Sichuan China region in summer and plum rainy seasons—taking Baiyang village in Yibin city as an example

ABSTRACT In hot summer and cold winter areas, the humid and sultry summer and rainy season problems have long affected the health of residents. Through a questionnaire survey and site measurements, the indoor thermal environment of typical southern Sichuan village houses was investigated. The average indoor humidity of the old traditional dwelling (85–95%) in the rainy season was much greater than that of the new rural house (70–80%), both of which are outside the standard thermal comfort range of the human body. In summer, the situation is slightly better but still uncomfortable. The APMV evaluation results reveal that in the rainy season, the new residential house is more comfortable than the traditional residential house, while in summer, the opposite situation occurs. The measurements show that the thermal inertia index of the old stone masonry house is large, which indicates that the house has a strong ability to resist temperature fluctuations. Therefore, we discussed different performance improvement strategies for these two types of rural residences. This study is conducive to improving the thermal environment of local residential buildings and provides a reference for the future design of rural ecological residential buildings.

Energy-saving regulation methods and energy consumption characteristics of office air-conditioning loads in hot summer and cold winter areas

The air-conditioning system of an office building may have much higher operational energy consumption than its designed value due to the actual use behavior which significantly deviates from the predicted one. To precisely analyze the actual air-conditioning energy consumption, in this paper, based on the impact of occupant air-conditioning behavior on the energy consumption of air-conditioning systems, a Supply-Side Cooling Load Regulation Method (SSRM) is proposed, and its air-conditioning energy consumption analysis model is established. The energy consumption characteristics of the air-conditioning system under SSRM were analyzed, with the assumption that the example office building is located in a hot summer and cold winter areas. The results indicate that the indoor air conditioning set temperature and the actual fresh air volume are important factors affecting the variation of the air conditioning system cooling load under the Demand-Side Cooling Load Regulation Method (DSRM) method, whereas under SSRM, the air conditioning system cooling load is not affected by the variation of the indoor set temperature and the fresh air volume; meanwhile, regulating human air-conditioning use behaviors is the key point of reducing air-conditioning cooling load. The increasing fresh air volume from 30 m3/(p∙h) to 90 m3/(p∙h) can result in about a 5°C increase in the average daily indoor air temperature in the rooms used by SSRM, and it also causes an increase in the total air-conditioning load in the rooms under DSRM by more than 45 kWh/day. Further, compared to the DSRM, the SSRM can well regulate occupant air-conditioning use behaviors, which reduces energy consumption by more than 35% in the summer.

Preparation and performance study of a novel radiant panel for thermal and cooling storage with phase change materials

Phase change radiant panels (PCRPs) with thermal storage can enhance the heat capacity of buildings, and reduce building energy consumption. In this paper, a composite phase change material (CPCM) was prepared by paraffin wax-lauric acid/expanded graphite (PW-LA/EG) and applied to radiant panels. This CPCM exhibits a broad temperature range for phase change (10°C - 40°C), with EG at the optimal mass fraction of 14% and PW-LA at the optimal ratio of 1:1. It has a moderate latent heat capacity, a thermal conductivity of 1.692 W/mK, and excellent thermal stability. Furthermore, the simulations were performed in this paper, and the year-round comfort, thermal storage/release characteristics, and the influencing factors of PCRPs were evaluated by TRNSYS software. The results show that the PCRP can enhance indoor comfort throughout the year and exhibit excellent thermal storage and release properties. The analysis of influencing factors indicates that the thickness of the PCM has a small impact on the PCRP. It is recommended that a radiant panel coverage rate of at least 70% and a water supply time of 10 h in summer and 8 h in winter. These optimized parameter values can offer valuable guidance for the design and practical application of PCRPs. Practical application Phase change materials have been widely studied as materials used for thermal energy storage. The radiant panel with phase change materials can enhance the heat capacity of buildings, and reduce building energy consumption. This paper proposes a phase change radiant panel that can be used to solve the problem of year-round energy storage of radiant panels in hot summer and cold winter areas. Furthermore, this paper uses TRNSYS software to study the performance of the phase change radiant panels and offers valuable guidance for the design and practical application of PCM radiant panels.

Multi-objective optimization of residential building energy consumption, daylighting, and thermal comfort based on BO-XGBoost-NSGA-II

The energy consumption, daylighting, and thermal comfort of buildings directly affect the three key goals of residents. However, there is little research on the optimization of energy consumption, daylighting, and thermal comfort in residential buildings in China. Therefore, this study proposes an optimization framework that combines Bayesian optimization with extreme gradient boosting trees (BO-XGBoost) and non-dominated genetic algorithm-II (NSGA-II) to study the multi-objective optimization of residential building performance. This paper first uses Grasshopper to simulate and obtain a dataset through Latin hypercube sampling (LHS). BO-XGBoost is used to establish the regression relationship between building envelope design parameters and residential building performance. Then, the obtained regression model is used as the fitness function of NSGA-II to get the Pareto optimal solution set. Finally, the ideal point method is used to obtain the optimal combination of building envelope structure parameters for residential buildings. Taking a residential building in a hot summer and cold winter area as an example, the effectiveness of this method is verified. The results show that (1) BO-XGBoost has excellent predictive performance, with R2 values of 0.997, 0.960, and 0.994 for energy consumption, thermal comfort, and daylighting, respectively. (2) The proposed BO-XGBoost-NSGA-II can effectively achieve multi-objective optimization. Compared with the initial scheme of the case building, energy consumption is reduced by 44.1%, thermal comfort index is reduced by 10.9%, and daylighting performance is improved by 1.7%. Therefore, the proposed method can effectively optimize the performance goals of residential buildings and provide practical ideas for similar problems.

Optimization of energy-saving renovation technology for existing buildings in a hot summer and cold winter area

Retrofitting existing buildings significantly improves indoor thermal comfort and reduces building energy consumption and greenhouse gas emissions. The optimal combination of energy-saving technologies can improve the energy performance of a specific building. The effective energy-saving renovation of existing buildings is vital for improving the poor indoor comfort and high building energy consumption caused by the inadequate thermal performance of the external enclosure structure. This study proposed a new multi-objective optimization model based on Latin hypercube sampling (LHS). It combines a genetic algorithm (GA) with an artificial neural network (ANN) to evaluate and optimize the technology used for retrofitting projects, aiming to provide solutions for the energy-saving renovation of existing buildings. This study selected an old building in a hot-summer and cold-winter area for the retrofitting project, aiming to optimize indoor comfort, building energy consumption, and retrofitting cost. The proposed model was used to determine the optimum energy-saving technology combinations suitable for the building. The results showed that the optimized model could be used to explore conflicting objectives and determine the Pareto front when retrofitting existing buildings. Subsequently, the optimal technology combinations included using energy-efficient PVC Low-E double-glazed windows (5+6A+5) and XPS insulation with a thickness of 0.315m for the roof and external walls.

A simulation study on the heating characteristics of residential buildings using intermittent heating in Hot-Summer/Cold-Winter areas of China

Radiant air conditioning system is an important heating method with better thermal comfort, less noise and greater energy-saving potential. However, different intermittent heating modes may significantly impact both the heating efficiency and indoor thermal comfort, which has been neglected in existing studies. Therefore, to obtain optimal intermittent heating modes for achieving higher energy efficiency and better indoor thermal comfort for the residential buildings in Hot Summer and Cold Winter areas, a TRNSYS model of the radiant air conditioning system was developed and validated. The indoor thermal comfort and energy consumption characteristics during the coldest day and entire heating season were simulated and analyzed based on four different intermittent heating modes. The results demonstrated that the supply water temperature of the air source heat pump unit and the radiant terminals stabilized at the set temperature in about 1 h during the start-up stage, and the indoor air temperature stabilized at 24.0 °C after 7.5 h during the shutdown stage. The proportion of time that meets first-level thermal comfort under the four intermittent heating modes was above 90.1% and even higher at over 96.1% when considering the sleeping period. Compared to the continuous heating mode, the four intermittent heating modes saved 22.3%, 25.8%, 40.4% and 48.4% of energy. Overall, the preferred intermittent heating mode for residential buildings with the radiant air conditioning system in Hot Summer and Cold Winter areas was identified as switching on from 7:00 to 15:00 and 19:00 to 3:00, while switching off from 15:00 to 19:00 and 3:00 to 7:00. This model not only considered the immediate benefits of improved indoor thermal comfort and energy efficiency, but also showed great advantages in developing sustainable construction.

Analysis of ineffective heating in intermittently heated office buildings in hot summer and cold winter areas

ABSTRACT To reduce room heating energy consumption and improve energy utilization efficiency, this paper proposed a method for evaluating the energy efficiency of office heating based on ‘ineffective heat supply’ and ‘ineffective heat supply ratio’ and established an energy consumption analysis model. Using the office in hot summer and cold winter areas as an example, the heating energy consumption and energy utilization efficiency were simulated. The results indicate that better thermal comfort is achieved in the working area of Air Conditioning Lower Installation (ACLI) compared to Air Conditioning Upper Installation (ACUI). The ineffective heat supply ratio of the room increases with the rise of air supply temperature and decreases with the increase of air supply speed. As the supply air temperature increases from 25°C to 50°C, the ineffective heat supply ratios for ACUI and ACLI increase by 35.9% and 14.9%, respectively. The use of low-temperature heat medium is more energy-efficient than high-temperature heat medium. When the air supply speed increases from 0.8 to 3.2 m/s, its ineffective heat supply ratio decreases by 44.6% and 7.8%, respectively. Air speed change significantly impacts ACUI's ineffective heat supply ratio, with ACLI more energy efficient at lower speeds.

Optimisation method of residential building energy conservation in hot summer and cold winter areas: particle swarm optimisation

Optimisation method of residential building energy conservation in hot summer and cold winter areas: particle swarm optimisation