Hot Summer Cold Winter Research Articles

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.

Effects of solar energy absorbed by south wall on carbon emission from space heating in hot summer-cold winter region

Carbon emission caused by space heating (CEH) in hot summer and cold winter climate zone has increased dramatically. Taking advantage of the solar energy absorbed by south wall (SEASW) can effectively reduce CEH, however, the accurate quantification of its impact remains a challenge. The study investigates the potential of SEASW in mitigating CEH. Key parameters affecting CEH, such as sunny day ratio, insulation form, and outer surface heat transfer coefficient of south wall (h), were analyzed. Results show the reduction in carbon emissions caused by the solar energy absorbed by each unit area of the south-facing wall (ΔCreduction) can be as high as 18.61 kgCO2⋅m−2 for the wall employing internal insulation and smaller h. A prediction model of ΔCreduction was further developed by using multivariate nonlinear regression, which can estimate the reduction in CEH for different fuels as heating source by a south wall in different sizes. Besides, the potential of SEASW on the reduction of carbon emission per unit floor area can reach 12.2 %. This study underscores the importance of SEASW as a carbon-neutral heating strategy, particularly for regions characterized by short winter heating periods and lower heating loads compared to colder climates. It provides valuable insights for sustainable energy practices and policy formulation.

Source tracing the bedroom bacteria across different climate zones in China during the heating season

Approximately 1/3 of people's time is spent in bedrooms. Regulating the health implications arising from the bedroom bacterial community demands an in-depth understanding of both the bacterial composition and the influential factors. This study employed high-throughput 16 S rRNA amplicon sequencing to characterize the bacterial community in 23 residential bedrooms across five climate zones in China. Our findings reveal that the bacterial richness and diversity were highest in the Hot-Summer-Cold-Winter (HSCW) zone, possibly due to its lowest indoor temperature during the heating season. Employing an advanced source tracing algorithm, we identified ventilation rate as the dominant factor affecting outdoor bacterial presence, with each additional air change per hour (ACH) increasing the outdoor bacterial abundance by 13.7 %. The integumentary system was the largest contributor to the occupant-associated bacteria, particularly in the residences located in the Severe Cold and Cold zones. Our study provides valuable insights into the diverse bacterial communities in residential bedrooms across various climate zones in China, elucidating the key factors and sources that contribute to shaping these complex microbial ecosystems.

Morphology Optimization of Residential Communities towards Maximizing Energy Self-Sufficiency in the Hot Summer Cold Winter Climate Zone of China

Further research is needed on the capability of residential communities to achieve energy self-sufficiency under the constraints of current standards of land use, in particular for the Hot Summer and Cold Winter climate zone (HSCW) of China, where the majority of communities are dominated by high floor-area ratios, thus high-rise dwellings, namely less solar potential per unit floor area, while most residents adopt a “part-time, part-space” pattern of intermittent energy use behavior, thus using relatively low energy per unit floor area. This study examines 150 communities in Changsha to identify morphological indicators and develop a prototype model utilizing the Grasshopper platform. Community morphology is simulated and optimized by taking building location, orientation, and number of floors as independent variables and building energy consumption, solar PV generation, and energy self-sufficiency rate as dependent variables. The results reveal that the morphology optimization can achieve a 4.26% decrease in building energy consumption, a 45% increase in PV generation, and a 13.2% enhancement in energy self-sufficiency, with the optimal being 39%. It highlights that energy self-sufficiency cannot be achieved solely through morphology improvements. Moreover, the study underscores the crucial role of community orientation in maximizing energy self-sufficiency, with the south–north orientation identified as the most beneficial. Additionally, a layout characterized by a horizontally closed and staggered pattern and a vertically scattered arrangement emerges as favorable for enhancing energy self-sufficiency. These findings underscore the importance of considering morphological factors, particularly community orientation, in striving towards energy-self-sufficient high-rise residential communities within the HSCW climate zone of China.

Thermal comfort of students in naturally ventilated secondary schools in countryside of hot summer cold winter zone, China

People experience four seasons every year, and their thermal comfort usually changes with the season. However, a little is known about the dynamic characteristics of secondary students’ thermal comfort in the countryside under different seasons. This study aims to investigate thermal comfort of students in the countryside under various seasons and reveal the underlying mechanism. One year long-term field study was conducted in a countryside secondary school in Hengyang City, located in the hot summer and cold winter zone of China. A paper questionnaire was used to collect subjective thermal comfort. The surrounding physical environment was also measured. A total of 450 subjects voluntarily participated and returned 2349 valid datasets. The results indicated students had the lowest acceptance rate with temperature (71.9 %), humidity (74.9 %), and velocity (70 %) in summer season. Neutral temperature was 25.7 °C in summer, 19.2 °C in transition, and 14.9 °C in the winter. An inverted U relationship was found between perceived air quality and air temperature. Cold extremities (53.0 %), shivering (37.2 %), and stuffy nose (60.4 %) were prevalent in winter. Adaptive comfort model was only effective in the summer in naturally ventilated secondary school buildings. Estimated learning performance was the highest in transition and lowest in summer. Behavioral adaptation was determined by the relationship between air velocity clothing insulation and operative temperature. The findings of this study provide fundamental knowledge of thermal environment, subjective comfort, and health status in naturally ventilated educational buildings in countryside area. Engineers and designers can use professional comfort indicators to guide their future construction or renovation.

Investigation on Mechanical Properties and Temperature Control Efficiency of Novel Load-Bearing and Heat-Storing Metastructure Walls in Hot Summer-Cold Winter Regions

Investigation on Mechanical Properties and Temperature Control Efficiency of Novel Load-Bearing and Heat-Storing Metastructure Walls in Hot Summer-Cold Winter Regions

The Effect of Greening Layout on Microclimate in Urban Residential Areas in Hot Summer–Cold Winter Zones

Appropriate greening design can enhance the microclimate of residential areas. This study investigated different greening cases for residential buildings in hot summer–cold winter zones. Four sorts of greening layouts were tested in a residential area in Chongqing, China. Arbor–grass mix and arbor–shrub–grass mix showed effective cooling and humidifying effects, and were chosen for further study using the ENVI-met model. The simulations were conducted in Chongqing, comparing sixteen greening cases for determinant and enclosed building forms. Results indicate that the greening design for determinant layout should give priority to ensuring the greening area and shortening the distance from the sidewalk. While enclosed layout should concentrate greening in dense populations, using arbor–shrub–grass mix to improve the wind environment. In cases where the distribution of arbors and shrubs covers a ratio of 7:4, constituting 30% of the overall green space, there is a reduction in environmental temperature by 1.4 °C and in PET by 4.8 °C. This study provides the optimal greening layout for two types of residential areas in China’s hot summer–cold winter zones, guiding landscape construction in these residential areas to optimize the microclimate.

Combination optimization, importance order of parameters and aging consequence prediction for thermal insulation coating with radiation characteristics

Thermal insulation coating (TIC) is beneficial for reducing building energy consumption. In this work, a joint optimization and analysis approach for multi-parameters of TIC was proposed to determine its optimization trend, importance order of parameter and available parameter combinations. Its radiation characteristics and thermal resistance were comprehensively considered. Based on the approach, TIC was evaluated from energy saving rate of cooling (ESRcool), heating (ESRheat), and total energy consumption (ESRtotal) in two climates: hot summer cold winter (Shanghai), and hot summer warm winter (Guangzhou). Results indicated that constantly positive ESRcool was only achieved by optimizing solar absorptivity, while constantly positive ESRheat can be obtained by optimizing different parameters. To guarantee positive ESRtotal, thermal resistance should exceed 0.11 m2·K·W−1 or solar absorptivity should be between 0.2 and 0.6 in Shanghai, while solar absorptivity should be between 0.1 and 0.3 in Guangzhou. For these two cities, the most important parameter was thermal resistance or solar absorptivity. The optimal TIC for Shanghai was “high thermal resistance + low solar absorptivity + low emissivity”, while high emissivity was suitable for Guangzhou. By utilizing the approach and results, energy-saving effect of TIC can be optimized during material design, and influence of material aging can be predicted.

A Review of Building Energy Retrofit Measures, Passive Design Strategies and Building Regulation for the Low Carbon Development of Existing Dwellings in the Hot Summer–Cold Winter Region of China

Retrofitting buildings to achieve improved levels of energy performance is a key strategy in the transition to a low-/net zero carbon future. In China, there has been an enormous growth in residential construction in recent decades in response to the country’s economic development and population growth. However, although these buildings are structurally solid and have long functional life spans, most have very poor thermal performance. Therefore, they would be very suitable for energy retrofitting. Because of the variety of retrofitting options, it is important to review the retrofit measures, regulations and possible outcomes to find effective, long-term solutions that strike a balance between the energy saved, the carbon emitted and the financial costs over a building’s lifetime. This paper reviews suitable retrofit measures for the hot summer–cold winter region of China, because this is an area with huge numbers of residential buildings that are suitable for energy retrofitting. The study explores the current conditions of targeted residential buildings, retrofit schemes, building regulations, and policy gaps towards achieving China’s 2060 carbon neutrality goal. The review indicates that current mandatory building energy regulations in this region are not ambitious enough to achieve a significantly lower carbon future, and one-step deep Passivhaus retrofit schemes are recommended to achieve decarbonization goals.

Multi-Objective Optimization of Ultra-Low Energy Housing in Hot Summer Cold Winter Climate Zone of China Based on a Probabilistic Behavioral Model

Occupant behavior has an important impact on building energy consumption, and the accuracy of an occupant behavior model directly affects the reliability of energy consumption simulation results. Ultra-low energy buildings are crucial to achieving building energy conservation and carbon dioxide reduction in China. In order to effectively promote the development of ultra-low energy buildings in Hot Summer and Cold Winter Climate Zones. where most residents adopt a “part-time, part-space” pattern of intermittent energy use behavior, and to solve the problem of poor indoor thermal environments and the high incremental cost of ultra-low energy, the study described in this paper takes Changsha as an example to carry out a multi-objective optimization study on ultra-low energy housing using a probabilistic behavioral model. On the basis of a probability model representing the residents’ actual behavior in Changsha, the optimization objective indicators, key variables and the technology benchmarks for ultra-low energy building were determined, then multi-objective optimization was carried out for a range of energy efficient technologies to obtain the Pareto optimal solutions. The results showed that the set of optimal solutions could reduce energy demand by 50.2 to 60.2% and reduce indoor thermal discomfort time by 3.52–11.09% compared with those of a reference base case, which just meets the requirements of the current design standard for energy efficient domestic buildings. An optimum solution for energy savings and indoor thermal comfort, along with economic costs, was identified, which can assist in decision-making by providing different preferences and provide useful reference for the design of ultra-low energy buildings in Hot Summer and Cold Winter Climate regions.

The method of reducing heat loss from thermal bridges in residential buildings with internal insulation in the hot summer and cold winter zone of China

The higher demands for energy efficiency in nearly zero energy buildings (nZEBs) give rise to concerns on the impact of thermal bridges on building's thermal performance. The extra heat loss by thermal bridges needs to be reduced especially for residential nZEBs with internal insulation in China's Hot Summer–Cold Winter (HSCW) zone. This paper defines and compared four typical types of thermal bridges based on their constructional and thermal characteristics. A novel multi-objective optimization method for determining the best construction to improve thermal bridges is also proposed. The heat loss through thermal bridges was estimated through the linear thermal transmittance using COMSOL Multiphysics software. Optimization of design parameters was carried out by Pareto-based multi-objective optimization tool in Python, while heat loss reductions and quantities of material have been comprehensively considered. Corresponding suggested values for design parameters of each thermal bridge type have been put forward. Results obtained by a case study of a typical residential nZEB under various thermal bridge conditions and different air-conditioning patterns also highlight the importance of insulation design of envelope considering the influence of thermal bridge, where the proportion that on annual heating and cooling loads can be reduced from 1.7%-8.2% to 0.4%–2.5%. • Definition and comparation of thermal bridges' impacts on heat loss. • Proposed thermal bridge improvement methods for each type of junction. • Multi-objective optimization for both energy efficiency and material saving. • Energy performance in a residential nZEB considering effects of thermal bridges.

Heat and moisture transfer in wall-to-floor thermal bridges and its influence on thermal performance

A significant portion of the cooling or heating load of buildings is contributed by relatively large heat flux through thermal bridges. Water vapour concentration significantly alters thermal conductivity and heat transfer characteristics within the thermal bridges, affecting building energy consumption, particularly in humid climates. Moreover, the condensation on the building envelope is highly related to the temperature and moisture distribution, which threatens the safety of the building structure. The heat and moisture transfer presents strong coupling effects. Nevertheless, the coupled heat and moisture transfer (HAMT) within thermal bridges and its influence on the building energy consumption were less studied. In this study, field experiments and validated numerical models were conducted to investigate the heat and moisture transfer in the wall-to-floor thermal bridge (WFTB) in a humid and hot summer cold winter region of China (Hangzhou city). The results show that the heat transfer is underestimated if the moisture is not considered. The differences in heat transfer between the WFTB and the main part of the wall were reduced when considering the coupling effect of heat and moisture transfer, as the thermal performance of the wall is more sensitive to moisture than that of the WFTB region. Furthermore, if the significant moisture transfer is considered, the overall thermal conductivity of the WFTB has a risk of counterintuitively increasing when a thermal insulation layer is added. The reason for this is that the thermal insulation layer may raise the moisture content in the WFTB region, subsequently increasing the thermal conductivity.

Characteristics of Urban Heat Island in China and Its Influences on Building Energy Consumption

Urban heat island (UHI) draws more attention as it affects not only the health of residents but also the energy consumption of buildings at the city scale. To achieve carbon neutrality goals, it is crucial to better understand the mechanism of the UHI influences on building energy consumption. The characteristics of urban heat island intensity (UHII) and the relationship between the UHII effect and building electricity and related coal consumption were analyzed, based on the long period of monitoring data with hourly weather data from 1 January to 31 December 2019. Results show that a strong correlation between the annual mean UHII and the median daily mean UHII exists. The synthetic diurnal UHII of most cities presents a U-shaped variation trend. In different building climate zones in China, namely, severe cold region (SCR), cold region (CR), hot summer cold winter region (HSCWR), hot summer and warm winter region (HSWWR), and mild region (MR), the influences of UHII on building energy consumption were analyzed. The existence of UHI reduces building energy consumption in 96.7% of SCR cities and 60.8% of CR cities, while in HSCWR, HSWWR, and MR cities, the percentage of cities where the building energy consumption is increased by UHI is 69.4%, 80%, and 63.6%, respectively. Urban climate strongly influences building energy consumption, indicating that it should be considered and analyzed in detail for making future urban development or carbon emission reduction strategies.

Energy benchmarking analysis of subway station with platform screen door system in China

The energy consumption of Ventilation and Air Conditioning (VAC) systems in subway stations has attracted much attention, aiming to figure out energy-saving potentials and improve energy efficiency. Benchmarking is a useful method to evaluate energy performance of VAC systems during the operational stage. This study describes the development of an energy benchmarking model for the analysis of VAC energy consumption in subway stations with platform screen door systems in a variety of climate regions in China. Firstly, the Constraint Value (CV) and Leading Value (LV) of VAC energy use were simulated using a validated theoretical energy model, which represent the “general” and “superior” level of the VAC energy use, respectively. Results show that, for the 2,520 simulated cases, CV ranges from 184 to 859 × 103 kWh/year and LV ranges from 178 to 529 × 103 kWh/year, with different ranges for cold, hot-summer cold-winter, and hot-summer warm-winter region. Next, the simulated values of CV and LV were applied to establish an energy benchmarking model using the ordinary least square approach. For each climate region, the regressive energy benchmarking models for CV and LV were established and validated by cross-validation. Results show that R2 are 0.753–0.903 and MBE of the test set are 2.1–7.1%, indicating a good fit for the regressive benchmarking models. In order to further test their application, the regressive models were then applied to existing subway stations. Finally, the impacts of service-related variables, i.e. number of passengers, train departure density, and tunnel length, on the CV and LV were discussed. The proposed energy benchmarking model and analysis provide a convenient and effective tool for operators and managers to evaluate VAC energy consumption status and assess energy-saving potentials for subway stations.

Performance test of medium-temperature chiller with induction air-conditioning system

Abstract In this paper, medium-temperature chiller with induction air-conditioning system is introduced. Several onsite measurements were carried out on temperature and relative humidity distribution and energy consumption in summer 2020 in order to study the potential performance when applied in hot summer cold winter zone. The performance test results show that (1) the indoor temperature and humidity both comply with the range of design parameters; (2) the corresponding indoor air dew point temperature is much lower than the supply air temperature of air inductive unit, which implies no condensed water or dew on surface of air inductive unit; (3) the performance of the circulation pump, extensive type air handling unit fan; and medium-temperature chiller has exceeded the requirements of national standards.

Impacts of Courtyard Envelope Design on Energy Performance in the Hot Summer–Cold Winter Region of China

This paper aims to investigate the effects of courtyard envelope design on the energy performance of office buildings in the hot summer–cold winter region of China. Two types of courtyard buildings were simulated with 200 energy models by changing the following variables: window–wall ratio (south, north, east, and west walls), window U-value, wall U-value, solar heat gain coefficient, and orientation. The treed Gaussian process (TGP) sensitivity analysis method was employed to quantify the contributions of parameters related to courtyard design that result in the changes of annual cooling, heating, lighting, and total energy consumption. The results show that the courtyard envelope design has a significant effect on the energy consumption in this case study. The most influential factor affecting annual cooling energy consumption and the annual total energy consumption is the orientation, which is responsible for 37% and 81%, respectively, in two layouts to annual cooling energy use. The corresponding proportion increased to 45% and 86% in terms of the total energy consumption. The most influential factor influencing annual heating energy use is the window U-value, which explained nearly 60% of the changes to the heating energy use. The effect of the solar heat gain coefficient in two kinds of layouts is as high as 82% and 79% for lighting energy use in this case study. Due to the different courtyard forms, the magnitude of the effect of the parameters on energy consumption and the main trend of the effect is slightly different.

Characterizing regional building energy consumption under joint climatic and socioeconomic impacts

Building energy consumption (BEC) control is of significance in the context of pursuing more intensive carbon emission reduction. How climatic and socioeconomic conditions dually drive regional BEC remains to be explored in depth. This study tracks the whole-process BEC in 24 Chinese provincial regions with diverse climatic and socioeconomic conditions and reveals the spatial pattern and driving mechanism. The results indicate that the BEC is 1.51 billion tons of oil-equivalent in 2016, with 51.7% for material preparation, 4.0% for construction-demolition and 44.3% for operation stage. More economically developed regions have larger BEC (Jiangsu, Shandong, Guangdong). Climatic conditions have more decisive effect on regions with larger energy consumption of operation (mainly distributed in severe cold zone and hot summer warm winter zone), which is determined by thermal performance of buildings. Socioeconomic conditions have more decisive effect on regions with larger energy consumption of material preparation (mainly distributed in cold zone, hot summer cold winter zone and temperate zone), which is determined by trends in urbanization rate and population. Based on the findings of this work, more consideration regarding climatic and socioeconomic conditions can be incorporated into the formulation of regional building energy conservation policies for more pertinent BEC control.

Energy Consumption Characteristics of Wall-Hanging Gas Boilers in Hot Summer–Cold Winter Zone of China

Energy Consumption Characteristics of Wall-Hanging Gas Boilers in Hot Summer–Cold Winter Zone of China

Building energy comparison for dynamic cool roofs and green roofs under various climates

Recently, dynamic cool roof (DCR), with the ability to reduce its solar reflectance during heating period, is introduced as a proper replacement for traditional cool roof. Another ideal roof solution is green roof (GR), which can reduce both heating and cooling loads of a building. This study aims to compare air-conditioning energy demands of a residential building with DCRs and GRs, based on numerical analysis with EnergyPlus. Different climatic conditions, thermal mass and insulation levels were considered in the simulation. Also, in order to assure the validity of the results, optimal properties for GRs and the best strategy for switching coatings of DCRs were found before the comparison analysis. The results show that for hot and humid climate, GRs with regular irrigation system are the best roof technique, which can reduce annual thermal loads of the reference building with conventional concrete roof by 17.8–171.4 kWh/m2 (21.3–66.0%), depending on thermal mass and insulation levels. In hot summer-cold winter city, DCRs outperform both dry and wet GRs with the potential to decrease annual energy demand by 11.8–66.7 kWh/m2 (22.4–35.4%). While in area where space heating dominates, dry GRs have the best energy performance, as they can save annual energy of the reference building by 5.5–124.0 kWh/m2 (6.9–44.1%). Applying these optimal roof techniques can reduce annual CO2 emissions of the reference building by up to 20.2–34.5 kg/m2 (38.3–56.6%), depending on the region.

Numerical study on performance of a hybrid indirect evaporative cooling heat recovery heat pump ventilator as applied in different climatic regions of China

Indirect evaporative cooling (IEC) and heat recovery are key technologies for decarbonising heating, ventilation, and air-conditioning (HVAC) while their performance is affected by the ambient environment. This paper presents a numerical investigation of a recently developed hybrid ventilator integrating the IEC and heat recovery. A TRNSYS-Matlab model was used to evaluate the ventilator's adaptability (operational and energy performance) in a public building at five typical cities in China. According to the validated model analysis, the ventilator shows a superior adaptability to the temperate region, with the lowest annual energy use at 96.70 kWh/m2 and the minimum energy input of the auxiliary source at 39.29% of the total energy use. The hybrid ventilator's adaptability is followed by the hot summer cold winter region and cold region where the ventilator covers 85% of the total heating/cooling loads in transition seasons. The severe cold region and hot summer warm winter region requires a significant auxiliary energy use for the stable indoor air parameters, which consumes 70.64% and 60.1% of the annual energy use, respectively. Future works are to improve the performance of the IEC and heat pump unit in the two climatic regions for better adaptability of the ventilator.