Cold Winter Zone Research Articles

A field investigation on thermal comfort of kindergarten children in China’s Hot Summer and Cold Winter zone during winter

A field investigation on thermal comfort of kindergarten children in China’s Hot Summer and Cold Winter zone during winter

A simplified method for calculating air conditioning load of multi-family housing community considering the spatiotemporal distribution of occupants

Occupant behavior is considered a vital factor influencing housing energy consumption by adjusting the indoor thermal environment and the use of service system. Multi-family housing is popular in the hot summer and cold winter (HSCW) zone of China, where residents typically adopt a “partial time, partial space” approach to environmental control. Therefore, the behavioral differences among families pose challenges for predicting hourly energy consumption at community scale. Taking Changsha, a typical city in the HSCW zone, as an example, this study investigates and summarizes the spatiotemporal distribution characteristics of multi-family occupants, analyzing their impact on air conditioning (AC) load under ideal environmental control conditions (i.e., AC is on where is occupied). Hourly AC load modified equations and multi-family occupancy modified coefficients are introduced to construct a method for estimating hourly AC load of residential communities that comprehensively considers the spatiotemporal distribution of multi-family occupants. The results show that the proposed method achieves fitting degrees of 87%-92.4% for predicting heating load and 77.9%-84.9% for predicting cooling load. This method not only dramatically reduces the workload and time required for physical modeling of residential communities, but also enables fast and refined simulation of the hourly AC load.

Matching analysis between the heating/cooling capacity of PVT heat pumps and the heating/cooling demand of residential buildings across various regions in China

PVT-HP (Photovoltaic-Thermal Heat Pump) is a novel type of energy saving technology. Existing researches on PVT-HP technology focuses only on its operating performance under some specific conditions, ignoring the matching of its energy supply capacity with the energy demand of buildings, which is very important for its engineering design and application. In this paper, the matching relationship between the heating/cooling capacity of the PVT-HP system and the heating/cooling demand of residential buildings in major cities of China has been analyzed. To achieve this goal, a novel prediction model used to calculate the heating/cooling performance of the PVT-HP system has been proposed. And the daily heating guarantee rate and daily cooling guarantee rate have been put forward to evaluate the matching relationship. Based on the evaluation indexes, the applicable matching relationship between the installed capacity of the PVT-HP system and the heating/cooling area of residential buildings has been analyzed. The result of case study shows that for the selected cities of Shenyang, Beijing and Wuhan, the heating/cooling area of residential building for PVT-HP system with installed capacity of 1hp should not exceed 17m2, 31m2 and 25m2, respectively. Further matching analysis of major cities in China shows that the PVT-HP system is more suitable for application in hot summer and cold winter zones of China, in where the suggested heating/cooling area for the PVT-HP system with installed capacity of one horse power is within the range of 30m2 to 37m2.

Economy and energy flexibility optimization of the photovoltaic heat pump system with thermal energy storage

Photovoltaic systems have been widely applied in building energy systems. However, with the sharp increase in demand of electricity in buildings during heating and cooling seasons, the uncertainty of photovoltaic generation further exacerbates the peak-valley difference in electricity use. To improve the economy and energy flexibility of buildings in hot summer and cold winter zones of China, a rule-based operation strategy was proposed for the photovoltaic heat pump with thermal energy storage system to optimize the size of the thermal energy storage system and system operation, with aims of minimizing the total annual cost of the system and maximizing the self-consumption rate of the photovoltaic generation. The effects of grid export power limits, grid import power limits, feed-in tariffs, and PV generation on the system operation optimization results were also investigated. The results indicated that by integrating the thermal energy storage system into the photovoltaic heat pump system, the self-consumption rate of the photovoltaic generation was reduced by 2.39 %, the total annual cost of the system was decreased by 6.61 %, and the payback period of the thermal energy storage system was 1.31 years. The optimum size of the thermal energy storage system and the self-consumption rate of the photovoltaic generation decreased with the increasing grid export power limits and grid import power limits. In contrast, higher grid export power limits, grid import power limits, feed-in tariffs, and PV generation all resulted in a lower total annual cost. This study provided a systematic design and operation optimization method for building energy systems.

Daylighting and energy performance of window with transparent insulation slats combined with building shading in the hot-summer and cold-winter zone

The shading from surrounding buildings significantly affects the energy and daylighting performance of transparent insulation materials (TIM) systems. In previous studies, the performance of TIM systems was primarily discussed in ideal situations without considering the influence of surrounding buildings. However, this is not realistic in actual urban scenarios. This study presents a case study conducted in Changsha to evaluate and compare the energy and daylighting performance of the window with transparent insulation slats (WTIS) and normal double glazing (NDG). The study considers the varying degrees of building shading effects. The results show that windows facing west exhibit the best energy efficiency, while windows facing south have the worst. WTIS achieves a higher Useful Daylight Illuminance (UDI) when building shading effects are not significant, whereas NDG achieves a higher UDI when building shading effects are significant. Despite increasing lighting energy consumption by 69.8 % to 84.3 %, WTIS consistently outperforms NDG in terms of total energy savings. Furthermore, strategically utilizing or deactivating WTIS according to recommended periods during winter can enhance the total solar gain for the building by approximately 22.3 %. This study provides valuable recommendations for the application of WTIS systems and the design of buildings in the hot-summer and cold-winter zone.

Thermal Performance and Building Energy Simulation of Precast Insulation Walls in Two Climate Zones

Traditional concrete buildings exhibit low energy consumption and high heat loss, which results in a larger environmental problem. Precast insulation walls are proposed for strengthening thermal insulation efficiency and mitigating heat loss. Numerous studies have investigated the thermal performance of insulation walls over the past decades. However, gaps remain in practical engineering applications. This study aims to bridge these gaps by providing practical design recommendations based on experimental research. Nine different types of precast insulation walls were tested to examine the thermal performance, and the parameters of the insulation material, insulation form, insulation layer thickness, and concrete rib width were investigated. Then, numerical models of these walls were developed for simulating the thermal performance of the tested specimens. Finally, a six-story student apartment model using designed walls was developed to assess energy consumption in two distinct climate zones: the hot summer and cold winter zone of Changsha City, and the cold zone of Harbin City. The results indicate that the precast insulation wall with external insulation form shows better thermal performance than the sandwich insulation form. It is recommended to use precast insulation walls with 50 mm extruded polystyrene (XPS) external thermal insulation form in Changsha City and 80 mm XPS external thermal insulation form in Harbin City. Furthermore, buildings using precast insulation walls can significantly reduce energy consumption by 49.25% in Changsha and 49.38% in Harbin compared to traditional concrete wall buildings. Based on these findings, suitable design suggestions for this precast concrete wall panel building composed of insulation walls are given.

APPLICATION ANALYSIS OF PHOTOVOLTAIC INTEGRATED SHADING DEVICES CONSIDERING INDOOR ENVIRONMENT AND ENERGY CHANGE IN GREEN BUILDINGS

ABSTRACT Constructing solar-powered cities with photovoltaic panels installed on building façades saves energy and reduces carbon emissions. Since photovoltaic integrated shading devices (PVSDs) differ from rooftop photovoltaics, their design must consider power generation capacity, indoor thermal environment, and lighting control to maximise the energy-saving potential. This study simulates and evaluates the performance of PVSDs combined lighting control in energy-efficient buildings based on EnergyPlus and addresses the conflict between the indoor environment and photovoltaic power generation by optimising the geometric parameters of photovoltaic systems in China's hot summer and cold winter (HSCW) zones. The findings indicate that the combined lighting control mitigates the detrimental effects of PVSDs on lighting, and the design optimisation makes it possible to acquire positive shading benefits and significantly boost the performance of PVSDs, thus saving more energy than rooftop photovoltaics. The maximum energy-saving rate of a room with 12.5% of its façade wall utilised reached 49.295%. This study provides an example of the practical application and evaluation of PVSDs in HSCW zones.

Numerical study of the impact of make-up air in a residential kitchen on the heating and cooling demands of ULEBs

Ventilation significantly impacts energy consumption in ultra-low-energy buildings (ULEBs). However, in Chinese residential kitchens, the influence of mechanical ventilation formed by range hoods and make-up air systems on energy consumption has received limited attention. This study assesses the heating and cooling demands in ULEBs resulting from kitchen make-up air across different climate zones in China. The results reveal that in natural make-up air mode, there is a substantial rise in annual heating demand in cold and severe cold zones and a notable increase in annual cooling demand in hot summer and warm winter as well as hot summer and cold winter zones. Additionally, the natural make-up air mode often poses challenges in maintaining a satisfactory thermal environment in kitchens during both heating and cooling seasons. Conversely, the mechanical make-up air mode, especially with pretreatment of outdoor air to ensure thermal comfort in kitchens, significantly elevates both annual heating and cooling demands, making it hard for the building to meet the ULEB specifications, particularly in cold and severe cold zones. Furthermore, despite a generally small increase in annual cooling demand, the percentage rise in heating demand often exceeds the ULEB limits, ranging from 12.0% to 36.0%, depending on the climate zone.

Thermal performance assessment of exterior building walls under intermittent air-conditioning operation in China's hot summer and cold winter zone

Optimizing the design and accurately assessing the performance of building envelopes are critical for substantially reducing energy use in the building sector. Existing studies on methods for evaluating the thermal performance of building envelopes have primarily focused on periodic unsteady conditions (often associated with continuous air-conditioning operation). This study aims to investigate the initial transient thermal performance of exterior building envelopes. Specifically, we examined varying insulation distributions considering the hot summer and cold winter zone of China as an example. To simulate real-world conditions, we developed a dynamic hot box facility that mimics both outdoor and indoor environments, enabling the measurement of key parameters of the dynamic thermal process of the wall. We evaluated the thermal response, energy performance, and heat storage metrics of the wall to understand the impact of the insulation distribution and air-conditioning operation modes on the thermal performance of opaque building walls. This assessment covered six intermittent operation stages—four construction structures and two types of building usage—for both summer and winter conditions. The proposed methodology provides a quantitative approach for assessing the dynamic thermal processes of the wall, with the results indicating that the heat transmission of walls during intermittent operation exhibited initial transient characteristics. As a result, thermal performance indices suitable for periodic unsteady conditions could not be directly applied to initial transient conditions. To address this issue, the metrics of daily mean dynamic thermal transmittance and daily mean dynamic thermal resistance were proposed and validated. These metrics accurately reflected the actual fluctuations in total transmission loads, thus providing an accurate rapid index-oriented method for assessing the energy-saving performance of walls. Overall, this study lays the groundwork for evaluating dynamic thermal behaviour of building envelopes.

Strategies for Mitigating Risks of Government-Led Energy Retrofitting Projects in China

Residential energy retrofitting projects in the hot summer and cold winter (HSCW) zone of China face various risks related to project activities, which incur transaction costs (TCs), such as search, negotiation, and monitoring costs. As the leader in project implementation, the Chinese government is responsible for project planning, organisation, and coordination. However, TCs impede the government’s ability to execute risk-related project activities effectively, subsequently increasing the probability of the occurrence of risk. Drawing on transaction cost economics (TCE), this study proposes a theoretical framework to understand the barriers—such as asset specificity, uncertainty, and frequency—that prevent the government from performing project activities and mitigating risks effectively. An artificial neural network (ANN) is applied to verify the hypotheses. The results underscore experience and operational maturity in project activities, cost and time constraints, and the immature retrofitting market as significant impediments to the government’s execution of risk-related activities. Considering the varying roles of the government in reducing different risks, this study concludes by offering policy recommendations to alleviate these activity barriers and mitigate risks. By employing a TCs perspective, this study not only identifies key barriers but also deepens our understanding of risk mitigation mechanisms, providing robust policy insights tailored to the specific regional context of China, thereby enhancing both the execution and the framework of government-led retrofitting projects.

Prediction models for building thermal mass of intermittently heated rooms for balancing energy consumption and indoor thermal comfort

Building thermal mass (BTM) plays an essential role in maintaining a comfortable indoor environment for intermittently heated rooms (IHR). However, how to properly determine the BTM in IHR is unclear for the comprehensive consideration of the opposite effects on the reduction of heating energy consumption (HEC) as well as the improvement of indoor thermal comfort (ITC). This study aims to investigate the comprehensive impact of BTM on the HEC and ITC of IHR in the hot summer and cold winter (HSCW) zone of China using the validated EnergyPlus model. The results indicate that BTM can significantly improve the ITC of IHR, whereas increase HEC. The degree of impact is mainly related to the internal wall heat accumulation coefficient, external wall insulation layer thermal resistance, and outdoor air mean temperature during non-heating periods. Response surface methodology is further employed to quantify the effects of BTM on HEC and ITC of IHR. Based on the predictive models, the range of parameter variations for BTM that simultaneously meet HEC and ITC requirements is obtained. The predictive models can provide a theoretical basis for balancing HEC and ITC in intermittently heated buildings in the HSCW zone of China.

Comparison of thermal comfort between different heating systems and adaptation to different indoor climates in winter.

Individual heating systems, such as the air-source heat pump (ASHP) air-conditioner or floor heating (FH), are usually used by people living in the hot summer and cold winter (HSCW) zone of China to heat indoor climates in the winter. However, little research has been conducted in the HSCW zone on the thermal comfort difference between indoor climates heated by ASHP air-conditioners and those heated by floor heating, as well as how occupants adapt to different indoor climates. We conducted a comparative field experiment in ASHP-heated and FH-heated apartments in Nanjing to investigate how different types of heating systems influence the thermal sensation of occupants, and we conducted a comparative field experiment in ASHP-heated office buildings and naturally ventilated teaching buildings in Shanghai to investigate how occupants adapt to different indoor thermal environments. Indoor environmental parameters and body surface temperatures were measured using instruments, and occupants' thermal sensation, activity level, and clothing were evaluated using the questionnaire. The results show that floor heating improves thermal comfort by raising foot temperature compared to the ASHP air-conditioner, and that occupants become acclimatized to different indoor climates by adjusting neutral operative temperature. According to the findings, there is no need to overheat the indoor environment in the HSCW zone because occupants can adapt to their experienced thermal environment and it is critical to maintain warm foot temperature in the cool/cold indoor environment.

Exploring the dynamic evolutionary trajectories for urban residential building carbon emissions toward 2060: Evidence from the HSCW zone in China

Revealing the long-term development trajectory and peak scenarios of the urban residential building sector is crucial for formulating targeted emission reduction strategies and contributing to achieving the “Dual carbon” target. Given that, significant variables affecting carbon emissions from urban residential buildings (URBCE) at both macro and end-use building levels are identified in this study. Furthermore, an innovative dynamic simulation model is developed by integrating the Monte Carlo simulation model with the Kaya identity model, taking into account the uncertainties of the variables. Subsequently, the long-term evolution trajectories, potential emission peaks, and peak time of the URBCE close to 2060 in China's hot summer and cold winter (HSCW) zone are simulated. Results indicate that URBCE is expected to reach its peak of 272.43 Mt CO2 in 2040 under the baseline scenario. Through the dynamic simulation, the probable peak time of energy consumption in the HSCW zone is 2044 (±1.85), with a peak of 145.42 (±6.91) Mtce, and the possible peak time of carbon emissions is probably 2039 (±1.60), with a peak of 271.93 (±13.40) Mt CO2. According to dynamic sensitivity analysis, carbon emission factor, per capita residential space, and heating energy intensity can promote the peak size and timing. These findings lay a robust foundation for the formulation of regionally specific carbon reduction targets and initiatives.

Relationship between indoor and outdoor temperatures in winter in the Hot Summer and Cold Winter Zone of China - Considering two sources of outdoor temperatures and different indoor heating methods

Thermal exposure is a global issue related to health. Environmental health studies often overlook indoor temperature in comparison to outdoor temperature. Exploring indoor and outdoor temperatures and their relationship is an important part to understand individual heat exposure. The aim of this study is to explore the indoor and outdoor temperatures and their relationship during winter, using weather station and ERA5-Land reanalysis outdoor temperature. Field experiments were conducted in both districting heating and non-district heating dwellings in the Hot Summer and Cold Winter zone of China, taking into account the influence of cold spells. Significant linear correlation was found between the weather station and reanalysis outdoor temperature. The indoor temperature of the district heating group was 8.4 °C higher than that of the non-district heating group. When the outdoor temperature approached 0 °C, the indoor-outdoor temperature difference of the district heating group was twice that of the non-district heating group. The non-district heating group experienced greater fluctuations in indoor temperature during the cold spell. The outdoor temperature could only partially explain indoor temperature, especially under the condition of district heating. The study suggests that outdoor temperature alone is insufficient when evaluating individual thermal exposure in winter. Furthermore, occupants with district heating and non-district heating may have different vulnerabilities, and thermal safeguard strategies in winter are suggested to be designed more targeted. This study may provides insights from the perspective of thermal environment for temperature and health studies.

Research on the heat–humidity coupling transfer model of the CRTS Ⅱ type track slab and its characteristics

After operation for more than 10 years, CRTSⅡtype track slab structures have developed interlayer diseases in continuous extreme high-temperature environments, which are dominated by track slab-CA mortar layer cracking. To reveal the formation mechanism of track slab-CA mortar layer cracking under complicated operation conditions, a heat–humidity coupling transfer model, which is utilized to analyze track slab deformation, was developed. Furthermore, to enhance the precision of the model, we investigated the variation law that regulates relevant parameters of concrete materials with respect to temperature and humidity. Moreover, a testing apparatus was established to validate the accuracy of the transfer model under natural conditions. The analysis revealed that the maximum temperature error in the track slab was 3.33 K, and that the maximum error of relative humidity (RH) was 6.04 %. The distribution characteristics of temperature and humidity fields in the track slab during 10 consecutive rainless days under different seasonal climates in a hot-summer and cold-winter zone (Hangzhou) in China were calculated and analyzed using COMSOL Multiphysics® software. The results indicated that in the distribution of the summer temperature field, the maximum negative temperature gradient could attain -48.67 K/m, and that the maximum positive temperature gradient could attain 76.37 K/m. Moreover, RH values at 10 mm, 20 mm, 30 mm, and 40 mm decreased by 30.85 %, 15.51 %, 9.17 %, and 5.9 %, respectively. In a year, a higher track slab temperature, a greater temperature fluctuation range, and more apparent positive and negative temperature gradients were observed during summer, and the influencing depth of water also attained the maximum value during summer.

Carbon emissions analysis of office building renovation: a case study in China’s hot summer and cold winter zone

Abstract Building renovations in climates characterized by a hot summer and cold winter (HSWC) pose significant challenges in managing carbon emissions due to increased energy demands and material use. Despite advances in sustainable design, the carbon footprint of renovation activities remains a critical concern, particularly regarding the balance between initial emissions from construction and long-term operational efficiency. This study addresses these pressing issues through analyzing the carbon emissions associated with a building complex renovation in an HSWC zone of China. The research examines both the construction stage, where material production and transportation contribute significantly to emissions, and the operational stage, where energy consumption and equipment degradation influence long-term carbon output. By evaluating the effectiveness of renovation strategies and integrating building-integrated photovoltaic systems, this study demonstrates a reduction in annual carbon emissions from 1176.28 tCO2 to 1007.25 tCO2, a reduction of approximately 14.4%. The findings showed that the renovation process would achieve a carbon payback period of 7.46 years and a 24.9%–37.8% reduction in carbon emission intensity. This work underscores the potential significant environmental benefits of innovative materials and efficient design, offering valuable insights for future low-carbon building renovation projects.

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.

Heating transition in the hot summer and cold winter zone of China: District heating or individual heating?

Heating transition in the hot summer and cold winter zone is crucial for China's energy transition towards carbon neutrality. However, future heating solutions for this region remain debated, particularly whether to use district heating. This study proposes an analytical framework for this region to compare district heating with individual heating from a novel energy system perspective. Taking Shanghai as an illustrative case, this study simulates and compares five heating solutions based on energy systems for 2019, 2030 and 2060, considering future trends of energy transition. The results reveal that switching to a clean district heating system from the current individual heating system has the potential to save energy by up to 1.4 % and reduce emissions by up to 3.9 %. Moreover, this strategy could result in a cost reduction of 0.2 % and a biomass saving of 5 % in a carbon-neutral energy system of 2060. Sensitivity analyses confirm the desirability of the clean district heating system for achieving carbon-neutrality in terms of energy and cost savings. Therefore, district heating should not be outside the heating strategy for the hot summer and cold winter zone, and the proposed analytical framework is suggested to be applied in heat planning for this region.

Performance Study of Intermittent Heating Mode Combining Air‐Source Heat Pump with Radiator in Hot Summer and Cold Winter Zones of China

An intermittent heating mode combining air‐source heat pumps and radiators (ASHP‐R) was proposed to meet the time‐sharing heating demand of office workers’ residential buildings in hot summer and cold winter zones. Taking Hefei City as an example, the heating performance of the ASHP‐R system under intermittent operation was experimentally studied from January 18 to 21, 2017. Based on the data on a typical day (January 19), the variation characteristics of thermal parameters and thermal comfort of heating rooms were analyzed, and the economic and environmental benefits of the ASHP‐R system were evaluated. The results show that the water supply temperature of 60°C at the startup stage can rapidly increase the indoor air temperature; in the stable stage, the water supply temperature is 40°C, the indoor air maintains a suitable temperature and relative humidity, and the indoor thermal environment is basically unaffected by the change in outdoor temperature and humidity; the inner surface temperature of the envelope (except the window) presents a similar trend to the indoor air temperature, which reduces the asymmetry of the thermal radiation field around the human body. The air temperature distribution in the human activity area is uniform, and the indoor PMV is in an acceptable, comfortable, and satisfactory state; compared with all‐day continuous heating with an air‐source heat pump, the expense can be saved by 24.4% (by 21.5 yuan/m2) in each heating season, and the system can reduce the emissions of CO2, SO2, and NOX by 988, 29.73, and 14.86 kg/year, respectively. Therefore, the system exhibits good environmental performance and economic performance.

Evaluating Energy Efficiency Potential in Residential Buildings in China’s Hot Summer and Cold Winter Zones

Evaluating Energy Efficiency Potential in Residential Buildings in China’s Hot Summer and Cold Winter Zones