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In previous studies, the concept of degree days has been widely used to indicate heating or cooling energy requirements, but it does not consider the dehumidification effect. In the present study, the concept of dehumidification degree days based on moisture content is used, and the degree days over the past 57 years for temperature decreasing and dehumidification in 4 cities belonging to major climate zones of China are analyzed. The results showed that the number of cooling degree days showed a significant increase (1.2–4.6 days/10 a) in all the selected cities, corresponding to the warming climate. In contrast, the degree days of dehumidification accounted for 19%–45% of the total days in summer and showed significant decreases (2.0–3.7 days/10 a) in the cold, hot summer and cold winter, and hot summer and warm winter climate zones. Comfortable days, i.e., days requiring no cooling and no dehumidification, accounting for 8–45% of the total days in summer, decreased significantly in the extreme cold and cold zones (0.9–1.8 days/10 a) but showed no apparent changes in the hot summer and cold winter and hot summer and warm winter climate zones. This study suggests that energy consumption for cooling increases linearly with climate warming, and only the energy consumed for dehumidification had an apparent decrease. The degree days of dehumidification, as well as those requiring no cooling and no dehumidification, should be fully considered in the capacity design of air-conditioning units, especially air-conditioning systems with temperature- and humidity-independent control (THIC). This study indicates that the assessment of energy consumption for requests for air-conditioning in relation to climate change should be carried out after separating energy consumption for cooling from energy consumption for dehumidification to improve building energy efficiency and indoor comfort. [ABSTRACT FROM AUTHOR]

Cooling energy consumption of buildings is not only used for decreasing temperature, but for dehumidification. Therefore, cooling degree day (CDD) based on only temperature is insufficient for estimating the cooling energy consumption in buildings. In the present study, we aim to propose an efficient climate index (i.e., CDD based on wet bulb temperature [WBT], WCDD) based on the combination of cooling energy consumption in a building and joint probability of temperature and humidity. In addition, the adaptation of the new WCDD was verified in 14 cities of different climate zones in China. The results showed that CDD based on dry bulb temperature (DBT) (DCDD) can only explain 17%–60% of cooling energy consumption, whereas WCDD explaining 86%–97% of cooling energy consumption in the different climate zones. The optimal base WBTs are generally 17.74, 19.44, 21.04 and 22.56°C for the four climate zones, respectively. The present study reveals that WCDD by combining effects of temperature and humidity on cooling energy consumption can be much more efficiently used to estimate the cooling energy consumption compared with DCDD. More importantly, the WCDD is suitable for reflecting the cooling energy consumption for different climate zones. The collaborative changes of temperature and humidity under the conditions of climate change should be fully considered to take measures for decreasing the energy consumption for decreasing temperature and dehumidification. [ABSTRACT FROM AUTHOR]

This paper investigates the climate change impact on cooling energy consumption of office buildings in four major architectural climate zones in China. The results show that there are apparent differences in the responses of monthly or yearly cooling loads to climatic change in different climates. Dominant factors affecting monthly cooling loads change from dry bulb temperature (DBT) to wet bulb temperature (WBT) with the climate zones changing from severe cold to hot. The yearly cooling load was mainly afftectd by DBT in severe cold climate, whereas the WBT had the dominant effect in the other climates. With the continuous warming climate, the yearly cooling load did not rise significantly for any climate zone except for severe cold climate zone where cooling load had a significant increase ( p  < 0.01). More importantly, the cooling load showed a weak decrease in Guangzhou. These results suggest that different measurements for buildings cooling energy conservation should be made in different climate zones. The humidity effect should be fully considered to improve buildings energy efficiency, especially in the hot climate zones. The continuous increase of temperature in the future does not necessarily increase cooling loads of buildings in the cold, hot summer & cold winter and hot summer & warm winter climate zones, and change trendency of humidity in the future need to be considered to predict cooling energy consumption. [ABSTRACT FROM AUTHOR]

Meteorological parameters are the basis for building energy-saving design and operation of Heating, Ventilation and Air Conditioning systems (HVAC). In this study, changes in meteorological parameters of Harbin, Tianjin, Kunming, Shanghai, and Guangzhou, representing the five major climate zones of China, were analyzed to determine the effects of climate change on meteorological parameters. The results demonstrated that outdoor design temperatures for heating or air-conditioning significantly increased in all five climate zones. The increasing rate of design temperatures for both heating and air-conditioning in winter were in the range of 0.2 °C–0.7 °C/decade, and the rate of design temperature for air-conditioning in summer was in the range of 0.1 °C–0.4 °C/decade. The design load was calculated by outdoor design temperature. Compared with the design load during 1961–1990, the heating design load decreased 2.8% and 4.4% in Harbin and Tianjin during 1981–2010, respectively. The design load for air-conditioning in winter decreased 1.7%, 1.4%, 2.4% and 3.2% in Harbin, Tianjin, Shanghai and Guangzhou, respectively. By contrast, design load for air-conditioning in summer during 1981–2010 increased 0.8%, 1.1%, 2.9% and 2.2% in Harbin, Tianjin, Shanghai and Guangzhou, respectively. On average, the effect of climate change on design loads is more intense in winter than summer, which may be beneficial for building energy-saving design. The results in this study suggest that climate change has evident effects on design meteorological parameters and design load. It is necessary to note that responses of design meteorological parameters to climate change are apparently different in five climate zones. Hence, different design strategies for building energy-saving should be considered appropriately according to different climate change characteristics in different climate zones. [ABSTRACT FROM AUTHOR]

ABSTRACT The present paper concerns the impact of climate on building heating energy consumption for different types of energy in Tianjin, a large city in northern China. The results show that heating energy consumption is dominantly related to dry bulb temperature ( DBT), but the impacts vary with energy types and time scales (day, month or year). DBT can explain 97.7% of the coal consumption at different time scales and 83.0-89.7% of the natural gas consumption. DBT can also account for 25% of the daily and monthly heating electricity consumption and 89% of the annual heating electricity consumption. These results suggest that different measures for building energy conservation should be taken because of the differing climate impacts for different energy types. Especially, likely increase in temperature in the future should be considered to improve the energy efficiency of buildings. In addition, different models should be used to predict building energy consumption at different time scales. This would be helpful for energy policy makers and energy providers for adjusting energy use strategies. [ABSTRACT FROM AUTHOR]

Previous studies revealed that building climatic zoning has largely changed in China due to the influence of climate change. However, the possible impacts of changing building climatic zoning on energy consumption for cooling or heating are not clear. In this study, eight representative cities were selected from changed climate zones, and the heating and cooling energy consumption of office and residential buildings of the representative cities under the conditions of the current and new climate zones was simulated to reveal the effect of the climate zone change on building energy consumption. The results showed that there was no heating or cooling energy consumption with the climates changing from hot summer and cold winter (HSCW) and cold (C) to mild (M). Also, no heating energy consumption occurred with the climate zones changing from HSCM to hot summer and warm winter (HSWW), whereas the cooling energy consumption showed a weak decrease. For the climate zones that shifted from severe cold (SC) to C, decreasing heating energy consumption and increasing cooling energy consumption trends were observed, and the total energy use exhibited a decreasing trend. However, in the climate zones changing from C to HSCW, the heating and cooling energy consumption increased, especially for residential buildings (e.g., the heating energy consumption of Zhengzhou and Baoji increased 78.7% and 77.7%, respectively). This study suggests that new climate zones should be fully considered and the new design standard according to the changes of climate zones should be adopted to improve building energy efficiency. The design of residential buildings in the climate zones changing from C to HSCW may not consider the changes of climate zone. [ABSTRACT FROM AUTHOR]

In this paper, 16 cities representing four major architectural climate zones of China were selected, and the heating and cooling loads of office building during the period of 1961–2017 were simulated by using TRNSYS software. Daily extreme heating and cooling loads were determined by percentile methods, and the climate change impact on extreme loads was analyzed. The results showed that the days of extreme heating load of office building significantly decreased in almost all the selected cities, whereas there were no significant changes in the days of extreme cooling load. The daily extreme heating load was dominantly affected by the temperature (R2 = 0.43–0.79), but the daily extreme cooling load was related to multiple climate factors, including temperature, relative humidity, and solar radiation. Single temperature can only explain 3–37% of the changes of daily extreme cooling load, and the combination of multiple climate factors can explain 58–85%. Importantly, the effect of temperature on extreme cooling load showed decrease from the cold to hot climate zones, but the impacts of relative humidity and solar radiation gradually increased. These results suggest that the maximum design capacity of heating systems can properly decrease, and the design capacity of cooling systems may not largely increase with the climate warming. In addition, the combined effect of multiple climate factors rather than the single temperature, as well as the different responses of extreme cooling energy consumption to climate change in different climate zones, should be considered when making measures for improving operating efficiency of air-conditioning system. [ABSTRACT FROM AUTHOR]

Climate plays an important role in heating energy consumption owing to the direct relationship between space heating and changes in meteorological conditions. To quantify the impact, the Transient System Simulation Program software was used to simulate the heating loads of office buildings in Harbin, Tianjin, and Shanghai, representing three major climate zones (i.e., severe cold, cold, and hot summer and cold winter climate zones) in China during 1961-2010. Stepwise multiple linear regression was performed to determine the key climatic parameters influencing heating energy consumption. The results showed that dry bulb temperature (DBT) is the dominant climatic parameter affecting building heating loads in all three climate zones across China during the heating period at daily, monthly, and yearly scales (R2 ≥ 0.86). With the continuous warming climate in winter over the past 50 years, heating loads decreased by 14.2, 7.2, and 7.1 W/m2 in Harbin, Tianjin, and Shanghai, respectively, indicating that the decreasing rate is more apparent in severe cold climate zone. When the DBT increases by 1 °C, the heating loads decrease by 253.1 W/m2 in Harbin, 177.2 W/m2 in Tianjin, and 126.4 W/m2 in Shanghai. These results suggest that the heating energy consumption can be well predicted by the regression models at different temporal scales in different climate conditions owing to the high determination coefficients. In addition, a greater decrease in heating energy consumption in northern severe cold and cold climate zones may efficiently promote the energy saving in these areas with high energy consumption for heating. Particularly, the likely future increase in temperatures should be considered in improving building energy efficiency. [ABSTRACT FROM AUTHOR]

As an important component of building energy consumption, wall heat loss needs to be studied urgently. Wall implanted with heat pipes (WIHP) is one of the latest research hotspots in this field. Firstly, the internal temperature distribution characteristics of WIHP are studied by numerical simulation in this paper. Secondly, the thermal conversion efficiency is proposed to evaluate the utilization of solar energy by WIHP. Finally, the energy saving potential of WIHP in heating season is analyzed. The results show that: (1) WIHP has a significant anisotropic heat transfer characteristic compared with the conventional wall; the average time lag of the inside surface is reduced by 2.3 h, and the average decrement factor is increased by 0.008. (2) The time lag difference between the upper and lower parts of WIHP is 6 h, and the time lag of the WIHP structural layer is increased by 1 h compared with the conventional wall. (3) The heat transfer of heat pipe increases with the increase of solar radiation, but the thermal conversion efficiency decreases. (4) WIHP can decrease the heat loss of the wall by 56% on average, and the cumulative heat loss is reduced by 5.29 kWh/m2. • WIHP has a significant anisotropic heat transfer characteristic. • The thermal conversion efficiency as a new evaluation indicator is proposed. • The thermal conversion efficiency of WIHP decreases with the increase of solar radiation. • The time lag of WIHP inside surface is reduced by 2.3 h. [ABSTRACT FROM AUTHOR]

Building thermal climate (BTC) zoning is important for building energy efficiency. However, previous BTC zoning has been mainly performed at national and regional scales, without sufficient attention to small-scale regions and even less so for terrain-complex regions. Typically, the complex terrain in mountainous areas causes the spatial heterogeneity of city and local climates, which can reduce BTC zoning accuracy if city and local climate variability is not considered. Therefore, this study aims to refine BTC zoning scheme for mountainous areas, by examining the accuracy of refined BTC zoning scheme and analyzing its benefit for building energy efficiency. Chongqing, a mountainous China municipality consisting of 38 districts and towns, was chosen as a representative case to perform BTC zoning scheme refinement. The results indicate that the refined zoning scheme is conducive to improving zoning resolution, coverage, accuracy, and reliability. First, the BTC zones based on China National Standard GB50176-2016 only cover four districts and towns while the zoning types of all other 34 districts and towns are assumed based on spatial proximity. The refined one can determine the zoning types of all 38 districts and towns based on robust quantitative analysis. Second, Chongqing was refined into three BTC zone types, while there were only two BTC zone types in Chongqing Standard DBJ50-102–2010. The zoning types of 21 districts and towns changed, two of which were reclassified to Mild Zone A (MZ_A) from the original Hot Summer and Cold Winter Zone A (HSCWZ_A). The refined zoning scheme can help improve building energy efficiency potential. Based on the refined zoning scheme, the annual heating energy use reduction ranged between 14.0 %–21.7 % over 2011–2020, the annual cooling energy use increase ranged between 4.3 %–7.6 %, and the reduction of energy use for heating and cooling was ∼ 2 %. Overall, this study provides a theoretical and methodological reference to understand BTC zoning refinement in mountainous areas. Based on the refined zoning scheme, all districts and towns in Chongqing can practically adjust their building energy efficiency strategies for better climate adaptation. [ABSTRACT FROM AUTHOR]

This method is based on the measured data of the efficiency of the heat pipe PV/T system under different solar radiation, and the typical meteorological year data, the system efficiency proposed in the existing literature, and the annual distribution of solar radiation in the region where the system located is comprehensively considered, then the annual average efficiency of heat pipe PV/T systems in different regions is obtained, and the annual heat collection and power generation of heat pipe PV/T systems are calculated and analyzed by this method. [Display omitted] • Efficiency of heat pipe PV/T systems under different radiation are tested. • The duration of solar radiation of different intensities in the typical year is statistically analyzed. • Efficiency differences of different radiations and solar radiation distribution are considered comprehensively. • An annual average efficiency evaluation method of heat pipe PV/T systems is proposed. As a passive heat transfer system, the heat pipe is becoming an important way to solve the problem of heat loss and heat accumulation in PV/T systems. However, the evaluation of the annual average efficiency of heat pipe PV/T systems in the existing studies does not consider the efficiency under different solar radiation and the difference in the annual solar radiation distribution in different regions. The purpose of this study is to propose a method for the annual average efficiency evaluation of heat pipe PV/T systems (AEHP method), which comprehensively considers the efficiency differences under different radiation and the distribution of solar radiation of different intensities in the typical year. The calculation results are more accurate, which will promote the reasonable evaluation and engineering application of heat pipe PV/T systems. Firstly, the dimensionless models of different radiation and their performance (photovoltaic efficiency, photothermal efficiency, and comprehensive efficiency) are established by experimental tests on the heat pipe PV/T system in this paper. Secondly, the frequencies and frequency of solar radiation in different intervals of the typical year in major cities of China are analyzed statistically, and the radiation frequency method is proposed. Thirdly, the average efficiencies of heat pipe PV/T systems in the existing literature are obtained by statistical analysis. Combined with the radiation frequency method, an annual average efficiency evaluation method of heat pipe PV/T systems (AEHP method) is proposed. The annual average efficiency of heat pipe PV/T systems in different regions is obtained. Finally, the annual heat collection and power generation of heat pipe PV/T systems are calculated based on the AEHP method, and provide a scientific and reasonable evaluation method for the promotion and application of heat pipe PV/T systems. [ABSTRACT FROM AUTHOR]

Exploring changes of building energy consumption and its relationships with climate can provide basis for energy-saving and carbon emission reduction. Heating and cooling energy consumption of different types of buildings during 1981-2010 in Tianjin city, was simulated by using TRNSYS software. Daily or hourly extreme energy consumption was determined by percentile methods, and the climate impact on extreme energy consumption was analyzed. The results showed that days of extreme heating consumption showed apparent decrease during the recent 30 years for residential and large venue buildings, whereas days of extreme cooling consumption increased in large venue building. No significant variations were found for the days of extreme energy consumption for commercial building, although a decreasing trend in extreme heating energy consumption. Daily extreme energy consumption for large venue building had no relationship with climate parameters, whereas extreme energy consumption for commercial and residential buildings was related to various climate parameters. Further multiple regression analysis suggested heating energy consumption for commercial building was affected by maximum temperature, dry bulb temperature, solar radiation and minimum temperature, which together can explain 71.5 % of the variation of the daily extreme heating energy consumption. The daily extreme cooling energy consumption for commercial building was only related to the wet bulb temperature (R2= 0.382). The daily extreme heating energy consumption for residential building was affected by 4 climate parameters, but the dry bulb temperature had the main impact. The impacts of climate on hourly extreme heating energy consumption has a 1-3 hour delay in all three types of buildings, but no delay was found in the impacts of climate on hourly extreme cooling energy consumption for the selected buildings. [ABSTRACT FROM AUTHOR]

• Relationship among temperature, humidity, AQI and solar radiation are studied. • Four additional parameters are used to modify atmospheric extinction coefficient. • Four additional parameters are used to modify the diffuse radiation ratio. • The modified ASHRAE model is proposed, and its performance is better. In recent years, serious air pollution weakened the solar radiation received near the ground, which leads to a remarkable error between the calculated value of ASHRAE model and the measured data. Therefore, based on the day of year (D) of the existing model, this paper identifies air temperature (T), humidity ratio (d), air quality index (AQI) and relative humidity (φ) as correction parameters to obtain the modified ASHRAE model. Then ASHRAE model and its modified model are compared and analyzed based on the measured data. The results show that the accuracy of modified ASHRAE model is significantly improved compared with the ASHRAE model, and the calculated values of modified ASHRAE model are in good agreement with the measured data. The Nash-Sutcliffe Equation (NSE) is improved by 27.17%, and the root mean square error (RMSE) is reduced by 55.99%. [ABSTRACT FROM AUTHOR]