عامل صرفه جویی در انرژی ساختمان در تابستان گرم و زمستان سرد (HSCW) منطقه چین—تاثیر استانداردهای بهره وری انرژی ساختمان و مفاهیم آن

Hot Summer and Cold Winter (HSCW) region plays an important role in China's building energy conservation task due to its high consumption in recent years for both climate and social reasons. National and local building energy standards according to which the buildings are built and operated can affect the building energy consumption to a great extent. This study investigated the energy saving potential in Hot Summer and Cold Winter Zone under different level of energy efficiency standards (China local, China national, and UK standard). Chongqing was taken as an example, and the commercial energy simulation tool eQuest was applied to analyze the building end-use energy. With the existing situation as a baseline, the building energy saving for residential section could achieve 31.5% if the Chinese national standard were satisfied, and the value would further increase to 45.0% and 53.4% when the Chongqing local and UK standard were met. For public buildings, the corresponding energy saving potentials were 62.8%, 67.4% and 75.9%. Parameter sensitivity analysis was conducted. The analysis was able to provide suggestions on energy saving implementation priorities for residential and public buildings. Indications to improve building energy standards and their implementation were also discussed.

Driven by economic resurgence, the global energy consumption increased significantly in recent years. The world's total energy consumption growth reached 5.6% in 2010, which was the highest rate since 1973 (BP plc, 2011). Sharing 20.3% of the global energy consumption, China exceeded the US as the largest energy consumer in the world. The report from British Petroleum Company (BP) in 2012 (BP plc, 2012) indicated that China would account for 67% of global coal growth to 2030 and remained the largest coal consumer. China's building section accounts for 23% of the country's total energy consumption (Building Energy Conservation Research Center of Tsinghua University, 2010). With this trend, the building energy consumption will be 1.3 times higher than the current situation by 2020 (Jiang, 2008). Therefore promoting building energy conservation and carbon emission reduction is crucial and urgent for sustainable social and economic development. The climate condition varies greatly from region to region in China, leading to different regional characteristics of building energy consumption. The Chinese national regulation “Thermal Design Code for Civil Building” (GB 50176-93, 1993) (China Construction Ministry, 1993) defined five climate zones in China according to the mean temperature of the coldest month (tcm) and the hottest month (thm): Severe Cold (SC) Zone (tcm≤−10 °C), Cold (C) Zone (tcm=−10–0 °C), Hot Summer and Cold Winter (HSCW) Zone (tcm=0–10 °C, thm=25–30 °C), Hot Summer and Warm Winter (HSWW) Zone (tcm≥10 °C, thm=25–29 °C) and Temperate (T) Zone (tcm=0–13 °C, thm=18–25 °C). Compared with other climate zones, the Hot Summer and Cold Winter (HSCW) Zone showed special significance in energy conservation task of China due to the following reasons: This area covers 16 provinces, which is nearly half of the nation's total provinces; more than 40% of Chinese population lives in this area, which is less than 20% of Chinese total area, leading to much higher population density than other regions; the economy growth is more rapid than other region, and takes up 48% of the gross domestic product (GDP). The weather data of Typical Meteorological Year (Meteorological information center of China meteorological administration and Tsinghua University, 2005) showed that the average outdoor temperature is 0–10 °C in the coldest month and 25–30 °C in the hottest month. The relative humidity is 70%–80% or even higher all over the year. Together with the long period of summer and winter (summer: from early May to late September, winter: from mid-December to mid-February next year), the building energy consumption in HSCW Zone takes about 45% of the whole country (Yu, 2009). According to China design regulation (GB 50176-93, 1993) and local traditional habits, no central heating system was designed for buildings in the HSCW climate zone. However, people's increased requirement for thermal comfort aggravates the increase of building energy consumption, especially for the heating part. According to the data from China National Bureau of Statistics, energy consumption for heating in HSCW Zone raised 30.6% from 2003 to 2007 (National Bureau of Statistics of China, 2003, National Bureau of Statistics of China, 2004, National Bureau of Statistics of China, 2005, National Bureau of Statistics of China, 2006 and National Bureau of Statistics of China, 2007). Furthermore, the insulation performance of the building envelope was generally very poor. A survey showed that 54% of the existing urban dwellings in HSCW Zone only installed 370 mm depth brick wall with 20 mm cement plaster on both internal and external face of the wall (Fu, 2002), with the heat transfer coefficient of 1.53 W m−2 K−1. These social, climate and policy factors lead to the high building energy consumption and poor indoor thermal comfort in HSCW Zone. The serious building energy consumption situation had raised the government's attention. Researchers and experts from thirteen provinces in China gathered together for an “Integration and demonstration on the key technologies of building energy conservation in Hot Summer and Cold Winter Zone” project, which is a research project funded by “The Twelfth Five Year” national key technology program in 2011 aimed to improve this situation. It was vital to understand the current building energy consumption status and the effect of the national and local energy efficiency standards on energy saving potential in this area. Here, energy saving potential is a percentage value that is calculated between the energy consumption of existing situation and energy consumption of buildings satisfying various levels of standards. Chinese building energy efficiency standards can be divided into three grades, namely national standards (standard number start with GB, which is short for “national standard” in Chinese) released by the departments of standardization administration under the state council; industrial standards (standard number start with JGJ, which is short for “building industry construction” in Chinese) released by Ministry of Housing and Urban–Rural Development of the People's Republic of China and local standards (standard number start with DB, which is short for “local standard” in Chinese) released by local Urban–Rural Development Office. The scope of application decreased from national standard to local standards. National standard fit for the whole country. The industrial standards (JGJ134-2010, 2010) in this study were applied to a specific region and local standards were released for a province or a city. Industrial standards and local standards are generally sticker and are in more detail than national standards. The industrial and local standard must ensure the agreement and consistency with national standard. The specifications in those standards significantly influence the energy consumption of buildings designed accordingly. Therefore the building performance in terms of energy consumption under design requirements should be evaluated to study the effect of different energy standards. There were several approaches in estimating building energy saving potential. Energy audit and energy consumption simulation are the most commonly used methods. In China, the annual energy use per unit area in large scale public buildings with centralized HAVC systems ranged from 119 to 158 kWh/m2 (converted into electricity consumption) (Lam et al., 2008a) by computational simulation with DOE-2.1E. Chen et al. (2009) compared energy consumption characteristics between new and old residential buildings in Shanghai by statistical methods, and the results showed energy consumption by HVAC system took up 11.6% and 16% for new and existing dwellings separately. Wang et al. (2010) used Simplified Building Energy Model (SBEM), the recommended simulation tool in UK building regulation (Building Regulation Approved Document L1A & L2A, 2006), to estimate the energy use of a virtual commercial building in the Severe Cold Zone of China. The results showed that, the building had 29% saving potential according to the UK standard (Building Regulation Approved Document L2A, 2010) compared with Chinese building energy conservation standard (GB 50189-2005, 2005). It was shown that the standard according to which the building was designed presents significant influence on the building energy consumption characteristic. However, most of the literature studies were mostly limited to the energy consumption status of a specific case of residential buildings, without analyzing energy saving potential in detail when different energy saving standards was applied. This paper aimed at estimating the influence of different energy saving standards on building energy consumption in China's HSCW Zone. The energy audit method is significantly time and effort consuming, and is impossible for the current purpose as no buildings was built according to the standards to be discussed. The computer simulation costs less time and is suitable for comparing different scenarios and was used in current study.

This study started with a detailed comparison among building energy efficiency standards and green building rating system in China, UK and the US as those standards can significantly influence the energy consumption of buildings constructed accordingly. The building energy simulation tool eQuest was adopted to estimate the building energy saving potential in HSCW Zone of China according to those building energy standards. The results showed that heating energy consumption took one third of the building energy consumption for residential building in the HSCW Zone, which cannot be simply neglected. The building energy savings in Chongqing could achieve 31.5% and 62.8% for residential and public building sections respectively if the Chinese national standard was satisfied, the energy saving would increase to 45.0% and 62.8% respectively when the Chongqing local standard was met; the value would further increase to 53.4% and 75.9% if the UK standard was satisfied. The significant energy saving by just applying Chinese standard indicated that the priority of building energy conservation in China may be the solid implementation of existing standard, instead of establishing higher energy standard. This study also conducted parameter sensitivity analysis to evaluate the influence of various parameters on total energy consumption. The energy consumption by HVAC system took a dominant fraction in the total building energy consumption. The percentage is 50–70% for residential building and 40–60% for public building. However, the energy consumption of residential building appears to be the most sensitive to Cooling COP of air-conditioning system, followed by lighting power density and window shading coefficient; on the other hand, lighting power density is the most sensitive parameter for public buildings. These results can be useful in providing suggestions for existing building energy conservation renovation. Some additional suggestions for the building energy standard improvement and implementations are: • Benchmark case should be provided in detail in the corresponding energy saving standard to give reference for evaluation; • The illuminance level instead of lighting power density should be used for offices of different grades in standard for public buildings, as higher illuminance level may be achieved with a lower LPD but high illuminance efficiency lighting system. • Effort should be made to encourage case/regional specific energy saving measures, preventing a simple collection of various energy saving technologies in one certified “low energy building”. • Reinforce the implementation of current building energy efficiency standards is of more importance than pursuit of higher level standards in China.