تجزیه و تحلیل حساسیت از عملکرد انرژی برای پوشش بلند مسکونی در تابستان گرم و زمستان سرد منطقه از چین

Building envelopes are the interface between indoor and outdoor environment which affect the indoor heat gain and heat loss in the design of sustainable buildings. It is beneficial to identify the most important design parameters in order to develop more efficiently alternative design solutions. This study performs a sensitivity analysis of energy performance to assess the impacts of envelope design parameters and identify the important characteristics. Index of evaluation on energy and thermal performance (EETP) for residential envelops is introduced for the calculation of energy use. High-rise residential buildings with small and large window-to-wall ratio (WWR) are selected in four cities of hot summer and cold winter zone of China. Eight design parameters of envelope are analyzed and compared. Results show that: in cooling season, shading coefficient and WWR are the most vital factors; in heating season, wall heat-transfer coefficient and shape coefficient have crucial effects when WWRs are 25% and 50%, respectively; for annual energy use, wall heat-transfer coefficient and WWR are the most sensitive when WWRs are 25% and 50%, respectively; whether the WWR is small or large, solar absorptances of wall and roof and heat-transfer coefficient of roof have very slight effects.

Buildings, energy and environment are the key issues facing the building professions worldwide, and energy is a key element in the overall effort to achieve sustainable development [1]. In hot summer and cold winter zone of China, energy use of residential buildings has been increasing sharply over the last 10 years; there is a growing concern about the energy use in residential buildings. The climate here is extremely severe in both summer and winter, the average temperatures of the hottest month and coldest month are 25–30 °C and 2–7 °C respectively, which are about 2 °C higher and 8 °C lower than the same latitude all over the world [2]. Additionally, the thermal-insulating level for residential buildings is extremely poor. Single-clear glazing, clay brick wall and non-insulated roof are wildly used in the existing residential buildings, and more than 95% of new ones are high energy intensity buildings [3]. With the improvement of people's living standard, the numbers of air-conditioned buildings and the amount of energy use in these buildings have increased dramatically in recent years. Building envelopes are the interface between indoor and outdoor environment which affect the indoor heat gain and heat loss. One way to alleviate the ever growing demand for energy is to have more energy-efficient building designs and proper building energy conservation measures [4]. The national standard for energy efficiency of residential buildings is launched with the target of a 50% reduction in energy use compared with that of a base building under the same indoor thermal conditions, about 30% of reduction is projected to be achieved by building envelope [5]. Energy conservation of residential envelope is therefore becoming one of the major issues of concern to the local government. In an energy-efficient building, heat gain and loss through building envelope should be minimized [6]. The control of thermal performance of the building envelope is an important part of the overall scheme for building energy conservation. If the relationships and relative importance of envelope design parameters are well understood, we will be able to achieve the optimum building energy performance through proper selection of design variables. A sensitivity analysis makes it possible to identify the sensitive parameters in relation to energy performance and optimization of sustainable building. In the field of building energy models, combining sensitivity analysis with simulation tools can be useful as it helps to rank the input parameters and then to select the most important ones to be considered. This information is useful to help managers and engineers identify energy saving potentials and evaluate energy performance of the energy efficiency measures to be implemented. Different parameters lead to various optimal results directly; some researchers have studied the sensitivity analysis of energy and thermal performance of the buildings. Lam and Hui [7] examined the sensitivity of energy performance of office buildings in Hong Kong, 12 input parameters were studied which were categorized into building load, HVAC system and HVAC refrigeration plant. It has been found that the annual building energy use and peak design loads were sensitive to the measures affecting internal loads, window system, temperature set points and HVAC plant efficiencies. Tavares and Martins [8] conducted a sensitivity analysis of several parameters of a public building at the center region of Portugal, relating to wall and roof structure and materials, window frames, shading system, infiltration, mechanical ventilation, HVAC system, design temperatures and thermostats set-point. Corrado and Mechri [9] analyzed the heating and cooling needs of a two-storey single-family house in Turin with sensitivity analysis to calculate the uncertainties in energy rating. The sensitivity analysis showed that only 5 of 129 factors were responsible for most of these uncertainties: the indoor temperature, the air change rate, the number of occupants, the metabolism rate and the equipment heat gains. Heiselberg et al. [10] identified the most important design parameters in relation to a building's performance with focus on the optimization of an office building in Denmark through sensitivity analysis. They found that the mechanical ventilation rate in winter and lighting control were the most influential parameters in an office building. Breesch and Janssens [11] proposed the uncertainty and sensitivity analysis to evaluate the performance of different natural night ventilation designs and their relation to building design using the simulation code of TRNSYS-COMIS. Tian and Wilde [12] explored the uncertainties and sensitivity coefficients in the prediction of thermal performance of the buildings under climate changes, and a case study focusing on an air-conditioned university building at the campus of the authors was presented. Wang et al. [13] carried out the sensitivity analysis to guide the optimal design of the building cooling heating and power system and improve the robustness of the optimal results, the influences of the technical, economic and environmental parameters on the optimal results were analyzed and compared. Several studies have investigated the energy performance in sustainable design of residential buildings in hot summer and cold winter zone of China. These studies largely focused on the energy savings potential and energy performance of certain measures using energy simulation programs, such as the effects of shape coefficient [14] and [15] and WWR [16] and [17] on annual energy use, the relationship between insulation thickness and air conditioning load [18], the determination of optimum insulation thickness over the lifetime [19] and [20], the thermal performance of external windows/skylights [21] and [22] and shading system [23]; some focused on the low-energy envelope design and the comparison of energy performance based on a reference building using some strategies [24], [25] and [26]. There are few studies published about the sensitivity analysis of envelope design parameters on the overall building energy performance in hot summer and cold winter zone, which can quantitatively explain the effect of each parameter of building envelope on the energy use under given circumstances and identify the important design parameters in order to reduce the energy use in residential building. In response to the growing concerns about energy conservation in residential envelopes, some evaluation indices on the energy and thermal performance of envelopes have been carried out, which are able to help ensure cost-effective energy efficiency opportunities incorporated into the new buildings and achieve the sustainable building designs, such as the Overall Thermal Transfer Value (OTTV) for wall and roof [27] and the Envelope Thermal Transfer Value (ETTV) [28]. An index of evaluation on energy and thermal performance (EETP) for residential envelopes was proposed by our earlier work, which can be used as a simplified energy calculation method [29]. The primary aim of the present work is to conduct the sensitivity analysis of energy performance for high-rise residential envelope in hot summer and cold winter zone of China by a series of energy use calculations using EETP index, which delivers the pieces of information to architects and engineers involved in the design of high-rise residential building envelopes. The cities selected to represent A, B, C and D sub-zones are shown in Table 1; the present work involved the followings: (1) The sensitivity analysis method is presented to determine the contribution of an individual design parameter to the energy performance of the envelope design solution; EETP index is introduced for the calculation of cooling and heating energy use. The high-rise base case building with small and large WWRs is described. (2) Sensitivity analysis of energy performance for high-rise residential buildings in hot summer and cold winter zone is performed, the sensitivity coefficient is calculated and analyzed by observing the response of annual building energy use calculated by EETP index due to the changes in input envelope design variables, including the building shape coefficient, WWR, heat-transfer coefficients of roof, walls and windows, solar absorptances of external wall and roof and shading coefficient of glazing. (3) The impacts of input envelope design parameters are estimated and the important characteristics of input variables are identified from point of view of annual building energy use, the energy saving potentials of energy conservation measures are illustrated. Table 1. The selected cities in hot summer and cold winter zone. Subzone Determination of subzones Typical city A 1000 °C d ≤ HDD18 < 2000 °C d, 50 °C d < CDD26 ≤ 150 °C d Shanghai B 1000 °C d ≤ HDD18 < 2000 °C d, 150 °C d < CDD26 ≤ 300 °C d Changsha C 600 °C d ≤ HDD18 < 1000 °C d, 100 °C d < CDD26 ≤ 300 °C d Shaoguan D 1000 °C d ≤ HDD18 < 2000 °C d, CDD26 ≤ 50 °C d Chengdu

The present work intends to identify the important design parameters to bring more efficiently alternative design solutions or achieve optimized design solutions for residential envelope. In this study, the high-rise point blocks with small and large WWRs are selected in hot summer and cold winter zone of China; the effects of envelope design parameters on cooling, heating and yearly energy use are studied using EETP index in Shanghai, Changsha, Shaoguan and Chengdu of this zone; the sensitivity analysis of energy performance for high-rise residential envelope is investigated; eight envelope design parameters are analyzed and compared; this analysis leads to the following conclusions. In cooling season, shading coefficient and WWR are the two vital factors on cooling energy use for residential envelope, the influence degree become more notable with the increase of the window area. Sensitivity coefficients of shading coefficient in four cities vary from 41.4% to 44.3% for WWR of 25% and from 60.8% to 85.9% for WWR of 50%; those of WWR vary from 38.2% to 42.7% for WWR of 25% and from 52.3% to 88.5% for WWR of 50%. The adjustable shading system is advocated which can be adjusted according to the requirement and taken-down in winter. While solar absorptances of wall and roof, and heat-transfer coefficients of roof and window have slight impacts on the cooling energy use. In heating season, the sensitivity coefficients of heat-transfer coefficients of roof, wall and window, and the shape coefficient on heating energy use are positive. The shading coefficient has the maximum negative effect on heating energy use, the sensitivity coefficients vary from −10.4% to −21.8% when the WWR is 25%, and from −12.8 to −76.8% when the WWR is 50%. The sensitivity coefficients of solar absorptance on heating energy use are negative and the effect can be ignored. When the WWR is 25%, the sensitivity coefficients of wall heat-transfer coefficient are the highest which are 50%, 46%, 61% and 40% in Shanghai, Changsha, Shaoguan and Chengdu, respectively; the influence of building shape coefficient on heating energy use is secondary to wall heat-transfer coefficient. When the WWR is 50%, building shape coefficient is the most important factor, the sensitivity coefficients are between 54.2% and 95.5% in four cities, the effect of wall heat-transfer coefficient on heating energy use is reduced and that of window heat-transfer coefficient is increased. For the whole year, when the WWR is 25%, the wall heat-transfer coefficient is the most sensitive factor considering both the cooling and the heating energy use in Shanghai, Changsha and Chengdu, and ranks the second in Shaoguan city; the sensitivity coefficients of wall heat-transfer coefficient range from 24.4% to 35.8% in four cities, so employing insulation material is an effective way to reduce the heat-transfer coefficient; the effect of building shape coefficient is secondary to wall heat-transfer coefficient except Shaoguan city, the sensitivity coefficients are from 21.7% to 32.0% in the four cities; WWR is the third key parameter in Shanghai, Changsha and Chengdu, and is the most important one in Chengdu. When the large WWR of 50% is adopted in the building, the change of WWR is the most sensitive on yearly energy use in Shanghai, Changsha and Shaoguan, and is the second sensitive in Chengdu, the sensitivity coefficients in turn are 36.9%, 39.7%, 45.7%and 34.8%; the effect of building shape coefficient is secondary to WWR except Chengdu city, the sensitivity coefficients are from 27.6% to 44.3% in the four cities; the overall shading coefficient shows more important effect with the increase of window area, especially in Shaoguan; the sensitivity coefficient of wall heat-transfer coefficient is basically the same with that of window heat-transfer coefficient. Whether the WWR is 25% or 50%, the effects of roof heat-transfer coefficient and solar absorptances of wall and roof on yearly energy use are very slight. The results give a general indication which design parameters are the more important ones to change to reduce the energy use for high-rise point block. The information can help designers get some ideas about the potential energy savings and evaluate the energy performance of prospective energy conservation measures.