[雙語翻譯]節(jié)能建筑外文翻譯--節(jié)能建筑中氣凝膠玻璃的前景（英文）

1、Perspective of aerogel glazings in energy efficient buildingsTao Gao a, b, *, Takeshi Ihara a, c, Steinar Grynning a, d, Bjørn Petter Jelle b, d, Anne Gunnarshaug Lien da Department of Architectural Design, History

2、and Technology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway b Department of Civil and Transport Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway c Takenak

3、a Corporation, Osaka, Japan d Department of Materials and Structures, SINTEF Building and Infrastructure, Trondheim, Norwaya r t i c l e i n f oArticle history:Received 10 August 2015Received in revised form8 October 201

4、5Accepted 9 October 2015Available online 22 October 2015Keywords:Silica aerogelWindowGlazingEnergy efficient buildingEnvironmental impacta b s t r a c tThe application perspective of aerogel glazings in energy efficient

5、buildings has been discussed byevaluating their energy efficiency, process economics, and environmental impact. For such a purpose,prototype aerogel glazing units have been assembled by incorporating aerogel granules int

6、o the air cavityof corresponding double glazing units, which enables an experimental investigation on their physicalproperties and a subsequent numerical simulation on their energy performance. The results show that,comp

7、ared to the double glazing counterparts, aerogel glazings can contribute to about 21% reduction inenergy consumptions related to heating, cooling, and lighting; payback time calculations indicate thatthe return on invest

8、ment of aerogel glazing is about 4.4 years in a cold climate (Oslo, Norway); moreover,the physical properties and energy performance of aerogel glazings can be controlled by modifying theemployed aerogel granules, thus h

9、ighlighting their potential over other glazing technologies for windowretrofitting towards energy efficient buildings. The results also show that aerogel glazings may have alarge environmental impact related to the use o

10、f silica aerogels with high embodied energies and po-tential health, safety and environment hazards, indicating the importance of developing guidelines toregulate the use of aerogel glazings.© 2015 Elsevier Ltd. All

11、 rights reserved.1. IntroductionAs an important building element in modern architecture, windows allow light, solar energy, and fresh air to promulgate the living area and offer an irreplaceable indooreoutdoor interactio

12、n, thus having a huge impact on the occupant comfort. However, the fact that windows are usually made of clear glass may bring with some drawbacks, such as glare and solar overheating, which may degrade the user comfort

13、and increase the energy consumption of buildings [1]. Another issue associated with clear glass windows is their poor thermal insulation performance compared to other building envelope components such as walls or roofs.

14、In general, windows represent a large thermal bridge and can constitute up to 45% of the total energy loss though the building envelope [2]. Consequently, improving the thermal insulation level of windows has without dou

15、bt been an important research topic [1e3]. Highlyinsulating glazing units or windows with U-values (heat transfer coefficient) lower than 0.7 W/(m2K) have been under rapid devel- opment [2]; commercial products such as m

16、ultilayered windows [4,5] and aerogel glazings [6e8] have been sold for a wide range of applications, i.e., for both new buildings and window renovations towards energy efficient buildings. Aerogel glazings are an intere

17、sting glazing technology and may address simultaneously the energy efficiency and user comfort requirement placed on windows [6e9]. Aerogel glazings are architecturally similar to the conventional double glazings, where

18、the air cavity between the two clear glass panes is filled with silica aerogels with low thermal conductivities (about 0.013 and 0.020 W/(mK) for monolithic and granular aerogels, respectively) [8,9]. Aerogel glazings ha

19、ve usually a high level of thermal insu- lation and a typical U-value of about 0.6 W/(m2K) can readily be achieved [6e9]. In practice, due to the weak mechanical strength of monolithic aerogel panes [10], aerogel glazing

20、s are usually assem- bled with aerogel granules, which results in translucent glazing units with improved thermal insulation, enhanced light scattering, and reduced sound transmission [11e14]. Aerogel glazings are of* Co

21、rresponding author. Department of Civil and Transport Engineering, Nor-wegian University of Science and Technology (NTNU), Trondheim, Norway.E-mail address: tao.gao@ntnu.no (T. Gao).Contents lists available at ScienceDir

22、ectBuilding and Environmentjournal homepage: www.elsevier.com/locate/buildenvhttp://dx.doi.org/10.1016/j.buildenv.2015.10.0010360-1323/© 2015 Elsevier Ltd. All rights reserved.Building and Environment 95 (2016) 405e

23、413beam mode in the specular include (8?/h) or specular exclude (8?/ d) geometries. Reflectance spectra were calibrated with a 2.000Labsphere diffuse reflectance standard.2.3. Energy simulationEnergy Plus (version 8) was

24、 used to estimate the energy con- sumption (heating, cooling, and lighting) of an office building located in Oslo. A simplified simulation was used to evaluate the energy performance of different glazing technologies. As

25、 shown in Fig. 3, the simplified office model consisted of one story with a heating floor surface area of 784 m2 and a corresponding heating/ cooling air volume of 3136 m3. Window to wall ratio was set to 32.1% and the t

26、otal window area was 143.8 m2. The windows were equally distributed in the east, south, west, and north directions. The window frames were not considered during the energy calculation (i.e., windows have a 100% glazed ar

27、ea); moreover, window shadings were not considered in order to simplify the comparison. The U-value of the exterior wall was set to 0.16 W/ (m2K). For the lighting energy calculation, four perimeter zones were modeled, a

28、s shown in Fig. 3. When illuminance exceeded 500 lx in a cross point of two diagonal lines of each perimeter zone, artificial lighting was turned off to save the lighting energy. Details of the office model and the relat

29、ed energy calculation were re- ported previously [17,22].3. Results and discussion3.1. Thermal properties of AGUsIncorporating aerogel granules into the cavity of DGUs improves significantly their thermal insulation leve

30、l. As shown in Table 1, the assembled AGUs have a typical U-value of about 1.19 W/(m2K), compared to about 2.86 W/(m2K) for the corresponding DGUs. Such a significant reduction of U-values is obviously related to the emp

31、loyed aerogel granules, which reduce the heat transfer through the corresponding DGUs. It is known that, for DGUs, the heat transfer is through conduction (~17%), convection (~17%), and thermal radiation (~66%) [11]; con

32、sequently, every individual contribution has to be minimized to achieve thermally insulating glazing units with lower U-values. First of all, the presence of aer- ogel granules inside the air cavity will reduce the condu

33、ctive heattransfer due to the lower thermal conductivity of aerogels (~0.020 W/(mK)) than that of the normal air (~0.026 W/(mK)). Secondly, small aerogel granules can suppress the airflow loops and reduce significantly t

34、he convective heat transfer within the air cavity of DGUs, which has previously been discussed by Ihara et al. [23]. Thirdly, silica has a relatively larger extinction coefficient than that of air [24], which helps to re

35、duce the corresponding radiative heat transfer. With the aforementioned discussions, the better thermal performance of AGUs compared to the corresponding DGUs (Table 1) is understandable. AGUs have a rather stable therma

36、l performance when compared to that of the corresponding DGUs. For example, horizontal DGUs usually have a larger U-value than that of vertically placed DGUs due to the convection effect in the air cavity. In contrast, a

37、 previous study indicated that the measured U-values of AGUs are almost the same regardless of how AGUs are placed [23]. In this regard, AGUs can be integrated into the building envelope as either conventional vertical w

38、indows or tilted roof windows without changing their thermal insulation performance. This may enable AGUs as a multifunctional building envelope component from a viewpoint of architectural design and energy simulation. A

39、nother interesting feature of AGUs is that their thermal per- formance can be readily controlled by modifying the employed aerogel materials, as revealed by Fig. 4. On the one hand, AGUs with lower U-values (i.e., better

40、 thermal insulation performance) can be achieved with thicker aerogel granule layers. For example, for a U- value of about 0.62 W/(m2K), the corresponding AGUs can be assembled with a 30-mm-thick layer of aerogel granule

41、s with a thermal conductivity of about 0.020 W/(mK); whereas increasing the aerogel layer thickness up to 60 mm will result in an AGU with a U-value of about 0.33 W/(m2K). On the other hand, AGUs with better thermal insu

42、lation performance can also be achieved by employing aerogel granules with lower thermal conductivities. For example, at a given insulation layer thickness of about 30 mm, the U-value of the corresponding AGUs would be 0

43、.67, 0.62, and 0.54 W/(m2K) if the thermal conductivity of the employed aerogel granules is 0.023, 0.020, and 0.018 W/(mK), respectively. Employing aerogel granules with lower thermal conductivity is preferred for high p

44、erformance AGUs with improved process economics (i.e., reduced material use and cost). Since the thermal conductivity of aerogel granules may vary with many factors such as porosity, particle size and packing density [9]