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Envelope Information
Published in Steve Doty, Commercial Energy Auditing, 2020
Low E (low emissivity) coatings are made from thin layers of metal deposited on one or more surfaces of glass. The result is a partial reflection of infrared waves and a reduction in the transmission of heat between layers; thus improving the SC (SHGF) values of all glass and U-values of multi-pane glass. LowE2 (squared) glass is a thicker layer of metal deposit. For low-E coatings, the soft coating is superior in performance, but is subject to abrasion and so soft LowE is not applied to the outer surfaces. For multi-layered glazing, soft coating on an internal and protected layer is effective. Different types of low E coatings are advantageous in different climates, e.g. “southern Low E” would be designed to keep more heat out, compared to other types that would be designed to keep heat in (cold climates).Different locations of the low E coatings help keep heat out or keep heat in. This is specified on the particular surface the coating is to be applied. The coating applied to the warmer inboard glass panel of a double pane glass keeps radiant energy in during cold weather better than if applied on the colder outer pane—the reverse being true for summer and hot climates.
Energy Efficient Design Strategies for Affordable Housing
Published in AbdulLateef Olanrewaju, Zalina Shari, Zhonghua Gou, Greening Affordable Housing, 2019
The most effective way to cut down the energy consumption of lighting is to maximize the use of daylight. As a critical sustainable strategy for high-performance building, the introduction of daylight not only contributes to substantial energy reduction but also improves the occupants’ health in the physical and psychological sense. The Visible Transmittance (VT), with a value between 0 and 1, is an important variable that measures the percentage of the visible spectrum (390 to 700 nanometers) that pass through the glazing. The higher VT value, the more visible sunlight can be transmitted into the building. However, increasing the sunlight incidence would also mean more solar heat gain, which could cause more energy used for cooling the building. Trade-offs must be made between admitting daylight and controlling solar heat gain. In response to that, glass with low emissivity coating (low-E coating) has been developed to reflect the majority of ultraviolet and infrared light without compromising the level of visible light.
Patterns of Daylight Illumination
Published in Lisa Heschong, Visual Delight in Architecture, 2021
Simple clear glass, manufactured since Roman times, filters out most of the UV and some of the IR in sunlight, while allowing almost all the visible spectrum to pass through. Low-emissivity glass (low-E) reduces the amount of infrared heat that can pass through glass. ‘Selective’ is a term used for glazing material that has been formulated to specifically optimize the amount of illumination measured in lux that passes through a window while reducing all other wavelengths. As a result, many selective glass windows tend to look greenish, since they optimize for those wavelengths to which the human visual system is most sensitive.2
Assessment of polycarbonate material as a sustainable substitute for glazing in hot climates
Published in International Journal of Sustainable Energy, 2023
Mohammed Alhaji Mohammed, Mazin M. Menkabo, Ismail M. Budaiwi
The U-values and solar heat gain coefficients (SHGC) are essential for studying building envelopes, particularly transparent ones such as glass and polycarbonate. These two parameters determine heat transfer and solar transmission through the envelope. Solar Heat Gain Coefficient (SHGC) measures how much solar energy passes through a window, expressed by a ratio of 0–1. It combines the glass solar transmittance and the re-radiated glass-absorbed heat to the indoor space (Liu and Wu 2022). Low emissivity glass has a comparatively low SHGC and high reflectance in the mid-infrared band. Low-e coatings save energy by reflecting thermal radiation from the outside (in summer) and inside (in winter) environments (Yi et al., 2021). Glazings’ total radiation transmitted, reflected, and absorbed is vital in calculating the SHGC. It is affected by the material’s optical properties, solar factor, incident solar radiation, overall heat transfer coefficient (U factor), and temperature difference between the outdoor and indoor environments (Sacht et al. 2021). The U-values and SHGC of all the conventional Glass and polycarbonate assemblies are presented in Table 3.
2000W Blue laser directed energy deposition of AlSi7Mg: process parameters, molten pool characteristics, and appearance defects
Published in Virtual and Physical Prototyping, 2023
Zijue Tang, Qianglong Wei, Zhenyang Gao, Huihui Yang, An Wang, Le Wan, Cheng Luo, Yi Wu, Haowei Wang, Hongze Wang
The characteristics and forming mechanisms of the molten pool images obtained by the paraxial high-speed camera in Figure 2(b) are simpler than that of the coaxial camera. This is due to the fact that the active lighting can avoid the effect of overexposure and varied emissivity. Some key characteristics have been shown in Figure 3. The infrared images of Figure 2(c) can refrain from the interference of flying powders and overexposure. However, the inner region grayscale is smaller than the outer region. Two reasons may cause this phenomenon: Low emissivity of the liquid metal: the liquid with the low emissivity breaks into the slags scovering the molten pool, and the low emissivity causes a small grayscale.High-power laser beam: the high-power laser beam with a special wavelength impacts the optical signal transmission with a wavelength range of 7.5 ∼ 14 μm during monitoring. Similar phenomena can also be found in the references (Yan et al. 2019) and (Doubenskaia et al. 2013).
Development and performance evaluation of a passive solar liquid desiccant regenerator
Published in International Journal of Ambient Energy, 2022
Jignesh R. Mehta, Nirav R. Chaudhari, Shaileshkumar M. Gandhi
In the solar passive regenerator, the heat transfer from liquid desiccant surface to the inner surface of glass only by evaporation. The convective heat transfer between these two surfaces is coupled with evaporative heat transfer and it may not be possible to alter it. Efforts should be made to reduce radiative heat transfer from LD surface to glass, which is undesired as it doesn’t help in moisture removal from LD. LD regeneration takes place at a temperature higher than those encountered in the case of solar water desalination units as LD exerts much lower water vapour pressure. Due to this, the emission loss here would be higher than that of the solar still. So, it would be beneficial to apply selective coating on the basin absorber surface, which has low emissivity for far infrared wavelength. Absorption of solar radiation was increased by laying irregular shape gravels on the absorber surface, allowing less radiation to escape.