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Auditing, Planning, and Retrofitting
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
To choose the right material, be sure that the solar reflectance of the coating is 65% or higher when it is new and that its thermal emittance is 80 to 90% or more. Thermal emittance is the ability of a material to release absorbed heat. A surface on a roof that has a high thermal emittance will absorb heat from the sun and then radiate it back into the atmosphere more readily than a surface with a low thermal emittance. Even just applying white industrial grade paint to the exterior ductwork, doors, window louvers, or awnings can help reduce heat gain on a home. Installing solar film, louvers, or shading on the south, west, or east facing windows can have the same effect. Appendix A gives information on what measures are allowed under the weatherization program. In the private arena, the clients decide what they will pay for.
Energy and the First Law of Thermodynamics
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
There are two properties that will influence the surface temperature of opaque materials under the sun, one is solar reflectance and the other is thermal emittance. Solar reflectance is the portion of solar radiation that is reflected from a surface. The thermal emittance (ε), on the other hand, is the rate at which a surface radiates energy as compared to that of a black body operating at the same temperature.
Material and Construction
Published in Vishal Garg, Jyotirmay Mathur, Aviruch Bhatia, Building Energy Simulation, 2020
Vishal Garg, Jyotirmay Mathur, Aviruch Bhatia
As radiant barriers reduce the radiant heat transfer, a decrease in thermal emittance reduces energy consumption. Exercise 3.6Repeat this tutorial for the DUBAI INTERNATIONAL, United Arab Emirates weather location (Table 3.11).
Experimental analysis and evaluation of a vacuum enclosed concentrated solar thermoelectric generator coupled with a spectrally selective absorber coating
Published in International Journal of Sustainable Energy, 2018
Phalanis Cheruvu, V. Praveen Kumar, Harish C. Barshilia
A typical STEG system design predominantly consists of three major subsystems namely the optical concentrator, the collector surface and the integrated thermoelectric material. The operation and efficiency of the entire system varies depending on the working conditions of these three subsystems. The optical concentrator (e.g. Fresnel lens) increases the average solar irradiation flux falling on the absorber coating thus contributing in attaining higher hot-side temperatures (Kraemer et al. 2011). The collector surface modified by spectrally selective absorber coatings is designed so as to achieve high absorbance of the useful solar radiation (between 0.4 and 2.5 μm) at the same time have less thermal emittance in infrared range (2.5–30 μm) (Stair, Johnston, and Bagg 1954), which improves the overall efficiency of the absorber surface (Chebotayev et al. 1979; Selvakumar and Barshilia 2012).
The microstructure and optical properties of novel Al2O3–Ag composite coating
Published in Surface Engineering, 2021
S. Kamali, F. Dehghan, H. S. Mardanpour, S. Alirezaei
The development of solar cells as a green technology has been paid attention in recent years. For instance, an ideal blackbody with zero reflection and transmission can absorb all incident radiation, and it can be a suitable choice for solar absorbers. Blackbody in a thermal equilibrium state has equal absorption and emission in every wavelength according to the second law of thermodynamics. The unique optical properties of the blackbodies made them suitable for several applications such as solar energy collectors, stray light interruption, thermal detectors, and pyroelectric sensors [16,17]. For example, the surfaces of these materials are suitable for radiative cooling of buildings because of very low reflectance and a high thermal emittance. Many methods have been used to improve solar energy harvesting. One of the most and effective methods to achieve this goal is fabricating the porous structures [3,18]. Anodizing is a process which makes the aluminium sheets or tubes suitable for solar absorbers. It was found that the size of columnar pores and the thickness of the anodic film could strongly affect the emissivity of solar radiation. One of the most important factors on the morphology and structure of the anodic film is the type of electrolyte. For example, Pavlovi and Ignatiev [19] studied the effect of the acidic solution on the optical and microstructural properties of the conventional anodic film on aluminium substrate. They reported that the emissivity of the anodic film synthesized in sulphuric acid was higher than that of chromic acid and phosphoric acid, because of the larger wall volume of the anodic film structure.