Browsing by Author "Kecebas, M. A."

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Passive radiative cooling design with broadband optical thin-film filters
(Elsevier, 2017-09) Kecebas, M. A.; Mengüç, Mustafa Pınar; Kosar, A.; Sendur, K.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
The operation of most electronic semiconductor devices suffers from the self-generated heat. In the case of photovoltaic or thermos-photovoltaic cells, their exposure to sun or high temperature sources make them get warm beyond the desired operating conditions. In both incidences, the solution strategy requires effective radiative cooling process, i.e., by selective absorption and emission in predetermined spectral windows. In this study, we outline two approaches for alternative 2D thin film coatings, which can enhance the passive thermal management for application to electronic equipment. Most traditional techniques use a metallic (silver) layer because of their high reflectivity, although they display strong absorption in the visible and near-infrared spectrums. We show that strong absorption in the visible and near-infrared spectrums due to a metallic layer can be avoided by repetitive high index-low index periodic layers and broadband reflection in visible and near-infrared spectrums can still be achieved. These modifications increase the average reflectance in the visible and near-infrared spectrums by 3–4%, which increases the cooling power by at least 35 W/m2. We also show that the performance of radiative cooling can be enhanced by inserting an Al2O3 film (which has strong absorption in the 8–13 µm spectrum, and does not absorb in the visible and near-infrared) within conventional coating structures. These two approaches enhance the cooling power of passive radiative cooling systems from the typical reported values of 40 W/m2–100 W/m2 and 65 W/m2 levels respectively.
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Spectrally selective filter design for passive radiative cooling
(The Optical Society, 2020-04-01) Kecebas, M. A.; Mengüç, Mustafa Pınar; Kosar, A.; Sendur, K.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Radiative cooling is potentially one of the most innovative approaches to reducing energy density in buildings and industry, as well as achieving higher levels of energy efficiency. Several studies have reported the design of spectrally selective layered structures for daytime passive radiative cooling. However, a comprehensive design of such systems requires the spectral behavior of different materials and radiative heat transfer mechanisms to be addressed together. Here, we introduce a design methodology for daytime passive radiative cooling with thin film filters which accounts for the spectral tailoring at the visible and infrared spectrum. The major difference of this method is that it does not require a predefined target ideal emittance. The results show that higher cooling powers are possible compared to the previously reported thin-film structures, which were designed from a purely spectral perspective. The underlying mechanisms of the resulting spectral profiles, which give rise to improved performance, are investigated by wave impedance analysis. Cooling powers up to 100 W/m(2) are obtained with seven layers on Ag. The findings of this study indicate that structures with better performance in terms of cooling powers and temperature reduction rates can be obtained following the procedure discussed.
Metadata only
Spectrally selective filter design for passive radiative cooling
(The Optical Society, 2020-04-01) Kecebas, M. A.; Mengüç, Mustafa Pınar; Kosar, A.; Sendur, K.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Radiative cooling is potentially one of the most innovative approaches to reducing energy density in buildings and industry, as well as achieving higher levels of energy efficiency. Several studies have reported the design of spectrally selective layered structures for daytime passive radiative cooling. However, a comprehensive design of such systems requires the spectral behavior of different materials and radiative heat transfer mechanisms to be addressed together. Here, we introduce a design methodology for daytime passive radiative cooling with thin film filters which accounts for the spectral tailoring at the visible and infrared spectrum. The major difference of this method is that it does not require a predefined target ideal emittance. The results show that higher cooling powers are possible compared to the previously reported thin-film structures, which were designed from a purely spectral perspective. The underlying mechanisms of the resulting spectral profiles, which give rise to improved performance, are investigated by wave impedance analysis. Cooling powers up to 100 W/m(2) are obtained with seven layers on Ag. The findings of this study indicate that structures with better performance in terms of cooling powers and temperature reduction rates can be obtained following the procedure discussed.