The Experts below are selected from a list of 45327 Experts worldwide ranked by ideXlab platform
Eden Rephaeli - One of the best experts on this subject based on the ideXlab platform.
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passive radiative cooling below Ambient Air Temperature under direct sunlight
Nature, 2014Co-Authors: Aaswath Raman, Marc Abou Anoma, Linxiao Zhu, Eden Rephaeli, Shanhui FanAbstract:A multilayer photonic structure is described that strongly reflects incident sunlight while emitting heat selectively through an atmospheric transparency window to outer space; this leads to passive cooling under direct sunlight of 5 degrees Celsius below Ambient Air Temperature, which has potential applications in Air-conditioning and energy efficiency.
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Passive radiative cooling below Ambient Air Temperature under direct sunlight
Nature, 2014Co-Authors: Aaswath P. Raman, Marc Abou Anoma, Eden RephaeliAbstract:A multilayer photonic structure is described that strongly reflects incident sunlight while emitting heat selectively through an atmospheric transparency window to outer space; this leads to passive cooling under direct sunlight of 5 degrees Celsius below Ambient Air Temperature, which has potential applications in Air-conditioning and energy efficiency. Shanhui Fan and colleagues demonstrate a practical radiative cooling device that is effective in direct sunlight, requires only sky access and needs no electricity input. The device operates by — whilst avoiding sunlight absorption — radiating heat into the cold darkness of space via what is known as the atmospheric infrared transparency window, wavelengths of 8 and 13 micrometres. The device differs from previous designs in that it can function in full daylight. The authors have designed and fabricated a multilayered photonic structure that reflects 97% of incoming sunlight while emitting strongly in the atmospheric transparency window. When exposed to direct sun, the device cools to a Temperature 5 °C below Ambient with a cooling power of 40 watts per square metre. The authors calculate potential annual energy savings for a typical roof covered with this passive cooling system to be equivalent to 120,000 kilowatt hours. Cooling is a significant end-use of energy globally and a major driver of peak electricity demand. Air conditioning, for example, accounts for nearly fifteen per cent of the primary energy used by buildings in the United States^ 1 . A passive cooling strategy that cools without any electricity input could therefore have a significant impact on global energy consumption. To achieve cooling one needs to be able to reach and maintain a Temperature below that of the Ambient Air. At night, passive cooling below Ambient Air Temperature has been demonstrated using a technique known as radiative cooling, in which a device exposed to the sky is used to radiate heat to outer space through a transparency window in the atmosphere between 8 and 13 micrometres^ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 . Peak cooling demand, however, occurs during the daytime. Daytime radiative cooling to a Temperature below Ambient of a surface under direct sunlight has not been achieved^ 3 , 4 , 12 , 13 because sky access during the day results in heating of the radiative cooler by the Sun. Here, we experimentally demonstrate radiative cooling to nearly 5 degrees Celsius below the Ambient Air Temperature under direct sunlight. Using a thermal photonic approach^ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , we introduce an integrated photonic solar reflector and thermal emitter consisting of seven layers of HfO_2 and SiO_2 that reflects 97 per cent of incident sunlight while emitting strongly and selectively in the atmospheric transparency window. When exposed to direct sunlight exceeding 850 watts per square metre on a rooftop, the photonic radiative cooler cools to 4.9 degrees Celsius below Ambient Air Temperature, and has a cooling power of 40.1 watts per square metre at Ambient Air Temperature. These results demonstrate that a tailored, photonic approach can fundamentally enable new technological possibilities for energy efficiency. Further, the cold darkness of the Universe can be used as a renewable thermodynamic resource, even during the hottest hours of the day.
Maria Elivânia Vieira Almeida - One of the best experts on this subject based on the ideXlab platform.
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Models to predict both sensible and latent heat transfer in the respiratory tract of Morada Nova sheep under semiarid tropical environment
International Journal of Biometeorology, 2017Co-Authors: Vinícius Carvalho Fonseca, Edilson Paes Saraiva, Josinaldo Araújo Silva, Edgard Cavalcanti Pimenta Filho, Carolina Cardoso Nagib Nascimento, Alex Sandro Campos Maia, Walter Esfraim Pereira, Maria Elivânia Vieira AlmeidaAbstract:The aim of this study was to build a prediction model both sensible and latent heat transfer by respiratory tract for Morada Nova sheep under field conditions in a semiarid tropical environment, using easily measured physiological and environmental parameters. Twelve dry Morada Nova ewes with an average of 3 ± 1.2 years old and average body weight of 32.76 ± 3.72 kg were used in a Latin square design 12 × 12 (12 days of records and 12 schedules). Tidal volume, respiratory rate, expired Air Temperature, and partial vapor pressure of the expired Air were obtained from the respiratory facial mask and using a physiological measurement system. Ewes were evaluated from 0700 to 1900 h in each day under shade. A simple nonlinear model to estimate tidal volume as a function of respiratory rate was developed. Equation to estimate the expired Air Temperature was built, and the Ambient Air Temperature was the best predictor together with relative humidity and Ambient vapor pressure. In naturalized Morada Nova sheep, respiratory convection seems to be a mechanism of heat transfer of minor importance even under mild Air Temperature. Evaporation from the respiratory system increased together with Ambient Air Temperature. At Ambient Air Temperature, up to 35 °C respiratory evaporation accounted 90 % of the total heat lost by respiratory system, on average. Models presented here allow to estimate the heat flow from the respiratory tract for Morada Nova sheep bred in tropical region, using easily measured physiological and environmental traits as respiratory rate, Ambient Air Temperature, and relative humidity.
P K Mcgregor - One of the best experts on this subject based on the ideXlab platform.
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Season and Ambient Air Temperature influence the distribution of mites (Proctophyllodes stylifer) across the wings of blue tits (Parus caeruleus)
Canadian Journal of Zoology, 2000Co-Authors: P R Wiles, J Cameron, J M Behnke, I R Hartley, F S Gilbert, P K McgregorAbstract:Changes in the distribution of the wing-feather mite Proctophyllodes stylifer (Buckholz 1869) on the flight feathers of blue tits (Parus caeruleus) were studied throughout the seasons and in relation to Ambient Air Temperature at three combinations of study sites (Lancashire, West Midlands, and South Midlands). We tested the hypotheses that the distribution of mites is influenced in part by season and Ambient Air Temperature. In the winter months mites clustered predominantly on the tertiary feathers, whereas in late spring, summer, and autumn, mite-infestation scores were higher on the proximal primary and secondary feathers. Three approaches were employed to determine whether this seasonal redistribution of mites arose as a response to changes in microclimate, probably Ambient Air Temperature, rather than to season per se. Firstly, meteorological data for the Lancashire study sites, and our own monitoring of the precise Air Temperature at the time of handling and inspection at the West Midlands study sites, enabled us to establish a link between distribution pattern and Ambient Temperature. Secondly, limited observations on the distribution of mites on birds recaptured when Ambient Air Temperatures differed by 5°C or more between first and second nettings, one Temperature being below 10°C and the other above, supported the idea that the change in distribution was associated with Air Temperature. Finally, the results of a small experiment in which heavily infested birds caught on a day when Air Temperatures ranged from 9 to 11°C were taken indoors and temporarily subjected to a higher Ambient Air Temperature (20 min) prior to re-inspection and release also confirmed that mite movement was associated with the Temperature of their environment. We conclude that the seasonal changes in distribution were driven by microclimatic changes, in part by Temperature.
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Wing feather mite infestations on passerine birds : season and Ambient Air Temperature influence the distribution of Proctophyllodes stylifer across the wings of blue tits (Parus caeruleus).
2000Co-Authors: Roy Wiles, J Cameron, J M Behnke, I R Hartley, Francis Gilbert, P K McgregorAbstract:Changes in the distribution of the wing-feather mite Proctophyllodes stylifer (Buckholz 1869) on the flight feathers of blue tits (Parus caeruleus) were studied throughout the seasons and in relation to Ambient Air Temperature at three combinations of study sites (Lancashire, West Midlands, and South Midlands). We tested the hypotheses that the distribution of mites is influenced in part by season and Ambient Air Temperature. In the winter months mites clustered predominantly on the tertiary feathers, whereas in late spring, summer, and autumn, mite-infestation scores were higher on the proximal primary and secondary feathers. Three approaches were employed to determine whether this seasonal redistribution of mites arose as a response to changes in microclimate, probably Ambient Air Temperature, rather than to season per se. Firstly, meteorological data for the Lancashire study sites, and our own monitoring of the precise Air Temperature at the time of handling and inspection at the West Midlands study sites, enabled us to establish a link between distribution pattern and Ambient Temperature. Secondly, limited observations on the distribution of mites on birds recaptured when Ambient Air Temperatures differed by 5°C or more between first and second nettings, one Temperature being below 10°C and the other above, supported the idea that the change in distribution was associated with Air Temperature. Finally, the results of a small experiment in which heavily infested birds caught on a day when Air Temperatures ranged from 9 to 11°C were taken indoors and temporarily subjected to a higher Ambient Air Temperature (20 min) prior to re-inspection and release also confirmed that mite movement was associated with the Temperature of their environment. We conclude that the seasonal changes in distribution were driven by microclimatic changes, in part by Temperature.
Marc Abou Anoma - One of the best experts on this subject based on the ideXlab platform.
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passive radiative cooling below Ambient Air Temperature under direct sunlight
Nature, 2014Co-Authors: Aaswath Raman, Marc Abou Anoma, Linxiao Zhu, Eden Rephaeli, Shanhui FanAbstract:A multilayer photonic structure is described that strongly reflects incident sunlight while emitting heat selectively through an atmospheric transparency window to outer space; this leads to passive cooling under direct sunlight of 5 degrees Celsius below Ambient Air Temperature, which has potential applications in Air-conditioning and energy efficiency.
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Passive radiative cooling below Ambient Air Temperature under direct sunlight
Nature, 2014Co-Authors: Aaswath P. Raman, Marc Abou Anoma, Eden RephaeliAbstract:A multilayer photonic structure is described that strongly reflects incident sunlight while emitting heat selectively through an atmospheric transparency window to outer space; this leads to passive cooling under direct sunlight of 5 degrees Celsius below Ambient Air Temperature, which has potential applications in Air-conditioning and energy efficiency. Shanhui Fan and colleagues demonstrate a practical radiative cooling device that is effective in direct sunlight, requires only sky access and needs no electricity input. The device operates by — whilst avoiding sunlight absorption — radiating heat into the cold darkness of space via what is known as the atmospheric infrared transparency window, wavelengths of 8 and 13 micrometres. The device differs from previous designs in that it can function in full daylight. The authors have designed and fabricated a multilayered photonic structure that reflects 97% of incoming sunlight while emitting strongly in the atmospheric transparency window. When exposed to direct sun, the device cools to a Temperature 5 °C below Ambient with a cooling power of 40 watts per square metre. The authors calculate potential annual energy savings for a typical roof covered with this passive cooling system to be equivalent to 120,000 kilowatt hours. Cooling is a significant end-use of energy globally and a major driver of peak electricity demand. Air conditioning, for example, accounts for nearly fifteen per cent of the primary energy used by buildings in the United States^ 1 . A passive cooling strategy that cools without any electricity input could therefore have a significant impact on global energy consumption. To achieve cooling one needs to be able to reach and maintain a Temperature below that of the Ambient Air. At night, passive cooling below Ambient Air Temperature has been demonstrated using a technique known as radiative cooling, in which a device exposed to the sky is used to radiate heat to outer space through a transparency window in the atmosphere between 8 and 13 micrometres^ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 . Peak cooling demand, however, occurs during the daytime. Daytime radiative cooling to a Temperature below Ambient of a surface under direct sunlight has not been achieved^ 3 , 4 , 12 , 13 because sky access during the day results in heating of the radiative cooler by the Sun. Here, we experimentally demonstrate radiative cooling to nearly 5 degrees Celsius below the Ambient Air Temperature under direct sunlight. Using a thermal photonic approach^ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , we introduce an integrated photonic solar reflector and thermal emitter consisting of seven layers of HfO_2 and SiO_2 that reflects 97 per cent of incident sunlight while emitting strongly and selectively in the atmospheric transparency window. When exposed to direct sunlight exceeding 850 watts per square metre on a rooftop, the photonic radiative cooler cools to 4.9 degrees Celsius below Ambient Air Temperature, and has a cooling power of 40.1 watts per square metre at Ambient Air Temperature. These results demonstrate that a tailored, photonic approach can fundamentally enable new technological possibilities for energy efficiency. Further, the cold darkness of the Universe can be used as a renewable thermodynamic resource, even during the hottest hours of the day.
Shanhui Fan - One of the best experts on this subject based on the ideXlab platform.
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passive radiative cooling below Ambient Air Temperature under direct sunlight
Nature, 2014Co-Authors: Aaswath Raman, Marc Abou Anoma, Linxiao Zhu, Eden Rephaeli, Shanhui FanAbstract:A multilayer photonic structure is described that strongly reflects incident sunlight while emitting heat selectively through an atmospheric transparency window to outer space; this leads to passive cooling under direct sunlight of 5 degrees Celsius below Ambient Air Temperature, which has potential applications in Air-conditioning and energy efficiency.
