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Blackbody Radiation and Light
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
The terrestrial solar spectral irradiance on the surface actually applied in solar energy conversion differs from the extraterrestrial irradiation due to the effect of the filtering by the atmosphere. The scattering by the atmosphere disperses the blue light more than the red part of the spectrum, which is the cause of the red color of sunset. Therefore, the atmospheric extinction affects predominantly the shorter frequencies of the incoming radiation. In addition, selective absorption by low concentration gases causes a strong decrease or even full extinction of the radiation in certain specific ranges of wavelengths that are indicated in Figure 17.2. In the infrared, the terrestrial solar spectrum is especially highly structured by the principal agents of opacity that are carbon dioxide and water vapor.
Blackbody Radiation and Light
Published in Juan Bisquert, The Physics of Solar Cells, 2017
The terrestrial solar spectral irradiance on the surface actually applied in solar energy conversion differs from the extraterrestrial irradiation due to the effect of the filtering by the atmosphere. The scattering by the atmosphere disperses the blue light more than the red part of the spectrum, which is the cause of the red color of sunset. Therefore, the atmospheric extinction affects predominantly the shorter frequencies of the incoming radiation. In addition, selective absorption by low concentration gases causes a strong decrease or even full extinction of the radiation in certain specific ranges of wavelengths that are indicated in Figure 1.2. In the infrared, the terrestrial solar spectrum is especially highly structured by the principal agents of opacity that are carbon dioxide and water vapor.
The Earth–Sun Relationship
Published in Matt Fajkus, Dason Whitsett, Architectural Science and the Sun, 2018
For solar geometry purposes, sunrise is that moment when the center of the solar disc crests the horizon and begins to illuminate the reference location. Sunset occurs when the center of the sun drops below the horizon. Day is any time the center of the sun is above the horizon with respect to the reference location, while night is the time when the sun is not visible from that position. All latitudes along a local meridian will experience the same solar time, while times of sunrise and sunset vary along that meridian. Days for the points along this local meridian will be longest toward the summer pole and shortest at the winter pole.
Blue skies and red sunsets: Reliability of performance parameters of various p-n junction photovoltaic module technologies
Published in Cogent Engineering, 2019
Edson L. Meyer, Ochuko K. Overen
Scattering of light by gas molecules in the atmosphere is proportional to λ−4. This implies that blue light (λ ~ 0.4 μm) is scattered about eight to ten times more than red light (λ ~ 0.7 μm) (Nazeeruddin et al., 1993). During daytime, light from the sun appears yellow-white and the sky (not towards the sun) is perceived as blue. Towards sunset, when the sun is further away from the observer (higher AM), scattering will remove blue light preferentially, with the sun and sky appearing red. Therefore, high air mass numbers are associated with a spectral content dominated by long wavelength photons. Consequently, higher solar cell bandgap materials are less efficient under these high AM conditions. Figure 11 shows Isc normalized to Isc at AM 1.5 for the various module technologies. The values for Isc were simulated with Sandia’s Solar Design Studio software (S. D. Studio, 2000).
Cloudy with a Chance of Sunbeams
Published in LEUKOS, 2018
The spectral nature of daylight is a function of how the earth’s atmosphere modifies extraterrestrial solar radiation. When the sun is in different sky positions, it passes through different densities of atmosphere before arriving at the ground. When the sun is near the horizon the path-length through the atmosphere is greater, leading to more diffusion and scattering by aerosols. Shorter wavelengths are diffused while longer wavelengths make it through, which we see as red and yellow sunrises and sunsets. Figure 3 plots several measurements of real daylight, illustrating common variation in daylight spectra.