What is diffuse sky radiation?
Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere.
What is the difference between solar radiation and diffuse radiation?
It is used to describe solar radiation traveling on a straight line from the sun down to the surface of the earth. "Diffuse radiation", on the other hand, describes the sunlight that has been scattered by molecules and particles in the atmosphere but that has still made it down to the surface of the earth.
What is direct radiation?
"Direct radiation"is also sometimes called "beam radiation" or "direct beam radiation". It is used to describe solar radiation traveling on a straight line from the sun down to the surface of the earth.
What is direct beam solar radiation?
The solar radiation that reaches the Earth's surface without being diffused is called direct beam solar radiation. The sum of the diffuse and direct solar radiation is called global solar radiation. Atmospheric conditions can reduce direct beam radiation by 10% on clear, dry days and by 100% during thick, cloudy days.
What is direct and diffuse radiation?
In simple terms, direct radiation has a definite direction but diffuse radiation follows a much more scattered, uncertain path. Because when the radiation is direct, the rays are all travelling in the same direction, an object can block them all at once.
What is diffuse solar radiation Mcq?
d) Diffuse radiation. Explanation: Solar radiation that has not been absorbed or scattered and reaches the ground from the sun is called direct radiation or beam radiation.
What is the difference between diffuse and direct insolation?
Direct solar irradiance is the solar radiation that passes directly through the atmosphere from the sun without being scattered or absorbed by the atmosphere. Diffuse solar irradiance reaches the ground and has been scattered by an atmospheric component such as air and water molecules, dust, or clouds.
What is diffuse shortwave radiation?
Diffuse radiation is the solar radiation scattered by particles in the atmosphere and received at a horizontal plane at the Earth's surface. Diffuse radiation comes from the entire sky dome, whereas direct radiation comes from a single direction.
What is direct solar radiation *?
The solar radiation that reaches the Earth's surface without being diffused is called direct beam solar radiation. The sum of the diffuse and direct solar radiation is called global solar radiation. Atmospheric conditions can reduce direct beam radiation by 10% on clear, dry days and by 100% during thick, cloudy days.
What is reflected solar radiation MCQS?
Clarification: Reflected solar radiation is that sunlight/radiation that is reflected from a non-atmospheric obstacle. The obstacles could be trees, ground, light poles, cars, etc.
What is beam and diffuse solar radiation?
Beam radiation is the solar radiation received from the Sun without having been scattered by the atmosphere. Diffuse radiation is that received from the Sun after its direction has been changed by scattering by the atmosphere.
Do solar panels use diffuse radiation?
The sun's rays follow a direct path to the solar panels without encountering any obstacles. Then there is diffuse radiation. This kind is of radiation is indirect because it is scattered by clouds and molecules in the atmosphere as it travels through them. The third and last type is reflected radiation.
What are 4 types of radiation from the sun?
4 types of sun's radiation include:Infrared rays,Visible rays.Ultraviolet light.radio waves.
What is longwave and shortwave radiation?
Shortwave radiation (visible light) contains a lot of energy; longwave radiation (infrared light) contains less energy than shortwave radiation (shortwave radiation has a shorter wavelength than longwave radation).
How do you calculate diffuse solar radiation?
A fair estimate of the diffuse irradiance can be obtained by subtracting the direct normal beam radiation projected onto a horizontal surface from the global irradiance.
What are the types of solar radiation?
Depending on the form in which it reaches the Earth:Direct solar radiation. This type of radiation penetrates the atmosphere and reaches the Earth's surface without dispersing at all on the way.Diffuse solar radiation. ... Reflected solar radiation.
What is solar collector Mcq?
Explanation: A solar collector is a system to collect heat by absorbing sunlight and use it for various applications. It is neither a system to collect rainwater nor electricity. However, it could be used to perform such processes.
Which of the statement is correct about solar energy Mcq?
Which of the statements is correct about Solar Energy? Explanation: Solar energy is a source of energy that has not been used traditionally and is relatively new in terms of usage. Hence it is a non-conventional source of energy. It is unlimited and inexhaustible and hence is a renewable source of energy.
What type of radiation does Earth emit Mcq?
What type of radiation does earth emit? Explanation: Earth emits infrared radiation. This is typically called as outgoing long-wave radiation (OLR) of wavelength between 3 and 100um. They are also called as thermal radiation.
In what form is solar energy is radiated from the sun Mcq?
Explanation: solar energy is radiated from the sun in the form of electromagnetic waves of shorter wavelength of 0.2 to 0.4 micrometers. out of all the solar energy radiations reaching the earth's atmosphere, 8% is ultraviolet radiation, 40% is visible range light and 46% is by infrared radiation.
What is diffuse radiation?
Diffuse sky radiation is solar radiation reaching the Earth 's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. Also called sky radiation, the determinative process for changing the colors of the sky. Approximately 23% of direct incident radiation of total sunlight is removed from ...
What is the equation for total solar radiation?
One of the equations for total solar radiation is: where Hb is the beam radiation irradiance, Rb is the til t factor for beam radiation, Hd is the diffuse radiation irradiance, Rd is the tilt factor for diffuse radiation and Rr is the tilt factor for reflected radiation.
What is the dominant scattering efficiency of blue light?
solar radiation reaching the Earth's surface. "Red sky" redirects here. For other uses, see Red Sky (disambiguation). In Earth's atmosphere, the dominant scattering efficiency of blue light is compared to red or green light. Scattering and absorption are major causes of the attenuation of sunlight radiation by the atmosphere.
What are the two processes that are dominant in radiative scattering?
The dominant radiative scattering processes in the atmosphere are Rayleigh scattering and Mie scattering ; they are elastic, meaning that a photon of light can be deviated from its path without being absorbed and without changing wavelength.
Why is the sky blue?
During broad daylight, the sky is blue due to Rayleigh scattering, while around sunrise or sunset, and especially during twilight, absorption of irradiation by ozone helps maintain blue color in the evening sky.
What causes the attenuation of sunlight radiation?
Scattering and absorption are major causes of the attenuation of sunlight radiation by the atmosphere. Scattering varies as a function of the ratio of particle diameters (of particulates in the atmosphere) to the wavelength of the incident radiation.
How much sunlight does a cloud get?
The intensity ranges (roughly) from 1⁄6 of direct sunlight for relatively thin clouds down to 1⁄1000 of direct sunlight under the extreme of thickest storm clouds.
What is the maximum diffuse radiation?
Maximum diffuse radiation values tend to occur during hours of broken thin cloud. The diffuse radiation from partially clouded skies is normally substantially higher than the diffuse radiation from clear skies and from typical overcast skies. It is thus an invalid scientific process to attempt to calculate monthly mean diffuse radiation by linear interpolation between estimated overcast sky and estimated clear-sky diffuse radiation values. The typical hourly sunshine amount producing the highest diffuse irradiation conditions is about 0.3 to 0.5 hours within the hour. Surprisingly high global-radiation levels can occur under thin high cloud conditions, but the radiation is very diffuse dominated.
How do clouds affect solar radiation?
They report broken cloud fields typical of humid tropical climates create mosaic radiative landscapes with interchanging cloud shaded and sunlit areas. While clouds attenuate solar-radiation incident on cloud shaded areas, sunlit ground surfaces may actually receive more irradiance than under a clear sky due to light scattering and reflection from neighbouring clouds. The authors analysed a high-resolution time series of radiation measurements made in the wet season of 1999 in southern Brazil. Surface solar irradiance frequently (more than 20% of the time) exceeded clear-sky levels and occasionally surpassed the extraterrestrial radiation. They found the clouds created a bimodal frequency distribution of surface irradiance, producing an average of approximately 50% attenuation for about 75% of the time and 14% enhancement for about 25% of the time, respectively, as compared to the corresponding clear-sky levels of irradiance. The study is helpful in drawing attention to the actual patterns of irradiance likely to be found on solar cell systems across the humid tropics.
How does the reflectance of the ocean bottom affect the radiation in the water?
Also, in shallow waters, the reflectance of the ocean bottom influences the diffuse radiation in the water and the radiation leaving the water surface. The reflectance and transmittance of a surface depend upon both the angles of incidence and reflection or transmission.
How many sources of radiation does a flat plate receive?
A flat plate at any angle α to the horizon receives radiation from all four sources on both its surfaces. To estimate how the irradiance from each of these sources depends on α, the atmosphere and the ground can be replaced by two hemispheres AOC and AO ′ C ( Figure 7.13 ).
How many streams of radiation are there in nature?
In addition to any incident flux of direct radiation, natural objects are exposed to four discrete streams of diffuse radiation with different directional properties.
What is the wavelength of solar radiation?
Solar, or short-wave, is radiation originated from the sun, mostly in the wavelength range of 0.3–3 μm. Unless otherwise specified, it includes both beam and diffuse components.
What are the two main components of solar radiation?
There exits two main components of solar radiation: beam and diffuse radiation (Fig. 5.5 ). Beam radiation is the solar radiation received from the Sun without having been scattered by the atmosphere. Diffuse radiation is that received from the Sun after its direction has been changed by scattering by the atmosphere.
What percentage of solar radiation is diffuse?
On an extremely overcast day, pretty much 100% of the solar radiation is diffuse radiation. Generally speaking, the larger the percentage of diffuse radiation, the less the total insolation.
What is the ratio of direct to diffuse radiation?
When the sky is clear and the sun is very high in the sky, direct radiation is around 85% of the total insolation striking the ground and diffuse radiation is about 15%. As the sun goes lower in the sky, the percent of diffuse radiation keeps going up until it reaches 40% when the sun is 10° above the horizon.
What happens when you tilt solar panels?
As discussed in sun angle and insolation, when you tilt your solar panels so that the sun's rays are hitting them at a 90° angle, you are maximizing the amount of direct radiation that they receive.
Why do shadows appear when radiation is blocked?
Because when the radiation is direct, the rays are all travelling in the same direction, an object can block them all at once. This is why shadows are only produced when direct radiation is blocked.
What is the average irradiation in London in June?
In London's sunniest month (June), the average daily irradiation is about 5.5 kWh/m 2 and about 50% of that is diffuse. In December, the irradiation is less than 1 kWh/m 2 and by far the majority of that radiation is diffuse. In Aden's sunniest month (May), the average daily irradiation is about 7 kWh/m 2 and less than 30% ...
What is direct radiation?
It is used to describe solar radiation traveling on a straight line from the sun down to the surface of the earth.
Can solar energy use diffuse radiation?
Not all technologies can use diffuse radiation. Photovoltaic and solar hot water systems can make use of both direct radiation and diffuse radiation. Concentrated solar power, on the other hand, requires a lot of direct radiation to do much of anything at all.
When crossing the atmosphere, solar radiation is subjected to reflection, refraction, absorption, and diffusion by?
When crossing the atmosphere, solar radiation is subjected to reflection, refraction, absorption, and diffusion by the various atmospheric gases to a variable degree as a function of frequency.
How Does Solar Radiation Affect Health?
Ultraviolet radiation can have various effects on human skin depending on its intensity and the length of its waves.
What are the different types of ultraviolet rays?
In turn, ultraviolet (UV) rays are subdivided into three types: 1 Ultraviolet A or UVA: They easily pass through the atmosphere, reaching the entire earth's surface. 2 Ultraviolet B or UVB: Short-wavelength. Has greater difficulty passing through the atmosphere. As a result, they reach the equatorial zone more quickly than at high latitudes. 3 Ultraviolet C or UVC: Short-wavelength. They do not pass through the atmosphere. Instead, the ozone layer absorbs them.
What are the effects of UVB radiation on the body?
It can also cause eye and immune system problems. UVB radiation causes sunburn, darkening, thickening of the outer layer of the skin, melanoma, and other types of skin cancer. It can also cause eye and immune system problems. The ozone layer prevents most of the UVC radiation from reaching Earth. In the medical field, UVC radiation can also come ...
What layer prevents UVC radiation from reaching Earth?
The ozone layer prevents most of the UVC radiation from reaching Earth. In the medical field, UVC radiation can also come from certain lamps or a laser beam and is used to kill germs or help heal wounds.
Why do tropical areas receive the most solar radiation?
For example, tropical areas receive the most solar radiation because the Sun's rays are nearly perpendicular to the Earth's surface.
What percentage of radiation is visible rays?
Visible rays (VI): represent 43% of radiation and provide light.
What is diffuse radiation?
Diffuse radiation, on the other hand, describes the sunlight that has been scattered by molecules and particles in the atmosphere but that has still made it down to the surface of the earth. In simple terms, direct radiation has a definite direction but diffuse radiation follows a much more scattered, uncertain path.
What percentage of the sun's radiation is diffused?
As the sun lowers into the sky, the percent of diffuse radiation keeps increasing until it reaches 40% when the sun is 10° above the horizon. Atmospheric conditions like clouds and pollution also increase the chances of diffused radiation. On an extremely overcast day, pretty much 100% of the solar radiation is diffuse radiation.
What is the direct diffuse ratio?
Direct/diffuse ratio varies with latitude and climate. The percentage of the sky’s radiation that is diffuse is much greater in higher latitude, cloudier places than in lower latitude, sunnier places. Moreover, the percentage of diffuse radiation tends to be higher in the winter than the summer in this higher latitude, cloudier places.
Why is the amount of radiation missed by tilted solar panels more than compensated for by the extra radiation gained by?
However, because direct radiation is much more intense than diffuse radiation, the amount of radiation missed by tilted solar panels is generally more than compensated for by the extra radiation gained by tracking the sun constantly. Reflected radiation.
What is the difference between direct and diffuse radiation?
Direct radiation also known as “beam radiation” or “direct beam radiation” is used to describe solar radiation travelling on a straight line from the sun down to the surface of the earth. Diffuse radiation, on the other hand, describes the sunlight that has been scattered by molecules ...
What is the average irradiation in London in June?
In London’s sunniest month (June), the average daily irradiation is about 5.5 kWh/m 2 and about 50% of that is diffuse. In December, the irradiation is less than 1 kWh/m 2 and by far the majority of that radiation is diffuse. In Aden’s sunniest month (May), the average daily irradiation is about 7 kWh/m 2 and less than 30% ...
Where is the most diffuse radiation gathered?
However, it is found to be that diffuse radiation is pretty equally distributed throughout the sky and that the most diffuse radiation is gathered when your solar panels are laying down horizontally.
Overview
Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. Also called sky radiation, the determinative process for changing the colors of the sky. Approximately 23% of direct incident radiation of total sunlight is removed from the direct solar beam by scattering into the atmosph…
Color
Earth's atmosphere scatters short-wavelength light more efficiently than that of longer wavelengths. Because its wavelengths are shorter, blue light is more strongly scattered than the longer-wavelength lights, red or green. Hence, the result that when looking at the sky away from the direct incident sunlight, the human eye perceives the sky to be blue. The color perceived is similar to that …
Under an overcast sky
There is essentially no direct sunlight under an overcast sky, so all light is then diffuse sky radiation. The flux of light is not very wavelength-dependent because the cloud droplets are larger than the light's wavelength and scatter all colors approximately equally. The light passes through the translucent clouds in a manner similar to frosted glass. The intensity ranges (roughly) from 1⁄6 of direct sunlight for relatively thin clouds down to 1⁄1000 of direct sunlight under the extreme o…
As a part of total radiation
One of the equations for total solar radiation is:
where Hb is the beam radiation irradiance, Rb is the tilt factor for beam radiation, Hd is the diffuse radiation irradiance, Rd is the tilt factor for diffuse radiation and Rr is the tilt factor for reflected radiation.
Rb is given by:
Agriculture and the eruption of Mt. Pinatubo
The eruption of the Philippines volcano - Mount Pinatubo in June 1991 ejected roughly 10 km (2.4 cu mi) of magma and "17,000,000 metric tons"(17 teragrams) of sulfur dioxide SO2 into the air, introducing ten times as much total SO2 as the 1991 Kuwaiti fires, mostly during the explosive Plinian/Ultra-Plinian event of June 15, 1991, creating a global stratospheric SO2 haze layer which persisted for yea…
See also
• Atmospheric diffraction
• Aerial perspective
• Cyanometer
• Daylight
• Nighttime airglow
Further reading
• Pesic, Peter (2005). Sky in a Bottle. The MIT Press. ISBN 978-0-262-16234-0.
External links
• Dr. C. V. Raman lecture: Why is the sky blue?
• Why is the sky blue?
• Blue Sky and Rayleigh Scattering
• Atmospheric Optics (.pdf), Dr. Craig Bohren