4. energy meteorology (eee 483)
DESCRIPTION
that all about energy methodologyTRANSCRIPT
Md. Rashedul HaqueAdjunct Faculty, EEE
Energy Meteorology –EE483
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Black Body: An ideal black body absorbs all incident electromagnetic radiation fall on it and also emits e-m radiation of all frequencies when heated.
Radiations Laws: Plank’s Black Body Radiation Law: The energy radiated
away from a blackbody at temperature T and wavelength λcan be obtained from Planks Black body radiation law:
Basic Law
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Wien’s displacement law : The relationship between the wavelength of a black body’s maximum emission λm and the corresponding absolute temperature is given by:
Stefan-Boltzmann law: Integration of Planck’s function over the entire wavelength domain leads to the fundamental Stefan-Boltzmann law, which gives the total radiant flux density emitted by a blackbody at temperature T (emitted radiation per unit time and area):
Basic Law
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The is the largest member of the solar system, having a diameter of 1.39 x 109m.
An average distance from earth is 1.495 x 1011m. The core temperature estimated between 8x106 to 40x106
ok. The Sun is a natural fusion reactor. Several fusion reaction
have been suggested to be source of the energy radiant by the sun. The most important of them is four hydrogen atoms combine to form helium, the difference of the mass have been converted to energy.
The Sun as a Source of Energy
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The Diameter of the Earth about 1.275 x 107 m. Its axis is inclined at an angle of 23.5o. The Earth reflects about 30% of sunlight that fall on it.
The Earth
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Sun, Earth Radiation Spectrum
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Absorption Scattering Beam Radiation Diffuse Radiation Global Radiation Air mass
Depletion of Solar Radiation
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Extraterrestrial and Terrestrial Radiation
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Spectral Energy Distribution of Solar Radiation
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Pyranometer
Pyrheliometer
Measurement of Solar Radiation
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For calculating the solar radiation and design the solar device, we have to know the Sun’s path in the sky on the various day in a year at a particular place.
Position of Sun
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It is the angle between sun’s ray incident on the plane surface(collector) and the normal to that surface.
Its depends on Geographical location (Latitude), ф Time of the year (Declination angle), δ Time of the day (Hour angle), ω Orientation of the plane (slope(β),
Surface azimuth (γ))
Θi=f(ф,δ,ω,β,γ)
Angle of incidence (θi)
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Solar Radiation Geometry
Latitude (Angle of Latitude), ф: The latitude of a location on the earth’s surface is the angle made by a radial line joining the given location to the center of the earth with its projection on the plane. Positive for northern hemisphere Negative for southern hemisphere
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Declination angle, δ: The angular displacement of the sun from the plane of the Earth’s equator. Positive when measured above the equatorial plane in thenorthern hemisphere. The declination angle can be approximately determine from the
equation.
Solar Radiation Geometry
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Hour Angle, ω: The hour angle is the quantity which describe the solar time in trigonometric relationship. It is equal to the angular displacement of the sun from local meridian due to the rotation of earth. Earth completes one rotation in 24 hours. Therefore one hour
corresponds to 15o of rotation. At solar noon, hour angle is zero. It is –ve in the forenoon and +ve in the
afternoon.
ω = [solar time-12.00] in hour x 15 degree
Solar Radiation Geometry
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Inclination Angle, : The angle between the sun’s ray and its projection on a horizontal surface is known as the inclination angle
Zenith Angle, θz: It’s the angle between the sun’s ray and the perpendicular (normal) to the horizontal plane.
Solar Radiation Geometry
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Solar Azimuth Angle( γ): The angle on a horizontal plane, between the line due south and the projection of the sun’s ray on the horizontal plane. It is positive taken from south towards west.
Slope (Tilt angle): It is the angle between the inclined plane surface (collector), under consideration and the horizontal.
Solar Radiation Geometry
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Angle of incidence (θi):
Slope angle varies 0o to 90o.
For Horizontal surface: β=0(cosβ=1, sinβ=0)
For Vertical surface. β=90o, γ=180 for northern hemisphere, 0 for southern hemisphere.
Solar Radiation Geometry