solar energy and ions

8/14/2019 Solar Energy and ions

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Solar constant

The solar constant is defined as the quantity of

solar energy (W/m) at normal incidence

outside the atmosphere (extraterrestrial) at the

mean sun-earth distance. Its mean value is

1367.7 W/m.


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longitude

Unit: degree

The arc or portion of the earth's equator intersected

between the meridian of a given place and a

reference meridian (usually the one from Greenwich,England). The longitude is taken positive east of the

Greenwich meridian and negative west of the

Greenwich meridian


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Latitude Unit: degree

The angular distance north or south from the

earth's equator measured through 90 degrees.The latitude is taken positive in the northern

hemisphere


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equation of time

Unit: minute

The equation of time describes the difference

between clock time and true solar time due to

the eccentricity in the earth's orbit and the tilt

of the earth's axis with respect to the ecliptic

plane. It is computed according to therecommendations of the Illuminating

Engineering Society of North America


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extraterrestrial normal irradiance

Unit: W/m2

Irradianceproduced by the sun, on a surface

perpendicular to its rays, on the outer limit of

the Earth's atmosphere


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extraterrestrial solar radiation

Solar radiation incident on the outer limit ofthe Earth's atmosphere


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Global horizontal irradiance

Unit: W/m2

Irradianceproduced by solar radiation on a

horizontal surface on the earth.


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Global solar radiation

.Sum ofdirect solar radiation and diffusesolar (sky) radiation.


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Greenwich

Borough of East GreaterLondon in England,

located at a latitude of 51.47N and a longitude

of exactly 0.


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Clearness index Unit: 1

Ratio of the global horizontal irradiance to the

extraterrestrial horizontal irradiance


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Clock time

Unit: hours from midnight

Time used in a country, or part of a country.

Usually expressed relatively to the Greenwich

Meridian Time (GMT) used in the United

Kingdom: GMT+3 means three hours more

than GMT.


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Clock Time

In some countries, for energy saving purposes,

one hour is added to clock time from the lastSunday of March, to the Saturday before the

last Sunday of October. This is called daylight

saving time or summer clock time.


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Daylight

.Visiblepart ofglobal solar radiation.


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Diffuse fraction

Ratio of the diffuse horizontal irradiance to

the global horizontal irradiance.


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Diffuse horizontal irradiance

Unit: W/m2

Irradianceproduced by the diffuse solar

radiation on a horizontal surface on the earth.


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Diffuse solar (sky) radiation

That part of solar radiation that reaches the

Earth as a result of being scattered by airmolecules, aerosol particles, cloud particles or

other particles.


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Direct horizontal irradiance

Unit: W/m2

Irradianceproduced by the direct solar

radiation on a horizontal surface on the earth.


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direct normal irradiance

Unit: W/m2

Irradianceproduced on the earth by the direct

solar radiation on a surface perpendicular to

the sun's rays.


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reflectance

Unit: 1

Ratio of the reflected radiant orluminous flux

to the incident flux in the given conditions.

The reflectance is also called the albedo for a

radiant flux.


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relative optical air mass

Unit: 1

Ratio of the slant optical thickness to the

vertical optical thickness of the atmosphere .

When the curvature of the atmosphere and

atmospheric refraction are neglected.


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Sky, cloudy

Sky condition corresponding to a cloud index

larger than 0.6.


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Sky, intermediate


larger than 0.15 and smaller than 0.6.


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Sky, sunny


smaller than 0.15.


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Skylight

. Visiblepart ofdiffuse sky radiation.


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Slope

Unit: degree

Angle of a plane with respect to the horizontal.

A horizontal surface has a slope angle of 0

degree. A vertical surface has a slope angle of

90 degrees.


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Solar azimuth

Unit: degree

Azimuth angle of the sun. Measured clockwise

with respect to true north.


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Solar constant

Irradianceproduced by the extraterrestrial

solar radiation on a surface perpendicular tothe suns rays at mean yearly sun-earth

distance (150 Million km).

Its value is equal to 1367 W/m2


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solar declination

Unit: degree

Angle between the sun's rays and the earth's

equatorial plane. Declination values arepositive when the sun is north of the equator(March 20 to September 23) and negative

when the sun is south of the equator. Itsmaximum and minimum values are +23.45 and-23.45 degrees.


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solar hour angle

Unit: degree

The angle at which the earth must turn to bring themeridian of the given point directly under the sun.

Negative in the morning: sun coming from the east.

Positive in the afternoon: sun going west. This angle

increases by 15 degrees an hour.


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solar radiation

Electromagnetic radiation from the sun. On

average, 98% of the sun's radiation reaching

the earth falls in the spectral range between0.29 m and 4 m.


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Solar zenith angle

Unit: degreeAngle between the centre of the sun's disc and

the vertical: sunlight

CIE. Visiblepart ofdirect solar radiation.


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Transmittance (for incident radiation of given spectral composition,

polarization and geometrical distribution)

Unit: 1

Ratio of the transmitted radiant orluminous flux to

the incident flux in the given conditions.


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True Solar Time

Unit: hours from midnight

True solar time differs from clock time. It is specificto a location. The difference between true solar time

and clock time is due to (1) differences between the

site longitude and the standard meridian (thereference for clock time), (2) the equation of time ET

and (3) summer time (one hour), if applied:


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zenith angle

Unit: degree

Angle between a point in the hemisphere and

the vertical


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site

http://www.satel-light.com/guide/glosstoz.htm

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