The document defines sunshine as direct sunlight of at least 120 w/m2 measured on the ground. It provides details on the sun's composition and radiation, including that 53.12% of its energy is in the infrared region. It also discusses how the Earth reflects 1/3 of sunlight and is inclined at 23.5 degrees on its axis. Finally, it describes various instruments used to measure solar radiation, including pyranometers and pyrheliometers, and concepts like beam radiation, diffuse radiation, and solar declination.

1. From:- Amitesh
kumar

2.  The World Meteorological Organization (WMO)
defines “Sunshine” as direct irradiance from
the sun measured on the ground of at least 120
w/m².
 Direct Sunlight gives about 93 lux of
illumination per watt of electromagnetic power.
 Bright sunlight provides illumination of approx.
100,000 lux/Sq.m at Earth’s surface.
 Sun’s surface temperature, T = 6000k.
 About sun’s total radiated energy,
Ultraviolet region(λ<0.40μm) - 8.73%.
Visible region (o.40μm<λ<0.70μm) – 38.15%.
Infrared region (λ>0.70μm) – 53.12%.

3.  Earth’s inner core is a solid made of iron and
nickel.
 2/3 of earth is covered with water rest 1/3 is
land.
 It reflects 1/3 of the sunlight received.
 Earth is inclined about its axis at an angle of
23.5º.
 The earth’s atmosphere absorbs the UV &
infrared radiation and allows only radiation
having λ between 0.29μm and 2.3μm (Short
wavelength radiation).
 Radiation of λ>2.3μm is not allowed.

4.  Photovoltaic (PV device) – A device used to
convert SWR into direct current(dc) electricity.
 Solar still – used for desalination for saline
water.
 Sunshine recorder – Pyranometer Or
Pyrheliometer.
 A Pyranometer

5.  Solar radiation reaching earth is classified into
two components : Beam & Diffuse radiation.
 Beam radiation(Iь) – Direct Sunlight.
 Diffuse radiation (Id) – solar radiation scattered
by aerosols, dust and molecules.
 Total radiation (It) – (Iь+Id) also known as global
radiation.
 Pyrheliometer – broadband instrument that
measures the direct component of solar
radiation at normal incidence. It is sensitive to
λ’s in the band from 0.284μm to 0.3μm.
 Sensor - Thermopile.

6.  Pyranometer – is a type of actinometer used
to measure solar irradiance. It is designed to
measure solar radiation flux density (in
w/m²) from a view of 180º.
 Silicon solar cells have the property that the
light current (approx. equal to Isc at normal
radiation) is a linear function of the incident
solar radiation. But their spectral response is
not linear.

8.  Where, θz = is Zenith angle,
α = solar altitude (is Zero at sunrise &
sunset),
α + θz = 90º.
γsun = solar Azimuth angle.
 Solar declination – the angle that sun’s rays
makes with the equatorial plane.
Where, n = no. of days of the year (1≤n≤365).
 Its maximum value is 23.45º on 21 December &
the minimum value is –23.45º on 21June.