Solar Angle Determination:

The sun's position in the sky with respect to vertical, sloping and horizontal surfaces is
expressed in terms of a number of factors. These factors are defined below and as
shown as Figure 3.


Fig. 3 Solar angles for vertical, sloping and horizontal surfaces

Solar Altitude--
Solar altitude (b) is the angle QOH (Fig. 3) on a vertical plane between the sun's rays and
the horizontal plane on the earth's surface. (see Example 1)
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Solar Azimuth--
Solar azimuth (f) is the angle SOH (Fig. 3) on a horizontal plane between the due-south
direction line and the horizontal projection of the sun's rays.
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Surface-solar Azimuth--
Surface-solar azimuth (g) is the angle HOP (Fig. 3) on a horizontal plane between the
normal to a vertical surface and the horizontal projection of the sun's rays.
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Surface Azimuth--
Surface azimuth (y) is the angle SOP (Fig. 3) on a horizontal plane between the normal
to a vertical surface and the north-south direction line.
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Angle of Incidence--
Angle of incidence (i)is a angle between the sun's rays irradiated on a surface and
the line normal to this surface.
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Solar Declination--
Solar declination (d) is the angle between the earth-sun line and the equatorial plane
(Fig 2). Solar declination will vary throughout the year between +23.5^o and -23.5^o.

Hour Angle--
The hour angle (H) is an expression describing the difference between local solar time
and solar noon. Although it is calculated directly from measurements of time, it is
expressed in angular units, typically degrees. The hour angle can be calculated from
the following equation:

H = [360 (12-T) / 24]        degree

where T = solar time
In the morning, the hour angle is positive. At noon the hour angle is zero. In the
afternoon, the hour angle is negative.

You can use the calculator in examples page to calculate the Hour angle.



Other solar angle explanation