## Solar azimuth angle z

The solar azimuth angle, z, is the angle of the sun's rays measured in the horizontal plane from due south (true south) for the Northern Hemisphere or due north for the Southern Hemisphere; westward is designated as positive. The mathematical expression for the solar azimuth angle is sin(z) = cos(8)sin(h) (2.13)

This equation is correct, provided that (ASHRAE, 1975) cos(h) > tan(6)/tan(L). If not, it means that the sun is behind the E-W line, as shown in Figure 2.4, and the azimuth angle for the morning hours is —tc + |z| and for the afternoon hours is tc — z.

At solar noon, by definition, the sun is exactly on the meridian, which contains the north-south line, and consequently, the solar azimuth is 0°. Therefore the noon altitude a„ is an = 90° - L + 6 (2.14)

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