Page 147 - Alternative Energy Systems in Building Design

SOLAR POWER SYSTEM DESIGN CONSIDERATIONS 123

ROOF PITCH TILT ANGLE, DEGREES
4/12 18.4
5/12 22.6
6/12 26.6
7/12 30.3
8/12 33.7
9/12 36.9
10/12 39.8
11/12 42.5
12/12 45.0

PV array azimuth angle (0–360 degrees). The azimuth angle is the angle measured
clockwise from true north in the direction facing the PV array. For fixed PV arrays
facing south, the azimuth angle is therefore 180 degrees clockwise from the north.
PV arrays mounted on sun-tracking platforms can move in either one or two axes
of rotation. In one-axis rotations, the azimuth angle is rotated clockwise from true
north. In PV modules installed on platforms with two axes of rotation, the azimuth
angle does not come into play.
As a rule, for optimal energy output, PV arrays in the northern hemisphere are
mounted or secured in an azimuth angle of 180 degrees, or north facing south. In the
southern hemisphere, the azimuth angle is reversed to south facing north. Figure 3.64
shows PV array fixed-tilt mounting positions.

The following table shows the relationship of azimuth angle and compass headings.

COMPASS HEADING AZIMUTH ANGLE, DEGREES
N 0–360
NE 45
E 90
SE 135
S 180
SW 225
W 270
NW 315