Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

Sun-Path Diagrams

If you want to know:

• Where in the sky the sun will be at any time of day throughout the year;

• The hours of direct sunlight a building, garden, or surface will receive at any time of the year; and/or

• How objects will beneficially or negatively shade a building, garden, or other surface on different dates and/or at different times;

…all this can be determined with the help of the sun-path diagram for the latitude closest to your site. See appendix 7 of the new 2nd edition of Rainwater Harvesting for Drylands and Beyond, Volume 1 for guidelines on applying these diagrams to your site.

For an example, see the sun-path diagram for Tucson, 32ºN latitude, below.
Click here to access similar diagrams for the following latitudes (every 4º from 68ºN to 68ºS):

64–68º North
48–60º North
32–44º North
16–28º North
0–12º North
0–12º South
16–28º South
32–44º South
48–60º South
64–68º South

Sun-path diagram for Tucson—and for any other location at or near 32º North latitude.
Control-click or right-click image to download full-sized version.

Sun-path diagram for 32º South latitude. Control-click or right-click image to download full-sized version.

Sun-path diagram for 32º South latitude.
Control-click or right-click image to download full-sized version.

How to use a Sun-Path Diagram
to figure out where the sun will be at your latitude any time of day, any day of the year.

More-detailed info, along with how-to-use illustrations for northern latitudes, is given in appendix 7 of Rainwater Harvesting for Drylands and Beyond, Volume 1, 2nd Edition.

Meanwhile, below you’ll find distilled how-to steps and illustrations using a Sun-Path Diagram for 32º South latitude.

Step One

a7-9sh-rwm2

Figure 1. Use the Sun-Path Diagram that relates most closely to your latitude (in this case, 32º South latitude).
Find the line representing the sun’s path for the date you are seeking (in this case, June 21—the winter solstice in the southern hemisphere); the line representing the sun’s path on this date is highlighted in bold.
Then, find the time you are seeking (in this case, 3 pm) and note where the lines intersect for this time (dashed bold) and the date of June 21 (solid bold); this location is marked here with a bold dot.

Step Two

a7-12sh-rwm2

Figure 2. Now find the sun’s altitude angle (fig. 3) and azimuth angle (fig. 4) for 3 pm on June 21 at 32º South latitude.
Starting from the center of the circle, make a line that runs through the intersection point of the “3 pm” and “June 21” lines; continue your line beyond the outermost circle of the Sun-Path Diagram. This will show you that at 3 pm on June 21, the sun will be 44º (azimuth angle) west of True North.
Finally, look again to the dot indicating the date/time intersection; note that it is on the 20º concentric circle (representing the altitude angle), thus signifying that on June 21 at 3 pm the sun will be 20º above the horizon.

 

a7-10-sunface-20-deg-rwm2

Figure 3. Altitude angle of the sun: 20º above the horizon at 3 pm on June 21 at 32º South latitude.

Figure 4. Azimuth angle of the sun: 44? west of True North at 3 pm on June 21 at 32?South latitude.

Figure 4. Azimuth angle of the sun: 44º west of True North at 3 pm on June 21 at 32º South latitude.

 

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Umbrella Newsletter

The Umbrella: Spring Equinox 2017

THE UMBRELLA:
A catch-all of resources,
events, media, and more
from Brad Lancaster
Spring Equinox 2017
Around here we like to rhyme with the seasons whenever possible. In this case, that means welcoming the fast-approaching beginning of SPRING (the Vernal Equinox (in the northern hemisphere) is March 20 this year in Tucson, and marks one of only two […]

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