DemoSolarAngles
These tests will be for a site in Golden, Colorado unless otherwise noted. The date selected will be June 21 unless otherwise noted.
This demonstrates the ability to calculate the local civil and solar time for a location with a specific distance from the standard meridian, and also with daylight savings time on.
The clock time is, as expected, equal to the hour of the day in the time stamp. However, because Daylight Savings Time is on, the civil time is actually one hour lower. The solar time is offset from the local civil time by a value of the equation of time. For this day, the value of EOT is only about 1 minute, so civil and solar time are almost equal. This is why the civil time is shown as a heavier line.
This demonstrates the ability to calculate the current solar angle for a Golden, Colorado, for a summer day.
Because of daylight savings time, the hour angle goes to zero at a clock time of 13 hours, or 1pm. On a non-DST day, the hour angle would go to zero closer to a clock time of noon.
The solar altitude angle is calculated for each hour of the day for December 21 (shortest day of the year), and June 21 (longest day of the year). The results are shown here:
The solar azimuth angle is calculated for each hour of the day for June 21 for Golden, Colorado. The azimuth angle is measured positive clockwise from North, so that East is 90 degrees, and West is 270 degrees.
Note that when the sun is down, the function reports an azimuth of None so that the irrelevant hours are not reported on the plot to reduce confusion. At sunrise, the sun is east, slightly north. This is validated using the NOAA solar position calculator.
The wall azimuth angle is calculated for each hour of the day for June 21 for Golden, Colorado for east, south, and west facing surfaces. The wall azimuth angle is essentially the horizontal difference between the solar azimuth and the surface normal vector.
Note that when the sun is down, or if the sun is behind the surface, the function reports an azimuth of None so that the irrelevant hours are not reported on the plot to reduce confusion. The sun first comes in front of the east facing wall, then the south facing, then the west facing. And because of the declination of the sun, the south facing surface does not receive direct solar in the early morning or later afternoon.
The solar incidence angle is calculated for each hour of the day for June 21 in Golden, Colorado, for an east facing surface. The solar incidence angle is essentially the trigonometric combination of the altitude and azimuth angles.
For clarification and verification, the azimuth and altitude angles are plotted alongside the incidence angle. The azimuth and incidence angles are only shown when the sun is up and facing the surface.