The Effect of Azimuth Angle on Energy Output

The wrong azimuth angle could reduce the energy output of a solar PV array down to 35%. Here is a table to better explain the azimuth angle effect.

Azimuth is the array’s east-west orientation in degrees. In most of the solar PV energy calculator tools, an azimuth value of zero is facing equator in both northern and southern hemispheres. Positive 90 degrees is facing due west, negative 90 degrees is facing due east. The compass angle shows 180 for south, 90 for east and 270 for west.

In northern hemisphere, between the latitudes of 23 and 90, the sun is always in the south. Therefore, the modules on an array are faced to south in order to get the most out of the sun’s energy. In the southern hemisphere, it is the opposite.
As a rule of thumb, system designers tend to use an array azimuth of zero, or facing the equator.

The north facing roof sides are obviously not suitable for installing solar panels in North America, whereas the east and west facing roofs could be acceptable. Usually, west facing roofs are more advantageous than east facing roofs, since the solar radiation is more powerful in the afternoon. 

  • The meteorological conditions of the location is an important factor to consider. For example, the insolation analysis (please look at the above picture) in Hawaii shows that an array facing to east could generate more power compared to that of an array facing to south or west. The reason could be the frequent afternoon rains in that location.
  • The second factor to consider is the shading. If there is a predominant morning or afternoon shade at a specific location (due to a tree, a chimney, a nearby building or a high hill in the vicinity) the azimuth angle selection would compensate the energy loss.

I've run the same analysis as I’ve done in the in the previous article; the sample 3.4 kW system consists of 16x Sanyo HIT-N215A modules, tilted 20 degrees and is assumed to be located in Phoenix, AZ.

Azimuth Angle
(degrees)
Phoenix, AZ (33 North)
Annual Production
(kWh)
Delta
(%)
+90 (West)5,551-14%
+60 (SWW)6,006-7%
+45 (SW)6,190-4%
+20 (SSW)6,400-1%
0 (South)6,4610
-20 (SSE)6,421-1%
-45 (SE)6,230-4%
-60 (SEE)6,053-6%
-90 (East)5,601-13%
180 (North)4,298-34%

This example shows that the optimal azimuth angle to be due south. The array on the east roof would generate slightly more energy than the one on the west roof.  If the array is installed on the north facing roof, the annual energy production would reduce up to 35%.

One solution to overcome the azimuth angle effect would be to install solar pv system on a single-axis solar tracker. The single axis tracker system rotates about the tilted axis from east in the morning to west in the evening to track the daily movement of the sun across the sky. 

>Also read "The Effect of Array Tilt Angle on Solar Energy Output"

Here are some links that I recommend for conducting similar calculations:

Comments

It's great to see these numbers in a table. I also like seeing how PV can work even when installed on the completely wrong roof (North) - this illustrates how resilient the technology is even when installed incorrectly. Thanks.
Thank you SFox! I actually included that information on the bottom of the table. It looks like the energy output may reduce up to 35% in the north face of the roof in the selected site. (That amount may decrease or increase depending on the pitch of the roof and the latitude of the location)

Thanks for this article, I agree it is great to see this illustrative article.   Why does the state of California put so much emphasis on optimal azimuth direction of due South if the loss is so small?

In the document of NREL below for the station at phoenix the monthly radiation is high in april/may but shouldn't it be high in the summer i.e. June/July/August? for a typical tilt of 20 deg.
www.nrel.gov/docs/legosti/old/5607.pdf refer (page 38)
Can anyone answer this?

Usually, that dip is due to atmospheric particles or pollution. The daylight might be longest on June 21-22, but the air is usually less clear than in spring or fall. It may also be that they aren't normalizing for temperature - the high temps of July and August could also cause that dip if they are reading straight output.

Can horizontal single axis trackers like http://www.scorpiustrackers.com/products.html help to improve it?

How about Suntrix Company Limited from China? They just shipped 8MW trackers to Greece's biggest EPC company.