Solar PV Array: Orientation and Tilt

A common misconception when it comes to the placement of your solar PV panels is that you can put them anywhere that there is sun light. While it is true that a solar panel will generate electricity when there is sun light, the amount of electricity can vary greatly based on its tilt and orientation. 

Orientation:

In the northern hemisphere the general rule of thumb is that, when possible, you should face your panels "true" south. When using a compass it will point you to magnetic south. True south is about 14° west of magnetic south in CT. So if you are purchasing/ building a ground mounted solar array you will want to make sure that it is facing true south. 

Tilt:

Once you have the proper orientation the next step would be to determine the optimal tilt. A panel will produce most effectively when it is perpendicular to the sun. The suns elevation changes throughout the year so you should take the average elevation/ the latitude for your arrays specific location to use as the tilt. Something to keep in mind is that you may be limited to the engineering specifications. Here in CT we have winds that cause most ground mounted arrays to be restricted to a tilt of ~35° or less. In this case you should tilt the array to that 35° when possible. 

Example: The following will be based on a project in CT at a 41° lattitude

We have a project in New Milford CT that is a top-of-pole mounted solar array. With this type of mount you are able to adjust the tilt of the panels.

The array was installed facing south/ south-west (as seen from Google maps screen shot below). In some cases true south isn't always the best option because of shading or obstructions. For this particular site we adjusted the orientation to avoid shading. 

With this design you are given six different tilt options:

As previously mentioned, our engineers recommend a tilt no greater than
35° for a ground mounted array in CT.

Now that you have installed an array facing true south with the ability to adjust the tilt, the next question is: When and how often should we change the tilt?

We'll first start with how often. Compared to an array that is constantly following the sun (solar tracker) a fixed tilt array will collect approximately 71% of the available energy (assuming ideal conditions). An adjustable array which you change twice a year will yield approximately 75.2%. Finally, if you were to adjust the array four times a year, or every season, you will be able to collect approximately 75.7% of the available sun. 

Given the small benefit increase of changing the tilt more than twice a year we recommend adjusting your array once in the spring in once in the fall. The best dates for a project in CT would be around March 30th and September 12th. 

For this specific project we recommend the 15° setting starting at the end of March through early September. For the fall and winter we recommend no greater than the 35°, again because of engineering loads.