Optimizing Solar Panels

It happens every year--actually twice every year.  The track of the sun through the sky changes drastically and rapidly.

In the spring, the sun is rising higher in the sky each day, and that means we can do our bi-annual adjustment of the solar panels to get the maximum amount of power possible.  During the fall, it's time to readjust and get ready for the sun to ride lower in the horizon.

The Problem

There are a number of factors that affect the efficiency of a solar panel, and one of those is the angle at which the solar rays hit the panel.  The ideal angle would be perfectly perpendicular (90°).  And while it is impossible to keep a perpendicular angle all day without an expensive tracker, we can set our panels at an average that maximizes their potential.

The problem for those of us who don't live on the equator, is that the sun's position in the sky changes throughout the year.  The further one moves from the equator, the more drastic this variation is.  In the summer, the sun arcs high in the sky, while the winter months see the sun skimming much lower to the horizon, particular in northern latitudes (if you are located in the northern hemisphere).  But don't despair, there are two simple rules to follow when aiming your solar panels.  And for those of you who want to generate the maximum amount of power with the minimal amount of work throughout the year, you need only make one simple adjustment twice per year to achieve that.

Initial Settings

First we will deal with the horizontal azimuth of the solar panels.  This would be the equivalent to you standing up and looking straight ahead while spinning in a circle.  You could be facing North, South, West, or East.  This is your horizontal azimuth.  For maximum efficiency, the panels should be aiming at 180° true south (not necessarily magnetic south).  If you are in an area where magnetic south (what your compass reads) is significantly different than true south, you should do a quick search on Google to learn how to compensate for this magnetic deviation (so your panels are point at the true south pole rather than the magnetic south pole--which is in a different location).  Once we set the horizontal azimuth, we will not change it.  This will always be the best location for the panels to face whether summer or winter.

There is one exception I must mention to the above rule.  If your location has a significant obstruction to the south that cannot be moved, you may be better served by turning the solar panels slightly so they are perpendicular to the portion of the southern horizon where they are able to get direct sunlight.  An example could be a location where a mountain range is blocking significant sunlight from the southeast.  In that situation, it may make sense to angle the panels more to the southwest to maximize what direct sunlight is present.

Next, we need to set the vertical tilt of the solar panels.  If you are going to be setting up a solar array this summer, here is a simple rule of thumb for determining the optimum vertical angle:  Your latitude minus 15°.  Here is a simple online tool to help you find your latitude.  If your latitude is 30°, take 30 - 15° = 15°.  This is assuming that 0° is horizontal and 90° is vertical.  You can buy a clinometer (aka inclinometer) or build one yourself or use a protractor, speed square, or even a tape measure (for those of you are are geometrically inclined).  If you were setting up the solar panels in the winter, the rule of thumb changes to this:  your latitude plus 15°.  Back to our example, latitude of 30° + 15° = 45°.  If you get confused, just remember that the solar panels should be more horizontal (pointing high into the sky) during the summer and more vertical (pointing towards the southern horizon) in the winter.

Adjustments

One could get carried away with this adjustment business and make a 1° adjustment every week, but the amount of additional power produced would not be worth the work required.  In my opinion, the best balance between effort and efficiency may be found by making an adjustment two times per year, once in the spring and once in the fall.  When spring arrives (usually March/April) move the panels to their summertime position.  When fall arrives (Sept./Oct.) adjust to the winter position.  An added benefit of placing your solar panels in a more vertical position each fall is the increased ability to shed snow.  If your solar panels are mounted in an accessible location (not on the roof), there may be a few times every year when you choose to brush them off, but you may find that they shed the snow quite well as soon as the sun comes out.

Mounting

The obvious caveat here is that your solar panels must be mounted in such a way that the vertical tilt may be easily adjusted.  There are a number of ways to accomplish this, but we have had good success with these mounts mounted to a false wall (basically a number of large pressure treated posts in a row, set in concrete and connected with 2x6's).  An even better (albeit more expensive) option would be here or here.

And for the creative person with more time than money, the sky is the limit!  I have heard of everything from mattress rails (basically angle iron) to a homemade tracker utilizing an old c-band satellite dish motor.