Why does the tracker reach 45 deg. tilt earlier ?

Question:

I’ve noticed a problem with our single axis tilt tracker that we replaced.  It’s begun reaching 45 degrees west earlier and earlier in the day rather than later, which you would expect going into summer.  A recent plot shows it reaching 45 at 2:20 in the afternoon.  A month prior it was reaching it a 3:00.  What is up?

Answer:

Because the panel tilt is flat at local apparent noon or Z=0 we need to look at the solar azimuth for positioning so in this case Az of 180 = 0 tilt. We continue this way 45 degrees to either side from where we resume using the Zenith value for the tilt. In the winter the span of Azimuth is narrower hence as we approach summer we will reach the 45 deg position sooner because the Azimuth of 225 is reached sooner.