While planning for our photovoltaic roof array, we were looking into optimizing the solar exposure. There are various online resources one can use, and there are site tools such as the solar path finder.
We did an assessment with the solar path finder tool, and knew that certain parts of the roof (or the photovoltaic array) would receive some shade around the winter solstice. With the photovoltaic roof array now installed, we could test those findings.
The biggest shade contributor, as expected, is the roof access enclosure. The good news is that by February 16th the sun is high enough over the horizon that the first row of modules no longer receives shade from the roof access structure.
The vent stacks to the right of the array are also shade contributors. But because all those vents were higher than they needed to be, I was able to lower them and reduce their shading potential.
We also knew that the American ash tree to the west would cast some shade in the afternoon. That tree has since succumbed to the Emerald Ash Borer, and we are now waiting for it to come down.