Renderings of solar panels on buildings are very helpful in visualizing the scale and look of a project. However, there are practical reasons to develop 3D computer models of solar panel layouts, and one of the most important is evaluating shading.

When obstruction exist like trees, buildings, power lines, and others, it is important to evaluate the impact of shade. Whether performing a scientific analysis or a rudimentary estimate, there are tools available to solar designers to help with this task. Fortunately, it is very easy to do at least rudimentary solar shading analyses with the modeling tools we use. For example, Sketchup provides a geolocated sun path that will cast shadows from modeled obstructions. It can greatly assist in deciding where to put solar panels, and more importantly, where not to put solar panels.

Below is a video showing a home  with solar panels and a large tree on the property. The shade path is tracked from sunrise to sunset on December 21, the day of the year when the sun is the lowest on the horizon. It compresses the 10 hour and 28 minute day into 15 seconds.  It shows that there is a substantial amount of shade on the panels on this day of the year, and performance will be severely hampered. Some things can be done to mitigate the production losses through product selection, or perhaps an alternate installation location should be selected.

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Solar design is more than just creating a pretty picture. We perform important functions that make the modeling effort very valuable for more than just visualization purposes. Advanced tools can be used to calculate the actual percentage of shade on a solar panel over time, allowing us to do detailed production estimates. Because these studies are complex (and consequently expensive), a detailed analysis of a site is often not done in favor of a more simple analysis that uses a designer’s experience to come up with a rough estimate that is close enough for most purposes. It is impossible anyway to get a perfect answer because trees grow, foliage levels vary, and weather varies. Using Sketchup or other tools to estimate shading is a powerful and efficient way to use 3D computerized solar designs for a practical purpose.