The post explores the impact of shading on solar panels by objects to their east or west on generation, in Northern India.
While assessing a site for installation of solar panels, most surveyors have a good understanding of how to handle shading impact from objects to the South of a given area. However, for objects to the East and West there aren’t too many established “rules of thumb”. While there are plenty of tools such as PV Syst to assess shading impact for solar power plants, a quick reference is quite useful while on site doing initial surveys.
Length of shadows varies year around- being longer in winters and shorter in summers. In locations where solar plants have been installed to maximize annual units generated or to take benefit of net metering, it is instructive to look at reduction in annual generation due to shade.
Sunkalp Energy used some data to determine the impact on annual generation of solar power plants from shade of objects to the East or West of them.
The graphic above shows a shading object such as a staircase room on a roof, of a height H. A solar panel is placed at a distance D from the object. The yellow slice of the pie shows the reduction in generation for each case of H/D. We can see that the closer the solar panel is to the object, greater is the reduction in generation.
In the first case, where the distance between the solar panel and the object is half the height of the object, annual generation is 9% less than that of a solar panel in a shade free area.
When the distance between the object and solar panel is same as the height of the object, the annual generation is 3% less than optimum.
As we increase the distance between the solar panel and object, the impact of shading decreases. However, we typically want to optimize the kWp installation and annual generation. The graph below shows that the reduction in generation changes quadratically with distance.
For this purpose, Sunkalp Energy recommends that the optimal distance between a solar panel and a shading object to its East or West should be 1.25 times the Height different between the two.
It is important to note that if even one solar panel is shadow, the entire string will be impacted.
In urban India, roof space is scarce and we can’t always install good capacities of solar panels if we leave out large amounts of space due to shading. One way to counter this is by installing the solar panels on raised structures. The graphic below indicates how by raising the solar panels, the height difference between the object and panels reduces. Thus increasing the D/H ratio and reducing the impact of shading.
If you have more questions about shading, are solar in general, feel free to get in touch with one of Sunkalp Energy’s trusted solar advisors or call us at +91 11 41620247.