Sir! Solar Mein Itna Chalta Hai! – Site Assessment & Shadow Analysis

Thursday, 20 August, 2015

Site Assessment & Shadow Analysis – An important step before Rooftop Solar PV Installation.

According to MNRE, approximate 10 sq. meters “Shadow Free” area is required for 1 kWp Rooftop Solar PV Installation. The term “Shadow Free” is very important and in this blog we will be discussing about “Site Assessment and Shadow Analysis for Rooftop Solar PV Installation”.

Shadow is one of the factors that will affect the performance of Solar PV system.

Your Solar PV System Array should be designed such that Shadow will not fall on the Solar PV Panels. Shadow can be from parapet walls, tanks, structures, trees, inter row shadow and other objects.

There are many objects , like parapet walls, water tanks , O/D units of AC’s, Dish of antennas, Mummty etc. which can cause shadow. As, shown in the picture above, the objects that are situated at the South Direction of the building will cause shadow on the Solar PV System. So, the system should be designed such that it avoids the shadow of these objects.

Ideally, Solar PV Rooftop System should be designed such that no shadow falls on array, on the day with longest shadow (i.e. usually from 9am to 3pm, on December 21 in Northern Hemisphere). For Shadow analysis from nearby objects and inter rows of solar array, “Solar Path Finder” should be used at the time of Site Assessment.

The thumb rule says, that we should leave at least 1.5 to 2 times the Height of object (placed in South of the building), to avoid the Shadow effect on the PV modules. The same goes with Inter Row Spacing of the Solar PV Array, at least 1.5 to 2 times the Height of the Structure should be left in between the two rows, to avoid the Shadow effect.

Now all you need is to cross check the layout design of the Rooftop Solar PV System, as provided by the installer or need to clarify this with the installer, that what distance they had left to reduce the losses due to shadow.

If it is less than 1.5 to 2 times the Object Height, and if he says “Sir! Solar Mein Itna Chalta Hai!!”, then you surely needs to change your installer.

We’ll be talking on more such issues in our future blogs.