What is Near shading loss in solar PV system

What is Near Shading Loss in Solar Photovoltaic (PV) System?

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As you have already seen the Title, in This topic, we are going to discuss about the Near shading Losses in a Solar PV System and what causes such loss. But, Before we begin, allow me to share some important facts with you regarding the System losses in Solar PV System.

Alos, We have made a explanation video on this topic. Shared the video here for your reference.

What is Near Shading Loss in Solar PV System

We segmented the losses in Solar PV system in, 4 major categories, based on our knowledge, experience and mostly per industry’s acceptance. First is optical losses, 2nd is Solar Panel related losses, 3rd one is the DC to AC conversion losses and 4th one is AC system losses.

Main System Loss Categorized for Solar PV System
Main System Loss Categorized for Solar PV System

Let’s know more about the Optical Losses. Before we proceed further, please take note of two things.

  • First, we are discussing at Solar PV module level, not at solar cell level. Because solar cells have their own different set of losses, and that is another video.
  • And the 2nd point is we are talking about the losses which are occurring at the module’s plane, which is from GII onwards. SO, losses happened due to tilt angle and azimuth not considered here. Okay, lots of discussion already, let’s come to the main subject now.

Near Shading Loss

So, in optical losses, first we should talk about Near shading loss. As the term suggests, this type of loss occurs because of shadows on solar panels from the objects that are near to it. Now, this may happen because of two main reasons. 

First,

the nearby obstacles like buildings, trees, overhead electrical lines and specifically, for rooftop installations, situations like service areas including water tanks, Satellite dishes, Air condition chillers etc.

If such cases are there near to solar arrays that cause shades directly in the solar panel, then it is advisable to avoid such areas for Solar photovoltaic installation.

Shadow on Solar Panels from Near by Trees
Shadow on Solar Panels from Near by Trees

Similarly, for Large Scale Megawatt solar plants, shadows from transmission lines, even near-by Wind-turbines will cause shadow on Solar PV arrays. 

Wind Turbines : Create Shadows on Large Solar Plants

Because shading not only decreases the total electricity production of solar panels, but also can create Thermal Hotspots which eventually results in long-term degradation of PV panels.

Hotspot Due to Shadow
Hotspot Due to Shadow
Burnt out Module due to Hotspot
Burnt out Module due to Hotspot

There is research shown that these kinds of shadows cause Junction diode failures and fire hazards even.

Fire Hazard Due to Long term Hotspots and Diode Failure
Fire Hazard Due to Long term Hotspots and Diode Failure

Commercially, if you install solar panels in the shaded area, even the manufacturers won’t provide you the product and performance warranty. So, in any case, you should avoid installing solar panels in shaded areas.

Consider taking the shade area on 21st December as the length of shadow is highest on that day in a year.

Consider taking the shade area on 21st December as the length of shadow is highest on that day in a year.

Summarizing the Above discussion on Near Shading for near-by Obstacles are as follows:

  1. Avoid installing Solar Panels very near to Buildings, Trees, Electrical poles etc which causes direct shadows on solar panel’s surface.
  2. Avoid such shades for Solar Panel’s long life
  3. COMMERCIAL IMPLICATIONS: Module Warranty shall be Void
  4. EXTREME CASE: Hotspot occurs, junction diode failure, even fire hazards like situation may happen

Second,

The Inter-Row Shading. This occurs due to the shading from the modules that are ahead of each row especially if the row spacing is narrow or if the tilt is high. To mitigate this issue, you have to keep a certain distance between two rows and at an optimized tilt angle, so that there is no inter-row maintaining the GCR or Ground coverage ratio optimized.

A Pictorial Representation of Inter Row Pitch Calculation
A Pictorial Representation of Inter Row Pitch Calculation

This is a very complex scenario, we will cover these topics GCR and How to Calculate Inter-Row Spacing in separate posts. Do Follow our works for more insight.

Back to the near shading loss, again in this case also, modules can develop hotspots, which causes losses not only in generation but also both in safety and assets.

Proper Design of Inter-Row Pitch for Solar PV Plant

So we highly recommend that during project site survey and assessment, please make note of any nearby obstacles.

Annual Shading loss  upto 2% is considered to be moderate and within acceptable limits.

So, while you will be designing your PV system in software like PVsyst or Helioscope, you’ll make sure of the exact amount of shadow loss by creating the 3D shading scene.

So, drawing conclusion to the 2nd part of the discussion on cause-effect of Near Shading are as follows:


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