Technical feasibility (Shading Assessment)

A crucial step in preparation to installation of solar PV plants is the shading assessment. The shading analysis is detrimental because the performance of a PV module is heavily dependent on the amount of exposure it receives throughout the day and the year. Shading can damage a PV panel by creating hotspots and as panels are mostly arranged in arrays, damage to one panel will have a ripple effect on the entire array. Let us read further to understand the importance of shadow analysis.

What are the different types of shadings that affect solar PV modules?

The different types of shadings that affect solar PV panels are solid shadows, partial shadows and partial shading due to improper cleaning.

What is shadow analysis and why is it important?

Shadow analysis is the assessment of the site of installation of the solar PV modules for the casting of shadows. This technical analysis is of utmost importance before proceeding with installation because the casting of shadows on a solar PV module has a considerable impact on its efficiency and shelf-life.  The effect of shading is to reduce the photocurrent per unit area of the cell.

A shadow falling on a solar PV module blocks the flow of solar energy and eventually, the modules generate hotspots and are damaged through the rise in temperature. The shading could be of nearby trees, buildings or even inner-row shading of the installed PV module array. The efficiency of a PV module at any time reduces in direct proportion to the area of the shadowed part of the module, therefore it becomes highly important to conduct shadow analysis during the feasibility study and proper designing a rooftop solar power plant.

The shading experienced in solar PV plants can be identified as follows:

  • Self-shading– the shadow that occurs on a PV module due to another PV module.

  • Shading due to near objects – the shadow that occurs due to nearby objects which may be present within the vicinity or rooftop, around the installed PV modules. Some of these may affect the plant for a certain time of the day or for the entire day depending on their location, height, distance from the solar module. There may also be shadows that are cast due to newly built high-rise buildings, towers etc. which are at times unpredictable.

Why should the length of a shadow be considered while identifying PV array location?

The size of a shadow depends on:

  • size of the object
  • location of the object
  • date and time of the day

Taking these into account, the length of a shadow should be estimated accurately when designing a solar system so that row spacing between solar PV modules can be properly decided. Keeping in mind that the sun travels in an arch, therefore both the sun’s altitude (position) and the azimuth must be considered when determining the length of a shadow.

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