SHADING LOSS IN PV SYSTEMS AND TECHNIQUES TO MITIGATE THEM

June 1, 2021

Solar is going to be the future of energy and the growing demand can be taken as unequivocal proof of that. More than 130 GW of new solar panel system capacity is expected to be added globally in 2021. With growing solar demand (expected to grow 15% by 2021) their world is leaning towards high-efficiency modules. Besides evolution in solar cell technology that can harness more energy from sun rays, the higher efficiency modules are also focusing on reducing shading loss to enhance solar module functionality.

What is Shading Loss?

PV systems generate electricity from the sunlight they receive. Therefore, when a shadow is cast on a panel due to obstructions that come from a variety of sources like trees, antennas or poles, passing clouds, and other nearby objects-., Self-shading from other PV panel rows, Horizon shading from the terrain surrounding the installation site, and various other factors such as panel orientation, soiling, etc. the power output of the panel decline proportionally to the amount of shading. This is known as shading loss.

Why Shading Causes Power Loss?

To understand the effect of shading on solar panels, let us take the example of water flowing through a pipe.

In this scenario, the PV module is a pipe and the water is the energy harnessed from the sun. Every single solar cell in the panel works as an inlet that lets in some more water. The flow rate of water through the pipe is constant, much like the current through a cell string is constant for a given irradiance level. Now, shading a solar cell is similar to introducing a clog in a pipe of water. The clog in the pipe restricts the flow of water through the entire pipe.  Similarly, when a solar cell is shaded, the current through the entire string is reduced.

However, fortunately, evolving solar technology has brought forth several methods to reduce shading losses. They include stringing arrangements, bypass diodes, and module-level power electronics (MLPEs).

Arranging Strings: The arrays arranged in parallel strings can reduce shading loss than the series arrangement does.

Bypass Diodes: Using Bypass Diodes can allow the current to “skip over” shaded regions of the string, thus keeping the whole system operational.

Creepage distance: Higher creepage distance will lead to less soil accumulation on the last row of the cell and in the process will resolve the problem of hotspot due to shading.

MLPEs: MLPE devices include micro inverters and DC power optimizers. These are typically coupled to just one (or a few) solar modules and can improve the energy production of the system. MLPE can help mitigate production losses from a variety of different factors such as shading, module mismatch losses, and orientation mismatch losses. Further, they monitor each module and hence any problem on a particular module can be detected and removed from the strings.

New Solar Technology

With the advancement in solar technology, top solar panel companies have developed new and efficient solar panels that offer better performance in low light and shaded conditions.

For example, Vikram Solar’s new M6 cell-powered Series 6 PV modules come in Mono & Bifacial variants titled Somera Series 6 and Prexos Series 6 respectively with Mono PERC technology and Multi Bus Bar features.

This new M6 series modules offer-

• Module configuration: Solar module’s behavior under partial shading conditions is improved and its energy characteristics are raised by using half cut-cell technology, changing the module configuration and design. Since the configuration has two blocks of series-connected cells, so if one is shaded the other will keep on working.
• Performance guaranteed in partial shadow– Bypass diodes and Innovative Series Parallel connection to ensure shadow optimization in portrait mode.
• Reduction in hotspot temperatures– With half-cell, one cell generates half of the current than the standard. This declines the heat production further minimizing the chances of hot spot when one cell of the module is shaded. Lower heat production positively affects module longevity.
• Triple JB in Half cut module: Triple JBs are more reliable and cause less power loss due to shorter cable length. Also if one JB gets burnt then the other two JB’s will keep working and prevent the module from the hotspot.

Therefore, it is apparent that although shading is a real threat to solar module performance, now there are different options that you can choose from to ensure high performance of your solar panels. Although, selecting new and evolved solar panels can reduce challenges in protecting your solar system from shading losses, but simultaneously you also need to check the module performance, feature list and portfolio of the best solar panel company (manufacturers/sellers) to ensure the right purchase.

So, what are you waiting for, go green, go solar!