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Shading Effect: How to Mitigate + Panel Products with Less Impacts

Beyond equipment configurations, the efficiency and power output of solar panels largely depend on the solar irradiation conditions. Under shading circumstances, you might think that only those shaded areas or panels will be impacted.

Unfortunately, in many cases, shading can significantly influence the performance of the complete system.

This article will elaborate on the shading effect on solar panels, with suggested ways for mitigation. You can also expect to see panel products with less shading impacts.

Exploring the Shading Effect on Solar Panels

What Is the Shading Effect on Solar Panels? What Causes It?

The shading effect on solar panels refers to the decrease in their efficiency and output when something blocks sunlight from reaching the solar cells.

Literally, why didn’t we use the scenario of when something blocks sunlight from reaching solar panels? This is aimed at assisting in a better understanding of the principles behind the effect.

The solar cell is the basic unit of a solar panel. A panel typically consists of dozens of cells connected together using series or a combination of series and parallel connections. Nonetheless, series connection is the essential means by which solar cells are connected.

In physics, ideally, the current through each connected device in a series circuit is the same. If one device is in an abnormal state, ‘mismatch’ will occur, and the overall current of the circuit will be limited by the device with the lowest current output.

Hence, even just a shaded cell can outcome a negative impact on the performance of the complete solar panel, subsequently, the system.

Below are several factors that can cause this shading effect:

  • Nearby Obstructions: Trees, buildings or other structures that cast shadows in the daytime.
  • Dirt and Debris: Accumulation of dirt, leaves or snow can cover portions of the panel or array.
  • Bird Droppings: These can create small shaded areas on the panels.
  • Angle and Orientation: Improper configured angle or orientation of the panels can also lead to reduced exposure to direct sunlight during parts of the day.

Impacts of Shading (Besides Panel Performance)

Some studies reveal that shading on just one solar cell in a panel can reduce the power output of the entire panel by 50-80%, being is a considerable figure.

On panel level, shading induces not only performance decrease, but hotspot effect that can potentially pose severe results. 

As one principal factor in producing hotspot effect, shading makes the shaded cells absorb less sunlight and generate less power compared to the unshaded cells. This ‘imbalance’ in power production can cause the shaded cells to heat up as they dissipate the excess energy as heat. If the shaded cells go through prolonged exposure to hotspots, they are more likely to get accelerated degradation, reducing their lifespan.

Additionally, the localized heating caused by hotspots can also damage the materials within the solar panel, such as the encapsulant and backsheet. Over time, this damage can compromise the structural integrity of the panel and reduce its overall lifespan.

In extreme cases, hotspots can reach the flammability point of panel materials and lead to a fire, which presents a danger to both assets and users.

Ways to Reduce Shading and Mitigate Shading Effects

Reducing shading represents the goal to minimize the negative impacts of shading from the source. While mitigating shading effects means lowering the impacts based on existing shading conditions with technical measures.

Measures to Reduce Shading

  • Comprehensive Site Assessment & Planning: For new and upgrade solar projects, conducting thorough shading analyses during the sit survey stage is crucial to help in installing solar panels in positions with minimal shading in the daytime.
  • Regular Maintenance: Trimming nearby trees can reduce shading and improve the system's efficiency. You should also make use of solar panel cleaning tools and robots to clean any coverings on the panels, including dirt, debris and droppings, regularly.

Technologies to Mitigate Shadding Effects

  • Panels With Bypass Diodes: Many modern solar panels have added bypass diodes to mitigate shading effects. As shown in Figure #1 below, these panels group cells into several groups, each equipped with a bypass diode. These diodes provide an alternate path for current to bypass shaded cells, preventing the entire panel's output from dropping drastically.
  • Inverters With Panel-Level Functionality: Although string inverters are the go-to option for many projects due to their cost-effectiveness, they cannot manage the performance of each panel individually. Optimized string inverters and microinverters are types of MLPEs that provide panel-level power monitoring and optimizing. The former adjusts the voltage and current at each panel to maximize output despite variations in performance due to shading. The latter converts DC to AC at each panel, isolating the underperforming panel(s) from the rest.
  • Optimized Panel Configurations: After a thorough evaluation, panels can be connected in parallel to ensure that the output of unshaded panels is not affected by shaded ones.
Solar Panel With Bypass Diodes
Figuire #1: Panel with bypass diode design | Source: Mohamed Amer Chaaban / The Pennsylvania State University

Panel Products That Have Less Shading Impacts

If your projects are located at a site that might have large amount of shading that cannot be well managed, put these advanced panel products into your consideration.

Half-Cut Solar Panels

Due to their design with solar cells cut in half, half-cut solar panels exhibit increased tolerance to partial shading, which translates to improved efficiency and less power losses compared to standard ‘full-sized’ panels.

This increased tolerance to shading is attributed to the higher number of substrings in half-cut panels, allowing them to mitigate the impacts of shading more effectively.

Bifacial Solar Panels

Bifacial solar panels capture sunlight from both their front and back surfaces. Though their front surfaces may be shaded as traditional panels, their back surfaces can still absorb reflected light from the rooftop, ground or nearby structures.

This mechanism can partially compensate for the loss of direct sunlight due to shading on the front side.

Singled Solar Panels

As the smaller solar cells are overlapped and interconnected in a shingle-like manner, shingled solar panels also reduces shading losses and improves overall efficiency.

Those shingled panels integrated with matrix technology even demonstrate more robust performance than those designed with the standard string approach. Plus, if you or your clients feel disgusted about traditional dark black or blue with visible grid lines, try shingled panels. They are also renowned for their appealing aesthetics, with a uniform appearance and smoother surface.

Final Words

Shading effect could be bound to happen on solar panels because of the constraints imposed by principles of electrical circuits. Be frank and be confident to transfer this fact to your clients.

In addition to carrying out some manageable measures to reduce the occurrence of shading, some advanced technologies and panel products bring about less impacts by shading and can provide better efficiency and output for you.

Without a doubt, you should weigh up the cost, payback time and your expected power outcome.

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