Does Shading Affect the Performance of PV Panels?

We all want to make the best of our solar panels, and sometimes we need a little bit of information on how they work.

A typical concern for solar PV system owners is whether or not shading will affect the performance of their panels, and how much impact shading will have on their system's production.

Here is what you need to know.

Shading has a big effect on solar panels' performance, and how much power they will produce over the course of the day. However, the size of the shade and its location in relation to the panel make a difference in how much power is lost.

For example, a solar PV system with a 1m2 block of shade on the corner specific part of a single panel will likely experience less energy production drop than another solar PV system with the exact same size of shade but randomly distributed on multiple panels.

Shading distribution is an important factor that affects energy efficiency.

Also, not all shading is created equal. Shading that occurs early or late in the day won't have as large an impact as shading which occurs during peak summer hours when your system would be producing the most energy.

Here are the factors that affect how much energy is lost due to shading:

• How much shade is there? (surface area)
• Is shading uniform or non-uniform?
• How frequently the shade occurs (e.g., does it happen twice a year or every day?)
• What time of day or year does this shading occur?
• Where are these shaded areas located on your system?
• Do you have a single panel or multiple panels? (The size of panels)
• What technology do your panels use?
• What is the orientation of your panels throughout the year, and are you using a tracking system?
• Is shading from trees, buildings, clouds, or something else?
• Do you have bypass diodes?

This has an effect on how much power output your system may lose at any given time. It's difficult to give you an accurate answer without knowing all of these variables.

However, keep in mind that even small amounts of shade, especially if distributed in a non-uniform pattern on random spots on your panels, can have a significant impact on their energy generation.

Also, shading is not a black or white issue, but rather a spectrum. For instance, solar panels installed under a canopy with clear plastic or glass will still experience shading issues from the glass or plastic, even if these materials allow sunlight to pass through. Therefore, it’s important to consider shading in your installation plans.

Shading reduces the energy efficiency of a PV panel by blocking sunlight. If a shadow is cast on a portion of an array, the cells under the shadow will be unable to produce electricity.

This, however, will have an impact not only on the performance of the cell in the shadow but also on the overall energy efficiency of the PV system.

All PV panels have a peak power output, which is calculated based on the panel receiving direct sunlight with no shading.

Most people buy solar PV systems with the expectation of recouping their money in less than a decade. If there are shading issues, the system's efficiency will suffer, and the investment's return period will be much longer.

Shading also results in electrical mismatches and uneven energy generation across modules. Shaded cells can overheat, resulting in the hotspot effect and irreparable damage to the PV module.

This occurs when solar cells receive non-uniform irradiance, are partially shaded, or if differences between solar cells are inherent in the manufacturing process.

Also, reverse-biased behavior may cause the solar cell to overheat. As a result, if the PV module is not protected, hotspot failure can occur, and in extreme situations, the panel can be permanently destroyed.

A hotspot failure occurs when a portion of a cell or PV module has a higher temperature than its surroundings. A hotspot is typically formed as a result of power dissipation in a reverse-biased PV cell.

When a PV cell achieves breakdown voltage, which is defined as the maximum allowable reverse voltage for the safe operation of the p-n junction, permanent damage might ensue.

When this voltage is reached, the reverse current skyrockets, resulting in device destruction.

What are the common sources of shading on solar PV systems?

Trees and their leaves

The trees are a common source of shading on solar PV systems. It is generally best to keep trees and large shrubs at least three meters away from the panels or else you might find that they are cutting your energy production in some cases by up to 50%.

Leaves falling off trees is a common source of shading on solar PV systems.

It is important to keep leaves and other plant matter away from the panels, as much as you can. This emphasizes the importance of regular and thorough cleaning of the panels.

Buildings and their roofs

Buildings can also cause shading on PV systems especially if they are taller than your solar PV installation or built too close to where the PV modules are mounted. Similar to trees, buildings can also affect your solar energy production.

You might need to check with a professional if it is possible for you to move the PV panels or relocate them on your property in order to avoid shading from tall and nearby buildings.

Other Panels

Solar panels can also be shaded by nearby panels if they are installed too close or without proper planning.

This is why it's important for you to know how much space your PV panels need in order to operate at optimal levels and produce the maximum amount of energy possible with each day.

Clouds

The amount of sunlight reaching the solar panels is heavily influenced by the weather.

Clouds do not entirely obscure the sun, but they do lower the amount of sunlight that reaches the panel, reducing the amount of solar energy captured and converted to power.

However, this is not something to worry about too much. Clouds are typical in many areas, so this should not have a negative impact on your solar energy production unless the installation location is consistently covered by clouds.

Uniform shading vs Non-uniform shading

Shading patterns have an impact on the overall energy efficiency of the array, thus it's critical to understand the consequences of shading patterns ahead of time.

Uniform shading

Uniform shading occurs when an entire solar panel is shaded by something like clear glass or plastic that allows some light to pass through.

Another example of uniform shading would be solar panels operating on a cloudy day. Although cloud cover reduces the energy efficiency of solar cells, they can still produce energy.

Also, a neighboring building casting a shadow can also be considered uniform shading because the shading footprint is generally uniform.

Non-uniform shading

Non-uniform shading occurs when something is obstructing the solar panel in a way that isn't uniform, like tree branches or leaves during different seasons of the year, since some parts will be fully shaded while others may have more direct sunlight.

The amount of energy efficiency loss will be depending on the size size of the shade and how it is distributed across the PV modules.

How much of a difference does shading make on the performance of PV panels?

Researchers have made the following case study. They have covered a portion of the solar panel with cardboard and then measured the difference in power production.

They have found the following results:

One would expect a corresponding decrease in power to shade, i.e. a 25% reduction for a 25% loss in power.

However, this is nothing but a wrong assumption. Because shaded cells are not only able to produce energy but also to absorb energy, which can lead to overheating and damage of the panel.

How to fix shading issues of solar PV systems?

Shading issues can be fixed if you plan the solar power system accordingly, and maintain it regularly.

To avoid shading issues, you can observe the sun's path and identify where it will fall, before installation of your system. You can also check if any trees or structures might obstruct sunlight from falling on panels in the future.

Once installed, you should monitor the performance of solar panel systems to notice areas that are shaded more than others so that you can act accordingly.

Use a tool to see the sun's path on a map

Although shading will affect the entire system, it is important to understand where and how often shading occurs on your roof.

The best way to do this is by using a solar pathfinder tool like Solmetric's System Advisor Tool (SAT) or Solar Pathfinder: Shading Error Calculator.

These tools can help you identify which areas on your roof are affected most by shading, and help you determine the ideal panel layout.

Ensure that trees a trimmed

Ensure that trees are trimmed regularly so they don’t grow too large and block the sun. If you have control over the landscaping, ensure that the trees are not planted in a way to create shade on your roof.

Certain trees will almost always cause shading issues and block sunlight from reaching your PV system. You should plan ahead and avoid these trees at your site early on.

Use a solar tracker

Solar trackers keep your panels pointed at the sun throughout the day so you can get the most out of your PV system. If your system does not have a solar tracker, you may want to consider using one if shading is an issue at your site.

Use shade data and assess if you need a tracker or not. A solar tracker will cost more than having some landscaping done. However, it is a good investment that may save you more money down the road.

Assess the Situation

First, you should perform an analysis of the shading in your area using data from satellite imagery or aerial photos.

Both Google Maps and Bing Maps offer free access to high-resolution images that show how much shade is cast by surrounding trees and buildings on a specific location at different times throughout the year.

The Solar Pathfinder tool can help you get a quick overview of the shading in your area.

After identifying any trees that are blocking sunlight and perhaps getting a few estimates for trackers or having some landscaping done, assess what can be done in regard to shading and how much it will cost.

Certain shading issues are unavoidable but can be improved. For instance, if you have a building that is taller than your PV system and casts a shadow, you may want to consider relocating the panels somewhere else.

The level of shade (is it partial or complete? ), the time of day when shading occurs (is it for a couple of hours, midday, or all day? ), and the annual variation of shade (is it seasonal, such as from a tree that loses its leaves in winter, or is it permanent, such as from a building) all play a role in determining whether solar energy makes sense for your specific situation.

Furthermore, the design of the solar panels will be important. Even though the actual area of shade is small, solar modules linked in series with a central inverter will be more severely affected than those connected in parallel with micro-inverters.

Redistribute your PV system layout

If there is significant shade covering one or more panels (typically from nearby objects), it may be necessary to redistribute your array's current layout in order to maximize its performance. This can usually be done by rearranging modules or changing their orientation.

If you don't have enough space to reconfigure your layout, or reconfiguring is not an option, you can add more panels to make up for the loss in energy production caused by shade.

Although this will not solve the issue, it will allow you to maintain your system's current energy output.

Use micro-inverters (rather than a central inverter)

Micro-inverters are more pricey than central inverters, but they could pay for themselves generously if your roof has some shade and/or a complex geometrical design.

Shade on your solar panels can affect your system's energy efficiency similar to old-school Christmas lights connected in series. You very probably know what I am talking about. If one bulb fails in a series, all bulb fails.

Solar panels connected to a central inverter suffer from the same vulnerability: one shaded panel can prevent the entire string from working.

Because the central inverter optimizes the output depending on the weakest link in the chain, this will result in a major or complete loss of electrical supply.

On the other hand, micro-inverters allow each solar panel to function at its maximum capacity regardless of weather conditions, shading, or other external influences.

So if one solar panel is shaded, it will not have a big effect on your entire PV system. As a result, a single solar panel will not diminish the energy performance of your entire solar array.

Consider community solar

After considering all factors you can conclude installing a solar PV system for your property doesn't make much sense for your case. In fact, this can happen for a lot of homeowners.

For instance, having a tall neighboring building would very likely block the sunlight from hitting your solar panels for a large part of the day.

In this case, it may make more sense to join a community solar project where you can share the electricity output with nearby residents.

Typically, it will not cost more than if you had installed your own solar system on your property. Besides getting to support clean energy projects and reducing pollution, which is another great reason for joining community solar initiatives.

Keep your panels clean

Keeping your panels clean and free from dirt and grime will ensure that they can capture as much sunlight as possible.

You should regularly clean them to get rid of any dirt, leaves, bird droppings, etc., that may have accumulated on the surface over time. This is really something you have control over, and you don't want to neglect it.

What Equipment Can Help Reduce the Impact of Shading?

Reduced sun exposure is the biggest contributor to the decreased energy efficiency of solar PV systems.

Lower exposure to sunlight is largely influenced by the design layout of your solar installation and the type of inverter.

Specific solar inverters may not function effectively for you if your home's roof is shaded for the majority of the day.

The inverter is basically the solar energy system's brain. Inverters convert direct current (DC) to alternating current (AC) and are critical to the operation of solar panels. The correct inverter will aid in reducing efficiency losses caused by shaded solar panels.

String Inverters

An inverter is a device that converts electricity from direct current (DC) to alternating current (AC) (alternating current). String inverters are the most basic sort of inverter technology.

A string inverter configuration links a number of solar panels to the same inverter in a solar energy system.

This means that the entire solar array will be powered by the lowest solar panel. String inverters are the worst form of an inverter to use for solar panels that receive varying quantities of sunshine throughout the day.

String Inverter with Power Optimizers

Power Optimizers enable string inverters to circumvent their most significant shortcoming.

Power optimizers function similarly to microinverters in that power is optimized at the panel level before being transferred to the single string inverter.

They essentially function as a hybrid of a string inverter and a microinverter. Power optimizers, like microinverters, can assist mitigate the effect of a single panel being shaded on an overall system. Also, you only need one inverter, which saves money.

Microinverters

Microinverter-equipped solar panels are most suited to dealing with shading concerns. This is because, in a microinverter configuration, each solar panel has its own microinverter.

If one solar panel is entirely shaded, the other solar panels in the same array stay unaffected.

Conclusion

Shading will reduce the amount of power produced over time, resulting in lower overall returns on investment (ROI) due to lower electricity production.

Minimizing shading exposure is recommended if you want to get the most out of your solar panels.

Because of the electrical characteristics of solar cells, power losses are not proportional to shaded areas, but rather greater.

As a result, even a few areas of shading can significantly reduce the PV system's overall performance. Even minor shading can result in significant power losses or system failure in small PV systems with few or no parallel connections.