Do Solar Panels Work in the Shade?

In this article you will learn about how solar panels work in the shade.

There’s no doubt that low quality light is detrimental to the performance of any solar array whether it’s on your house, RV, or elsewhere.

When making an installation it’s important to analyze all the factors that could reduce the amount of electricity you will generate.

Any mistakes could leave you underpowered and take you more time to recoup your investments.

With the incredible rise of solar power over this century, there has been a rise in fly-by-night operators or DIYers who do a less than satisfactory job when installing the systems.

So if you’re planning on adding solar to your life, keep reading.

We’ll answer the question as to whether solar panels work in the shade and how to get the best performance. And armed with this knowledge you can avoid the costly mistakes made by others.

Yes, solar panels still produce electricity in the shade but performance will be significantly reduced.

You see, solar cells need sunlight. They work when photons of sunlight hit the cell to energize electrons and produce a current.

The best performance comes from direct sunlight as the concentration of photons is at its highest. When a solar panel is shaded it means an object is blocking light from hitting it directly. Most commonly this is due to trees and cloud cover. This is known as diffuse light.

The good news is that solar panels still charge from diffuse light as the photons bounce around the atmosphere and reflect to eventually reach the cells.

Unfortunately, performance is significantly reduced in the shade.

How Much Does Shade Affect Solar Panel Efficiency?

Around 30% of energy absorbed by solar panels is from diffuse light. And studying the power of a shaded solar panel backs up this data. You are likely to see a 70% – 80% reduction in electricity production in the shade.

If you already have a system installed you will clearly be able to see this by monitoring the power levels on a cloudy day compared to a bright sunny day.

Another point to consider is that shading is rarely uniform as sunlight can break through gaps in clouds or beam in between tree leaves.

So what happens to performance when only half a solar panel is shaded? Or what if you have one panel in the shade and one in direct sunlight?

Well, this type of dappled or variable light often causes a larger performance drop than you might expect. The small solar cells making up a panel are all interconnected. When one cell is shaded and one is not, the voltage of all of them drops to match the lowest.

This problem can affect the output of an entire system too when shade varies from panel to panel. When wired up in series (which they often are), the power will drop in a similar manner across the whole system to match the lowest current.

So yes solar panels will work in the shade, but performance can drop by 70% or more!

But don’t worry just yet, there are things we can do to reduce the effect or avoid blocking out the sun.

What Causes Solar Panel Shade?

To avoid the shade, we must first find out what causes it.

Clouds

Cloud cover is the number one cause of shading on solar panels around the world. To be honest, it’s pretty much inevitable unless you live on the International Space Station (which runs on solar.)

Of course, clouds can completely block out direct sunlight or create variable conditions from minute to minute. Unfortunately, there’s nothing you can do to control this but don’t get too downhearted if you don’t live in perennial sun. I’m an Englishman so I know a thing or two about overcast grey days. Yet, the roofs of countries like this are still extensively clad with solar arrays. In fact, Germany, the UK, and Netherlands continue to be some of the top solar powered countries in the world.

So even if it’s cloudy, not all is lost and we’ll discuss ways to increase efficiency in this scenario below.

Trees

I guess you could say that trees are natural predators to solar panels. Just like plants fight for sunlight in the rainforest, trees everywhere are looking to spread their branches to absorb more and more light.

And us humans are trying to do the same thing without solar panels which need sun like the leaves of a plant. So it stands to reason that they can get in the way of each other.

Trees can easily cast a shade on your array. It might even vary at different times of the year so a tree might only become a problem after you’ve made the installation. For example, it may grow added branches, put out more leaves in the spring, plus shadows change based on the sun’s position in the sky.

Roofs and Other Buildings

Your own rooftop might cause unexpected shadows. As the sun moves through the sky various aspects will cause shading across a roof. This could be from a chimney, pitch angles, and ridges. So what might appear like a strong South facing position might become obstructed at certain times. In addition, other buildings might knock out sunlight. You might stumble upon this issue during winter months as the sun starts to sit lower in the sky.

Wrong Orientation

A crucial factor when making an installation is the orientation of the solar panels. This means making sure they are facing the right direction. This is always towards the equator. In the US and Northern Hemisphere, that’s facing South. This will reduce chances of shading and increase the system performance. Accidentally orientating panels North could result in complete eradication of direct sunlight. Oops.

Other Panels

This is a silly mistake that happens regularly with sloppy installation. It’s particularly prevalent on flat roofs that use tilt angle mounts. As the panels are not mounted flat to a surface they create a shadow. If it’s too close to the next one it can cause shading on the lower cells. You might not notice this problem in mid summer, but at other times of year or day, shadows become longer as can unearth this issue.

How to Increase Solar Panel Efficiency When Shaded

Now you understand the issues with shade on a solar panel, let’s look at ways to help alleviate the drop in performance.

Microinverters

Microinverters are growing in popularity thanks to their added performance when it comes to each individual panel.

They are particularly useful in large systems where some panels become shaded and others are not. This is because each panel has its own little power inverter attached to convert the DC into AC power. This means the panel works as an individual power source and is not reliant on the rest of the system.

So when another solar panel is shaded it does not reduce the performance of the rest. It’s similar to what you experience with fairy lights where if one bulb blows the rest don’t stop working.

Power optimizers

Power optimizers work in a similar fashion to microinverters but they don’t convert DC to AC. Instead they regulate the DC output of a solar panel. It enables constant tracking of the maximum power point (MPPT) to reduce the effects of variable shade across a system. So the output is regulated at each individual panel before sending the DC power to a string inverter. They help to increase the efficiency across the whole array and add smarter monitoring and control.

What About String Inverters?

A string or power inverter is traditionally used to convert the DC power to AC power. AC or ‘alternating current’ is what the main grid uses and is required to run your home appliances.

Commonly, solar panels are connected directly to an inverter without the use of an optimizer or microinverters. When you get partial shading of a solar array the current across the whole system drops to protect itself. A string inverter will not be able to affect this performance as it simply makes the electrical conversion.