Building a solar installation to work in the shade

Do solar panels work when there’s shade?

Sometimes no matter how much planning you try to do for your solar installation, you can still come up against the challenge of dealing with shade. Will your solar panels still work in the shade? How can you design a system that continues to operate at optimal efficiency even when there’s partial shading?

How exactly do solar panels work and will they work in the shade?

First off, let’s talk about how solar energy works. Solar panels are made up of many solar cells made of silicon and have both a positive and negative layer. This creates an electric field. When sunlight hits a solar panel, it creates an electric current.

To move that current, you’ll connect your solar panels to a charge controller, battery, and inverter. Charge controllers limit and monitor how much current goes through a battery. Batteries then store and produce DC power. In order to use household AC appliances, such as blenders, laptops, and phone chargers, an inverter is installed to change that power from DC into usable AC power.

As we know, solar panels collect energy from the sun and convert it into electric current that our solar installations can use, store in batteries, and power devices and appliances in our home. As noted above, we need sunlight in order to create electric current. If your solar panels are in the shade they will in fact still work, just at a lower capacity due to lower sunlight exposure levels. Though how much it will be impacted is dependent on exactly how much shade the solar panels are facing, a rule of thumb is that solar panels will produce about half as much energy as they would in direct sunlight.

What can I do to build a system that operates best in the shade?

The short answer to this is: inverters. There are two main types of inverters: microinverters and string inverters. Microinverters are attached to each panel in a solar installation, so if one of your panels is shaded, it will not impact the output of the other panels.

In the case of string inverters, each of the panels are part of a connected system, similar to a plumbing installation. If solar power is like water flowing through your pipes, shade is something that blocks that flow. The output of the entire string will be greatly reduced as long as there is shade.

What are string inverters?

String inverters are the most common inverter for household installations. In a string inverter system, all of your solar panels are connected to the same inverter. While this cuts down on the need for lots of separate inverters, it also means your system is only as strong as the weakest link. So if one or two of your panels is covered by the sun, the rest of the panels will operate at that same decreased efficiency.

What can I do if there’s partial shading on my system?

1. Plan your solar array to be mounted where there will be no regular shading: When first planning where you want to mount your solar panels, try to plan for mounting them where they will get the most sunlight. Consider all times of day as well as all seasons of the year to consider whether a tree, chimney, or your roof itself will cast a shadow over where you plan to mount your solar panels. An installer can use a range of advanced mapping tools to see if shading will be a problem. If you are in a situation where there’s not a feasible, unshaded spot on your roof to mount your solar panel array, you can consider installing ground mounted solar panels.
2. Install a system with microinverters: Solar panels with microinverters are best equipped to deal with shading issues because as noted, each panel has a separate microinverter. If you want to use string inverters, we’d recommend purchasing power optimizers.
3. Use a string inverter that has MPP Tracking capability: You may be familiar with the highly efficient Maximum Power Point Tracking charge controllers. MPPT is also now a technology that comes standard in most quality inverters. An inverter equipped with an MPP Tracker (or several of them) is able squeeze the most usable energy possible out of a string of solar panels (even when shaded) by adjusting the voltage to always suit the inverter’s preferred input range. In a nutshell, an MPP Tracker helps to minimise output losses associated with partial shading and other panel output mismatches.
4. Use power optimizers: Power optimizers are small and usually installed at a ratio of one per solar panel. However, unlike microinverters, a central inverter is still required to convert the DC electricity from the panels into usable AC electricity. The job of the optimizers is to condition the power produced by the panels so be as friendly to the inverter as possible – thus maximising overall solar system energy yields.
5. Consider staying on-grid if much of your roof is in the shade: Staying connected to the grid will give you the ability to collect energy with your solar panels when you have access to sunlight and give you the option to tap into the grid during the times of day when your panels are exposed to the shade or during cloudy weather.

Conclusion

Although shade is a challenge, it’s not a solar death sentence. We recommend doing some research and planning to best understand the specifics of your roof and ensure if you are encountering shading issues, your system is designed to best deal with them.