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The Rise of Electroluminescence in the Aerial Data Industry

By September 6, 2021November 22nd, 2023One Comment

Electroluminescence (EL) is the new buzzword of the solar industry. In this blog, we will explain what Electroluminescence is precisely, and why it’s worth keeping an eye on it when it comes to complementing thermal inspections.

Let’s start with the basics: What exactly is Electroluminescence, and who is it for?

In short, Electroluminescence (EL) relies on the same type of technology as a led emitting diode (LED). As an example, these are usually found in modern illumination solutions in your home. But in the case of EL and solar panels, the current is pushed into the solar cells, which are technically large LEDs. The cells then emit light in the near-infrared range (NIR), but this light is outshone by the sun in daylight. Therefore, these emissions are recorded at night with unique high-resolution cameras. When the cell is damaged, there is either less current passing through or none at all. This results in a less bright or completely dark cell when compared to the working cell.

One of the leading EL capturing companies in the industry is Aerial PV Inspection. Their inspection software employs a neural network (CNN) to identify and categorize faults in EL images. The neural network was trained through thousands of EL images in which faults were marked for each category by human experts. The impact of cracks and inactive cell areas stems from their experience and several expert studies.

For customers who want to take that extra step in knowing which panels are causing losses in yield and why EL is the perfect way to obtain that. And this is where our Sitemark Fuse Platform becomes a powerful tool. Together with Aerial PV Inspection, we create a fully integrated mix of aerial thermography and EL, all in one place.

This makes it a valuable tool for

  • Quality control during the commissioning of a new PV plant
  • Any asset manager or owner that wants to delve deeper into which panels are causing losses in yield, or
  • O&M companies that want to know which panel issues they are dealing with to recommend more accurate maintenance routines for their clients

How are EL inspections performed exactly?

The most traditional and best-known way is sending solar panels to a laboratory, which is an expensive and very time-consuming method.

But EL inspections can also be performed on-site. One option is through a tripod mount with multiple cameras that are aligned above the panels. These cameras take images of the panel and find potential issues in the cells of each panel during processing.

Keep in mind that when inspecting a hard-to-reach place such as a rooftop, a drone is a more efficient way of performing the photography for an EL inspection.

For our most recent webinar, we did extensive testing on rooftops. To find out more about the outcome of the test, check out our webinar.

So, what are the benefits of either using a tripod or a drone?

Various reasons make mounted tripods the preferred method:

  • The images have higher resolution
  • The images are always taken at the same height
  • There is less movement when taking the images
  • And it is much quicker as you can mount more cameras on the tripod.

This always involves manual labor, and the geography of the area must be considered as well.

But the usage of drones is gaining terrain as well as:

  • A substantial number of panels can be inspected
  • Geography is less of a problem
  • Drone footage also supplies high-resolution images
  • No heavy equipment is needed on site

Another important question is “How has EL evolved, and how will it impact the industry?”

EL is giving the solar industry a desirable tool to perform quality controls on high volumes of delivered and installed modules. It gives exceptional results from inspections of incoming modules on-site to commissioning with allocation of liabilities to manufacturers, transportation, EPCs and investors. This has never existed in the PV industry before.

For troubleshooting and/or warranty claims, manufacturers or EPCs request detailed statements at cell level, and span of the entire power plant. To obtain these statements, EL can be used on-site in the installed state without collateral damage due to disassembling for any sample size. However, EL is currently about 6-10 times more expensive than IR in MPP operation.

Thermography (IR-MPP)

100 000 – 200 000 modules/day

Evaluation of modules:

  • inactive modules
  • lost substrings
  • hot-spot patterns & PID

Electroluminescence (EL)

800 – 4 000 modules/night

Evaluation of cells:

  • cell cracks, microcracks
  • busbar & contact problems
  • LeTID (Light and elevated Temperature Induced Degradation), PID (Potential Induced Degradation)
  • inactive modules & substrings


We have mentioned in the webinar and in this blog, EL will play a major role in the future of asset management and O&M of the photovoltaic industry. Module owners will get similar results through their own means, on-site, which before was only acquired by sending the panel to a laboratory.

Meanwhile, it is important to understand that EL is not meant to scan your whole site, especially larger ones. Instead, we recommend using it as a complementary service to your aerial thermography.

Getting a snapshot of your entire site will allow you to find problem areas that cause losses in yield. You can then bring in an EL team to conduct a deeper analysis of issues under the surface.

All this information is integrated to Sitemark’s Fuse Platform, consolidating it in one place, making it easily accessible for all stakeholders.

To access the installed quality, especially of new PV parks, EL is the way to go.

If you would like to speak with our team at Sitemark about anything you have read in this article or our services, please contact us.

Our Belgium-based team develops digital solutions that empower field teams and asset owners. Using drones, satellite data, and an analytics platform rooted in AI, we create digital twins of physical sites to collect critical data more efficiently and effectively than most clients use today.