How to Operate Portable EL Testing (Electroluminescence) for Solar Panels

What is Electroluminescence?

Electroluminescence (EL) is the process where certain materials emit light when electricity passes through them. In the case of Solar Panels, when we apply a small electrical current to a panel in a dark environment, the cells glow with a special kind of light that we can’t see with our eyes—but special cameras can detect it. This glow shows how healthy each part of the panel is.

If there’s a defect like a tiny crack, broken wiring, or a weak connection, that part of the panel won’t shine as brightly. In EL images, these show up as dark or faded areas, helping engineers and technicians find problems early and fix them before the panel loses too much energy output.

Methods of Applying EL Solar Testing

EL testing can be done in a couple of ways depending on where the solar panels are. Some are tested inside laboratories or factories, and others are tested directly where they are instalLed—on rooftops or in solar farms. The environment changes how the test is done and what equipment is needed.

Indoor EL Testing

This method is used inside buildings where conditions like light, temperature, and humidity are controlled. The solar panels are placed in a dark room, and high-quality EL cameras take pictures while a small voltage is applied to the panel. It’s often used in production lines or labs to make sure new solar panels meet quality standards before they are sold or installed.

Outdoor EL Testing

When solar panels are already installed outdoors, they can’t be moved to a lab. Instead, technicians go to the site with portable or flying equipment. These tools must handle changes in weather, lighting, and terrain. There are two main types of outdoor testing tools: portable EL testing devices and EL testing drones.

Portable Outdoor EL Testing

Portable devices are small, mobile systems that include a power supply, EL-sensitive camera, and sometimes a foldable tent or cover to block sunlight. A technician places the device in front of the solar panel and uses it to take EL images one panel at a time.

This type of testing is useful when checking rooftop panels or doing small-scale inspections. The setup is easy, but it takes time to inspect a large number of panels because the equipment has to be moved manually between panels.

Drone Outdoor EL Testing

For bigger solar installations, drones equipped with EL cameras are used. These flying tools can scan hundreds of panels quickly and from hard-to-reach places. They fly in the air while panels are activated, capturing EL images from above.

Drone-based EL testing is faster but needs more expensive equipment and experienced operators. Also, weather and sunlight can impact the results. Because this technology is still developing, there are fewer rules and standards for how to do it properly.

What is a Portable EL Testing Device

A portable EL testing device is a compact inspection system designed to check solar panels for hidden damage or performance issues using electroluminescence. It usually includes a constant current power supply, an EL camera that sees near-infrared light, and sometimes a blackout tent or hood to create a dark testing environment during the day.

These devices are carried by hand or on small carts and are used directly in the field. They allow technicians to inspect solar panels one by one without removing them. Because the system is simple to operate and relatively affordable, it's widely used for maintenance, small solar projects, and training purposes.

How to Operate a Portable EL Testing Device

Using a portable EL tester requires careful setup. First, the solar panel being tested is disconnected from its regular wiring and connected to the device’s power supply. The voltage must be controlled to ensure the panel glows without overheating or damage.

The technician places the EL camera in front of the panel and either uses a blackout cover or performs the test at night to avoid sunlight. The EL image is captured and then analyzed with software to highlight any weak or damaged areas. Panels with dark spots may need repair or replacement.

Pros and Cons of Portable EL Testing Device

Pros of Portable EL Testing Device

Affordable and Simple: Portable devices are usually cheaper and easier to operate than drone-based systems or large lab setups. They are a great learning tool for students or small teams.

Accurate for Individual Panels: These devices give clear EL images for one panel at a time, making it easier to focus on specific issues during repairs or testing.

Safe and Non-Destructive: The test doesn't harm the panel and can be repeated many times without wear or damage.

Cons of Portable EL Testing Device

Time-Consuming: Since the device needs to be moved and set up for each individual panel, it's not suitable for checking hundreds of panels quickly.

Lighting Limitations: Testing during the daytime can be tricky unless a blackout tent is used, because sunlight interferes with the faint EL glow.

Manual Labor: Technicians have to do everything by hand, including moving the camera and resetting the power supply, which can be tiring for large-scale jobs.