Aerial PV Inspection and ISFH develop LIEL technology for efficient PV module testing without electrical contact
Each module inspection takes only 50–200 milliseconds, with a complete measurement cycle for each module in just 12 seconds
The lightweight, battery-powered inspection hood can perform up to 200 inspections per charge, is adaptable to various module sizes and is usable in any lighting condition
Aerial PV Inspection GmbH and the Institute for Solar Energy Research Hamelin (ISFH) have teamed up to develop Light Induced Electroluminescence (LIEL) – an EL inspection method to analyze PV field systems and to identify failures in PV modules. In contrast to the common technique, no electrical current needs to be induced in the PV modules, which decreases the measurement effort drastically. The technology was the finalist for The smarter E AWARD 2024.
LIEL is a unique measurement technology specifically for inspecting half-cell solar modules in large solar parks. The technique involves exciting one half of the module with a short flash of light, causing a current to flow through the other half, which then emits electroluminescence similar to an LED. As part of the project, the team developed a light-weight inspection hood, adaptable to different module sizes. This method offers several distinct advantages over conventional techniques: measurements can be performed in both daylight and nighttime conditions, electrical connections of the modules do not need to be disconnected, and inverters can remain operational during the process. The technology also supports on-the-spot measurement without the need for any prior setup.
Each measurement requires only 50 ms to 200 ms, depending on the module, and produces a high-resolution electroluminescence image. These images allow experts to assess the condition of the module and identify potential sources of failure. Additionally, the method can detect whether modules are actively controlled by the inverter or whether they are disconnected. The process is also fast: the current prototype system can inspect a module, move to the next one, and initiate another measurement in 12 seconds. Future iterations of the system are expected to reduce this time significantly, as the actual measurement takes only up to 200 ms. The device is powered by a light-weight battery capable of supporting at least 200 module inspections per charge. The LIEL project is funded under the Central Innovation Programme for SMEs (ZIM) by Germany’s Federal Ministry for Economic Affairs and Climate Action (BMWK).