The modules of the 7.4 MWp system, originally installed in 2010, were completely replaced and repositioned. Existing mounting profiles, generator junction boxes, and the AC-side installation were reused.

Kirchdorf/Radevormwald (Germany), 18 December 2025. One of the largest PV retrofit projects in Germany has been successfully completed on the roof of the former Goodyear central warehouse in Philippsburg. The modules of the 7.4 MWp system, originally installed in 2010, were completely replaced and repositioned. Existing mounting profiles, generator junction boxes, and the AC-side installation were reused.

"The project clearly demonstrates the significant potential of retrofitting aging PV systems," says Tobias Söhnchen, Managing Partner at PV³, which oversaw project management, planning, quality control, and commissioning. While maintaining the original rated capacity, the system can now generate up to 35 percent more energy - all while preserving the feed-in tariff under the current EEG contract. Despite the sensitive roof statics and ongoing warehouse operations, the project was completed within just 13 weeks. The rooftop system - the largest of its kind in Germany at the time of its original installation - is operated by PV julist GmbH.

The core of the modernization involved replacing around 96,000 roof-parallel thin-film modules with approximately 16,000 high-performance crystalline modules. The new modules were installed with a 10-degree tilt facing south to further optimize yield. For this, the Schletter Group developed a mounting concept that reused the existing Schletter Solo profiles, replacing only the module supports, struts, and clamps. "Reusing the profiles on a project of this scale saves a tremendous amount of time and money," explains Manuel Schwarzmaier, Project Manager at the Schletter Group. Schletter recalculated the system's structural load and provided the required static verifications. The aerodynamically optimized installation reduces the structural load on the roof and mounting system compared to the previous design.

During planning and reconstruction, PV³ placed special emphasis on minimizing yield losses. The system's ten inverters were therefore retrofitted one at a time, ensuring that no more than two inverters were offline simultaneously and that most of the system remained operational throughout the project. Because the roof of the 113,000 m² logistics hall could not be subjected to point loads, two 80-meter cranes were used to carry out the installation. The old modules were removed and the new ones installed in a single step, eliminating the need for intermediate storage and preserving the roof structure. GME clean power AG was responsible for module removal and installation.

"Retrofitting is not a plug-and-play solution but a complex process that requires in-depth technical and economic analysis," says Söhnchen. "Success hinges on customized planning and competent execution - which, in this case, worked extremely well thanks to the close collaboration of all project partners." After completion, PV³ conducted drone-based infrared scans, electroluminescence testing, and I-V curve measurements under light and dark conditions. The system was officially commissioned by a publicly appointed expert in October 2025.

About SCHLETTER GROUP
The Schletter Group is one of the world's leading manufacturers of photovoltaic mounting systems made of aluminum and steel. The company supplies mounting solutions for rooftops, façades, and ground-mounted solar parks. With a global network of manufacturing, sales, and service subsidiaries, the Schletter Group is active in all major international markets.
www.schletter-group.com

About PV³ GmbH
PV³ GmbH is a full-service provider for photovoltaic systems with many years of industry experience. Initially focused on technical operations management, the company has evolved into a comprehensive service provider - offering planning, optimization, quality assurance, and expert services.