A 3.6 MW foldable rooftop solar installation has been inaugurated at a wastewater treatment plant in Switzerland, making it the largest of its kind globally. The system spans treatment basins, allowing the site to serve dual purposes of wastewater treatment and solar power generation. The project is expected to produce 3 GWh of electricity per year, with most of it consumed on-site. The folding-roof technology, derived from Swiss cable car engineering, automatically retracts during extreme weather events for protection. This innovative project demonstrates a pragmatic and effective way to advance the energy transition, utilizing existing space intelligently for economic efficiency and climate protection.