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Inaugurating the world’s largest foldable solar roof system in Uetendorf, Switzerland, marks another step forward in integrating renewable energy into existing sites. The Uetendorf structure exemplifies a unique combination of extensive area coverage, infrastructure integration, and dynamic movability. Built as a multifunctional canopy over treatment basins and service areas, this project repurposes the existing facility footprint to generate renewable electricity. 
Located in the Canton of Bern, over the basins of the ARA Thunersee Wastewater Treatment Plant (WTP), it represents a pivotal achievement in the field of renewable energy infrastructure. Recognized as the world’s largest foldable solar roof system, it showcases Switzerland’s leadership in developing advanced photovoltaic (PV) solutions that maximize energy generation without consuming valuable land, a critical factor in densely populated and highly developed regions.
Portraying a striking example of energy innovation, the Uetendorf foldable solar roof covers 20,000 square meters, roughly equivalent to three standard football fields. The solar folding roof over the pretreatment and biological basins is strategically positioned to target one of the most energy-intensive public utilities, which accounts for more than 1% of total electricity consumption across Europe. 
The Uetendorf project utilizes the patented HORIZON system developed by dhp technology, which transforms an otherwise unproductive area into a significant power source. 
Scale and Performance: Spanning 20,000 square meters, it boasts an installed capacity of 3,000 kilowatt peak (3 MWp). The projected annual electricity output is substantial, ranging between 3.0 and 3.4 gigawatt hours (GWh), which is equivalent to powering approximately 700 homes annually. 
Technology: Featuring a cable-supported, lightweight structure and a patented folding mechanism, the HORIZON system achieves high material efficiency, allowing 50% less material usage compared to rigid, comparable fixed systems. 
Retractability: The core innovation lies in the system’s ability to automatically retract into a protective storage position during severe weather conditions. This automated feature simplifies structural requirements, enhances durability, and reduces long-term operational risks.
Inspired by the principles of cable car technology, where the non-glass photovoltaic (PV) modules are suspended from high-tension cables, the HORIZON system features a lightweight, aesthetic design supported by a patented cable-based mechanism. The construction process involves large-scale supporting trusses pre-assembled at ground level, minimizing complex, high-altitude work.
dhp technology AG, based in Zizers, GR, also integrates the automated GESIPA® GAV 8000 blind rivet system, ensuring secure installation, precision, and complete process monitoring during the assembly of the frame structures. The HORIZON system’s elevated and retractable solar offers a clear operational edge over floating photovoltaic (PV) solutions. Treatment basins require constant visibility, maintenance, and periodic access for technical interventions or chemical dosing activities that even a lightly covered floating structure can hinder. 
With wide 20-meter spans and a height reaching 7 meters, HORIZON maintains full accessibility when deployed and retracts completely to clear the basin’s surface. This balance of energy generation and operational flexibility prioritizes functional reliability over the marginal thermal efficiency gains typically associated with floating PV installations.
Traditionally, rigid steel truss constructions required heavy infrastructure to manage structural loads. However, dhp technology has successfully minimized material usage through its innovative cable-supported design and automated retraction system. By generating energy right where it’s consumed, the HORIZON solar system reshapes how the facility powers itself, cutting costs, strengthening resilience, and ensuring operational autonomy.
Photo Credit: © dhp technology
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