With the second phase of the foldable solar roof at the ARA Davos wastewater treatment plant, the Municipality of Davos is once again sending a strong signal for innovative energy solutions in alpine regions. For the first time worldwide, open circular secondary clarifier basins have been covered with a foldable solar roof – made possible by a newly developed structural concept.
More solar power – without additional land use
With the second phase of the foldable solar roof, ARA Davos is consistently expanding its on-site power generation. Since 2020, a foldable solar roof has been producing solar power above the pre-treatment and biological treatment basins. With the new installation above the circular basins, a second, independent foldable solar roof has now been added.
Together, both systems will generate around 606 MWh of solar power per year – entirely on existing infrastructure. The new foldable solar roof above the circular basins alone delivers around 351 MWh annually, utilising approximately 2,400 m² of existing surface area. This project clearly demonstrates how the on-site power supply of energy-intensive infrastructure facilities can be expanded step by step – without additional land use and while maintaining full operation.
Technological milestone: circular basins covered for the first time
What has now been realised was long considered technically hardly feasible: covering circular basins posed a particular challenge due to their geometry and operational requirements. As early as 2020, it was therefore deliberately decided not to cover these basins. Only through a fundamental further development of the structural system could the project now be implemented.
At the heart of the innovation is the first-time use of compression members within the foldable solar roof system. These elements absorb horizontal forces between the axes and relieve the load on the suspension cables, foundations and the sensitive edge areas of the basins.
Large spans, minimal intervention
The new structural concept enables very large support spacing – a decisive advantage during ongoing plant operation. The number of foundations could be significantly reduced, and interventions in the existing infrastructure were kept to a minimum. At the same time, the optimised structure led to a reduction in construction time of around three months.
The structural design of the system is engineered for extreme alpine conditions: temperatures from −20 °C to +40 °C, high snow loads, as well as wind pressure and suction, were comprehensively taken into account.
Proven technology, further developed
The foldable solar roof can be automatically retracted and extended in the event of snow, storms or hail. Snow-free modules enable the rapid resumption of power generation, while unrestricted access to the circular basins is guaranteed at all times – even during maintenance work.
A development step with strong signalling effect
For dhp Technology AG, the project marks an important development milestone: the successful implementation serves as a real-world test for the new structural principle and lays the foundation for future foldable solar roofs with even larger spans and more demanding geometries – for example at additional wastewater treatment plants or special structures.
The combination of proven cable-car technology and a new structural concept impressively demonstrates how existing infrastructure can be utilised for solar power generation even under complex framework conditions.
