While wind turbines and solar farms are often met with considerable resistance from the German public, an innovative solution is being studied that could offer a less intrusive future – solar motorways. A section of the Autobahn close to the Garzweiler opencast lignite mine in the German federal state of North Rhine-Westphalia is being considered as a suitable site for a flagship project. Drees & Sommer SE, a consulting firm which specialises in infrastructure, has produced a feasibility study for rehabilitation and repurposing of the land, Zweckverband Landfolge Garzweiler, which looks into ways of combining transport infrastructure with electricity generation to improve public acceptance.
In the Rhenish mining district, the energy transition is well underway. Wind turbines and solar panels are replacing lignite, the mining of which has left huge scars on the landscape. It is hoped that if a structural transformation is successful here, it can encourage innovation – both in North Rhine-Westphalia and beyond.
Founded in 2017, the special-purpose association Landfolge Garzweiler and the planned renewable energies innovation park (Innovationspark Erneuerbare Energien) have proposed a solution for the post-lignite electricity production era – solar motorways. To generate the level of solar power, it will be necessary to utilise not only neighbouring roof spaces but also greenfield areas and previously unutilised areas.
For this reason, as part of a sub-project of the Innovationspark Erneuerbare Energien structural transformation project, solar power systems are planned for embankments along the motorway A44n and on noise barriers on the motorway A46. Photovoltaic modules can also be mounted, vertically, on wind barriers.
Drees & Sommer’s study
The legal, technical and economic viability of carrying out the 24-MW project on the 30 km motorway section was researched by Drees & Sommer in a feasibility study completed in August 2024. The experts analysed issues including choice of technology, ease of implementation, and economic viability, as well as possible operator models and the time frames involved.
Alexander Vorkoeper, senior consultant at Drees & Sommer, added: “Our research has demonstrated the great potential of solar motorways for the development of sustainable infrastructure.” Of course, not every motorway section is suitable for the production of solar energy, as the senior consultant pointed out. As with projects involving open spaces, here too the systems have to be planned, mains connections established, applications for approval submitted – and so on. However, the expertise is there, and the design for the installation of solar panels along the motorway close to Garzweiler can be rolled out nationwide.
The Fraunhofer Institute for Solar Energy Systems (ISE) has calculated that 5 % of Germany’s land area is covered by transport routes, which holds the potential for 300 GW of additional PV output. To put this in perspective, as of April 2024, 81.5 GW of PV systems was installed on German roofs and land.
Test installations
In Ludwigsfelde, south of Berlin, the city government is also planning to erect a solar roof over the A10 motorway. Besides being an efficient use of land, this initiative will also have valuable synergistic effects, such as reducing noise and protecting the roadway from heat and rain.
And a small pilot system went into operation in the federal state of Baden-Württemberg in October 2023 – it is a half metre-high roof made of photovoltaic modules on roadway to the Hegau East rest and service area on the motorway A81. The Fraunhofer Institute is researching with partners the performance of the prototype in consideration of aspects such as stability, maintenance, drainage and road safety.
