Pilot project in Germany: Solar systems along motorways

Green energy projects often face public opposition in Germany. An innovative solution has been devised to ease the transition from lignite to renewable sources in the traditionally mining-focused Ruhr area: installing solar systems along motorways near the Garzweiler open-pit lignite mine. The pilot project could become a model for the energy transition.

For decades, the Garzweiler open-pit mine in the North Rhine-Westphalia region has significantly impacted local life. Although the mine is still operational, future land use and reclamation are now in focus. The Landfolge Garzweiler Association, an inter-municipal organization (Zweckverband) for land rehabilitation and repurposing, was established to address the issues. Renewable energy projects are part of the solution to replace lignite, but wind turbines and solar farms often encounter substantial public resistance in Germany.

“Action groups protest against wind farms or the construction of power lines, and in many areas, a battle is raging over the future use of the land,” said Volker Mielchen, managing director of Landfolge Garzweiler.

Rooftops and green spaces need to be utilized to optimize solar energy use. The association proposed an innovative solution: solar motorways to gain public acceptance.

Solar motorways have great potential for sustainable infrastructure

Drees & Sommer conducted a feasibility study demonstrating that it is legally, technically, and economically viable to install solar systems with a combined capacity of 24 MW along 30 kilometres of highways near the Garzweiler coal mine.

Plans include installing panels on embankments along the A44n highway and sound barriers on the A46 highway. Experts analyzed aspects such as the choice of technology, ease of implementation, and economic viability, as well as models of operation and the timeframes involved.

“Our research has demonstrated the great potential of solar motorways for the development of sustainable infrastructure”, said Alexander Vorkoeper, senior consultant at Drees & Sommer.

However, not all motorway sections are suitable for solar energy production. As with land-based projects, careful planning is essential.

Germany’s road network could generate 300 GW of solar energy.

Despite challenges, the company believes the pilot project near Garzweiler could be applied nationally. “At 13,200 kilometres, Germany’s motorway network is the fourth-longest in the world,”  Vorkoeper noted. The Fraunhofer Institute for Solar Energy Systems (ISE) has calculated that transport routes, including motorways, parking spaces, and noise barriers cover 5% of Germany’s land area.

The infrastructure could provide an additional 300 GW of solar energy. By comparison, Germany installed rooftop and ground-mounted photovoltaic systems with a total capacity of 81.5 GW by April 2024, the company said.

For Landfolge Garzweiler, solar motorways are just one step in its plans. “We aim to remain an energy region but without lignite,” said Mielchen. With one of the projects, the Renewable Energy Innovation Park, the association seeks to establish a large integrated energy system for generation, storage, distribution, and usage within five subprojects.

Solar roof over the motorway

Data highlights motorways’ promising potential for energy production, prompting additional solar power pilot projects across Germany. In Ludwigsfelde, south of Berlin, the city authority plans to install a solar roof over the A10 motorway. This approach avoids land use, reduces noise, and protects roads and vehicles from heat and precipitation.

Within a pilot project in Baden-Württemberg, a 5.5-meter-high solar panel roof was set up over the A81 motorway in October 2023. The Fraunhofer Institute and partners are studying the prototype’s performance, focusing on aspects like stability, maintenance, drainage, and road safety.

German law supports solar installations along roads

Solar farms are already present along many German motorways. The federal Autobahn agency plans to gradually increase the photovoltaic system capacity to achieve climate neutrality in motorway management.

German legislation supports such investments. The Renewable Energy Act prioritizes areas within 200 meters of roadway edges for solar system installations. A recent relaxation of the 40-meter restriction from road edges has enabled additional capacities for solar projects. Under the law, even land very close to roads can now be used for solar energy.

Photovoltaic roads

In addition to embankments and sound or wind barriers, experts have explored integrating solar panels into road surfaces. There are still no such systems in Germany. A 2016 experiment in the Netherlands on a first-class road, D5, failed due to traffic-induced damage to the road surface and solar cells.

However, a 70-meter-long solar bicycle path was installed in the country.

The most successful solar road to date is in China. In Jinan, the capital of Shandong province, a one-kilometre PV highway opened in 2017. Solar cells embedded under a transparent surface generate 1 GWh of electricity annually.