The energy transition often encounters resistance among the general public – especially when it comes to projects such as wind turbines and solar parks. But an innovative solution could now provide the answer to these challenges: solar highways. A pioneering project in Germany, on a section of highway near the Garzweiler open-cast lignite mine in North Rhine-Westphalia, could both increase public acceptance and make an important contribution to the energy transition. We at Drees & Sommer carried out a feasibility study for the project.

The Rhenish mining area (known as Rheinisches Braunkohlerevier) in west Germany is an important site for the energy transition in Germany. Open-cast lignite mining, which secured a significant part of the energy supply for decades, has left deep scars on the landscape. But structural change in the region shows it is possible to replace environmentally harmful lignite with renewable energies. In a region with plenty of wind and sun, there are numerous opportunities for wind power and photovoltaics.

However, it is not uncommon for infrastructure projects to encounter resistance in densely populated countries such as Germany. Citizens’ initiatives protest against wind farms, power lines, or the use of undeveloped spaces for solar parks.

To counteract this problem, the Landfolge Garzweiler organisation, founded in 2017, has developed a forward-looking solution: solar highways. The concept is based on the idea of using existing transport infrastructure – specifically motorways – to generate renewable energy without having to use valuable agricultural land or roof space.

As part of the structural change project known as Innovationspark Erneuerbare Energien (Innovation Park Renewable Energies), the plan is to place solar installations on the embankments and noise barriers along the A44n and A46 highways. Vertical photovoltaic modules on wind barriers could also contribute to power generation. The aim is to use space in line with infrastructure needs and create synergies with noise protection and wind energy.

The concept is based on the idea of using existing transport infrastructure – specifically motorways – to generate renewable energy, without having to use valuable agricultural land or roof space.

Feasibility study 
The feasibility study examines how a potential solar highway project can be delivered along a 30-km section of highway. With an output of 24 MW, the project could make a significant contribution to sustainable power generation. Our study looked at the technical, legal and economic requirements of the project. Studies have shown that solar highways have great potential for the development of sustainable infrastructure. The know-how to successfully implement this concept is available.

However, not every section of highway is suitable – in its current state – for the production of solar power. As with any projects involving undeveloped spaces, challenges such as planning, grid connections and permits must be taken into account. Nevertheless, the feasibility study shows the concept can, in principle, be extended to other parts of the German highway network.

In addition to the project in the Rhenish mining area, Germany has seen other approaches to using transport routes for solar power production. In Ludwigsfelde near Berlin, the local municipality is planning to install a solar roof over the highway. A small pilot installation is already in operation in Baden-Württemberg as well, where cars and trucks drive under a solar roof.

The solar installation not only produces power, but also helps reduce noise and protects the road surface from the effects of weather. Such projects demonstrate how valuable synergy effects can be achieved by both generating energy and optimising the space used by traffic.

The legal framework for such projects is provided by the German Renewable Energy Sources Act (EEG). Spaces along highways, up to 200 metres from the road itself, are considered suitable for the construction of solar installations. Lawmakers have recently relaxed the ban on creating solar installations in spaces within 40 metres of the road, provided assessment is carried out on a case-by-case basis. This favours the expansion of solar highways and opens up new possibilities for the use of transport routes.

The vision of solar highways could prove to be an important step towards a climate-neutral future. Die Autobahn GmbH, the federal body responsible for running Germany’s highways, has plans to achieve climate neutrality by 2040 and gradually push ahead with the expansion of photovoltaic installations along highways.

The idea of the solar highway is a prime example of the innovation driving the energy transition in Germany. If the project in Garzweiler is successful, it could serve as a model for other regions and make an important contribution to a sustainable energy future.

The views and opinions expressed in this article are strictly those of the author only and are not necessarily given or endorsed by or on behalf of the Energy Institute.

• Further reading: ‘Building the business model for decarbonised road transport’. How do you decarbonise a transport company? Alex Jensen, CEO of National Express, responsible for coach, rail and bus transport modes for the company, explains.
• The route to decarbonising road transport fleets is complex. Find more about some of the pathway options on the UK road to net zero, which are likely to be reflected globally.