The theoretical potential of a solar roof for Germany’s Autobahn is tremendous. Obviously, not all stretches of the Autobahn can be covered. Parts run below bridges, through tunnels, or in shaded regions that would be uneconomic for solar power production. However, a project is building a prototype at the Hegau-Ost rest area on the A81 Autobahn in Baden-Württemberg.
This project is part of a joint road construction research from the Fraunhofer Institute for Solar Energy Systems, Forster FF Verkehrstechnik, and the Austrian Institute of Technology. The prototype consists of a 10×17-meter roof surface made with photovoltaic modules located approximately 5.50 meters above the highway resting on a steel structure. It will demonstrate that solar power generation above flowing traffic works in reality and can potentially be operated permanently.
Parliamentary state secretary Steffen Bilger, from the Federal Ministry of Transport and Digital Infrastructure, explained:
With this research project, we want to develop the potential of the highway for renewable energy generation. Covering a highway is particularly technically challenging because of the fast-moving traffic underneath. But the vision of reusing an already sealed surface for generating the energy needed by the electric vehicles driving underneath it is something that simply has to be pursued.
Safety Requirements
When it comes to roads, safety is number one. If an accident occurs on the street below, structures over roads must be strong enough to endure possible vehicle impact to prevent collapse. This makes building photovoltaic modules over roads much more expensive than photovoltaics on existing roofs or open spaces. But that’s not all; from a length of 80 m, such support structures would be classified similarly to tunnels, and therefore, would have to meet even higher safety requirements.
Limited Areas of Application
The German-Austrian-Swiss research project’s primary goal is to demonstrate that such a structure is economically feasible under actual traffic conditions. While the modular design of the prototype has a few cost advantages, a widespread application of solar roofs over highways is unlikely. In contrast, there are many areas where renewable energy can be generated less expensively. However, the researchers see possible uses for solar panel-covered highways for locally limited application areas.
Another exciting solar panel-covered road is the Solar Véloroute- an illuminated bike pathway that generates energy. Solar Véloroute comprises a photovoltaic tunnel structure that serves as a solar canopy for cyclists and pedestrians and a public facility where commuters can recharge their e-bikes or smartphones; at night, they can enjoy an illuminated protected pathway.
However, roads aren’t the only thing we’ve seen covered by solar panels. In India, entire canals are topped with solar panels to reduce water evaporation. In addition, Indian researchers found that the water underneath those panels cooled them considerably, preventing overheating and resulting in an average efficiency boost of between 2-5%.
