The land limitations facing solar deployment in Germany have led to a bold vision: installing solar systems along highways and creating a vast DC smart grid in the process. The plan could even be implemented throughout Europe.
In addition to floating solar power systems and agricultural systems, highways could be an ideal solution to the surface problem of solar power. By 2030, up to 200 TWh of solar electricity per year could be produced on Germany’s highway. The implementation of such a project would lead to a smart electricity grid, but the benefits do not stop there.
The project would concern steel mesh masts, which are erected every 15 meters on the sides of highways. The PV modules would be mounted on steel trusses suspended between the masts. “Energy lanes” consisting of solar modules could extend along transport axes between cities, industrial areas and airports.
The energy band concept originates from the Altes Neuland Frankfurt foundation, which developed the project. It says that if 80% of highways and 65% of federal roads – a total of 45,000 km – were fitted with bifacial PV systems at 25% efficiency, up to 200 TWh could be generated per year.
If the full potential is utilized and construction processes are optimized, this could also be achieved at competitive costs, the foundation claims. Although a substructure made of steel lattice masts clearly exceeds the costs of traditional substructures, the service life of the masts would also be 100 years. New modules could be added again and again during this time at very low cost.
The idea originally arose from the need for space for solar energy and wind power. Current electricity consumption in Germany is 560 TWh per year. When mobility and heat are gradually electrified, an estimated 2,400 TWh of electricity will be consumed per year by 2050. The foundation assumes that this will also produce 1,000 TWh in Germany. The area needed for this would be 2.5% of the federal territory, i.e. three times the area of the state of Saarland.
Energy bands are intended as direct current systems. The 110 kV high current cable would run underground. The network connection should be set every 9 km to 87 km. The different lengths of the network connection depend on the use of the module specification. So it would be conceivable to put one, two or three rows of modules on top of each other, install cross-bridges with modules and, if necessary, even cover masts and highway bridges with solar modules. There is space between 2,000 and 20,250 modules per kilometer.
The Altes Neuland Foundation has also considered natural landscapes. If the energy lane passes through a city or past a forest, trees or a particularly attractive landscape, the energy lane can simply break. In this case, the project planners can leave out the masts and modules and continue only with the ground cable. The energy band group would start again only behind the village or the forest, when both parts would still be connected to each other by the ground cable.
The biggest advantage of such a system would be that the electricity is already distributed during production and thus directed to the right places, the Altes Neuland Foundation points out. Motorways connect metropolitan areas, industrial areas and airports. In addition, such long-distance routes have EV and EV charging infrastructure. In this way, electricity would already be produced in the right place or could at least flow to the right place.
Size vs. Volatility
The energy lanes would stretch over hundreds of kilometers, so there would also be an opportunity to equalize the fluctuations in consumption and electricity production throughout the system. According to the foundation’s project information, if it rains in one place, the sun can shine elsewhere. Such a project will be further optimized if more wind turbines are connected to the system. Smaller wind turbines can be placed on the masts, and existing systems located in fields along highways can also be fed into the energy zones.
Even if an expert analysis was needed for the wind loads on the masts, it would still be easier than covering the highway with solar power systems, according to the foundation. The latter option would require wind reports, drainage systems and lighting concepts. Researchers from the Austrian Institute of Technology (AIT), Germany’s Fraunhofer ISE and Forster Industrietechnik recently teamed up on a pilot project to generate solar energy for motorways with solar roofs.
Project promoters say their plan would cause fewer problems with space and permits. The matrices would be built only 1–2 meters away on the sides of the roads. This area is owned by the federal government, so there would be no need for permits from many different landowners.
The starting signal for expanding the energy bands could start on a small scale. A large infrastructure project would not be necessary. Municipalities and investors could develop small parts. It would only be important that they are developed in such a way that the parts can be connected together later and that the parts have a legal and technical basis for electricity trading.
Bergische Universität Wuppertal’s Professor Peter Birkner of the Electric Energy Department has followed the project’s development and feasibility study as a member of the scientific advisory board. He is convinced of its feasibility and says that it is now important to assemble a suitable consortium to develop the first part.
It remains to be seen how quickly such a consortium will form, but investors would have little reason to worry. All installed technologies are already ready for the market and have been tried and tested. The foundation claims that the necessary modules, steel poles and ground cables have been in existence for decades. The annual production potential of 200 TWh could be reached as early as 2030, it says.