ERFTSTADT — Standing in his down-quilted jacket on a small field path in Erftstadt, near the city of Cologne, Donald Müller-Judex points to a few bushes behind him and says: "Now it's getting exciting!" Behind him, three tilers from a local company are putting down the most original tiles they've ever laid: dark blue solar panels, each as large as a beer mat. Together, the tile carpet will form Germany's first solar street. "It's already producing electricity," Müller-Judex, 56, says proudly.

Each square meter supplies 80 kilowatt-hours per year. For this 200 square-meter cycle track, that means a total of 16,000 kilowatt-hours, which are fed into the local power grid. So far the track is only 90 meters long. But already it's a path to the future: Germany's first solar road can provide electricity, swallow noise, illuminate itself late at night, melt away the ice in winter and even think for itself. The surface is made of monocrystalline and has built-in sensors that, on larger roads, could measure traffic flows and thus, for instance, optimize traffic light circuits.

Müller-Judex explains that rooftop solar panels simply won't suffice if we are to reach the 100% renewable energy target, so the existing asphalt surfaces must be used in a sustainable manner too. In a joint research project with the RWTH Aachen University, the University of Bayreuth and the Jülich Research Centre, Müller-Judex and his small company, Solmove, developed a "multi-functional solar carpet" whose tiles click into place and connect.

"It was a balancing act because the road must also be robust and slip-resistant," he says.

The panels have a nub structure that Müller-Judex compares to a micro-mountain range. "Dirt collects in the valleys, where the water flows, so the water also takes the dirt away," he explains. "The car tires are supported by the road's mountaintops. These crests are covered with corundum, a particularly abrasion-resistant rock that lies just behind diamond on the hardness scale."

Just getting started

A special glass factory in the Bavarian Forest produces the glass for the tiles. In lab tests, the glass tiles can withstand the weight of one-and-a-half trucks. But now, the practical test begins.

Why Erftstadt of all places? Because the people here managed to present a convincing cycle-path concept and thus also won federal funding for the solar tiles. When asked about the financial aspect, the large figures involved make Müller-Judex hem and haw. "Don't forget: The first microchip cost $10 million. If people had said back then that it was too expensive for PCs, then we wouldn't have computers at all today," he argues.

Working on Solmove's solar tiles — Photo: Facebook page

If the solar road were to last 20 to 25 years, as predicted, the people of Erftstadt would even earn money from the electricity generated over the final 10 years. "A normal street costs money. A solar street earns money," Müller-Judex pledges. In any case, he ensures, also thanks to his own capital and the help of a Chinese investor, that the project won't cost the people of Erftstadt a dime.

Solmove has also installed a circuit so that the solar cells can be heated in winter. "Does is make ecological sense to heat the road's surface in winter?" Müller-Judex asked himself. Yes, because doing so is "much cheaper than having a winter road maintenance service," according to his calculations.

Jack of all trades

Müller-Judex came up with the idea almost 10 years ago, when he was looking for free surfaces for photovoltaic systems in the Allgäu region, in Bavaria. All suitable roofs were already covered. "Why don't we use the road, it lies in the sun, doesn't it?" the trained mechanical engineer thought.

He thus began to tinker with solar tiles. For Germany alone, he sees a 1.4 billion square-meter potential. "The road network in Germany, highways excluded, would be enough to supply 20 million electric cars," he says.

Roads and parking lots have the advantage that electric cars can be charged automatically by induction without a socket. They "suck" the electricity from the photovoltaic cells, so to speak. The process is already working, but not very well yet.

Müller-Judex isn't just an engineer and autodidact. He's also a journalist who left the profession because he wanted to do "something serious." His first startup idea, a payment system for mobile phones, came 13 years too early. He has since moved away from the Bavarian town where he was still living when he founded Solmove in 2014.

"Bavaria is always a bit sluggish and listless when it comes to technical innovations, but things are happening in Berlin," he explains.

Determined to act

Müller-Judex is a busy man. Besides his dreams of building a solar road for electric shuttle buses in China for the next Olympics and a part of the World Expo in Dubai, he's just completed a potential analysis with the German railway company Deutsche Bahn (“33,000 kilometers of railway track!” he enthuses). In addition, he is building a test facility in Cologne for energy company Rheinenergie, a parking lot for another regional company, a cycle path for a software company in Silicon Valley, and a test facility near Los Angeles.

Starting next year, individual home builders and companies will also be able to order tiles for their own private parking spaces. "We are overwhelmed by the demand," he says. His company consists of only two employees.

We are at the very beginning.

Müller-Judex faces international competition too, with similar ideas springing up in China, America, France and the Netherlands. France and the Netherlands already have small test roads. However, their systems all have the disadvantage that existing roads have to be milled. Solmove's tiles, in contrast, can be glued to existing roads because the flexible tile carpet compensates for the surface's small bumps.

Will it all works out as the visionary hopes? Will the solar modules deliver electricity despite autumn leaves and November sludge? Will the grooves really allow for the dirt to be washed away? And will the road be as non-slip and resistant the lab tests suggest? These questions won't be answered until the coming months and years.

"The first aircraft was made of wood and fabric," Müller-Judex says to compare the current state of research in his sector. "If you look at the proportion of wood and fabric in a modern aircraft, you know how much development has taken place. It will be the same here. We are at the very beginning."

Müller-Judex is convinced he's on the right path — literally! "Anyone who deals with the climate knows that we're dangerously going off track right now," he says, raging at the thought of "how many millions we're transferring to Saudi Arabia every year to buy oil. Our grandchildren will be rubbing our noses in it. And we'll have to say: 'We knew, but we did nothing.'"

That reproach, at least, is not one that will apply to him.

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