How do solar cars drive

Driving with the power of the sun : The car that generates its own energy

The idea is old: a car is equipped with solar cells and drives with the electricity generated in this way. What has been on the street so far, however, has been quite impractical. Extremely lightweight construction, nerdy look, often only space for one person.

The boxes rolled along under the blazing Australian sun, a serious solar car in Central Europe seemed illusory. That should change, at least believe the founders of start-ups like “Sono Motors” in Munich and “Lightyear” in Helmond in the Netherlands.

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Both want to go into series production in 2021 with cars that can still charge electricity from the socket, but still create many extra kilometers using solar. In addition, there is the promise of climate-friendly, sustainable mobility. Is all of this realistic?

It all started in 2012, says Laurin Hahn, one of the founders of Sono Motors. "In view of the climate crisis, we decided to no longer just watch, but to do something."

Electromobility has three problems: price, range, charging infrastructure

Together with Jona Christians, he wanted to change the previously fossil-based mobility: "Around 60 percent of crude oil is used for transport, is simply burned and never comes back," he says. That speaks for electromobility. But it had and still has three problems: price, range, charging infrastructure.

Hahn and Christians' solution is called “Sion”: a five-seater for 25,500 euros, the outer skin of which is covered with solar cells that provide electricity for the electric drive when the vehicle is stationary and while driving. In the best case - Munich, summer, sunshine, shadow-free parking lot - a Sion should cover 34 kilometers a day.

Modeled over the year and all weather, it should still be 16 solar kilometers a day. With an average commuter distance of 20 kilometers in Germany, Sion could do most of the work with solar energy. In fact, the car is more suitable for short-distance use, the battery only lasts for 255 kilometers in accordance with the WLTP standard, which applies to light vehicles worldwide.

In terms of sustainability, the battery should get by with a lower cobalt content than comparable batteries. The metal is extracted in small-scale mining in Central Africa, often under inhumane conditions. “When shopping, we pay attention to the origin of the materials,” says Christians.

Only a quarter of the weight of conventional solar cells

The most striking feature of the car are the 248 solar cells integrated into the body. While conventional cells are embedded in glass, the Munich-based company uses a specially developed polymer. As a result, the modules only weigh around a quarter compared to conventional modules.

The developers promise that the polymer is stable enough to withstand large temperature fluctuations and humidity. Even small bumps, such as from a shopping cart in the parking lot, should survive. In addition, the combination of materials enables slightly curved modules.

“The engineers and designers worked closely together to accommodate as many solar cells as possible on the car,” says Mathieu Baudrit, who is responsible for solar integration. Thanks to special electronics, it is possible to generate a lot of electricity even in changing light conditions. If, for example, the car was parked under a tree, areas that were directly illuminated and in the shade would be recognized and power generation would be optimized accordingly.

The solar cells should also be replaceable, for example after an accident. The company wants to make this as easy as possible. The modules can be easily linked to the electronics via plug connections. Technical documents should also be freely accessible so that repairs can be carried out yourself or these can be done in every workshop.

Crowdfunding campaign until January 20th to secure funding

But whether a Sion from the former Saab factory in Trollhättan, Sweden, which was selected for production, will ever roll is questionable. Fresh money is needed for Sono Motors to continue. The conditions of a major investor, with whom the negotiations were well advanced, would have meant that the Sion would not have made it to the market in Europe, says Christians. He could not give details, it was about patents and developments.

"It would have been the worst option compared to everyone to whom we feel obliged and who want to see the Sion on the street." That would be at least those more than 10,000 who reserved a car and paid at least 500 euros for it. The bosses decided to start a crowdfunding campaign which, after being extended, should bring 50 million euros until January 20 at midnight, so that things can continue.

Orderers, smaller investors and supporters have already promised almost 48 million. Should it still not be enough in the end, there are various strategies. "In any case, it would mean that the Sion would come much later," says Christians. "Or not."

Solar system is "a gimmick"

Markus Lienkamp, ​​Professor of Vehicle Technology at the Technical University of Munich with a focus on electromobility, has been following the activities at Sono Motors for years and attests to "huge commitment". From his point of view, the solar system is more of a gimmick. If the car is in a garage or carport, they won't do anything. "You are basically building a normal electric car like Renault or VW, which are now coming onto the market, and that makes it hopeless."

The big automobile companies could agree much lower prices with their suppliers. In the case of a start-up that nobody knows whether it will still exist in two years' time, it would also make sense to request payment in advance. In addition, there is the development of the car, approval procedures, crash tests. “You need at least billions to get a car on the road,” says Lienkamp.

To offer the Sion as a vehicle for the mass market “at the price of a large automobile company” is unrealistic. The Sono founders, on the other hand, claim that their concept will cost a good 250 million euros until it is ready for series production.

"Solar cells belong on house roofs, not on car roofs"

Achim Kampker, professor for “Production Engineering of E-Mobility Components” at RWTH Aachen University, also sees solar cells as a marketing tool that underlines the claim to sustainability. He is co-founder of “Streetscooter”, known for the small e-delivery vehicles of the Post. “Back then, we calculated whether it was worth putting solar modules on the roof of the freight box,” he says.

"The material costs can be offset by the saved electricity, but we were still not convinced." A solar range extension is too unreliable for commercial use due to the changing weather. The big plus of a smaller battery was therefore not feasible. In addition, all components must withstand the typical vehicle vibrations and must not form sharp-edged splinters in the event of an accident.

In Kampker's opinion, solar cells belong on the roof of houses. "More electricity is produced on a free roof than on a car of the same size," he says. "If you use this electricity for the e-car, perhaps combined with a stationary storage system, that brings more."

Sympathetic concept, but for the niche

Nevertheless, he calls Sono Motors a “cool project”. I find the approach of "relying on sustainability from production to sharing concepts in use," sympathetic. But he, too, believes that solar cars only have a chance as a niche product.

The “Lightyear One” could achieve this. With a targeted unit price of 149,000 euros, the demand will be manageable. But then there is real high-tech: Thanks to consistent lightweight construction, the curb weight should be 1300 kilograms, the design will bring the lowest air resistance of a series vehicle, the company promises.

There is also five square meters of solar space, the cells are protected by safety glass - stable enough that supposedly an adult can walk on them. The range is to be increased by twelve kilometers per hour of sunshine, so that in the end up to 725 kilometers are possible. The team has sufficient experience with long distances, the company is a spin-off from the University of Eindhoven, which is very successful in numerous solar vehicle races, for example in Australia. It remains to be seen whether this will also be Lightyear in the automotive market.

Perhaps in the end the big companies with their financial and technological resources will win the race again. Toyota, Hyundai and Tesla, for example, are also working on cars with solar cells.

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