The holy grail of electromobility: solar powered cars. Free fuel from the sky. Kiss goodbye to worries about range and charging time. A simple, but brilliant idea that led two companies who pursued it, into bankruptcy. Sono Motors in Germany and Lightyear in the Netherlands. "We've seen there are a lot of ways to ruin the concept." They put everything into building their own solar cars and failed. So, what's the big deal breaker about solar cars? First we need to understand how they work. That's why we're here in Aachen, Germany, with the Solar Raceteam Sonnenwagen. "So, this is one of the most efficient electric vehicles in the world?" "Yes. I mean, you can look at it, right? It looks like a ping pong table, basically. So it doesn't have too much in common with the normal car." This is Enno Dülberg. Back in 2017 he was one of the founding members of Team Sonnenwagen in Aachen. A team to participate in solar racing competitions across the world. For example, in Australia. "It looks a bit like a soap box." "Yeah, like a bathtub you could say. And it rides like that, too." "So how many kilometers can we get out of this thing?" "Depends. It depends totally on the sun, right? If you're driving without the sun, it could be around 600 kilometers. That's a rather small six kilowatt hour battery. But if you have good sun, direct sun, like, then you can drive indefinitely. You can just keep going. Of course, it depends on the speed then, right? If you don't have too much sun you have to go slower." It has a top speed of 120 km/h and is covered in four square meters of solar cells. And it has only three wheels with the engine sitting directly in the wheel in the back. For the car to be as efficient as possible, aerodynamics are key." "Just to give you an idea how light this is. When I do this... like the whole car is shaking." "How much does this weigh?" "It depends a little bit on the battery chemistry but somewhere around 160 kilograms." "No way!" "Yeah. It's just purely made out of carbon fiber. Everything is milled out of titanium or LME aluminum. Carbon fiber. So, lightweight is definitely the way to go because everything else is more rolling resistance. More rolling resistance needs more energy." The first solar car was even lighter. In 1955, William G. Cobb at General Motors designed the Sunmobile. About the size of your hands. In 1962, this 50-year-old Model Baker was equipped with solar cells. In 1980, researchers at Tel Aviv University gave birth to the Ugly Duckling. A tiny car with solar panels on the roof and hood. But building a solar cars is a bit more complicated than just slapping solar cells onto a tiny car. The first big challenge is the sun's angle. Solar cells generate most energy when the panels are perpendicular to the sun. That's why some solar parks even turn throughout the day. But everything on a car is fixed and round. That means cells are operating in less ideal conditions. Unless, you own a competition car. During their mandatory stops while racing, they can pop up their hood. "So, you stop, pop up the hood and then you basically have the perfect angle for the sun to shine on it." "Yeah, I don't see that with any normal car happening." The second challenge is that you need to use special solar cells. These ones cost about 35 grand. "On the top, we have all monochrome crystalline silicon cells." "How efficient are these cells?" "These are around 25%. And about four square meters. So it gives you roughly a peak output of four kilowatt hours." "Are these the same cells that are on roofs these days for example?" "This one you can find on roofs, for example. But the difference here is the encapsulation, right? This is a very efficient encapsulation that traps the light a little better than you find in the stuff on the roof. Because the stuff on the roof – and also commercial soon to come solar cars – has to be more durable. Don't scratch so fast. And because, as I said, we don't want you even to touch them. And that is not feasible for commercial vehicles." But the real crux of commercial solar cars is that they are much heavier than this race car - and solar can only produce so much power. That's why making them run only on solar power is really, really hard. Like every other electric vehicle they also have batteries that can be recharged on the grid. But the solar cells are actually where bankruptcy started for solar car start ups like Sono Motors from Germany and Lightyear from the Netherlands. Because manufacturing these cells is quite complex. Usually solar panels are straight, but in solar cars they need to be curved. "The electronics become more of a challenge when the surface is quite curved. " This is Lex Hoefsloot. Co-Founder of Lightyear. He also comes from solar car racing. "Because then one solar cell is looking at the sun in a different way than the other solar cell and then you need complex electronics to still get most of the yield out of the solar panel." But that's not the only challenge, the cells should be robust, and shouldn't splinter if the car crashes. And integrating them into a car part isn't easy either. "So, you start with glass. Then, what you add is kind of a conductive backsheet. So, basically a printed circuit board, but then flexible, and then you pick and place the solar cells on top of that printed circuit board." Buying the machines, buying the materials, developing manufacturing processes and after you did all that, you need to get your newly developed solar car parts certified for everyday streets. And all of this costs a lot of money. Sono Motors would have needed 200-300 million euros just to go into mass production. No pocket money for start ups. But solar cells are only one part of the puzzle, the other one being how many kilometers you actually get out of it. And there are quite a lot things to consider. The size of the solar array: Bigger means more generated energy. The location on the globe: Some countries get more sun than others. Time of the year of course. Shading, dust on the panels, solar panels aging which makes them less efficient and more. Now, there are studies that factored in some of the things, but not all. And it's mostly calculations, and not real world, long-term tests. Keep that in mind. So how many kilometers do you get out of this? Well, it varies. Anything from 293 km at the low end, to 3,400, up to 5,100 kilometers per year. A problem is that all these studies assume different parameters like size of the solar array, possible power output, whether there's shade or not. Just as an example of how much of a difference that makes. By only increasing the PV area by half a square meter, you already get 2,078 km instead of 1,444 km per year. That's what Sono Motors and Lightyear did. They increased the size of the solar array. Sono went for six and Lightyear for five square meters. Projected ranges were 34 or 70 km per day. Both promises that couldn't be kept. Sono couldn't raise enough cash. The company is restructuring, and selling off their car manufacturing capacities. Lighyear underestimated manufacturing costs. They planned to sell their Lightyear 0 for 120,000 EUR, but increased it to 250,000 EUR due to expensive car parts. They filed for bankruptcy in 2023. "It is a very low volume exclusive vehicle that when financial markets change and a lot of focus comes on the actual margin that the product is generating, then that project is not the perfect fit for the market. So that's why we had to restructure." They are now trying to build a cheaper car called Lightyear 2. But are still looking for partners and investors. The US start up Aptera Motors, which shut down in 2011 due to lack of funds, but came back in 2019 with new backers, looks also great on paper: 643 kilometers of range, 64 additional kilometers per day, costs below 40,000 USD. But when NBC tested a prototype: "Our test model had some obvious flaws and it could barely make it uphill without overheating." "I think you are the first person to ever drive this up a hill." "Ooops. Not a good look!" But there are actually already solar cars on the road. Well...KIND of a solar car. The Hyundai Sonata for example. A hybrid car with a solar car roof, which, under IDEAL conditions, will give you three to four extra kilometers per day. Yeah not that much. It's more of a nice-to-have design feature. Talking to industry experts and car suppliers, big car manufacturers are mostly looking at solar roofs as optional. So it's really hard to project how many vehicles will be actually equipped with it. "If we don't fundamentally change cars' appearances solar panels impact on cars will always be quite limited. But what happens if we blow one parameter completely out of proportion?" Something that is being tested right now by the truck manufacturer Scania in Sweden in collaboration with Uppsala University. A real world trial that has been going on since September 2023. Instead of two square meters like most cars, the hybrid truck has 113 square meters of solar cells that charge a battery in the trailer. For an estimated 5,000 km of added range per year. "We expect maybe somewhere around five to ten percent of the energy that could come from solar energy. And that one should say that that is also in Sweden which is maybe not the best place to test this." This is Erik Johansson. He leads the trial and is in charge of the scientific data collection. "What we are seeing so far, looks to be rather similar to what we expected actually. So, that is almost surprisingly similar." They even ran the numbers for southern Europe, and that could turn out twice as much energy. So, there are some great use cases for solar. When vehicles are very light and they are deployed in sunny regions. Like here in Tunis with these delivery tricycles or these small buses for public transport in Nigeria that mainly run on solar power. "Solar cars. Two manufacturers almost went bust. We don't know how much energy we're going to get out of it, at which point. Today, you can already put a solar panel on your roof and power your electric vehicle. It's true. Your car's roof is dead weight that can be used otherwise. But until that has an impact, It's going to take a lot of time." "If you did like the video, please share, like and subscribe to our channel. We post new videos on the environment every Friday."
