In January I asked how far we were from a self charging solar car. At the time there was nothing on the market, just two or three prototypes that involve some kind of solar charging. That changed a couple of weeks ago with the launch of the Sion, from German start-up Sono Motors.
Last year Sono ran a successful crowd-funding campaign to develop the vehicle, and at the end of July they unveiled the final design. It’s a family sized car that comes completely clad in solar panels – 330 solar cells, adding up to 7.5 square metres. The company claims that will buy you 30 kilometres of driving most days, with the high efficiency panels able to charge even in cloudy weather. That may be enough for most people on shorter journeys, but a full charge will take the car 155 miles if you’re going further.
There are a couple of unusual features. The natural moss air filter is certainly an odd one. The bi-directional energy flow means you can use the car to run other devices, or even to charge other electric cars if you needed to for some reason. But perhaps the main selling point is that the Sion costs £14,500, or $17,600. That’s a genuinely affordable car, half the price of the much hyped Tesla 3, which is supposed to be the company’s first affordable mass market electric car.
Is it any good? Does it deliver on the self-charging promise? All that remains to be seen. But if Sono get 5,000 pre-orders, it will go into production. So perhaps a self-charging electric car isn’t that far away after all.
The Earthbound Report 
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I think 30 km on the solar charge is stil a bit optimistic. Just a back-of-the-envelope calculation: 7,5 m2 of crystalline solar panels would yield around 140 kWh per m2 per year when they’re in a good position. Let’s take this as an absolute maximum. So the maximum year total from solar panels would be 7,5 * 140 = 1.050 kWh per year. Averaging this out means 1.050 / 365 = 2,88 kWh per day. For this charge to bring you 30 km, would mean that the car uses 9,59 kWh per 100 km. This is what my small e-up! uses when it has a good day; this is the most efficient electric car on the market, in part because it’s just very small.
From the looks and specs of this car I would say it would use more on average, in the range of 15 kWh / 100 km. Also, the panels are probably of the flexible type, efficiency is drastically lower. Next to that, the panels are not in a great position. I think you can be happy when it reaches one third of the maximum yield I calculated above. Using these numbers, the average daily distance on solar would be just 6,5 km.
By all means, put solar panels on your electric car, because every little bit helps. But don’t pretend that they deliver more than a fraction of what the car uses. Since I’ve started driving my electric vehicle, it has just shown me how much energy a car actually uses- that is, ANY car. This means that even with an electric car, one should use it only when it’s really necessary.
Yes, not everyone is going to get 30km, and possibly not all year round. Maths isn’t my forte and I haven’t got an electric car to compare it to, but there are lots of details in the spec if you want to check it out:
Click to access Facts_ENG.pdf
The solar panels are 24% efficiency for example, so pretty good. The car weighs 1.4 tonnes to the E-up’s 1.1.
There’s no question that you’re going to have to top this up from a charger sometimes, especially in winter. But it all depends on what your needs are and where you live. Some people are going to find this is an electric car that they never need to plug in.
Thanks for the specsheet. From that, it seems the standardized test-usage is 14 kWh per 100 km, so that’s a little better than I anticipated. I’m surprised about the efficiency of the solar cells, but great if they can make that happen. So if they are comparably efficient to crystalline panels, the only thing left is orientation (you can’t have the sun shine on all sides of the car at once). So supposing instead of 1.050 kWh we get around 700 kWh a year (ca. 2 per day), that means with 14 kWh/100km you can drive 14 km’s on that charge.
By the way, I was not trying to be overly pessimistic or nay-saying. I do think that it’s a good concept to place solar panels on electric cars, if only because we need every bit of energy we can get. I just think in these cases, sometimes PR gets the better of common sense physics, which is a problem if you want to solve climate change.
You’re right, the PR will focus on the best case scenario – and the 30 km figure is going to be a summer’s day I imagine. Great if you live in a country with reliable sunshine, but expect lower mileage in the Northern Hemisphere.
Thanks for your calculations. I don’t take them as pessimistic. I’m aware that I’m an ideas person, and I need others with more analytic minds to balance things out!
Thanks for your great blog, and for keeping it up for as long as you have. Persistence is necessary 😉 I’ve been a silent reader for years and really like that you start from the idea that our wealth is the problem. In the end, that’s what the numbers tell us and it’s an unpopular message. I’ll keep enjoying the ideas you put on your blog for the years to come 🙂
It’s fantastic that people can ‘think’ and make it happen. It’s only when you ignore the naysayers that the magic happens.