Are the solar panels even efficient enough at those angles to the sun to generate more electricity than they cost in weight?
this post was submitted on 11 Dec 2023
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Yes, by a small amount, unless you live in the arctic circle or something.
But does that mean they're worth it? Probably not. There's the financial cost as well as the weight. Plus potentially eating into head room. Plus it's another thing to potentially go wrong.
I certainly see the use case for campervans - a large flat roof is ideal, and being able to park for a couple of days and charge a leisure battery without flattening your main battery or running an engine seems perfect.
But for a passenger car, the use seems more limited.
Maybe with some of the super cheap perovskite cells coming out? Maybe.
It's a very marginal idea, at best. Even in equatorial regions under perfect weather, there just isn't that much solar power you can collect with the space of a car roof.
Aptera is attempting to do this. They had to engineer their own solar panels for the car. Probably the closest thing they have to production ready. They also had to make the car super efficient to make it work. Peak output of their design is about 700W
So, fewer than 10 miles per day in perfect conditions?
700 watts = .7 kW
If you figure 10 hours of that (or longer but with less-perfect conditions) you can get 7kWh. I estimate about 3.5 miles per kWH on my Bolt. Not sure this car's efficiency, but it gives us a ballpark number. That would give about 25 miles of driving. I understand that there are plenty of other factors that can go into this, but "fewer than 10 miles in perfect conditions" isn't necessarily accurate either.
I would respectfully argue that 5 hours of peak output equivalent is more realistic as that's what you'd get from static panels at the proper angle. But I didn't figure in the claimed efficiency of the car.
My car, Ford cmax energi, was tested with a 500 watt panel and that only yielded 5 miles a day in great conditions. More like 2-3 miles most days, and that's at roughly 300wh/mi., similar to your bolt. Never made it to production with solar.
But even that number you say is realistic, about half of what I just said, would still give a little more than the "less than 10 miles under perfect conditions" - I still don't think it's really that practical or worth the cost for a number of reasons, but I also like crunching numbers to know what it would look like before making that judgment.
Curious, how did you get power from a solar panel into a high-voltage battery?
Wasn't me personally. Solar was tested by the university of Georgia iirc. And I'd assume some sort of DC boost converter to boost the 30v to 300v when connecting the panel to the battery pack
That's the other part, they've made the car as efficient as possible. They're estimating 40 miles/perfect day because of that.
Geeze, a <$1000 e-bike conversion kit can put out more than that.
First I've heard of them, hopefully they can get back to it soon. I'm still keeping my eyes on the Aptera
I'd love an EV charged only with solar power...but living in a place with 7h of daylight in the winter, and 200 rainy days per year, that'll never happen. During summer it is already possible (and then some) with a regular EV and rooftop solar panels to drive entirely on solar power, I don't charge my car from the grid from May to September.
Yeah, unless there's huge advances in solar panel efficiency and weight, it's probably better to focus on smart charging off static solar panels, even though it would be cool to own a car that just charges itself one day.
Companies like Aptera will need to find a niche use case where solar makes more sense than plugging in at home. I guess it would be useful for people that only have on street parking available to them?
Oh yeah it would definitely be cool to have a car powered by onboard solar panels, but I don't think that's ever going to be viable where I live. I'm getting a whooping 0.3kWh-1.5kWh of production per day at the moment on my 11.4kWp installation.
They're actually trying to do just that. Aptera developed their own solar panel assembly and charge controller to go in the car. It's designed to be super light weight and durable.
Also yes, plugging at home is not a valid option for many Americans. Even fewer can afford solar panels at home.
It probably won't happen even if you lived near the equator and had year round perfect weather. There is about 1000W/m^2^ to work with as a theoretical limit, and it's just not enough to power a car with the panels on its own roof. Not unless you keep the motor power to e-bike levels, but with way worse weight and aerodynamic cross section.
At best, it can be a supplementary power source. It needs to be low weight and low cost for even that to be worthwhile.
You could place the solar panel in orbit and beam the energy to your car as microwaves.
Hey, maybe instead you can have some 3 meter tall “solid state” wind turbines?
Nope, I live in a suburb
This seems really promising
This is a real bummer. I saw these guys on The Fully Charged Show a couple of years back and their first car looked incredibly promising. But the auto industry is not easy to break and investors know that. Hopefully the solar roofs will prove profitable enough for them to try again.
IIRC, part of the reason why and how they declared bankruptcy and restarted was because they then no longer had to fulfil any preorders (but also didn't pay customers back due to the bankruptcy). So customers got screwed over.
Car industry is difficult but these kinds of practices sound extremely fishy.
I was not aware of that! Thank you for mentioning it. It has always seemed crazy to me that customers have no charge over assets on bankruptcy. In a better world, that'd be the case but that's not the world we live in.
As an aside, this is the sort of thing that is going to hinder investment in small firms in the auto industry, further compiling the issue of a few manufacturers setting ridiculous prices for their vehicles.