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this post was submitted on 11 Dec 2023
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Are the solar panels even efficient enough at those angles to the sun to generate more electricity than they cost in weight?
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
Geeze, a <$1000 e-bike conversion kit can put out more than that.
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.