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Comment by jonas21 | Hacker News Reader

> Can't imagine you're getting much power from an extra panel on the hood over the course of a drive?

It's not just over the course of a drive. It's charging while your car is parked out in the sun all day long.

> Website also states that me, living in boston, driving 40 miles a day would only need to charge 6 times a year? There's just no way that's accurate.

Back of the envelope, that seems reasonable enough:

700 W * 12 hours/day * 2/pi (to account for sun angle over the course of the day) = ~5.4kWh/day.

Cut that in half to account for lousy Boston weather, and you get 2.7 kWh/day.

If they can get 10 mi/kWh (a Tesla gets ~4 mi/kWh), then that's 27 miles/day, which leaves you 13 miles/day short. Their battery provides 1000 miles of range, so you'd need to charge every 76 days, or about 5 times per year.

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> It's not just over the course of a drive. It's charging while your car is parked out in the sun all day long.

I know this is pedantic, but it said extra RANGE. Range to me asks how far can you go without stopping.

> Cut that in half to account for lousy Boston weather, and you get 2.7 kWh/day.

But if you have a lousy day you need to charge... you can't take a battery deficit and make up for it later with a reversion to the mean.

> you can't take a battery deficit and make up for it later with a reversion to the mean.

Sure you can. Let's say you have a lousy day where you get 30% of the peak power (1.6 kWh in the example). You'll use 2.4 kWh of battery power that day, and unless your battery was already extremely low, you won't need to charge (and even if you do have to charge, it won't affect total charges per year - see below).

If the next day is good weather and you get 70% of peak power (3.8 kWh), you'll only use 0.2 kWh that day. Overall, you've driven 2 days and used 2.6kWh of battery power. Which is exactly the same as if both days had delivered 50% of the peak power.

Even if you assume that the entire winter will be lousy and the entire summer will be nice, that just means your charging schedule will be different based on season - you might need to charge every 50 days in the winter and every 120 days in the summer - but you'll still end up with the same number of charges per year.

But it's a queuing theory problem. The average is not a good indicator. It's how often does it reach a level that is so low you need to charge. Not the averages of the system. And it's not 0%. It's a level low enough that you don't want to bet on the charge rates

There is no way that rooftop area is even as large as a standard solar panel (say 200 ft²). Even the most efficient panel is no more than 350W, so you're cutting your "700 W" more than in half right off the bat. Discounting less efficient cells, road dirt, and non-perpendicular angles and we'll be generous and say 300 W.

12 hours/day is the maximum possible solar duration so you really need to cut that in half to account for a full year on Earth. So we're down to 1 kWh/day and realistically much less if you happen to park under a tree or a bird poops on your roof. That will hopefully get you to a charging station but not much further.

The 700W number comes from Aptera's website [1]. You don't have to believe them -- but to achieve that, they'd need about 3.5 square meters of solar panels, and if you look at the overhead picture on that page, it looks like it has about that much.

12 hours/day is the average solar duration. You'll get more than 12 hours of sunlight in the summer and less in the winter, but it'll average out.

And sure, if you park under a tree or let your panels get dirty, you'll reduce the amount of charge you can get. Same thing if you park in a garage or paint the roof. We can sit around all day and come up with ways to kill the performance. But you can just choose not to do these things.

[1] https://aptera.us/vehicle/

They sound great for shared cars by the hour.

Kinda think govs should mandate one per suburb street to give people a mobility option, especially when they don’t require full licence.

Or we could just design cities that didn’t require cars.

I wish but it’s too late. All the cities (at least in the States) being designed now are sub/exerbs.

I thought this too until I heard about Amsterdam. Apparently it used to be car-centric as well. Then they decided whenever they were going to re-do some district, they would re-do it as walkable. Sure, it takes 40 years, but it's possible.

Sure, lets compare $25k solution vs trillions of dollars...

One issue is that much of the above is about ideal conditions. One has to think about the average car owner.

Even IC engines have ideal conditions like don’t use a lead foot and light on the brakes, but the average driver isn’t getting the ideal MPG. Similar issue with solar.

I think Aptera isn't intended for the average car owner. It's for someone who wants a specific type of performance, likely an enthusiast.

There's several square meters on there, and they could be using high efficiency panels.

700W is perfectly reasonable. I have a 200W panel acting as shade over a tricycle which is much smaller and can easily charge a 1kWh battery in a day..

That still seems optimistic to me. These are non articulated panels, so I'd expect to see decent charging rates around local solar noon, but steep drop offs before and after, not to mention that any part of the panel being in shade will totally kill the efficiency.

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