Posted by geox 3 days ago
I am worried about production. With all of the years it's taking them to get there, they can run out of money at any time it seems. It's unknown if they can raise enough money on their terms to get this thing to production.
I'd venture a guess - Aptera went for 3 wheeler because certification as a motorcycle is much easier than as a 4-wheel car. Unfortunately 3 wheels - 3 vertical columns resisting the upcoming air - may be less aerodynamic than 4 wheels which are only 2 vertical columns resisting the upcoming air. Add to that that for the same stability you generally need the paired wheels in a 3 wheeler wider than the paired wheels in a 4 wheeler - that again worsens the 3-wheeler aerodynamics.
thanks. That is in general what i meant by saying "4 wheels which are only 2 vertical columns resisting the upcoming air", i missed the shorter axle as being the most aerodynamic, and your description is just much better and more right detail level correct.
Let’s (generously) assume that was the minimum they saw, and let’s (generously) say they charged for 14 hours. That’s 7.63 kWh gained over the day, in almost ideal conditions. Flagstaff’s high altitude means stronger sunlight, and they can do regenerative braking as they come down the mountain. In my Nissan leaf, 6 kWh would get me about 20 miles. If they are much more efficient, they maybe got 50 miles from the charging on that day, and the other 250 from the charge they started with.
I’d love to be wrong about any of the above! Solar panels on cars would be so cool! It just doesn’t seem useful. Please correct me if I’m mistaken.
The average car travels less than 50 miles on the average day though (more like 30 I believe). This means you don't have to charge except on roadtrips (provided you can park outside in the sun, and don't drive more than average. The battery can provide some smoothing out of day-to-day variability though).
Whether not having to plug in at home is particularly useful... hard to know if it's something consumers want.
A car has about 5 m^2 of flat space on the roof/hood/trunk so that's the maximum surface area that can capture solar energy at any given time.
The total energy to hit the area is 1000 w/m^2.
The panels can't rotate to track the sun so the effective area is the cosine of the angle. So you end up with about half the amount of effective sunlight hours as the actual daylight hours. So in summer you get about 6 hours of effective sunlight.
Good panels in real world conditions can give you 22% efficiency.
So in optimal conditions you get: 5 * 1000 * 6 * 0.22 = 6.6 kwh
That will reflect your best days. It can be dramatically less if it's cloudy, overcast, winter, far from the equator, car is dirty, parked in shade, etc.
6.6 kwh is about one tenth of the battery in my Hyundai Kona EV. With very conservative highway driving, 6.6 kwh can get about 40km of range and about 50km in city driving. It's what I get from plugging into my home charger for 30 min and what you get from a fast charger in about 3 minutes.
So besides some very niche uses, there's no sense in massively increasing the cost and complexity of a car by installing solar panels. Far better to put the panel on the roof of parking and just plug in for a few minutes while you park.
500-600 watts is plenty for moving along at 30-40mph, and with such a light bodyshell, you don't want to be going a lot faster than that.
Standard automobiles are something of a vicious cycle energy-wise - weight, range and speed aren't a linear relationship, so on short-range trips we're paying a huge efficiency penalty for long-range capability. Golf buggies, ebikes and so on can be 1/10th the weight and 1/10th the energy consumption.
Sure it’s not enough on road trips, but why is that a problem?
> they maybe got 50 miles from the charging on that day
They claim it's up to 40.
Best case you charge more than you drive; so your car has a enough in the battery every morning to make it back home after work. Worst case, you delay the moment when you have to charge by plugging in by some large percentage. The difference between charging your car once or twice per week and once or twice every few months top top it up. Perfect if you don't have a charger at home. Removes a lot of the hassle and cost related to charging.
Road trips are not something people do on a daily basis. Especially not in light/small vehicles. But when you do, a light vehicle with a longish range is a nice thing to have. And this thing is very efficient by design (light, teardrop shaped) and the relatively small battery probably charges pretty quickly. And you get a few tens of miles extra because of the solar. So it can do a 300 mile journey despite having a smallish battery. Which is what they just demonstrated. 300 miles is pretty good. Most EVs don't do any better than that.
That length makes it too big in many countries, especially for just two seats.
I'd call something like a Golf/Focus "mid size". There's approximately two sizes below and two sizes above.
So, yes, that Trump's idea he expressed in the interview to Musk back then to plaster cars with solar panels isn't totally meaningless, at least in theory - you can have 2-3x solar panels on regular car compare to Aptera, so it would have made sense for daily commute if that plastering of the cars cost close to nothing, and unfortunately putting such thing in production would add thousands to the car cost, and given that even Musk/Tesla with their pile of cash available to dump into engineering of such a new feature haven't yet ventured into it it suggests that at least near future isn't bright for it.
>Even if it costs a couple thousand extra, the panels will pay for themselves by giving you basically free commutes forever.
Say you get 1.5KW, 3x of best Aptera, 8 hours, 12KWh, i.e. about $3.60/day or it can be thought as a replacement of 1 gallon of gas (at 30% efficiency), still $4. Thus $1000/year. And i don't think the feature can be put into cars at $2K. More like $3-$5K optimistically.
$/watt STC is more for big roof and ground mount PV financial calculations.
