Comment by kwakubiney

I recently read about Aptera, a company building a commercial solar car:

https://aptera.us/first-vehicle-off-validation-line/

I think it is quite interesting, because it also tries to be maximal efficient, which increases the "reach" that the panels provide.

Don't get me wrong, this is a enthusiast car, but I think the economics could actually work for a small city car. Currently here in Europe, buying a electric car makes sense for home owners, which can charge their vehicle for cheap at home (especially if you PV). But a lot of people living in cities don't have a cheap charging spot. A car with solar panels, which gains a few percents of charge each day (instead of losing some), e.g. enough for the daily commute to work, may be interesting for such people.

I would love to see a ultra cheap take on this. Maybe an electric tuktuk like someone else suggested, with some solar panels slapped on it.

> The solar energy you can collect is about 750W/sq meter.

> A car roof is about 5’x5’, and if we are generous and include a trunk and hood area, maybe you are getting 60 sqft?

We must think metric, every inch of the way!

Anyway, PVCs currently max out at about 300W / square metre - and that's in ideal conditions.

I believe theoretical maximum energy per square metre (when light actually arrives at the planet surface) is conveniently pretty close to 1000W, assuming you're in the right place, but maximum efficiency of contemporary panels is only about 30%.

I would love to see this laid out practically.

For example, if you had an electric golf cart with a solar roof, on a sunny day…

With two adults, a speed of 35 MPH, an LLM suggested a ratio of 10:1—that is, the power demands of the golf cart were 10x what the solar could deliver in real time. (LLM considered also aerodynamic drag, rolling resistance of golf cart tires…). When I suggest a speed of 25 MPH, the ratio came down to 5:1.

Regardless, assuming batteries to store energy on the cart, it suggests a 10 minute drive to your neighborhood grocery store would require the golf cart to sit in the parking lot for close to an hour before it will have caught the batteries back up to their charge before you left home. (And this is at the rather impatient 25 MPH drive.)

To get to a better ratio you would have to engineer like hell to start squeezing the numerator. Make it radically aerodynamic, low-rolling resistance tires (probably the lowest hanging fruit), cut the weight significantly…

I do love the idea of something like an electric rickshaw or tuk-tuk. Maybe not streamlined, but you could get much better rolling resistance with something like bicycle tires—and weight could be kept in check.

Ok, so lets say we didn't want 100% of the energy to come from those "self-sustainable panels on the car", but rather N%, so we keep most everything as-is, except switching all the outside body/chassi panels for solar panels, how much N% could we recover from that? Could it change so someone goes from needing to charge once every 3 days to once every 2 weeks lets say? Together with re-generative breaking, maybe it could at least have some impact.

consumer car needs hundreds of pounds of reinforcement... just to pass side impact test

[dead]

> The problem with green energy is that it is very democratic and hard to control.

It's not that I totally disagree with this - there is some truth to it. But it has no bearing at all on the question "can I put the panels on the car instead?" Which has been debunked in this thread and elsewhere many, many times.

The counterargument to what you say is that Solar is in fact booming. It is coming - oil money can slow it, but not stop it. They have more success in some countries than others. It's not a coincidence that China, which course desires energy independence but doesn't have access to a lot of oil, is leading the way. Sorry USA, you're laggards now.

But solar + battery is on an exponential ramp-up and getting big now. Each shock like the current Hormoz idiocy makes the case for it even more to the rest of the world. It's coming, fast.

Just, it's not useful on car roofs. That's a poor choice of panel location.

> Maybe someday the price will get so low it will be a no-brainer.

The cost of solar panels is already low, that's why it's booming. This cost isn't the main constraint any more.

Panels on a vehicle have stronger requirements for low weight, and vibration tolerance than those on a fixed structure. They contribute to the complexity of the vehicle's power systems. They have to be designed with vehicle aerodynamics in mind.

And of course the limited surface area means that you do all of that, for a component that's it's barely able to keep the vehicles' aircon running. The physics of that will remain the same. Even of the total costs are low (and factors such as the vehicle weighing more are an unavoidable cost), the benefits are lower.

At any price point, including free solar panels, there are good arguments to put the panels on a fixed structure instead.

So maybe it will happen when we have run out of non-moving surfaces to put the panels on. i.e. don't hold your breath.

Well but that would be a problem for keeping the car infinitely running with only solar power. But what about just passively charging it while idle? Cars sit idle most of the time.

> Aptera has this planned but not sure if they ever reach market maturity.

Yes, Aptera does not have a shipping product, and if they ship the current design it might not have a large market for it. The have been promising delivery for a long time now, so it certainly looks a lot like vapourware.

> but if I recall correctly it was quite difficult and expensive to manufacture

More importantly, seems they stopped manufacture it because they made a new version, that was supposed to be available in 2025, but I don't think I've seen it anywhere.

> However, in January 2023 Lightyear announced that it was halting production of the 0 model, redirecting their efforts towards production of Lightyear 2; Atlas Technologies B.V., the subsidiary responsible for the manufacture of the Lightyear 0, would be allowed to go bankrupt. As of 2023, the replacement, Lightyear 2, is slated to be US$40,000 and available in both Europe and North America, and to start production in 2025.