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xkcd #2929: Good and Bad Ideas
(imgs.xkcd.com)
Alt text:
While it seemed like a fun prank at the time, I realize my prank fire extinguishers full of leaded gasoline were a mistake.
I wonder why solar cars are bad?
It's way more effective to collect the solar energy from a station to charge batteries than to cary the whole thing around unless your car is a drone on some remote planet
Which is about as ineffective as personal transport gets. And also not a car.
I mean, maybe the muskrat is considering the car to take to Mars with him?
Should have strapped him into the Tesla he stuck on one of his ~~penis compensators~~ rockets when we had the chance..
The sun gives you around 1500W per m2. If sun shines at maximum brightness for 24 hours, you get 36kwh per day. That's enough to fully charge a small EV every day. That's a spherical chicken estimate.
Bringing this to numbers that exist in the real world, the sun will only give you about 20% of that over the course of the day, and the panels are around 20% efficient. You'll get more like 1.4kwh per day per m2. You can double or triple that, depending on how much surface area you can cover. An EV can get around 3 miles per kwh, so tripling that number will get you 12 miles. Considering the extra costs involved (both in buying the panels and adding weight), it's not even worth it as a supplementary source.
There's some possibilities for RVs, which have a lot of roof space for panels, tend to sit in one spot for days or weeks, and have other power usages that are a lot less than driving. Otherwise, put the solar panels over the parking places and roadways, not on the cars.
The benefits increase as the efficiency of the car increases though, check out Aptera. They say they get 10 miles per kwh, and they have a lot of surface area for panels. Enough that in ideal conditions they say they get 40 miles per day from solar. It is a bit different looking though.
https://aptera.us
It's also a three-wheeler, which gets around US safety regulations. It gets registered as a motorcycle or autocycle (depending on how your state handles it). However, it's still an enclosed metal box. There's not a lot of good data, but it's arguably better to be sitting loose on a motorcycle with a helmet and safety gear as opposed to being crushed inside a sardine can.
There's a certain point of shrinking cars where you have to ask "why not use an e-bike?", and this is that point.
Well, it has a carbon fiber frame with a crumple zone in the front. They are going to put it through 3rd party safety testing. It won't be as safe as a big SUV, sure, but I think it will be safer than an ebike. It also protects you from weather and has 35 cubic feet of storage in the back. I think ebikes are great too, but this does have more of the advantages of a car.
You know how the Internet made fun of Stockton Rush for using carbon fiber in a sub, which is a compression structure? Similar thing going on here. Carbon fiber is a great material for tensile strength and lightweight. It can be used in compression structures, but it needs more careful engineering to pull it off. The benefits do not always outweigh the costs.
As a more general issue, if a car the size of a Geo Metro or smaller can't be safe on roads, then motorcycles and bikes can't be, either.
Well, I just said carbon fiber, but to be more exact it is forged carbon SMC, so yeah, careful engineering involved. Same stuff Lamborghini is using for some structural components, so probably fairly fit to purpose.
https://en.m.wikipedia.org/wiki/Forged_composite
Cuz you can haul more, camp inside of it with the tent mod, travel further and faster.
They’re planning 250, 400 and 1000 mile versions. I’m also not taking an e-bike on the highway.
I'm not sure you can haul more. Cargo e-bikes can do a lot more than you think.
Ya I saw that cybertruck to cargo bike comparison. I automatically went to the mountain bikes. We don’t have the same cargo bikes the Dutch have but there is a guy around here with a cargo e-trike. I bet it’d be close. But the car can also take a second passenger not in the cargo space.
Solar cells of comparable scale don't provide nearly enough power to propel any kind of useful mass, and their output is only a trickle compared to even the slow-charging current of a classical EV. A solar-powered car would have to save mass everywhere, including safety devices (goodbye, crumple zones), backup propulsion, and batteries. No batteries means that the car would be limited by weather, time of day, and day of the year (winter -> sun at lower angle -> reduced solar cell power). Solar cells would have to be flush with the car's body lest they turn into sails/wings/airbrakes, which makes tracking the sun for better efficiency impossible. Driving through a city, a wooded area, or inside a tunnel would cast shadows on the car, especially at dawn/dusk.
I could go on.
They're not—as long as the PV cells are a supplementary charging solution, in addition to wall charging, to the batteries. You'll get a bit more range out while driving, especially when the car is a lightweight low drag design and PV cells may be the only thing needed to keep the constant 90 km/h speed in a sunny day. And when not driving the cells might be enough to get the 10...20 km or so commuting range back over your 8-hour workday.
But putting PV cells on a 3 ton electric SUV or pickup truck is stupid, it won't do jack all due to the inherent inefficiency of such vehicles.
Let's worry about the inefficiency of SUVs and pickup trucks for transporting one person to work. Compared to that solar panels are a drop in the bucket.
Not enough power. A car is not a 1500 watt appliance.
[Citation needed]
And a micro car wouldn't be able to have even a 750 watt panel on it.
The Sinclair C5 had a 250W engine:
https://en.wikipedia.org/wiki/Sinclair_C5
Wasn't really a car, though, rather
The energy one can get from a panel the size of a car roof is tiny and not worth the added weight.
They're not. If you make your car light enough, and potentially aerodynamic enough (things which should already be done to electric cars/cars in general), it makes sense, especially for the real life practical application of people who don't have outlets they can run to their car. Aerodynamics is mostly just an efficiency increase, but decreasing weight gives a myriad of benefits, potentially including increased power to weight ratio, decreased road wear, decreased road noise at speed, increased efficiency, improved crash safety as a result of decreasing the total amount of weight you have to stop, which can actually improve the efficiency of the interior space as you can now make things like roof pillars less thick. Could also lead to increased parking space, better maneuverability, and better visibility, if you make the car itself smaller as a result of decreased weight.
Cars should be like1/3rd of their current size. Clown cars ftw.