I think any bit helps. If solar panels will ROI over the lifetime of vehicle ownership, then that’s awesome!
Might also mean that people start looking for uncovered airport parking. Or that it's a lot harder to get really stranded with an electric car.
Even at 100% efficiency (which we'll never get) I think electric cars will still have to charge off of something. But dragging the panels around with you so that you always have some kind of charging seem pretty reasonable.
It might prevent the worst case scenario of being stranded in a desert without fuel. But for everyday driving, dragging around that extra weight has a real cost, which could quite plausibly outweigh the benefits to everyday driving.
Remember, our auto industry has moved to the point where spare tires are starting to become uncommon and full-size spares are almost unheard of. The market isn't trying to optimize for the worst case scenario.
I'm simply assuming that, for the foreseeable future, solar panels on your car won't put a noticeable dent in the frequency of those chores compared to with a current production Prius. If you can already go for two weeks of commuting and grocery runs without topping off the gas tank in your hybrid, stretching that by another day or two doesn't meaningfully change the ownership experience even if it does have a long-term impact on the economics of owning that vehicle.
Estimates of solar panel weight I found say that solar panels tend to weigh 2-4 lb per sqft.[1] Note that estimate is for roof-mounted solar panels, but if anything, car-based solar panels should be lighter.
A Prius has dimensions of 180"x69".[2] The sqft of the solar panels will be less than that, since the panels don't cover the windshield, and they don't go all the way to the edge of the hood, etc. That's 86.25 sqft, so that puts an upper bound on the weight of the solar panels at 345 lb. If we assume the lighter end of the scale for solar panel weight, that becomes 172.5 lb. That's 6-11% of the curb weight of a Prius. That's pretty substantial! For reference, a 50 lb spare tire kit can reduce fuel economy (and presumably mileage, for EVs) by 1%.[3]
Although that does imply that you're breaking even if the solar panels can increase your range by ~5%, not accounting for the weight. If you live somewhere like Arizona, that might work out. If you live in Seattle, maybe not.
[1] https://sunmetrix.com/is-my-roof-suitable-for-solar-panels-a....
[2] https://www.toyota.com/prius/features/dimensions/
[3] https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=...
Maybe we'll get cool solar panel crystal car roofs in the future!
It could still be used as a supplement while driving to extend the range. If the battery was fully discharged, you'd have to wait.
It would be like leaving a vehicle idling when you park it. Noisy, polluting, and potentially deadly.
I use a generator frequently. I leave it outside, unattended. So do the neighbors (when the power goes out). I never leave an idling car unattended because I worry about it. It's a much bigger deal than a little gas engine.
> It would be like leaving a vehicle idling when you park it. Noisy, polluting, and potentially deadly.
It certainly is a bad idea to run any sort of combustion engine in a poorly ventilated area. Perhaps I presume too much that people will have some common sense.
As for the noise, that's a design issue. ICE car engines are pretty quiet these days. There's no particular reason why a small ICE has to be loud like a chainsaw.
Not exactly, Prius uses two drive trains and some fancy gearing to be able to use both engines. The gas engine actually propels the vehicle (either alone or together with the electric)
Some 'hybrids' like the Volt only have EV drivetrains. The gas engine is just a generator and does not turn any wheels. Which also means that it can be much simpler – no transmission to worry about, you can run at whatever the ideal RPM is. And so on.
Yes, the gas engine can turn the wheels.