4 ms·

How far is the average commute? There are a lot of places where this level of additional range for "free" could potentially halve your charging needs. Might a

How far is the average commute? There are a lot of places where this level of additional range for "free" could potentially halve your charging needs. 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.

wtallis 7y ago
> 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.
- mattigames 7y ago
  You may be underestimating how much people dread chores like manually plugging their car to the electric outlet, and many people don't have those special garages with chargers on them, and if the house is a rented one modifying it is out of question (and renting is not only a poor people problem, a lot of people pay an insane amount of money renting, ask anyone in NYC).
  - wtallis 7y ago
    > You may be underestimating how much people dread chores like manually plugging their car to the electric outlet, 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.
- luminiferous 7y ago
  When I first read your comment, I thought that there was no way that solar panels could be heavy enough to affect your mileage. So I did some quick calculations. 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-and-what-is-the-weight-of-a-solar-panel/#targetText=On%20average%2C%20solar%20panels%20and,acceptable%20limits%20of%20your%20roof https://sunmetrix.com/is-my-roof-suitable-for-solar-panels-a.... [2] https://www.toyota.com/prius/features/dimensions/ https://www.toyota.com/prius/features/dimensions/ [3] https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=216 https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=...
  - baking 7y ago
    These are thin-film, light-weight, and flexible. Hanergy owned Alta Devices has a Gallium Arsenide lift-off process that produces the world-record efficiency for single junction PV.
  - insulanus 7y ago
    172lb is a lot! Thanks for doing that. But I think solar panels meant for rooftops have a lot of weight in the aluminium frame, and are think glass. I can't imagine a car manufacturer putting thick glass above the aluminium skin of the car if they didn't have to. Maybe we'll get cool solar panel crystal car roofs in the future!
WalterBright 7y ago
I've often thought these cars should have a small gas generator you could use to charge the car if there's no outlet available.
- blacksmith_tb 7y ago
  Most Prius-es are simple hybrids; the car they're testing with is a Prius Prime, a plug-in hybrid with ~25mi of all-electric range from an 8.8kWh battery, that's what they're trying to add range to. If that battery is exhausted you just drive on the gas engine as usual (I have a 2017 Prime). So this would just be a small boost, though to be fair I often can go a few days on a charge (but I don't drive a lot).
- milkey_mouse 7y ago
  That's essentially what a plug-in hybrid is, modulo the "small."
  - outworlder 7y ago
    > That's essentially what a plug-in hybrid is, modulo the "small." 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.
    - greglindahl 7y ago
      You're incorrect about the Volt's drivetrain: https://en.wikipedia.org/wiki/Chevrolet_Volt#Drivetrain https://en.wikipedia.org/wiki/Chevrolet_Volt#Drivetrain Yes, the gas engine can turn the wheels.
- outworlder 7y ago
  You are describing the Chevy Volt. Or the BMW i3.

wtallis 7y ago

> 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.

mattigames 7y ago
You may be underestimating how much people dread chores like manually plugging their car to the electric outlet, and many people don't have those special garages with chargers on them, and if the house is a rented one modifying it is out of question (and renting is not only a poor people problem, a lot of people pay an insane amount of money renting, ask anyone in NYC).
- wtallis 7y ago
  > You may be underestimating how much people dread chores like manually plugging their car to the electric outlet, 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.
luminiferous 7y ago
When I first read your comment, I thought that there was no way that solar panels could be heavy enough to affect your mileage. So I did some quick calculations. 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-and-what-is-the-weight-of-a-solar-panel/#targetText=On%20average%2C%20solar%20panels%20and,acceptable%20limits%20of%20your%20roof https://sunmetrix.com/is-my-roof-suitable-for-solar-panels-a.... [2] https://www.toyota.com/prius/features/dimensions/ https://www.toyota.com/prius/features/dimensions/ [3] https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=216 https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=...
- baking 7y ago
  These are thin-film, light-weight, and flexible. Hanergy owned Alta Devices has a Gallium Arsenide lift-off process that produces the world-record efficiency for single junction PV.
- insulanus 7y ago
  172lb is a lot! Thanks for doing that. But I think solar panels meant for rooftops have a lot of weight in the aluminium frame, and are think glass. I can't imagine a car manufacturer putting thick glass above the aluminium skin of the car if they didn't have to. Maybe we'll get cool solar panel crystal car roofs in the future!

WalterBright 7y ago

I've often thought these cars should have a small gas generator you could use to charge the car if there's no outlet available.

blacksmith_tb 7y ago
Most Prius-es are simple hybrids; the car they're testing with is a Prius Prime, a plug-in hybrid with ~25mi of all-electric range from an 8.8kWh battery, that's what they're trying to add range to. If that battery is exhausted you just drive on the gas engine as usual (I have a 2017 Prime). So this would just be a small boost, though to be fair I often can go a few days on a charge (but I don't drive a lot).
milkey_mouse 7y ago
That's essentially what a plug-in hybrid is, modulo the "small."
- outworlder 7y ago
  > That's essentially what a plug-in hybrid is, modulo the "small." 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.
  - greglindahl 7y ago
    You're incorrect about the Volt's drivetrain: https://en.wikipedia.org/wiki/Chevrolet_Volt#Drivetrain https://en.wikipedia.org/wiki/Chevrolet_Volt#Drivetrain Yes, the gas engine can turn the wheels.
outworlder 7y ago
You are describing the Chevy Volt. Or the BMW i3.