5 ms·

> Because the amount of energy captured by such a minuscule surface area would barely recoup the inefficiencies of the added weight Is this actually true? Sola

> Because the amount of energy captured by such a minuscule surface area would barely recoup the inefficiencies of the added weight Is this actually true? Solar Panels don't have to power 100% (or even 20%) of the car to still be super useful on an EV. An EV with a solar array that generated just ~0.7kwh during 6 hours of daylight, would still be charging itself an extra ~20 miles of range per day while parked. That's significant enough to be worth it to me. And that range can add up (imagine being parked at the airport for 3 or 4 days, and having an extra 60+ miles of "free" range sitting on your car when you return) Alternatively, that electricity could power an AC outlet or an air conditioner for camping trips or remote work while parked or whatever. "Dog mode" could keep parked cars safely cooled without draining any range. My EV sits outside an office, in direct sunlight, nearly every business day. And it's battery covers 70% (but not all) of my daily commute. Even if solar panels aren't the most efficient use of that space, surely they're better than nothing, right? Every watt from that solar panel, is a watt I didn't have to pull off the grid, or an ounce of petrol I did not have to burn.

mattmaroon 7y ago
You're not far off on the math for the most efficient cars, but I can't even get that much solar on top of a 23' camper, and that's with full sun and assuming I can park directionally. You're talking about 80 sq ft. Even taking into account these more efficient panels, you're looking at maybe 10 mi a day range added, best case. And that's assuming you're parking outside at all while at work. In suburbia you might be. Good luck in any big city. Overall I don't see how this is going to be economically efficient any time soon, even in the best use cases. It seems better to have fixed solar and a plug. But I hope I'm wrong.
- aembleton 7y ago
  There's also the extra weight involved. If you used that extra weight for more batteries instead of solar panels, you might have even more range.
  - jfengel 7y ago
    If they could paint the solar cells directly into the surface of the car, it would add little additional weight. Most of the weight of a solar panel is the backing and frame to provide stiffness, and you could use the car body for that. That's a big "if", though. Photovoltaic paint is currently around half as efficient as commercial solar panels.
    - codedokode 7y ago
      It doesn't have to be a paint, it could be a film.
- wiglaf1979 7y ago
  Something like this might be what you want. Hangs on the window and is solar powered. https://www.walmart.com/ip/Solar-Sun-Powered-Power-Window-Fan-Ventilator-Auto-Cool-Air-Vent-for-Car-Vehicle/110659418?athcpid=110659418 https://www.walmart.com/ip/Solar-Sun-Powered-Power-Window-Fa...
  - travisporter 7y ago
    That was proven to be useless. However, I found this project https://acool.global/ https://acool.global/. Anyone have any insights on this?
dangerface 7y ago
You can plug your car in so that it charges while it's parked. The same solar panels taken off the car and put on your works roof would be far more efficient because they face the sun.
- eloff 7y ago
  Yes, this exactly. Put the same panel on your roof and charge your car at home (which you do anyway.) You won't mar the car's appearance and you'll get more out of it. What I would love to see is a Tesla that can act as a powerwall and power your house when the grid fails. Some people hack them to do that but it doesn't look simple or without risk.
  - jsingleton 7y ago
    This already exists, although not for Teslas. It's called V2G (vehicle to grid) and it's already happening in the UK with the Nissan Leaf. Not only is this a backup for a rare outage but it makes you money by charging when power is cheap and selling back when expensive. Occasionally the price of power goes negative and you are paid to charge. https://electricinsights.co.uk/ https://electricinsights.co.uk/ is good for exploring the energy data and pricing.
    - goodcanadian 7y ago
      If you are in the UK and interested in participating in a trial, see https://www.ovoenergy.com/electric-cars/vehicle-to-grid-charger https://www.ovoenergy.com/electric-cars/vehicle-to-grid-char...
- pbhjpbhj 7y ago
  A car park with bays with solar panels could be better in that it provides shade/shelter and leaves the nearby building roofs clear to harvest photons to aid in lowering the building.
idiot900 7y ago
I'd want solar panels on my car for the sole purpose of running a ventilation fan while parked under the hot sun, so I don't come back to a scorching hot car. More appealingly, it might also prevent the death of pet or child (still incorrectly) left in there.
- stetrain 7y ago
  Teslas do this just running off of the battery pack. In my experience it doesn't use a ton of power to do it. A solar panel to make it net neutral energy to keep cool would still be nice.
  - idiot900 7y ago
    That would be ideal. At the moment (and hopefully not for much longer) gas engines meet my needs better, so the solar panels would be an interim solution.
- kube-system 7y ago
  Well you’re in luck. Go down to your local used car lot and pick up a used 2010 Prius. https://youtu.be/CchHIy7JgvA https://youtu.be/CchHIy7JgvA
- cr0sh 7y ago
  This is somewhat easy to do if you have a roof-rack or somewhere similar on your vehicle to mount a small-ish panel, and you are handy and understand your vehicle's electrical system (though this may be tough with newer models since everything isn't controlled by simple switches any longer). Basically, mount your panel, and install a block diode if it doesn't already have one, then run the wires (positive and negative) to your battery to keep it charged. Then, all you need to do is hook up a switch to your blower motor inside the vehicle, along with a simple speed controller (for this, it's best to use a cheap 12 vdc PWM controller - don't try to use the "low speed" resistor if your car uses a resistor pack, as it might not keep it cool enough) - so you can turn it off and on, and control the speed of the fan - while the car is parked and "off" (no-key). Park it in the sun (of course), set the vent controls to allow air in from the outside (hopefully it stays this way when the car shuts down - if not, you'll have to figure out a way around that), crack your windows slightly (1/4-1/2 inch), then shut off the car. Flip the switch and set the speed control for the fan to something "low" - the fan should run, but not at hurricane speed. Then get out and close/lock the doors. Air will be drawn in from the cooler outside, blown into the cabin, and exhausted out the windows. The battery will stay charged from the solar panel. If you are concerned about the battery being run down when the sun sets, then: 1. You can optionally use a separate battery to the fan, with a blocking diode to keep the fan from using energy from the car's battery. 2. Or you can add a thermostat to detect and only run when the sun is beating down hot (this could be in addition to the PWM control - so the fan doesn't run all the time, only when the cabin gets too hot). 3. Add a photoelectric switch to disconnect the fan from the battery, when the sun goes down. 4. A simple way would be by just wiring a standard Bosch SPST automotive relay (the coil) in series with the panel, and the fan across the contacts - when the sun goes down, the relay would open up, and shut off the fan. Note that this car ventilation mod does not require an Arduino, so you might not become popular or upvoted on the tubes, but your car might be cooler in the summer...
fred_is_fred 7y ago
This isn't new in the least. My 2010 Prius had solar panels that did "dog mode" - running the fan.
jsight 7y ago
>> An EV with a solar array that generated just ~0.7kwh during 6 hours of daylight, would still be charging itself an extra ~20 miles of range per day while parked. An EV uses ~250wh/mile. This varies a bit for some, but none of them are going to come close to 20 miles in .7kwh. Maybe 3-4 at most. The ability to use something like this when left parked at an airport would be nice, though. Though I suspect that readily available 120V outlets is actually a cheaper option in the long run, relative to deploying panels on every car.
- maxsilver 7y ago
  Sorry, I mixed up my units, I meant "average of ~0.7kw per hour, for 6 hours, for a total of 4.2kwh per sunlight-day". That should get you 16 miles in climates like mine, or up to 20 miles in clearer/warmer weather. That seems like a very realistic/feasible figure. (Lightyear One's claims their prototype car can pull almost 2kw per hour (7.5 miles of charge per hour), which at 6 hours, earns you 12kWh per sunlight-day)
  - mercutio2 7y ago
    Pedantic note: It’s not “.7kW per hour”. Watts is a measure of power, it’s already Joules/second. You just want “.7kW”. For 6 hours, you still won’t get 4kWh, because you need to adjust for less than ideal angle, and less than full sun days. But if you got 3kWh on a good day, that’s still 10-12 miles of additional range.
  - jsight 7y ago
    I think that is incredibly optimistic for a production vehicle. I think it is likely that production vehicles with setups like this will have one 350 Watt panel on the roof. A typical house roofmount of the same would produce ~1.5 KWh per day. Car environments tend to be worse than that due to the angle and likely regular proximity of even mild shading. Its certainly enough to eliminate vampire drain, which is helpful at times, but I don't see how it will add an appreciable amount of mileage otherwise.
varenc 7y ago
I'm pretty pro-solar and would be interested in seeing this on cars, but I'm very doubtful rooftop solar could ever run an AC continuously. Cooling air requires A LOT of energy. Assuming 0.7kwh in 6 hours of daylight, that means the solar cells are outputting ~115W. It's hard to estimate exactly how much power is needed to cool a Prius, but 115W seems far less than sufficient. Traditional car air conditioners run directly off of mechanical power from the engine for efficiency. Home window air conditioners typically draw 1000W-1800W. A Tesla user reports [1] that the Tesla electric AC takes 2.4kW when starting up and then switches to a steady state of ~600W. Looks like [2] the Prius climate fans on medium take up 100W without the AC even being on. Coming at this another way, using this online calculator if we plug in 250 cubic ft for an estimate of the Prius internal air volume, assume high-quality insulation, and a 25°F temperature drop, this online calculator says that requires 1500 BTUs or 450Watts. [3] That said, solar panels would still help somewhat! I also like the idea of exposing more people to solar and increasing general awareness around energy consumption (and how energy-hungry ACs are). Hope they do make it market in some form. [1] https://teslamotorsclub.com/tmc/threads/how-many-watts-does-a-c-use-heres-your-answer.73563/ https://teslamotorsclub.com/tmc/threads/how-many-watts-does-... [2] https://priuschat.com/threads/power-consumption.14026/ https://priuschat.com/threads/power-consumption.14026/ [3] https://www.calculator.net/btu-calculator.html?roomwidth=6.2&roomwidthunit=feet&roomlength=6.2&roomlengthunit=feet&ceilingheight=6.2&ceilingheightunit=feet&insulation=good&temperature=25&temperatureunit=f&ctype=house&x=69&y=17#housebtu https://www.calculator.net/btu-calculator.html?roomwidth=6.2...

mattmaroon 7y ago

You're not far off on the math for the most efficient cars, but I can't even get that much solar on top of a 23' camper, and that's with full sun and assuming I can park directionally. You're talking about 80 sq ft. Even taking into account these more efficient panels, you're looking at maybe 10 mi a day range added, best case. And that's assuming you're parking outside at all while at work. In suburbia you might be. Good luck in any big city. Overall I don't see how this is going to be economically efficient any time soon, even in the best use cases. It seems better to have fixed solar and a plug. But I hope I'm wrong.

aembleton 7y ago
There's also the extra weight involved. If you used that extra weight for more batteries instead of solar panels, you might have even more range.
- jfengel 7y ago
  If they could paint the solar cells directly into the surface of the car, it would add little additional weight. Most of the weight of a solar panel is the backing and frame to provide stiffness, and you could use the car body for that. That's a big "if", though. Photovoltaic paint is currently around half as efficient as commercial solar panels.
  - codedokode 7y ago
    It doesn't have to be a paint, it could be a film.
wiglaf1979 7y ago
Something like this might be what you want. Hangs on the window and is solar powered. https://www.walmart.com/ip/Solar-Sun-Powered-Power-Window-Fan-Ventilator-Auto-Cool-Air-Vent-for-Car-Vehicle/110659418?athcpid=110659418 https://www.walmart.com/ip/Solar-Sun-Powered-Power-Window-Fa...
- travisporter 7y ago
  That was proven to be useless. However, I found this project https://acool.global/ https://acool.global/. Anyone have any insights on this?

dangerface 7y ago

You can plug your car in so that it charges while it's parked. The same solar panels taken off the car and put on your works roof would be far more efficient because they face the sun.

eloff 7y ago
Yes, this exactly. Put the same panel on your roof and charge your car at home (which you do anyway.) You won't mar the car's appearance and you'll get more out of it. What I would love to see is a Tesla that can act as a powerwall and power your house when the grid fails. Some people hack them to do that but it doesn't look simple or without risk.
- jsingleton 7y ago
  This already exists, although not for Teslas. It's called V2G (vehicle to grid) and it's already happening in the UK with the Nissan Leaf. Not only is this a backup for a rare outage but it makes you money by charging when power is cheap and selling back when expensive. Occasionally the price of power goes negative and you are paid to charge. https://electricinsights.co.uk/ https://electricinsights.co.uk/ is good for exploring the energy data and pricing.
  - goodcanadian 7y ago
    If you are in the UK and interested in participating in a trial, see https://www.ovoenergy.com/electric-cars/vehicle-to-grid-charger https://www.ovoenergy.com/electric-cars/vehicle-to-grid-char...
pbhjpbhj 7y ago
A car park with bays with solar panels could be better in that it provides shade/shelter and leaves the nearby building roofs clear to harvest photons to aid in lowering the building.

idiot900 7y ago

I'd want solar panels on my car for the sole purpose of running a ventilation fan while parked under the hot sun, so I don't come back to a scorching hot car. More appealingly, it might also prevent the death of pet or child (still incorrectly) left in there.

stetrain 7y ago
Teslas do this just running off of the battery pack. In my experience it doesn't use a ton of power to do it. A solar panel to make it net neutral energy to keep cool would still be nice.
- idiot900 7y ago
  That would be ideal. At the moment (and hopefully not for much longer) gas engines meet my needs better, so the solar panels would be an interim solution.
kube-system 7y ago
Well you’re in luck. Go down to your local used car lot and pick up a used 2010 Prius. https://youtu.be/CchHIy7JgvA https://youtu.be/CchHIy7JgvA
cr0sh 7y ago
This is somewhat easy to do if you have a roof-rack or somewhere similar on your vehicle to mount a small-ish panel, and you are handy and understand your vehicle's electrical system (though this may be tough with newer models since everything isn't controlled by simple switches any longer). Basically, mount your panel, and install a block diode if it doesn't already have one, then run the wires (positive and negative) to your battery to keep it charged. Then, all you need to do is hook up a switch to your blower motor inside the vehicle, along with a simple speed controller (for this, it's best to use a cheap 12 vdc PWM controller - don't try to use the "low speed" resistor if your car uses a resistor pack, as it might not keep it cool enough) - so you can turn it off and on, and control the speed of the fan - while the car is parked and "off" (no-key). Park it in the sun (of course), set the vent controls to allow air in from the outside (hopefully it stays this way when the car shuts down - if not, you'll have to figure out a way around that), crack your windows slightly (1/4-1/2 inch), then shut off the car. Flip the switch and set the speed control for the fan to something "low" - the fan should run, but not at hurricane speed. Then get out and close/lock the doors. Air will be drawn in from the cooler outside, blown into the cabin, and exhausted out the windows. The battery will stay charged from the solar panel. If you are concerned about the battery being run down when the sun sets, then: 1. You can optionally use a separate battery to the fan, with a blocking diode to keep the fan from using energy from the car's battery. 2. Or you can add a thermostat to detect and only run when the sun is beating down hot (this could be in addition to the PWM control - so the fan doesn't run all the time, only when the cabin gets too hot). 3. Add a photoelectric switch to disconnect the fan from the battery, when the sun goes down. 4. A simple way would be by just wiring a standard Bosch SPST automotive relay (the coil) in series with the panel, and the fan across the contacts - when the sun goes down, the relay would open up, and shut off the fan. Note that this car ventilation mod does not require an Arduino, so you might not become popular or upvoted on the tubes, but your car might be cooler in the summer...

fred_is_fred 7y ago

This isn't new in the least. My 2010 Prius had solar panels that did "dog mode" - running the fan.

jsight 7y ago

>> An EV with a solar array that generated just ~0.7kwh during 6 hours of daylight, would still be charging itself an extra ~20 miles of range per day while parked. An EV uses ~250wh/mile. This varies a bit for some, but none of them are going to come close to 20 miles in .7kwh. Maybe 3-4 at most. The ability to use something like this when left parked at an airport would be nice, though. Though I suspect that readily available 120V outlets is actually a cheaper option in the long run, relative to deploying panels on every car.

maxsilver 7y ago
Sorry, I mixed up my units, I meant "average of ~0.7kw per hour, for 6 hours, for a total of 4.2kwh per sunlight-day". That should get you 16 miles in climates like mine, or up to 20 miles in clearer/warmer weather. That seems like a very realistic/feasible figure. (Lightyear One's claims their prototype car can pull almost 2kw per hour (7.5 miles of charge per hour), which at 6 hours, earns you 12kWh per sunlight-day)
- mercutio2 7y ago
  Pedantic note: It’s not “.7kW per hour”. Watts is a measure of power, it’s already Joules/second. You just want “.7kW”. For 6 hours, you still won’t get 4kWh, because you need to adjust for less than ideal angle, and less than full sun days. But if you got 3kWh on a good day, that’s still 10-12 miles of additional range.
- jsight 7y ago
  I think that is incredibly optimistic for a production vehicle. I think it is likely that production vehicles with setups like this will have one 350 Watt panel on the roof. A typical house roofmount of the same would produce ~1.5 KWh per day. Car environments tend to be worse than that due to the angle and likely regular proximity of even mild shading. Its certainly enough to eliminate vampire drain, which is helpful at times, but I don't see how it will add an appreciable amount of mileage otherwise.

varenc 7y ago

I'm pretty pro-solar and would be interested in seeing this on cars, but I'm very doubtful rooftop solar could ever run an AC continuously. Cooling air requires A LOT of energy. Assuming 0.7kwh in 6 hours of daylight, that means the solar cells are outputting ~115W. It's hard to estimate exactly how much power is needed to cool a Prius, but 115W seems far less than sufficient. Traditional car air conditioners run directly off of mechanical power from the engine for efficiency. Home window air conditioners typically draw 1000W-1800W. A Tesla user reports [1] that the Tesla electric AC takes 2.4kW when starting up and then switches to a steady state of ~600W. Looks like [2] the Prius climate fans on medium take up 100W without the AC even being on. Coming at this another way, using this online calculator if we plug in 250 cubic ft for an estimate of the Prius internal air volume, assume high-quality insulation, and a 25°F temperature drop, this online calculator says that requires 1500 BTUs or 450Watts. [3] That said, solar panels would still help somewhat! I also like the idea of exposing more people to solar and increasing general awareness around energy consumption (and how energy-hungry ACs are). Hope they do make it market in some form. [1] https://teslamotorsclub.com/tmc/threads/how-many-watts-does-a-c-use-heres-your-answer.73563/ https://teslamotorsclub.com/tmc/threads/how-many-watts-does-... [2] https://priuschat.com/threads/power-consumption.14026/ https://priuschat.com/threads/power-consumption.14026/ [3] https://www.calculator.net/btu-calculator.html?roomwidth=6.2&roomwidthunit=feet&roomlength=6.2&roomlengthunit=feet&ceilingheight=6.2&ceilingheightunit=feet&insulation=good&temperature=25&temperatureunit=f&ctype=house&x=69&y=17#housebtu https://www.calculator.net/btu-calculator.html?roomwidth=6.2...