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How Long Till Solar Powered Car?

How long to solar charging cars?

  • 2 Years

    Votes: 5 2.4%
  • 4 Years

    Votes: 6 2.9%
  • 6 Years

    Votes: 10 4.8%
  • 8 Years

    Votes: 34 16.2%
  • Never

    Votes: 155 73.8%

  • Total voters
    210

tander

Active Member
Jul 23, 2012
1,512
1,563
So a while ago Toyota had a Prius where you could get a solar roof panel. How long until someone has meaningful solar charging with panels or photo-voltaic paint or something (guessing it will be a decade or more before it could be relied on a sole charging source)?
 
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AnOutsider

S532 # XS27
Moderator
Apr 3, 2009
11,957
210
So a while ago Toyota had a Prius where you could get a solar roof panel. How long till we get a Tesla that basically charges itself when outside in the daytime with panels or photo-voltaic paint or something?

I'd guess when the technology gets up to speed? The Fisker Karma had a solar roof, and if memory serves me correctly, it powered the aux stuff? I don't believe it produced enough to charge the batteries.
 

jaguar36

Active Member
Apr 10, 2014
2,148
1,959
NJ
Not gonna happen. The solar energy available per square meter is about 1000 watts. The Model S has maybe 2 sqm of available surface area to put solar cells. So even if you assume some great leaps in efficiency and a solar cell gets to like 50% efficient that only works out to 1000watts per hour, which means a full charge is going to take like a week of sitting in the sun.

You can't take the batteries out, because then you wouldn't be able to drive at night or when its raining.

It just makes far more sense to put the solar cells on a house, and plug the car in. Then you don't have to worry about the weight of the cells and the inverter, as well as trying to fit them into a car.
 

tander

Active Member
Jul 23, 2012
1,512
1,563
I'd guess when the technology gets up to speed? The Fisker Karma had a solar roof, and if memory serves me correctly, it powered the aux stuff? I don't believe it produced enough to charge the batteries.

Yeah initially I was assuming that at some point when solar panels etc become more efficient the idea will make sense, but it occurs to me maybe there just wouldn't be enough usable surface area to soak up enough sun to make it worthwhile in the first place?
 

mspohr

Well-Known Member
Jul 27, 2014
10,968
14,035
California
So a while ago Toyota had a Prius where you could get a solar roof panel. How long until someone has meaningful solar charging with panels or photo-voltaic paint or something (guessing it will be a decade or more before it could be relied on a sole charging source)?
I have a solar powered car today! My solar panels generate all the power I need to charge my car and run my house.
If you're talking about solar panels on the car, then you will have a long wait. Solar insolation is about 2 to 5 kWh/m2/day depending on location. Solar panels are about 10% to 15% efficient so you might get 0.5 kWh/m2/day out of them. You only have a 2 or 3 m2 surface on a car so you would be hard pressed to get 1 kWh per day from your car. This will take most electric cars 3 or 4 miles.
So... not going to happen. Just install solar panels on your roof or carport or a sunny spot in the yard and plug your car into them to get a real solar powered car.
 

tander

Active Member
Jul 23, 2012
1,512
1,563
Not gonna happen. The solar energy available per square meter is about 1000 watts. The Model S has maybe 2 sqm of available surface area to put solar cells. So even if you assume some great leaps in efficiency and a solar cell gets to like 50% efficient that only works out to 1000watts per hour, which means a full charge is going to take like a week of sitting in the sun.

You can't take the batteries out, because then you wouldn't be able to drive at night or when its raining.

It just makes far more sense to put the solar cells on a house, and plug the car in. Then you don't have to worry about the weight of the cells and the inverter, as well as trying to fit them into a car.

Yeah the rooftop solar may just make the idea totally redundant. But it seems like if you drive your car work then park it in the sun for the next 8 hours at a 1000 watts an hour...I guess this all depends on how fast the photovoltaics improve? Fun to think about I guess, wonder how the idea translates to big rig trucks with trailers? When you figure that the amount of investment going into solar/batteries is growing at a super fast pace compared to in the past I'm hoping that pace will also happen with how fast the technology gets better.
 
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jaguar36

Active Member
Apr 10, 2014
2,148
1,959
NJ
Yeah the rooftop solar may just make the idea totally redundant. But it seems like if you drive your car work then park it in the sun for the next 8 hours at a 1000 watts an hour...I guess this all depends on how fast the photovoltaics improve? Fun to think about I guess, wonder how the idea translates to big rig trucks with trailers?

Solar cells can only about double in power output. There just isn't that much power available. Now they can drop in price by huge amounts which will make rooftop solar explode, but on a car itself it doesn't make sense.

Same thing is true for big rigs, they have much more area, but they also need much more power.
 

tander

Active Member
Jul 23, 2012
1,512
1,563
Solar cells can only about double in power output. There just isn't that much power available. Now they can drop in price by huge amounts which will make rooftop solar explode, but on a car itself it doesn't make sense.

Same thing is true for big rigs, they have much more area, but they also need much more power.

Okay so thanks for the comments and participation. It inspired me to actually do the math and yeah, the equation is not looking pretty for the foreseeable future for semi trucks, diesel is pretty powerful stuff, literally. I probably should have included a 10+ years category. I think with improvements to solar cells, batteries, aerodynamics, regen, and motors vs engines of course, it might make sense for semis, but by then maybe there will be graphene capacitors or Mr Fusion so who knows. I think the parking your car at work all day sort of logic could make sense within five or ten years, but by then maybe we'll have self driving cars that barely ever sit still.
 
A while back I did some calculations and found that if I could set out 6 310W solar modules over my Volt at work, on sunny days it would fully recharge the battery. 6 modules would more-or-less fit over a parking spot. Double the module efficiency and between the roof, hood and rear spoiler you'd almost have enough area.

So... Maybe someday?

Granted, while running it'll never be enough to keep it driving without the car being a super-aerodynamic weirdmobile, but it would be enough to cover quite a bit of the HVAC and accessory loads during the day, and would make airport chargers mostly redundant.
 
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I have a solar powered car today! My solar panels generate all the power I need to charge my car and run my house.
If you're talking about solar panels on the car, then you will have a long wait. Solar insolation is about 2 to 5 kWh/m2/day depending on location. Solar panels are about 10% to 15% efficient so you might get 0.5 kWh/m2/day out of them. You only have a 2 or 3 m2 surface on a car so you would be hard pressed to get 1 kWh per day from your car. This will take most electric cars 3 or 4 miles.
So... not going to happen. Just install solar panels on your roof or carport or a sunny spot in the yard and plug your car into them to get a real solar powered car.

+1, 2, 3.
 
I think you've got to separate the concept of "real-time" solar-powered car (i.e. the sun providing 100% of the needed power while driving) as opposed to solar stationary charging. We've already seen that to a limited extent with the Prius and Leaf. But with the improvements in solar efficiency, I could see a vehicle with a solar roof adding 30-50 miles over a 3-5 hour period with full sunlight, eventually. Of course, you'd sacrifice a moonroof or a clear glass roof, but I'd guess plenty of buyers would be willing to do that to get a "bonus" charge.
 

Saghost

Well-Known Member
Oct 9, 2013
8,224
7,091
Delaware
I think you've got to separate the concept of "real-time" solar-powered car (i.e. the sun providing 100% of the needed power while driving) as opposed to solar stationary charging. We've already seen that to a limited extent with the Prius and Leaf. But with the improvements in solar efficiency, I could see a vehicle with a solar roof adding 30-50 miles over a 3-5 hour period with full sunlight, eventually. Of course, you'd sacrifice a moonroof or a clear glass roof, but I'd guess plenty of buyers would be willing to do that to get a "bonus" charge.

Not necessarily. Several folks have been demonstrating 'transparent' solar panels, which mostly absorb in the UV range I believe, and look like tinted glass. They aren't as efficient, of course, but they could replace a glass roof - and there's no reason you couldn't have a full width section of it lift and move as a moon roof, like the current Pano roof or the VW Eos (it'd have a flexible cable connected to it.)
Walter
 
Not necessarily. Several folks have been demonstrating 'transparent' solar panels, which mostly absorb in the UV range I believe, and look like tinted glass. They aren't as efficient, of course, but they could replace a glass roof - and there's no reason you couldn't have a full width section of it lift and move as a moon roof, like the current Pano roof or the VW Eos (it'd have a flexible cable connected to it.)
Walter

In time, sure. But if you're going for maximum efficiency, then you might have to sacrifice transparency, at least initially. Gaining 30-50 miles of range from just sitting in a parking lot for a few hours seems like a pretty good deal to me.
 

Saghost

Well-Known Member
Oct 9, 2013
8,224
7,091
Delaware
In time, sure. But if you're going for maximum efficiency, then you might have to sacrifice transparency, at least initially. Gaining 30-50 miles of range from just sitting in a parking lot for a few hours seems like a pretty good deal to me.

Absolutely. Maximum efficiency will mean compromises elsewhere - it always does.

But my point is that you can potentially have (most of) your cake and eat (most of) it too - a little more weight and an undetermined amount of additional money but no other adverse impacts. The top of the X seems to be mostly glass anyway... :)
Walter
 

jbcarioca

Well-Known Member
Supporting Member
Feb 3, 2015
6,332
43,534
I think several of us are possibly being a bit absolutist in thinking. Certainly the highest currently available commercial efficiencies in solar panels are around the Sharp triple-junction at 37.9%. The latest developments seem to show Perovskite layers could add as much as 50% to efficiency, assuming the durability and other issues can be resolves, so might end out with commercial efficiency of more than 50%. Assume that happens, still a car will not have enough space for that to be useful in most populated latitudes.

Think a bit differently though. Say, an over the road truck, operating in areas near equatorial, with a long trailer or two. Then you'd have copious space, operation with high sunlight intensity and fairly controllable use variables. That could make enough difference to be highly useful in some conditions.
Even being optimistic I do not think it is likely that we'll have solar powered surface transportation within the next decade. I am confident that we will see special purpose solar powered aircraft within the next decade.
I will happily wager that we will have some disruptive technologies in this are within the next decade that we do not currently see. Among the candidates:
1) superconduction at normal operating temperatures that will increase operating efficiency of BEV's by 10% or more;
2) when combined with other measures to reduce internal resistance through batteries, connections, inverters, straight DC, motor redesign and so on I fully expect to see the same sort of efficiency improvements that we have seen in turbine and ICE engines, i.e. 5-7% per annum.
3) increasing energy density coupled with reduced total weight using lighter materials ought to be good for another 2-4% per year;
4) improved material such as carbon fiber nano-scale reengineering improvement to a wide variety of metals should be good for at least 3% per year improvement.

If we, following the path of battery development since li-ion, the auto industry in the last decade, and aerospace in the last three decades it seems those projections probably are realistic.

of those things happen, then solar cells on cars might do more than look pretty on the Fisker Karma. In the meantime solar power in stable locations is now a quite sound economic decision in residences, industrial plants and Superchargers.

So, yes, there will be some solar panels on transport vehicles of some sort within the next decade.

Now, I will record my predictions and will happily make book that these things will happen one way or another.
 

tander

Active Member
Jul 23, 2012
1,512
1,563
I think you've got to separate the concept of "real-time" solar-powered car (i.e. the sun providing 100% of the needed power while driving) as opposed to solar stationary charging. We've already seen that to a limited extent with the Prius and Leaf. But with the improvements in solar efficiency, I could see a vehicle with a solar roof adding 30-50 miles over a 3-5 hour period with full sunlight, eventually. Of course, you'd sacrifice a moonroof or a clear glass roof, but I'd guess plenty of buyers would be willing to do that to get a "bonus" charge.

Yes that was a distinction I should have made along with a 10+ years category. The completely powered by solar seems like a never since you can't drive at night without energy storage.

- - - Updated - - -

I think several of us are possibly being a bit absolutist in thinking. Certainly the highest currently available commercial efficiencies in solar panels are around the Sharp triple-junction at 37.9%. The latest developments seem to show Perovskite layers could add as much as 50% to efficiency, assuming the durability and other issues can be resolves, so might end out with commercial efficiency of more than 50%. Assume that happens, still a car will not have enough space for that to be useful in most populated latitudes.

Think a bit differently though. Say, an over the road truck, operating in areas near equatorial, with a long trailer or two. Then you'd have copious space, operation with high sunlight intensity and fairly controllable use variables. That could make enough difference to be highly useful in some conditions.
Even being optimistic I do not think it is likely that we'll have solar powered surface transportation within the next decade. I am confident that we will see special purpose solar powered aircraft within the next decade.
I will happily wager that we will have some disruptive technologies in this are within the next decade that we do not currently see. Among the candidates:
1) superconduction at normal operating temperatures that will increase operating efficiency of BEV's by 10% or more;
2) when combined with other measures to reduce internal resistance through batteries, connections, inverters, straight DC, motor redesign and so on I fully expect to see the same sort of efficiency improvements that we have seen in turbine and ICE engines, i.e. 5-7% per annum.
3) increasing energy density coupled with reduced total weight using lighter materials ought to be good for another 2-4% per year;
4) improved material such as carbon fiber nano-scale reengineering improvement to a wide variety of metals should be good for at least 3% per year improvement.

If we, following the path of battery development since li-ion, the auto industry in the last decade, and aerospace in the last three decades it seems those projections probably are realistic.

of those things happen, then solar cells on cars might do more than look pretty on the Fisker Karma. In the meantime solar power in stable locations is now a quite sound economic decision in residences, industrial plants and Superchargers.

So, yes, there will be some solar panels on transport vehicles of some sort within the next decade.

Now, I will record my predictions and will happily make book that these things will happen one way or another.

Yeah after crunching the numbers and looking at rates of tech improvement it looks like within the next decade it will make some sense. When you combine improvements/innovation in solar cells, solar glass, brake regen, battery density, engine v.s. motor efficiency, aerodynamics, and piezos and who knows what else, they will start chinking away at the equation faster than you might expect if you are only looking at improvements in one of those categories. One thing I barely remembered to add into the equation is how much more efficient motors are than engines, that alone can reduces the difference by a factor of 2 or 3 since engines are only like 25% efficient and motors get get way up there. I did the math for a Suburban sized vehicle and when you use only the rooftop sq footage (not windows or sides) and I wouldn't be surprised to see a company like Tesla start including panels within 5-6 years (it helps since they are closely related to what is now one of the top solar manufacturers SCTY). The most intriguing variable in the equation is how fast the innovation will accelerate (I just used flat rates of improvement). Considering that almost nobody is investing in coal and less and less are investing in oil, and nat gas investment could peak within a couple decades, if you imagine even a portion of that divested capital going into solar and the other variables, the technology could accelerate way faster than most can imagine right now. I wouldn't be surprised to see something like Moore's Law be applied to some of these areas.
 
Not gonna happen. The solar energy available per square meter is about 1000 watts. The Model S has maybe 2 sqm of available surface area to put solar cells. So even if you assume some great leaps in efficiency and a solar cell gets to like 50% efficient that only works out to 1000watts per hour, which means a full charge is going to take like a week of sitting in the sun.

You can't take the batteries out, because then you wouldn't be able to drive at night or when its raining.

It just makes far more sense to put the solar cells on a house, and plug the car in. Then you don't have to worry about the weight of the cells and the inverter, as well as trying to fit them into a car.

Yes, agree 100%. But this question KEEPS coming up every month. People for some reason seem to think no one has thought of this idea! Why hasn't Tesla put solar on the roof??! What are they, dumb?

Listen, people, they are engineers. They already know that solar on a car is silly. People park under shade, in garages, car ports, in store parking garages. Unless you are driving, guess what? NO SUN! And when you are driving, there are buildings, shade, clouds, night. Dumb idea. It's amazing to me that we start discussing how much solar can be captured in ideal conditions by some new type of solar panel not in production.

I have solar panels. Some on my house, some on a bank near my house. I sell to the power company, and buy back cheap at night. Couldn't be a better arrangement. Tesla builds one of the biggest baddest batteries for automotive use, and it works. They have solar backed supercharging, and it works. They are building a giant factory to bring the cost of batteries down, and I bet that will work, too. And Tesla cars will continue to cost less.

Solar panels on cars are now, and always will be, a gimmick. People that buy them advertise that they do not understand physics and science. Please stop asking why we don't have them on Teslas.
 

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