How Long Till Solar Powered Car?

[Red Sage]

I can just envision some uninformed members of the media reading that Teslas have solar roofs to help keep the 12V battery charged, misinterpreting that to mean the EV battery will be kept fully charged by this means. Just as articles conflating Autopilot with "self-driving" have led some to believe their Teslas can drive autonomously, some will be disappointed when they discover their cars won't charge themselves in the sun.

If Tesla does offer such an option, they need to make it abundantly clear what it can and cannot do in their press releases, on their website product and configuration pages and with sales staff training.

Correctomundo! Precisely why I quote Mr. Miyagi so often...

"Best block -- no be there."​

The best way to avoid discussing things that might be misunderstood, is to simply not go there to begin with.

 

[JRP3]

The best way to avoid discussing things that might be misunderstood, is to simply not go there to begin with.

Yeah, Tesla never should have tried to build EV's since so many people misunderstood the technology, claiming it would never work, explode, never last, kill the electrical grid, etc.....

 

[Topher]

Not every Tesla owner has a roof on which they can install solar.

True, presumably. For those people let me recommend becoming part of a Solar Farm. This is a community group which rents land upon which a solar system can be installed. The power is shared among all the members (proportional to their buy in). This does require some appropriate regulations (net-metering and community solar), so if you don't have those in your area, you will need to get that work done first. This is a good solution for people who rent, don't have an appropriate roof, or plan to move in the near future. We put the first one in my state, down the road from me, last year. We now have 7 installed and more on the way.

Thank you kindly.

 

[Topher]

I guess in your eyes Tesla should not have offered autopilot?

Cost-Benefit analysis says those aren't the same thing.

Thank you kindly.

 

[JRP3]

For those people let me recommend becoming part of a Solar Farm.

Which does nothing to help vampire drain, preserve the 12V battery, or add any actual power to the car when not plugged in. Otherwise, great idea.

Cost-Benefit analysis says those aren't the same thing.

True, since there will likely be no negative consequences for offering a solar option on the vehicles.

 

[Topher]

Which does nothing to help vampire drain, preserve the 12V battery, or add any actual power to the car when not plugged in. Otherwise, great idea.

It let's you actually charge your car instead. To full. Easily, quickly, and cheaply.

True, since there will likely be no negative consequences for offering a solar option on the vehicles.

Everything has negative consequences. For solar panels, there is embodied energy, mining issues, disposal issues, ...

Thank you kindly.

 

[JRP3]

It let's you actually charge your car instead. To full. Easily, quickly, and cheaply.

As does any plug, regardless of the power source. None of them do anything when you are away from a plug to address the points I made, and therefore not an effective counter argument.

Everything has negative consequences. For solar panels, there is embodied energy, mining issues, disposal issues, ...

The same consequences as roof mounted panels, so, not an issue particular to vehicle mounted solar, thus not supporting your argument at all.

You seem to be spending a lot of time and energy weakly arguing against an option that is likely to be offered at some point but which you are not obligated to ever choose. I wouldn't spend the effort arguing against sunroofs even though I know they are mechanically more complex, create potential leak points, add expense, and are not an option I would choose, because I know others would. That's why there are different options, because different people want different things.

 

[Topher]

The same consequences as roof mounted panels, so, not an issue particular to vehicle mounted solar, thus not supporting your argument at all.

No. The consequences need to be compared against the benefit. 1 bad thing for every good thing isn't as good as 1 bad thing for every 3 good things. I would have thought that this was obvious in any argument. I will be more careful in the future.

So, to be explicit, the negative consequences for a roof top solar system PER kWh produced, are much less than the negative consequences of a car top solar system PER kWh produced. Thus, using a roof top system is BETTER for the benefit it provides than a car top system for the benefit it produces.

Thank you kindly.

 

[jgs]

So, to be explicit, the negative consequences for a roof top solar system PER kWh produced, are much less than the negative consequences of a car top solar system PER kWh produced.

It's not immediately obvious to me why that would be so, if we assume the car top system is used by a driver who parks in the sun during the day most days. The additional weight is probably quite minor compared to regular roof glass. Under my assumption, the number of hours the cells spend producing energy are about the same. The energy is being stored and consumed. So what are the (non-negligible, please) negative consequences that are specific to the car application?

Stipulated that if the car is not kept in the sun most days then yes, it makes as little sense as building a PV array in your basement. And stipulated that some purchasers will do exactly that. But some won't.

 

[Topher]

Under my assumption, the number of hours the cells spend producing energy are about the same.

This assumption is incorrect.

Additionally, it takes more than 'being in the sun' to produce the most energy. This is why solar panels are carefully sited, aimed carefully with respect to the sun direction, tilted carefully, and vented to remain cool.

Thank you kindly.

 

[jgs]

This assumption is incorrect.

You're going to have to do better than emphatic assertion. On the face of it, it's perfectly correct: cells in sun all day = cells producing all day. Sometimes the obvious is also wrong, sure. But not by default, and not just because you said so.

Additionally, it takes more than 'being in the sun' to produce the most energy. This is why solar panels are carefully sited, aimed carefully with respect to the sun direction, tilted carefully, and vented to remain cool.

The "remaining cool" part seems relatively easily solved since the vehicle is chock-a-block with active cooling potential (albeit at some modest energy cost, modest assuming all the cells need is ambient-temperature airflow, but then again that's all they'd be getting in a regular PV array). "Careful siting" is just a forty-dollar term for "don't park in the shade". "Tilted carefully" and "aimed carefully" (these are not meaningfully different), agreed, but then again you've carefully neglected acknowledging any of the modest benefits that might offset this modest deficiency.

FWIW I wouldn't be a candidate to buy this feature if it ever existed -- my car doesn't sit out in the sun all that much and I don't need a PV roof just to look cool. However, I don't mistake my personal circumstances and preferences for those of the whole world.

Thank you kindly.

You're very welcome!

 

[Topher]

You're going to have to do better than emphatic assertion. On the face of it, it's perfectly correct: cells in sun all day = cells producing all day. Sometimes the obvious is also wrong, sure. But not by default, and not just because you said so.

Properly sited solar panels get sun from dawn til dusk. Car occasionally drive under overpasses. Q.E.D.

The "remaining cool" part seems relatively easily solved since the vehicle is chock-a-block with active cooling potential (albeit at some modest energy cost, modest assuming all the cells need is ambient-temperature airflow, but then again that's all they'd be getting in a regular PV array).

Using the energy you are generating to cool the cells isn't solving the problem, it's admitting defeat.

"Careful siting" is just a forty-dollar term for "don't park in the shade".

The earth rotates, shade moves, I can tell you from experience that people are not good at guessing where shade is going to be. I use a tool for the job.

"Tilted carefully" and "aimed carefully" (these are not meaningfully different)

They are to a solar installer. In the same way that pitch and yaw are meaningfully different to a pilot. These are the subtleties that make a difference.

Thank you kindly.

 

[jgs]

Properly sited solar panels get sun from dawn til dusk. Car occasionally drive under overpasses. Q.E.D.

If that's the kind of hair-splitting you're going to indulge in, I hope you've removed the floor mats from all the unoccupied positions in your car, because it wastes energy to accelerate that unused mass.

Thank you kindly.

You're very welcome!

 

[JRP3]

Properly sited solar panels get sun from dawn til dusk. Car occasionally drive under overpasses. Q.E.D.

Clouds occasionally pass over stationary panels. Sometimes for long periods.

They are to a solar installer. In the same way that pitch and yaw are meaningfully different to a pilot. These are the subtleties that make a difference.

Stationary panels are only optimally aligned for a short period each day and only at certain times of the year.

 

[Ulmo]

I keep coming back to physics first principles:

Google: Dimensions of Model S:
196"L x 77"W = 15,092 sq in = 97,367 cm^2 = 9.73 m^2

Solar insolation
Average Insolation in Los Angeles in the year is 5.4kWh/m^2/day.
5.4kWh/m^2/day * 9.73m^2 = 52.58kWh/day.

Which Solar Panels Are Most Efficient?
2.5 years ago: maximum efficiency of panels was at 36.7% in the lab.

Google: Solar Concentrator
"A solar concentrator uses lenses, called Fresnel lenses, which take a large area of sunlight and direct it towards a specific spot by bending the rays of light and focusing them. Some people use the same principle when they use a magnifying lens to focus the Sun's rays on a pile of kindling or paper to start fires."
Display Enhancement Solutions - Protection and Light Control Films: Display Enhancement Films: 3M United States
This is what Tesla Roof's 3M engineers already are able to do.
Holographic optical element - Wikipedia
I heard of these abilities in 1984. By now, they must be good at this. Similar ideas as previous link above.
This fully transparent solar cell could make every window and screen a power source (updated) - ExtremeTech
some other examples of glass being used for solar collection ideas

So, the fact that max efficient panels were at 36.7% a couple of years ago only in lab settings tells me that this is something that will not yet have been commercialized, but that the sets of capabilities I referred to regarding lensing, directing of solar energy into collectors, etc., will allow this both on opaque and on transparent surfaces.

So, let's assume that the target is to bring what was possible in the lab a couple of years ago on opaque surfaces to reality in production on mixed opaque and transparent surfaces within a decade, which is a grandiose assumption but allows me to use simpler math to boot, which is that covering the Model S's exterior surfaces 100% with these materials (all the way around, on top, all glass, all body panels, with exception of wheels and some crevices and equipment where it's just not cost effective, but that is in doubt too, since even cameras can be covered with transparent glass) would yield something in the ballpark of 36.7% efficiency somehow.

52.58kWh/day * 36.7% = 19.3kWh/day

Charging a Tesla Model S Might Be Costing More Than You Think
Charging efficiency of Model S is 81.5% (using current standard installations).
Charging efficiency of DC-DC power electronics is probably as good as AC-DC.

19.3kWh/day * 81.5% = 15.72kWh/day.

Lifetime Average Wh/mi
avg 363Wh/mile

15.72kWh/day/363Wh/miles=43.32miles/day

So, you drive your car to work, leave your car parked out in the sun while at work, then drive your car home. If you have a 60kWh Model S, then one quarter of your battery can be charged per day this way. If your commute to work is 15 miles and back from work is 15 miles, that's 30 miles/day. Let's assume you also go on errands, but not every day. So, on the days you don't go on errands, your 60kWh car battery will store some excess energy from the sun that you can use on other days for longer errands travel or for less sunny days.

I imagine having solar on cars as a way to increase general energy flexibility in transportation, and as an offset to energy use and land use. But, in the above exact calculation, that person with only a 15 mile commute to work would actually no longer need any additional energy for their commute during summer. Whenever they plugged in at home, it would unnecessarily use shore power (home solar, utility power) to give insurance that they will have more SOC after work or to make up for extra trips; they certainly don't need it to get to work or get home in regular commute. During winter, the driver would have to plug in more often.



When do I think this will happen? In the poll, I said 6 years, but that's optimistic. I actually think it's more like 3 - 15 years of constant R&D. Whenever R&D is put on pause, add that pause time to that estimate.


When do I think the costs will drop to reasonable? After all the above has been completed and more time passes during which more R&D continues, something that could be done by selling less cost efficient systems to the types of people who used to buy Roadster, Model S and Model X. So, I'd say about another 3 - 15 years from above, so about 6 - 30 years from today (plus pause time) before this is cost reasonable. That's within our lifetimes, if pause time is assumed to be low (and, at the extreme optimism end of the scale, is before Trump is out of office). Put another way, if no pauses are taken, by the time we have a colony on Mars.

 

[tander]

...


When do I think the costs will drop to reasonable? After all the above has been completed and more time passes during which more R&D continues, something that could be done by selling less cost efficient systems to the types of people who used to buy Roadster, Model S and Model X. So, I'd say about another 3 - 15 years from above, so about 6 - 30 years from today (plus pause time) before this is cost reasonable. That's within our lifetimes, if pause time is assumed to be low (and, at the extreme optimism end of the scale, is before Trump is out of office). Put another way, if no pauses are taken, by the time we have a colony on Mars.

The thing I try to think of is how much demand/competition/$/manpower is going into this stuff? After the merger Tesla alone will have 25,000+ employees whose collective job is to development this stuff and drive the cost down. The tree is large and there is still lot's of low-hanging fruit. Just think of how crude cell phones from the 80's or even 90's seem compared to what we have today. I'd guess that solar is about where cell phones were when smartphones were just beginning to make sense.20 years of the smartphone: an evolution in pictures

 

[SwTslaGrl]

Yes I think development is possible, like stacking 10 thin layers of solar cells on top of each other to get out more energy per area?

 

[Topher]

Clouds occasionally pass over stationary panels. Sometimes for long periods.

And of course that never happens over cars.

Stationary panels are only optimally aligned for a short period each day and only at certain times of the year.

And cars never are.

Seriously, it is ok to just admit that specifically designed fixed locations are better than random ones. no one will complain.

Thank you kindly.

 

[Topher]

Yes I think development is possible, like stacking 10 thin layers of solar cells on top of each other to get out more energy per area?

Yes, a stack of cells each tuned to a different part of the spectrum will give you more power per area. These do currently exist, but are (currently) more expensive than regular panels, such that they won't ever payoff. They will probably get better, but they need to drop in price faster than regular panels. None of that changes the total sun that falls on the car, even 100% efficient panels don't help much (5kWh per meter^2 per day at optimal tilt and orientation (average US insolation)).

Thank you kindly.

 

[JRP3]

Seriously, it is ok to just admit that specifically designed fixed locations are better than random ones. no one will complain.

It's also OK to just admit that solar panels on vehicles do have practical applications, even if you don't want them. Fixed location's are better, except for all those times you aren't hooked up to them, which is most of the day for most people.