Solar Panel on Model S - time to reconsider?

[Sir Guacamolaf]

A very long time ago, Elon had stated that Solar on Model S makes no sense.
It's cost and weight vs. the energy it generates make it totally not worth it as a primary charging source.
Okay, I feel it's time to reconsider that stance. Why?

- It is a known fact that Tesla puts a lot of strain on it's 12v battery. Solar will eliminate a big portion of that.
- Solar cells are a lot cheaper and better now.
- And yes while I agree that Solar on your car as a primary charging source is impractical, it will eliminate vampire drain. Imagine leaving your car at the airport, and not coming back to a dead battery - but instead finding an extra 10 miles.
- And it may just get you out of a bind to the next charging spot when you are completely out of options.
- Plus, if it can keep your battery and interiors at a certain temp, it will eliminate the initial 1000wh/mi drain when you first start driving your car.

Thoughts?

 

[n2mb_racing]

I think the vampire drain is about 100W. Can the roof accommodate enough panels for that? Also, you'd lose the pano roof, perhaps.

But yeah, maybe a well designed, semi transparent solar panel integrated into the all glass, non pano roof might work...

 

[Doug_G]

There's already an extensive thread on this topic in the Model 3 section: Model 3 may have Solar Roof that can charge the vehicle

 

[jaguar36]

No, no , no. Put the solar cells on your house or the ground. where they can always been outside, facing in the best possible direction.

A very long time ago, Elon had stated that Solar on Model S makes no sense.
It's cost and weight vs. the energy it generates make it totally not worth it as a primary charging source.
Okay, I feel it's time to reconsider that stance. Why?

- It is a known fact that Tesla puts a lot of strain on it's 12v battery. Solar will eliminate a big portion of that.

This was only an issue on the earlier cars and has been solved already on newer Tesla's.

- Solar cells are a lot cheaper and better now.

Great! Put them on the house.

- And yes while I agree that Solar on your car as a primary charging source is impractical, it will eliminate vampire drain. Imagine leaving your car at the airport, and not coming back to a dead battery - but instead finding an extra 10 miles.

Vapmire drain could easily, and cheaply be eliminated with some extra engineering. A phone lasts all day on a tiny battery, if Tesla cared they could drop the drain into the irrelevant range.

- And it may just get you out of a bind to the next charging spot when you are completely out of options.

You'd be waiting hours and hours to get a mile of charge, assuming its even sunny out. Just call a tow truck.

- Plus, if it can keep your battery and interiors at a certain temp, it will eliminate the initial 1000wh/mi drain when you first start driving your car.

Thoughts?

Most of the time in the winter the initial drain comes from when its been sitting overnight. In addition solar panels are much less productive in the winter due to the low angles of the sun, even more so on a car where they wouldn't be tilted south. If its sunny enough to provide decent juice from a solar panel, its probably sunny enough to warm up the car too.

 

[jmsurpri]

Why not fix the vampire drain instead? Perhaps the Linux update will enable better standby power..

 

[Sir Guacamolaf]

I think the vampire drain is about 100W. Can the roof accommodate enough panels for that? Also, you'd lose the pano roof, perhaps.

But yeah, maybe a well designed, semi transparent solar panel integrated into the all glass, non pano roof might work...

100W is absolutely no problem for a cheap $100 flexible solar panel. It won't even obstruct any portion of the pano roof. That black strip area in the front alone will provide that much power and more.

 

[Sir Guacamolaf]

Why not fix the vampire drain instead? Perhaps the Linux update will enable better standby power..

Yeah that'd be nice too. But I doubt the next linux update will fix this issue.

Re: 12V ..

This was only an issue on the earlier cars and has been solved already on newer Tesla's.

This is absolutely still an issue with the newest Tesla's.

 

[Haxster]

100W in standby! Yikes, that's a really thirsty vampire.

I would have guessed well under 10W...which is way more than a typical ICE uses when it's sleeping.

Where's all that juice going?

 

[gearchruncher]

100W is absolutely no problem for a cheap $100 flexible solar panel. It won't even obstruct any portion of the pano roof. That black strip area in the front alone will provide that much power and more.

Huh? Sunlight in the brightest area is about 1000 W per square meter when full bright. A good solar panel is 20%, so 200W per square meter (10 square feet). 100W a day is 2.4kWh, and the sun is out 12 hours a day, so you need 240W to cover vampire drain. Which means you need about 12 square feet. That area in front is 12' x 1' wide?

This assumes you're in the Arizona desert with no clouds too....

 

[Sir Guacamolaf]

Huh? Sunlight in the brightest area is about 1000 W per square meter when full bright. A good solar panel is 20%, so 200W per square meter (10 square feet). 100W a day is 2.4kWh, and the sun is out 12 hours a day, so you need 240W to cover vampire drain. Which means you need about 12 square feet. That area in front is 12' x 1' wide?

This assumes you're in the Arizona desert with no clouds too....

Thanks I love real numbers (always possible that I'm misinformed).

I see panels like this on amazon, this is 1/2 a sq. meter, and they claim 100W power, I realize that 100W is the best case scenario, but sure if they claim 100W in 1/2 sq. meter, and it should be possible to harvest 1 sq. m of roof space for solar without affecting the pano roof .. you should be able to easily get 100W-200W under all circumstances.

Also as far as area, that area in the front is about 2mx15cm, there is a similar area in the back, so right there you have 0.6 sq.meters. Add sides and you have 1 sq meter easy, and you don't even have to touch the trunk/hood. This is just the top of the car with pano roof unaffected.

So it seems feasible to have solar panels eliminate vampire drain completely.

 

[Sir Guacamolaf]

Where's all that juice going?

.. hard to say for sure .. but that big computer in the middle doesn't run on my good looks alone. And it runs most of the time (long durations, car goes into deep sleep, but still draws more power than your ICE).

 

[oktane]

You might get 200W in optimum conditions if the entire surface area of the roof had panels. There is no way to get that with the small areas around the pano roof. Also, there would be significantly less power in morning and afternoon when sun isn't directly overhead.

 

[Max*]

I like the concept, but for me it would make no real difference. The only sunlight my car sees is when I'm driving it or visiting family out of state.

 

[Sir Guacamolaf]

You might get 200W in optimum conditions ....

.. and 100W is all we need. At night the car is mostly in the garage and plugged in (for most of us anyway).
In fact, I feel that Tesla is obviously overloaded with Model 3 etc. but I'd be willing to bet that in the near future, we will see a solar option on Model S or 3.

 

[jaguar36]

A 100W solar panel on the roof would provide roughly 115kwhr of power per year (depending on latitude and climate obviously). That's about 20 bucks worth, no way is that going to be worthwhile. As previously mentioned the benefits you mentioned would either not be realized, or would be much easier to fix in other ways.

 

[nwdiver]

I used to hate the idea of putting solar on an EV. But... since electrical engineers appear to be having a hard time stepping ~350v down to 12v it might be worthwhile to have a ~18v panel to help keep the 12v topped off.... or put a separate 12v charger in the car to at least keep the 12v on a float when the car is plugged in.

The energy is in no way worthwhile... but if it can double the lifespan of the 12v it would be worth it.... there's also probably cheaper ways to do that than solar... like a 350v-12v converter that's capable of keeping the 12v on a float

 

[Sir Guacamolaf]

A 100W solar panel on the roof would provide roughly 115kwhr of power per year (depending on latitude and climate obviously). That's about 20 bucks worth, no way is that going to be worthwhile. As previously mentioned the benefits you mentioned would either not be realized, or would be much easier to fix in other ways.

It costs about 600$ to get your 12v replaced out of warranty, and the front end refresh is going to be more complex (i.e. more $)
I'd happily pay for a $200 solar panel once and be done with it.

Of course if the 12v issue is resolved properly - with or without solar - that would be ideal.

 

[nwdiver]

It costs about 600$ to get your 12v replaced out of warranty

It's closer to $300. I rolled it into my 100k mile service appointment so I didn't pay extra for labour. You can also get an aftermarket lithium ion battery that should easily last ~3x as long as the OEM AGM.... either way... Tesla needs a better solution than replacing that stupid battery every 18 months.

The downside to the solar solution is it's only effective when the car is parked. If there's 12v load then the DC-DC converter can keep a constant voltage on the battery so there's no benefit to a solar charger. My car is usually not parked in the sun.

 

[oktane]

Not sure why you think solar panels will obviate the need for a 12V battery. There is no correlation.

 

[Sir Guacamolaf]

It's closer to $300. I rolled it into my 100k mile service appointment so I didn't pay extra for labour. You can also get an aftermarket lithium ion battery that should easily last ~3x as long as the OEM AGM.... either way... Tesla needs a better solution than replacing that stupid battery every 18 months.

The downside to the solar solution is it's only effective when the car is parked. If there's 12v load then the DC-DC converter can keep a constant voltage on the battery so there's no benefit to a solar charger. My car is usually not parked in the sun.

I don't think a 12V LiIon is a reality .. yet! Is it? Plus Tesla won't fit it in for you - you can of course do it yourself, but I've seen how bad the 12V replacement is in the front end refresh Tesla .. dude, I think I'll drive a Prius before I'd deal with that nonsense.

Not sure why you think solar panels will obviate the need for a 12V battery. There is no correlation.

Not obviate, but reduce the load on the 12V. People have done studies on Tesla cycles the 12V as much as 5 times a day (which is CRAZY). Your typical ICE almost never fully cycles the battery if you drive it once a day. This paired with a) Tesla's 12V is the size of your garage door opener 12V, and that it's incredibly difficult to replace .. basically in my opinion qualifies it to be a faulty design .. no car should eat through 12V batteries this quick, and if it does, make it user-replaceable, not a service thing that you have to pay 300$ for (and get appointments). .. anyway I digress ..