The point is that today != tomorrow. Today, onboard PVs will only produce a few percent of an EV's consumption. Tomorrow will that number could be 20-30% or more.
I encourage you to read the discussion upthread.
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The point is that today != tomorrow. Today, onboard PVs will only produce a few percent of an EV's consumption. Tomorrow will that number could be 20-30% or more.
I encourage you to read the discussion upthread.
That point is a little off topic from what I was saying. While yes, solar panel efficiency will improve over time, it's not there yet today. Plus, you have to deal with the cost going up as newer panel technology is created.
I could see this as a gimmick to get the Model 3 name out there at best. Unless Solar City has been working on a new type of panel that has a higher output, I would be hard pressed to believe that it would debut on a car.
Therein lies the fundamental issue with this discussion. No serious proponent of solar roofs thinks they're a good idea today, for the reasons I outlined earlier...but many of the bullet points that come from opponents are regarding solar roofs today.
My point in responding to your post was that, in context, your argument against solar roofs today is irrelevant because there simply is no argument.
Edit: the following post is a good example of one of the unfortunate 'solar opponent' attempts to fabricate an argument when there is none.
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Garlan Garner
Banned
You're forgetting, he's a great marketer too. And like other options on Tesla's and other cars that aren't at all necessary (0-60 in 2.3 seconds anyone?) They are there because they sell cars and increase profit margins, not because they make any sort of mathematical or economic sense.
Some people who aren't remotely as solar savvy as you are going to think:
1) Car runs on electricy
2) Car generates its own electricity with solar roof
3) "Free" fuel? Count me in!
Maybe his genius extends further than you think?
(Most marketing, at the end of the day, is just malarkey in one form or another.)
#2? Not really (Producing its own power? not really) .
#2 is like a human producing an "ant dropping" amount of a hamburger each day. I don't believe many people would say "HORRAY" to that. ( an "ant dropping" portion of a burger does not a burger make).
When has Elon ever cared about the cost of engineering? What's the point of Tesla Glass if not to invent stuff.
Remember their $2bn spending (including R&D budget).
The Leaf has it (to charge the 12V) the new Prius has it, to charge the main battery.
Tesla Glass - more than one benefit.
Elon says they can do tiles cheaper than normal clay tiles. I imagine they can do a glass roof with the electronics for charging it at a few 10s of dollars and sell it at a $1000 premium - maybe a 500w panel. They can do 350w in a 1.6m x 1m area currently. Put in the pretty colours too when viewed from certain angles.
Remember Elon will look at it from first principles. Glass cheaper than metal - ok, let's do it!!
Quote numbers for if it was parked in full sun for 5 hours. Could be 2.5kw. That's possibly 12 miles in a Model 3. If the car died from lack of juice in the desert you might be able to crawl home the next day
Nope. Current PV runs about 15% efficient, even if you could make it 100% efficient (which you can't, 50% is roughly the *theoretical* limit), and even if free, that would only allow 6 kWh of production form this panel. At 4 miles/kWh that is only 24 miles. Anyone want a 24 mile range EV?
Put those panels on your house, or in a community solar farm.
Thank you kindly.
can't believe this thread is still going - and recycling the same arguments backwards and forwards
Summary of the last 24 pages for those who don't want to read the whole thing
Yes - solar panels produce some power, maybe even enough for 1-2 miles on a sunny day
Yes - parking in the shade will also get you 1-2 miles more range by not having to cool the car so much
Yes - the panel is only any use if you park outdoors all the time
Yes - parking in a parking garage negates any benefit the panel has
Yes - hot battery packs perform less well than cooler ones
Yes - hot solar cells produce less power than cooler ones
Yes - over the life of the car a solar panel will save money
Yes - it will never save you the cost of electricity
Yes - when you are really low on range the panel may get you that extra 300 yards of travel
Yes - the extra weight might reduce your range at all other times.
so - Yes is the answer, now, what was your question?
Summary of the last 24 pages for those who don't want to read the whole thing
Yes - solar panels produce some power, maybe even enough for 1-2 miles on a sunny day
Yes - parking in the shade will also get you 1-2 miles more range by not having to cool the car so much
Yes - the panel is only any use if you park outdoors all the time
Yes - parking in a parking garage negates any benefit the panel has
Yes - hot battery packs perform less well than cooler ones
Yes - hot solar cells produce less power than cooler ones
Yes - over the life of the car a solar panel will save money
Yes - it will never save you the cost of electricity
Yes - when you are really low on range the panel may get you that extra 300 yards of travel
Yes - the extra weight might reduce your range at all other times.
so - Yes is the answer, now, what was your question?
Residential panels are over 20%.
I buy CICs that are 30% efficient (they're not residential).
Technology is improving.
I realize you're trying to make the argument against solar, but in an ironic twist of fate, the answer to your question actually is: Anyone who understands what that means. 24 miles/day self-production is ~70% of the average American's mileage. People would line up to buy a car that only requires them to pay for 30% of its 'fuel'.
To be clear, I'm using your numbers, not my numbers.
My numbers, again, suggest [American] fleet average production of 20-25% in ~2 decades. For reference, those same numbers suggest something like 3.5% fleet average production for a hypothetical car of today.
As noted many times, not everyone has a house onto which they can put panels.
If you're making the suggestion that those people should go to community solar instead of EV solar that's a slippery argument that you should probably back away from, since the same argument could be made between home and community solar. Can't have it both ways.
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Where do you propose to get a tenfold increase in efficiency? Can't get it from PV they are already at 15% ( or 20% or 45% if you prefer).
Everyone has somewhere they can put panels (as has been noted many times (like that makes it true)).
Of course I can! I calculate whether people should get home based or community based solar, for a living. Some people it works out better one way, some the other. Only Sith deal in absolutes.
Thank you kindly.
omgwtfbyobbq
Active Member
If they offered it as an option, I'm guessing they would do it for the same reason they hired Jeff Dahn, which is to improve their products.
Another off-the-wall point - the DC-DC converter is known to be a 12V battery-frying beast. A solar roof with a smart controller could manage the 12V battery and keep the (oft-reported) annual replacements from happening.
A better idea is to upgrade the DC-DC controller, of course. And my batteries are still the stock ones. But a quick search here will show that I'm in the minority.
A better idea is to upgrade the DC-DC controller, of course. And my batteries are still the stock ones. But a quick search here will show that I'm in the minority.
omgwtfbyobbq
Active Member
If Tesla's BMS is as optimized as can be, then yeah, it's a red herring. The same applies to range, acceleration, energy efficiency, and so on. With that said, my guess is that there's still room for improvement in battery reliability/durability, and Tesla will continue to improve that just like they continue to improve everything else. They may decide against it or for it based on all sorts of things, but I doubt it's a red herring.
When did I propose that a tenfold increase in efficiency was required?
To get my '25% production in 20 years' number, you might be interested to know that the PV efficiency I'm using for 20 years from now is 30%. I repeat, 30%. Something you (or at least I) can buy today, commercially. Not some number in a lab, not some theoretical limit. Real hardware. Today. I knew that picking some theoretical efficiency or even some only-in-the-lab efficiency would come under great scrutiny, so I didn't shoot for the moon. For those reading between the lines, that means any advancement in cell efficiency beyond [today's] 30% would render my bottom line prediction conservative. Its not a stretch to assume PV technology 20 years from now will be more efficient than today.
I do make assumptions on two decades of technology advancement over real, current, commercial performance, none of which are outlandish. They include more cell coverage area, better off-angle performance, less system loss, less YOY degradation, and better thermal coefficient. All rolled up, the 30% efficiency plus the above advancements results in ~50% better yield over my current day numbers. I don't think any fair minded person would call that unreasonable for 20 years of nerding out on progress.
In fact, the three big factors in my '25% production in 20 years' are:
1. Vehicle coverage. As PV becomes more affordable, more robust, more aesthetic, and more versatile, it can be applied on more surfaces of the car. While a little clumsy, my 2 decade prediction simply assumes PV coverage on both the roof and hood of a M3 sized and MS sized vehicle. You can imagine what 20 years of design will do to make reality more appealing than just gluing cells on your hood and roof.
2. Vehicle efficiency. I assume ~3.96 mi/kwh for MS fleet average in 20 years. A challenge to be sure, but certainly not out of reach. The ace on this one is autonomous & networked driving that will allow vehicles to travel in close formation and also minimize the consumption impact from accel/decel events.
3. Autonomous sun positioning. A car that can drive itself and can check the weather and that knows what its surroundings look like (trees, buildings, etc) can maximize daily harvesting. Even if it needs to tuck itself back into a garage for the night.
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Absolutely, and that's the big takeaway here. 'Red Herring' may have not been the right choice of words, but the point is that trying to equate solar production to anything but total consumption facilitates a distracting tangent.
Vampire loss is a consumption problem. Battery thermal management is a consumption problem. They both need their own solutions; to conflate with PV production does a disservice to all of them.
Maybe so, and I agree that it substantiates that he could be knowledgeable on the subject, but at least I does now see his post in a different light then before knowing that he has an potential conflict of interest here. But yes, "disqualify" was perhaps to strong a word here.
ah... the confusion is myfault.... I mistyped my post... I'll fix it... (*Note the last line)
I do agree with this... I have bought a few books and brushed up on solar panels and energy. I have yet to come across anyone who knows the basics of electricity and solar panels.... I usually just blabber on about what I know and eventually quit as they don't care... lol.
I can definitely see how this could let people believe that they would get a lot of free miles out of the small surface of the roof. Solar panels just aren't up to snuff yet to make use of that little space. It's been a little since I've looked into the topic, but if I remember right, most polycrystalline and monocrystalline solar cells aren't above 30% efficiency yet. I have heard of some panels that stack translucent cells on top of each other so that each layer gets a little less light, but overall per sq/ft the space can generate over 50%. But... these are way out of reach for residential consumers at this point.
If Tesla could fit a 200 w panel up there, I could see a benefit if you are running an office in your car or something like that. I run a fridge in my Jeep that pulls about 1Ah in hot weather. With a normal car battery, it drains it in about 3-5 days if the vehicle is just sitting (not running). I need at least a 100W solar panel to reliably run it 24/7. The fact is that the panel when running at maximum efficiency is overkill, but after calculating the daily energy output with the panel lying flat and in the various seasons (think the height the sun tracks in the sky), it's just about right.
Now this is absurd, because I'm pretty sure my fridge won't fit in the Model 3, but it puts into perspective that the only use for the panel is parasitic drain... A full roof solar panel would be overkill for parasitic drain, but a smaller retractable one would make sense.
And Tesla continuously states that most people will charge their cars daily at home so really.... what is the point of a LARGE solar panel if your car will be charged up most of the time?
The point is still valid - put the panels either directly, or buy an investment in solar, and let them put them in a place with the proper angle to allow for maximum efficiency rather than on the roof of a car, which includes many efficiency losses and further complicates the vehicle. I'm not saying there won't be a point where it will make sense and add to flexibility, but I don't think the time is now or in the near future. (Near referring to the next 5 years)
If I could fuel 70% of my travel with a $2,000 option, I would get it in a heart beat. I don't think I will get that right now however.
