Is 200Wh/mi achievable?

[Topher]

a usable trunk which are going to make even that 0.19 number a stretch.

Why do you think a usable trunk is going to reduce Cd? A boattail is the biggest improvement ecomodders make to their cars. This increases the size of the trunk while lowering the Cd.

Tires

Rolling resistance is more than just tires. Weight is a factor as well. Dropping the weight by 12% would double your savings.

Thank you kindly.

 

[jaguar36]

Why do you think a usable trunk is going to reduce Cd? A boattail is the biggest improvement ecomodders make to their cars. This increases the size of the trunk while lowering the Cd.

I It makes it longer and narrower, which is a much less useful size. In addition on highly aerodynamci cars like the XL1 and EV1, they openings to the trunk have been tiny.

Rolling resistance is more than just tires. Weight is a factor as well. Dropping the weight by 12% would double your savings.

Thats a good point, but where are you getting that data from? Weight doesn't appear to be a large factor on range in a Tesla. Its quite difficult to figure out exactly with Tesla playing games with capacity and range numbers as well as continually changing the curb weight.

 

[Topher]

I It makes it longer and narrower, which is a much less useful size. In addition on highly aerodynamci cars like the XL1 and EV1, they openings to the trunk have been tiny.

I wish every day, that my trunk was longer (narrower would be fine, but I don't see any reason that narrower is required. A boattail on an existing car only makes the trunk longer). Trunk opening on those cars have nothing to do with aerodynamics.

Thats a good point, but where are you getting that data from? Weight doesn't appear to be a large factor on range in a Tesla.

No data at all. EQUATIONS. The term for rolling resistance in the power consumption equation is coefficient of rolling friction times Normal force (weight). So reducing the weight by some percentage, reduces the rolling resistance by that same percentage.

OTOH, claiming that "weight doesn't appear to be a large factor on range in a Tesla" would require data. Where did you get yours.

Thank you kindly.

 

[jaguar36]

I wish every day, that my trunk was longer (narrower would be fine, but I don't see any reason that narrower is required. A boattail on an existing car only makes the trunk longer). Trunk opening on those cars have nothing to do with aerodynamics.

Realistically you can't make the car significantly longer so you can't just add length onto the end of the car. If it was as simple as that everyone would already be doing it.

No data at all. EQUATIONS. The term for rolling resistance in the power consumption equation is coefficient of rolling friction times Normal force (weight). So reducing the weight by some percentage, reduces the rolling resistance by that same percentage.

OTOH, claiming that "weight doesn't appear to be a large factor on range in a Tesla" would require data. Where did you get yours.

So a 12% reduction in weight would equal a 12% reduction in rolling resistance, not half.
My data comes from various sources, such as Tesla's published range for various models, as well as the EVtriplanner data.

 

[thefortunes]

Having skipped the discussion about theoretical I wanted to put some real data out there for my Roadster:

59k miles 245 wh/mi (86% of my miles are commuting, with ~75% at highway speed)

Nov-Feb 20k miles 270 wh/mi (heater use, significant weather implications, winter tires)
Mar-May and Sep-Oct 28k miles 237 wh/mi (some weather implications, mainly summer tires)
Jun-Aug 11k miles 218 wh/mi (minimal weather implications, summer tires)

You can see that there is a fairly large variation in my wh/mi based on the use of the heater and weather.

But my takeaway is that the Roadster can certainly hit 220 wh/mi and I would expect that the ≡ can also do so in good weather.

 

[Topher]

Realistically you can't make the car significantly longer so you can't just add length onto the end of the car. If it was as simple as that everyone would already be doing it.

Can you show the actual physical laws that a longer car would break, rather than a fallacious argument?

oh look, a disproof by contradiction: Aerocivic - Honda Civic modifications for maximum gas mileage - aerocivic.com

So a 12% reduction in weight would equal a 12% reduction in rolling resistance, not half.
My data comes from various sources, such as Tesla's published range for various models, as well as the EVtriplanner data.

You have lost the context of my comment. If tires could be modified to reduce the rolling resistance to achieve a 12% reduction in energy use, then reducing the weight by 12%, that would also reduce the rolling resistance by another 12%, thus doubling the savings.

But you aren't able or willing to cite that data. Value of argument is thus 0.

Thank you kindly.

 

[jaguar36]

Can you show the actual physical laws that a longer car would break, rather than a fallacious argument?

oh look, a disproof by contradiction: Aerocivic - Honda Civic modifications for maximum gas mileage - aerocivic.com



You have lost the context of my comment. If tires could be modified to reduce the rolling resistance to achieve a 12% reduction in energy use, then reducing the weight by 12%, that would also reduce the rolling resistance by another 12%, thus doubling the savings.

But you aren't able or willing to cite that data. Value of argument is thus 0.

Thank you kindly.

Wow... Thought we were having a reasonable discussion here. Your response indicates you aren't interested in listening to anyone elses ideas, so I'll leave you be.

 

[SageBrush]

Here is the equation Topher is mentioning in spreadsheet format.
Make a copy and play with numbers to your heart's content.

Do keep in mind that drivetrain losses are not figured.

 

[Topher]

Wow... Thought we were having a reasonable discussion here. Your response indicates you aren't interested in listening to anyone elses ideas, so I'll leave you be.

I was listening, that's how I knew you were making fallacious arguments, and not providing the data that you claimed to have. You are the one who is leaving a conversation because you don't like what you hear. If be 'reasonable discussion' you mean "Let's respect each others' delusions, and not try to reach the truth", this may not be the forum for you.

Thank you kindly.

 

[WannabeOwner]

there is a fairly large variation in my wh/mi based on the use of the heater

Probably a naive question (but based on our Winter driving where we complain of "cold feet", and achieving the same cabin comfort as an ICE requires quite a lot of battery-consumption; my Winter wh/mi is 1/3rd more than summer, and our Winter is not in the same league as a cold country): could insulation be improved and cabin thermal-mass be increased? That's what we've done with our house In places where space was tight we have some very thin [couple of mm], highly efficient, insulation.

 

[Topher]

could insulation be improved and cabin thermal-mass be increased?

Yes. No.

Insulation can no doubt be increased, as always this will increase price, or decrease interior volume, or both.

Thermal mass is not recommended. Thermal mass is great if you keep it at temperature, in a constantly occupied space. Unless you spend all your time in your car, all it will do is make it take longer to get up to a comfortable temperature.

Thank you kindly.

 

[SageBrush]

I am unsure if the discussion about 200 Wh/mile practicality is in the car or from the wall, but it is interesting to note that 225 Wh/mile from the wall (equal to about 200 Wh/mile in the car) equals an MPGe of ~ 150. The Toyota Prius Prime is EPA rated 133 MPGe and the Hyundai Ioniq, 136 MPGe. So not that far away, and in cars with a Cd higher than we know Tesla can already design.

I suspect that battery energy density (and thus car mass) will have to improve quite a bit before we see a 200 Wh/mile Tesla, but I agree with Topher: these cars are on the horizon.

As an aside, what is a realistic, high goal for regen braking efficiency over the EPA cycles ? Is 75% an engineering possibility within the constraints of a mass market car ? Please don't glibly answer "super-capacitors" without some good references about cost and reliability.

 

[Topher]

As an aside, what is a realistic, high goal for regen braking efficiency over the EPA cycle

I don't think super-capacitors can get you over 50% energy storage. I figure about 200 Wh of kinetic energy in a model 3 going 65 mph.

Thank you kindly.

 

[bxr140]

I am unsure if the discussion about 200 Wh/mile practicality is in the car or from the wall....

As the defacto thread starter on this one, I can say my original comment was in context of fleet average. More specifically, a real [American], on the road fleet average.

Folding in wall losses is a little arbitrary I think. Other than who pays for those losses, its no different than including transmission losses or generation inefficiencies.

 

[kort677]

Moore's law refers to an observation made by Intel co-founder Gordon Moore in 1965. He noticed that the number of transistors per square inch on integrated circuits had doubled every year since their invention. Moore's law predicts that this trend will continue into the foreseeable future.

 

[ohmman]

Moore's law refers to an observation made by Intel co-founder Gordon Moore in 1965. He noticed that the number of transistors per square inch on integrated circuits had doubled every year since their invention. Moore's law predicts that this trend will continue into the foreseeable future.

And Moore's law is no longer law. It's been repealed.

 

[int32_t]

And Moore's law is no longer law. It's been repealed.

I'd argue that it did continue into the foreseeable future, so he was right, law or no law.

I'm curious ... what's the significance of 200 wh/mi? One could just as easily ask if 200 wh/km is achievable -- which it is, even in a Model S. I'd expect the 3 to do better, being smaller and probably lighter. The Americans were trying for 100 mpg, and some time ago (I thought) there was an X Prize for doing 100 mpg, and the i3 gets 138 mpge. Humans and numbers are funny.

Tesla already has optimised for aerodynamics. Semiconductor efficiency is always improving, which is good for the inverter efficiency (although that's already great anyway). Honestly, the Model 3's fuel efficiency is what it is at this point. Now that Linux machine, on the other hand, could use a talking-to about vampire drains and whatnot ... driving efficiency is already way-crazy-good compared to any other vehicle type, be it FC or ICE, but no other car loses the fuel you put in it so fast as a Tesla when it's not even driving anywhere.

Please excuse me for mixing Model S and Model 3 things together, but aren't we all making assumptions about the 3 based on the S?

 

[Brando]

Perhaps in 5-10 years perovskites will allow thin film solar on car and car glass along with better batteries and weight savings to get a self charging car. Multiple layers each gathers a different wavelength of sunlight.

Google search for details.
side note: School in Denmark all of the outside (including windows) covered with solar PV. School is electricity plant.

 

[Rowan256]

I think a motor could do it, a car might as well, but it won't be a normal car, it will be a car that clearly lost some things we are used so, which basically makes it 4 weels with an engine, a battery and a odd design. Not a real normal avarage dayly usable car.

 

[thefortunes]

I think a motor could do it, a car might as well, but it won't be a normal car, it will be a car that clearly lost some things we are used so, which basically makes it 4 weels with an engine, a battery and a odd design. Not a real normal avarage dayly usable car.

Ummm.....my daily driver Roadster can easily run <200 Wh/mi. As I mentioned upthread I have averaged 218 Wh/mi during June-August of the last 4 years.

In fact, last August I averaged 196 Wh/mi for the entire month (1,022 miles driven or an average of 53.8 miles/day which were 99% commuting).

I don't consider the Roadster an odd design (actually I think it is pretty cool).