BEV mass and Regeneration efficiency
 

This has been discussed elsewhere but deserves its own thread.
Any advantage or liability attributed to total vehicle mass appears to diverge when comparing ICE and BEV.
A look at the following will tell the tale:
'Comparison between Battery Electric Vehicles and Internal Combustion Engine vehicles fueled by Electrofuels'
Master's Thesis in Sustainable Energy Systems
Tobias Gustafsson & Anders Johansson
Department of Energy and Environment
Chalmers University of Technology
Gothenburg, Sweden, 2015
-------------------------------------------------------------------------------------
The takeaway for me was that, there is a 'sweet spot' for BEV inertia (vehicle mass ), at which an overall optimum efficiency is achieved, with respect to road load and the amount of energy that may be harvested by regeneration.
https://publications.lib.chalmers.se...621/218621.pdf

I didn't read it, but what is the theory saying it can be more efficient to have a heavier BEV?

At least with ICE there is a theory that having a denser vehicle can help extend the glide portion of a pulse and glide, and ICE become more efficient with more load.

saying
 

When every other consideration is made, one will discover that there is an optimum inertia for any particular BEV vehicle, from which its momentum will optimize the amount of regen that can be harvested during deceleration.
Lighter you lose.
Heavier you lose
A 'Goldilocks' mass.

In theory, relative recuperation efficiency (per 1kg) should be higher for heavier vehicle.
But absolute numbers should be less.

Still not getting it. It takes x amount of energy to accelerate y mass to z speed. Recovering that momentum is less than 100% efficient, meaning it would always be more efficient to reduce the amount of mass accelerated in the first place.

I do stuff like haul bags of coal, wood pellets with my leaf. Heavier does not appear to be more efficient at all.

relative
 

Yes, regen efficiency must be balanced against all competing criteria in the mix.

always
 

'Always' violates the specific attributes possessed by BEVs.
80% of 'braking' kinetic energy can be recovered into the battery of a BEV.
Zero braking energy of an ICE vehicle can be recovered into its fuel tank.
Also, the BSFC-e of a BEV is around 3.5 X lower than an ICE, so they're only using a fraction of the energy to accelerate a vehicle back up to speed.
The mathematics is significantly different.

does not appear
 

There's no implication that it wouldn't.
Volvo is the only company to test and report. And all data reflect only 'passenger car' applications, not towing.
If you were hauling, loaded, between Cloudcroft and Hope, that would be interesting data, compared to dead-heading empty, uphill.

Some fraction of x is always less than x, even if that fraction is very high. It would always be more efficient to avoid spending energy than attempting to recover it.

I wasn't sure always towing. I can put about 1,200 pounds of wood pellets in the car in the hatch, the back seat, the back floor, the front floor and front seat. Don't need a trailer for the little things.

recover
 

The solution lies with traffic light synchronization, and moratoriums on real estate development until the infrastructure can handle 100% throughput.
Any building permit officer caught issuing green tags goes to jail by default, immediately if it's found that there's any traffic congestion at the locale of the proposed development. Along with the architect, real estate agent, mayor / city manager, city council, county tax assessor, and lending institute.
Yep, I forgot my political correctness medication again.

1,200-pounds
 

It's awesome. And not polite conversation at the truck dealership.
I've hauled sand, gravel, Portland cement, rebar, angle iron, EMT, copper pipe, PVC, mortar mix, and structural lumber up to 16-foot length behind the CRX. Denton to Los Angeles and back for hospital batteries.
On one of the biggest remodels I was ever party to, none of the framers drove anything bigger than a Civic, Corolla, or Sentra. Their boss was the only one with a pickup. And typically, all materials were delivered directly to the jobsite on a slide-off, tilt-bed truck or 18-wheeler with forklift. If there was any warped, crowned, or twisted 2Xs, it was all accepted back by the jobber, as a condition of the contract. Nothing like 'television ads.'
The average person probably hasn't a clue about the utility of a modest automobile.

I've heard great things about central planning. A few geniuses making all the decisions in an infinitely complex and interconnected system is sure to go smoothly.

smoothly
 

If you're happy getting half the fuel economy then good for you!

It's not as simple as infrastructure not being designed with enough capacity. For one example, there's the "if you build it, they will come" problem. Make traffic flow easily between city and suburbs, and you simply extend out the suburbs, increase traffic and we're back to rush hour gridlock.

Another problem is that infrastructure built to handle peak capacity will be severely underutilized off-peak. The gridlock that occurs in cities encourages some people to modify when they choose to travel, carpool, or take mass transit to avoid congestion.

I'm not arguing for creating gridlock, only saying that it isn't a simple problem a couple geniuses can solve.

I kinda think commuting is outdated anyhow because most city jobs can accommodate distributed work rather than centralizing into a single location. Between that, and increasing automation, large gains in efficiency should be possible.

Proving once again that HTML needs another tag.

PBS terra did a show whereby they had one remotely controlled vehicle driving slightly slower than rated speed, spacing out traffic and improving flow in a traffic circle then implies that the same technique would be proper on a congested highway.

The delta infers that humans constantly do sub optimum decisions </sarcasm?>

[cue video of human in car flying over the middle of a traffic circle]

I just envisioned Duke's of Hazard ramp to bypass the circle part of the traffic circle. Set a minimum approach speed and one should clear the whole intersection by utilizing the 3rd dimensional space.

This is how I understand it too.

Plus more mass means more weight which means more rolling resistance.

Ideally all cars, with regen or not, would weigh as little as possible. A 1,000lb car will take about 1/6 the energy to accelerate to a particular speed than one that's 6,000lbs. If regen is 80% efficient on the 6,000lb car and the 1,000lb car has zero regen you'd still be using more net energy to accelerate and decelerate the heavier vehicle with regen than the lighter one with no regen.

I re-read some of the thread.
This is masterful trolling. Possibly catagorized as 'talking past the sale'. The optimum is a balance of a number of variables. I'm not sure of the equation, but the result would be expressed in Coulumbs.

Is that a real University? I finally clicked the stupid link, and the cover page for the "research" looks fake. I didn't go further if they aren't willing to put in enough effort to look legitimate from the get go.

And they don't have very good grammar. Plus I find it hard to believe that carbon-capture fuels would be cheaper than electricity.

Yes, Chalmers is a real (and well-known) university in Goteborg, Sweden. I've been there; my master's advisor was director of the GOArt organ building research department at Chalmers.

The paper argues that their models predict close to the same efficiency (as a % of total energy put in) for large vs medium vs small BEV (*on the urban cycle only*) but increased total energy consumption for heavier BEV, as one would expect. The claim that "BEV and ICE diverge" is quite correct according to this modeling, but not because BEV are more efficient as they get heavier but less, while ICE are more efficient with increased weight because the engines work at higher load and better BSFC:

https://ecomodder.com/forum/member-v...efficiency.jpg

And the authors note that, for the ICE model,

That is very different than claiming there is a "sweet spot at which overall optimum efficiency is achieved," as aerohead has used that to argue that increased weight of BEV isn't a detriment and may be a good thing. This paper doesn't show that. That's his own idea which he is attributing to another source to give it credibility.

I suppose there could be a "sweet spot" as far as how much cargo to carry if we were talking about something like semi trucks in which you could vary the load without worrying about extra load being just worthless dead weight.

means
 

When every conceivable engineering consideration is investigated, an optimum mass is found. Everything you can think of, and everything you'd never think of, has already been investigated. It's that simple.

'sweet-spot'
 

Page 26
4. Results
' The small BEV's efficiency is noticeably lower in the city cycle than the medium sized but responds predictably in the other the other two cycles in line with the larger cars. This rather strange behavior is connected to the regenerative braking which is dependent on available wheel power and mass.'
--------------------------------------------------------------------------------------
1) @ low velocity ( low aerodynamic drag ) , in an urban driving environment ( stop and go ) the 'medium' BEV has a 'regenerative' energy harvesting efficiency advantage over the less-massive 'small' BEV.
2) I'm not recommending the larger weight class vehicle, I'm simply pointing out the 'inertial' advantage of the 'medium' sized BEV.
3) I'm talking about the dynamics of a specific vehicle.
4) The 'small' BEV's efficiency ( its overall efficiency, including all other dynamic considerations ) benefits from a greater mass, and the context has to do with regeneration
5) That's all I ever said or implied.
6) All of your apologies are accepted.

vs
Moving the goal posts closer together?

I'll apologize for #22 just to be gracious, but not #17 nor #19. </sarcasm>

You have argued in the past:

https://ecomodder.com/forum/member-v...iciency-03.jpg

You contradicted oilpan4's (correct) assertion that a lighter Model 3 would be more efficient. This paper does not support that contradiction. It clearly shows that the heavier the car is, the more energy it uses per mile regardless of the effects of regenerative braking:

https://ecomodder.com/forum/member-v...iciency-02.jpg

You seem to be confusing efficiency of the movement of energy from battery to wheels with efficiency of energy per distance traveled. They are two different things.

closer
 

They were never moved in the first place.

# 17 ( permalink )
 

I have no idea what your comment meant.

# 19 (permalink )
 

I have no idea how to associate your comment in relation to BEV mass and regen.

I still have no idea what this thread is on about, and I don't care enough to look at the paper to try to decipher the footnote comments.

contradiction
 

1) If the Model 3 were already 'optimized' for mass, arbitrarily lightening it would have the potential to lower its overall efficiency in an urban setting, the exact context of the Master's Thesis on page -26. There is no contradiction.
2) The Thesis is discussing overall efficiency. All other mass-related potentialities are encompassed within their use of 'efficiency.' It could not be more clearly spelled out. Net efficiency.
3) It's impossible to contradict an ' assertion' when no one is in possession of the facts which would prove the correctness about how a Tesla Model 3 'might' perform at lower mass. It's pure speculation.

Of course, and this has already been brought out, more efficiency doesn't mean better total efficiency or better miles per kWh, etc. A lighter Model 3 will get better miles per kWh even if regen efficiency drops.

A Model 3 also ususally hauls only one person and not much more, and has a limit of 5 (or is it 4?) passengers and some 900lbs total weight of cargo and passengers (although I'm sure you could add more than that). But if you could lighten it and replace that mass with even more passengers and/or cargo, then miles per kWh per passenger or lb of cargo would also increase considerably.

This whole thing reminds me of the BSFC efficiency of an ICE being at around 80% load. But if you drive around constantly at 80% load you'd actually get worse fuel mileage.

This, exactly (emphasis added):

This is exactly what the paper shows, in these two charts which I posted previously:

https://ecomodder.com/forum/member-v...efficiency.jpg

https://ecomodder.com/forum/member-v...iciency-02.jpg

Even though BTW efficiency is slightly lower for the lighter EV, its overall efficiency measured in Wh/kilometer is better than the heavier EV.

As I pointed out before, you seem to be confusing the definition of "efficiency" in the paper (percentage of stored energy that makes it to the wheels) and "efficiency" meaning the amount of energy required to travel a given distance.

'heavier' EV
 

1) Not to sound like Bill Clinton, but we need to clarify exactly what you mean 'heavier' EV.
2) I'm only talking about the 2015 Volvo V40, 'small' SUV, at a different weight.
3) Not the Volvo S80, or XC90, both of which have different CdAs as well as higher curb weight.
4) None of the tables presented in the thesis reflects the V40 at a different curb weight.
5) Since last Monday, I located enough data from my archive to scientifically prove that a 'heavier' V40 would be 'totally' more efficient for all considerations. It all hinges upon the ' strange behavior... connected to the regenerative braking which is dependent on available wheel power and mass.'
6) It's a page full of data, including Volvo's own solution for the 2021 model year XC40 P8 AWD Recharge ( R-Design).
7) It's quite damning to your hypothesis.

You're messin with my head, it's not Wednesday.

Wednesday
 

Yeah, I thought I'd try Mondays and Thursdays for awhile and see how that goes.