Miles Per Gallon Equivalent by Four Different Methods

[IamIan]

Originally Posted by mnmarcus

Me too! But I'm equally suspicious of ;

"Given the much higher ~90%+ Efficiency of modern electric drive systems ... and given the much much broader range of higher operating efficiency ... efficiency less effected by cold ... by load ... etc."

and

"This makes the BEV about ~300% more energy efficient compared to the ICE , at the vehicle level... or for a given amount of energy , the BEV I would generally expect to travel about ~3x as far.BEVs that end up weighing more will have more rolling resistance ... which is linearly related to weight ... so in order to counter the ~300% vehicle level energy efficiency ... the BEV weight would have to increase by close to ~300% ... which even lead sleds don't get that much heavier."

Well sense I think these two are from me .. I can offer a bit more for these.

The first one ... I am describing the efficiency of the electric drive system itself ( electric motor , controller , battery ) have much better operating energy efficiencies than ICE's do ... and the efficiencies of ICEs vary much more as conditions change like RPMs, load, temperature, etc... this is easily verifiable from a variety of sources... I can dig up some for you if needed... for some specific comparisons.

Although it is only referring to the drive system efficiency ... and not the source of energy ... but if you want to talk about energy sources ... great ... all fossil fuels are horribly inefficient forms of using solar energy... and I do mean horribly inefficient.

- - - - - -

The second one at the vehicle level BEV are massively more energy efficient than ICEs... This seems to greatly agree with the studies you posted

Your #1>
BEV 88%
ICE 15%
at the vehicle level the BEV is ~5.8x more efficient ... or ~488% more efficient.

Your #2>
BEV 529.5 miles per Million BTUs
ICE 182.5 miles per million BTUs
at the vehicle level the BEV is ~2.9x more efficient ... or ~190% more efficient.

Your #3>
BEV 90% efficient
ICE 20% efficient
at the vehicle level the BEV is ~4.5x more efficient ... or ~350% more efficient.

Originally Posted by mnmarcus

But we get numbers from studies and (often in my case) searching the web. Should we just throw out the "bad" and "dirty" pro-gasoline info and ignore anything negative about "good" "clean" electricity?

excellent point ... and I 100% agree ... we should look fairly at either one or all other alternative options... but there are different ways to look at it ... and we do not all have the same perspectives / priorities.

Liquid hydrocarbons be it gasoline, diesel, bio-diesel, ethanol , etc... all have very good energy density per unit volume ... that is a significant benefit for those fuel options... that energy density allows for the significantly less efficient drive train to still be viable... it allows it to refuel quickly ... it allows for longer ranges from a given volume of energy/fuel storage... in short I think the vast majority of the benefits come from the volumetric energy density benefit.

But we should also be honest about the superior energy efficiencies of the BEV option ... even when well to wheels are counted ... and if you do a complete life cycle of the energy source ... it seems RE BEV always dominate the energy efficiency contests.

- - - - - -

I would also say cost effectiveness or MPGe based on cost is a different issue ... and it is important... and I think that is currently perhaps the weakest case BEVs have.

BEVs have low fueling costs ... but at present the initial up front costs are much higher ... thus on a cost basis ... ICEs still have a very strong case to make... and likely will for many years or decades to come.

[dcb]

Here is where 83% came from: Miles per gallon gasoline equivalent - Wikipedia, the free encyclopedia
"The D.O.E. reports that the lumped average efficiency of electrical production and transmission in the United States, electricity, is 0.303 while the efficiency of refining and distributing petroleum, gasoline, is 0.830."

if you give electricity a 30/83 handicap (source to plug vs source to pump) then it of course changes any mpge comparisons dramatically. I think this fact applies directly to the title of this thread an as to why comparing at a straight "how may btu are you carrying" comparison between fuels and electricity is flawed, which is precisely what MPGe tries to do, and it is very misleading.


A couple things to consider on EV efficiency

electric motors don't like low load


batteries don't like high load


batteries do not necessarily charge efficiently "The coulometric charging efficiency of nickel metal hydride batteries is typically 66%, " How to charge Nickel Metal Hydride Batteries.

and you have to charge the battery before you can discharge it.

Plus a few percents for converters/controllers/lights/heat/etc.

So even suggesting that an EV is %90 efficient from the wall is coocoo.

I also don't think %15 is a fair number for ICE, it takes the driver and any recent advancements out of the equation. It is entirely possible to operate a car near it's peak efficiency, folks here do it all the time. Even if you look at a reasonably idiot proof efficiency car, the prius, it is rated at %37 (link also shows a well to pump of %79 and a well to wheels of %29) EFFICIENCY: "WELL-TO-WHEEL" ANALYSIS. -- Britannica Online Encyclopedia

so, I'm still skeptical that electric is "all that" in the full life cycle efficiency department. I'm not convinced yet the BEV's dominate in efficiency full cycle. The land use is a good thing for electrics, but range and initial cost and availability make liquid fuels attractive for transportation.

Also, the rolling resistance/weight thing. The problem with extra weight is not just extra rolling resistance, but also you only get a small fraction of your acceleration energy back in electric regenerative braking.

[RobertSmalls]

The good news is, for the first time ever, we have EPA efficiency data on a PHEV in electric drive, and when running on fossil fuel.

The Chevrolet Volt is a deeply flawed vehicle, and hardly an exemplar of efficient use of gasoline. It has a parts bin, cast iron block, 1.4L engine without Atkinsonization, coupled to a transmission that leaves much to be desired in terms of efficiency. However, it gives us some numbers to compare: 37mpg in gasoline mode, versus 368Wh/mi in electric mode, on the same test cycle.

That is to say, 13.6 KWh = 1 gal, in terms of how far it will drive a Volt.

That's astonishingly close to the numbers I came up with in the first post in this thread. The fact that three different mpge methods are in such close agreement says something.

[JasonG]

Well tell ya what,
when you build an EV that can pull a 16,000lb trailer at 55 MPH for 350 miles I'll conceed that electric is on equal terms.

Heck, if you can find one that can do either I might

[roflwaffle]

Originally Posted by dcb

batteries do not necessarily charge efficiently "The coulometric charging efficiency of nickel metal hydride batteries is typically 66%, " How to charge Nickel Metal Hydride Batteries.

and you have to charge the battery before you can discharge it.

Plus a few percents for converters/controllers/lights/heat/etc.

That's only going to be true for DIY HEV conversions. Every mass produced EV/PHEV is going w/ Li batteries, and charging efficiency is much higher, around 90% or so.

Originally Posted by dcb

So even suggesting that an EV is %90 efficient from the wall is coocoo.

I also don't think %15 is a fair number for ICE, it takes the driver and any recent advancements out of the equation. It is entirely possible to operate a car near it's peak efficiency, folks here do it all the time. Even if you look at a reasonably idiot proof efficiency car, the prius, it is rated at %37 (link also shows a well to pump of %79 and a well to wheels of %29) EFFICIENCY: "WELL-TO-WHEEL" ANALYSIS. -- Britannica Online Encyclopedia

It's fair to say that most PHEVs/EVs aren't 90%. ~75% from the plug is closer to what most would see. Along the same lines a Prius isn't going to be at peak engine efficiency of 37% all the time, it'll be closer to high twenties in terms of average efficiency. The car has to warm up, light off the emissions system, and so on. Most new cars are probably around 20+% in terms of average efficiency and most hybrids are in the high twenties in terms of efficiency.

Originally Posted by dcb

so, I'm still skeptical that electric is "all that" in the full life cycle efficiency department. I'm not convinced yet the BEV's dominate in efficiency full cycle. The land use is a good thing for electrics, but range and initial cost and availability make liquid fuels attractive for transportation.

Also, the rolling resistance/weight thing. The problem with extra weight is not just extra rolling resistance, but also you only get a small fraction of your acceleration energy back in electric regenerative braking.

It depends on the specifics, but generally speaking an EV compact car will need ~1kWh/mile of electricity assuming we use something like subcritical coal, while a conventional gas version will need ~1.5kWh/mile of gasoline. A hybrid gas version would need about the same amount of energy per mile an electric would. As we move to generation methods like natural gas the EV drops to ~.75kWh/mile. Using renewables or fission can further reduce the amount of fossil fuel energy per mile needed.

Originally Posted by JasonG

Well tell ya what,
when you build an EV that can pull a 16,000lb trailer at 55 MPH for 350 miles I'll conceed that electric is on equal terms.

Heck, if you can find one that can do either I might

I don't think anyone is saying that either one is on equal terms. An engine can't beat a motor for reliability or efficiency and a motor can't beat an engine for refueling times or energy storage. Each one has it's advantages and disadvantages.

[dcb]

Let me try to pare it down a little, and this example still makes electrics look good.

Tesla lists itself as 135MPGe, which is inconceivable in a gas car with those performance figures. "Obviously" something has gone horribly wrong here in the comparison of electricity to gasoline, can we agree on that?

Now figuring out the exact numbers to use is a laborious process. But if we borrow the well(plant?) to "pump" efficiency numbers from the Department of Energy, %30 electric/%83 petrol, we get an adjusted mpg of 48MPG.

This still makes the tesla something to drool over, and 48MPG is certainly a lot more believable equivalence number than 135MPGe.

Does that reasoning make sense?

Note, I'm not promoting petrol, just trying to establish a fair basis for comparing the alternatives.

[roflwaffle]

I don't think I'd say it's gone horribly wrong, just that something with a motor is more efficient at using energy it has onboard than something with an engine. From the point of view of the EPA ratings someone isn't going to factor in average electricity generating efficiency just like they don't factor in gasoline production efficiency. Neither or those are what the EPA mpg rating entails. Someone could do that, but in that context what's more appropriate is Carbon emissions per mile, which I mentioned earlier in the thread.

[dcb]

Originally Posted by roflwaffle

I don't think I'd say it's gone horribly wrong, just that something with a motor is more efficient at using energy it has onboard than something with an engine.

but that is an arbitrary point in the system, ignoring all the conversion losses to that point (which are many), from the days when all there was was gasoline basically, and puts the alternatives at an unfair disadvantage.

[JasonG]

Originally Posted by roflwaffle

I don't think I'd say it's gone horribly wrong, just that something with a motor is more efficient at using energy it has onboard than something with an engine. From the point of view of the EPA ratings someone isn't going to factor in average electricity generating efficiency just like they don't factor in gasoline production efficiency. Neither or those are what the EPA mpg rating entails. Someone could do that, but in that context what's more appropriate is Carbon emissions per mile, which I mentioned earlier in the thread.

With liquid fuels it is figured in. For every X gals extracted from source Y, Z number of gallons is used in purification, processing, transportation etc. The 1 gal in your tank started as 1.X gal.
It's the reason alcohol from cellulose is impractical. It takes more energy to produce than it provides to the tank.

Originally Posted by dcb

Let me try to pare it down a little, and this example still makes electrics look good.

Tesla lists itself as 135MPGe, which is inconceivable in a gas car with those performance figures. "Obviously" something has gone horribly wrong here in the comparison of electricity to gasoline, can we agree on that?

Now figuring out the exact numbers to use is a laborious process. But if we borrow the well(plant?) to "pump" efficiency numbers from the Department of Energy, %30 electric/%83 petrol, we get an adjusted mpg of 48MPG.

This still makes the tesla something to drool over, and 48MPG is certainly a lot more believable equivalence number than 135MPGe.

Does that reasoning make sense?

Note, I'm not promoting petrol, just trying to establish a fair basis for comparing the alternatives.

Good example.

Or in fantasy terms :
If they made a 6cyl version of a VW TDI, say 3L range and put it in a roadster.
48 MPG would be reasonable for an average non-hypermiling driver. It would also have similar performance numbers.
Oh, and the one in my driveway would smell like Fried food

Rats, just looked out the window,......back to reality........

[euromodder]

Originally Posted by dcb

Land use wise solar wins by a wide margin.

And even more so when we put PVs on surfaces that are already taking up area for other purposes, like buildings.