Question about EV Value and environmental impact

[Jeff N]

Many models use the stoichiometry balance of 19.6 lbs of CO2/gal of gasoline burned. But if you add in the refining emissions it rises to 23.1 a substantial 17% rise. If you add this in then EV is cleaner than a Prius even in a coal state.

Those refinery emissions are already factored into the GREET upstream emissions (which assume a bit over 24 pounds CO2 per gas gallon) used to calculate CO2 numbers by zip code for fueleconomy.gov.

Look up a 2016 Prius in a heavier coal region in the upper Midwest like Michigan and you will see that an S70D has emissions of 280g per mile and a Prius is 205. A BMW i3 BEV, about the most efficient of the BEVs, is rated 230g per mile.

 

[Jeff N]

The numbers I used were 7.5 kWh (that's the 8 I was referencing) per gallon, or 2 kWh per litre. I'm pretty sure that's electricity, but I can go look and report back. Unfortunately I didn't write down where I got those numbers, but I checked several places on the great wide net before committing to a certain value.

Those number look similar to very early Nissan LEAF marketing that was later withdrawn.

 

[omgwtfbyobbq]

California is not typical. The fields are generally old and have been pumped dry over the decades. All that extraction energy goes towards steam and various techniques to get the very last bit of oil out of the ground. The national average extraction energy is far lower.

As far as I can tell, it is lower, but still substantial.

A description of the well-to-wheel life cycle GHG emissions of petroleum-based gasoline was presented in the CTL liquid sections and it is summarized again here: gasoline has a combustion emissions factor of 2.31 kg CO2-eq per liter (HHV) (EPA, 2006c). Using the GREET 1.7 model, upstream emissions from petroleum extraction, refining, and transportation result in an additional 0.59 kg CO2-eq per liter

http://www.cmu.edu/gdi/docs/energy-policy-2009-jaramillo.pdf

GREET assumes upstream emissions are roughly a quarter of total emissions, which is a fair bit.Given how good refinery efficiency is, I imagine the majority of that is due to energy inputs, which would put those at 8+ kWh. Granted, extraction in CA alone is 9+ kWh, but if the US average could still provide ~3-4+ kWh of electricity, that's ~12-16 miles in an EV at 250Wh/mile.[/quote][/quote]

 

[SageBrush]

however the energy inputs for extraction are usually a lot larger.

GREET willl give you a lifecycle analysis in terms of CO2. If you start from the C02 in combusted petrol (~ 20 lbs/gallon,) you can then calculate the upstream extraction and processing fraction.

However, the argument that NG and electricity is "wasted" by continuing the oil economy is a false accounting. We know that more energy is retrieved than spent, so all that matters is the cost of that net energy in $ and environmental terms. By similar reasoning, we don't complain that PV is "only" 15% - 20% efficient.

Addendum ...

GREET assumes upstream emissions are roughly a quarter of total emissions,

WtW by GREET is ~ 17%

 

[SageBrush]

Many models use the stoichiometry balance of 19.6 lbs of CO2/gal of gasoline burned. But if you add in the refining emissions it rises to 23.1 a substantial 17% rise. If you add this in then EV is cleaner than a Prius even in a coal state.

I use 24 lbs C02 /gallon petrol as a WtW number so we pretty much agree there, but not with regards to a Prius in a coal state being inferior to a coal driven EV:

Prius: ~ 11 Kg C02/50 miles gives 220 grams per mile by LCA

Tesla Model 'S' EV on coal:
3 miles per kWh
One generated kWh is in the range of 1.0 - 1.2 Kg C02 LCA, so even before we consider transmission and charging losses of over 20%, the EV is at 333 - 400 grams C02/mile.

Most efficient EV is about 4 miles/kWh, so
0.75x above numbers.

The best analysis is going to come from Toyota itself, when the 22 mile plug-in numbers are fully disclosed. Then we'll have the same car running on either petrol or electricity, and both drivetrains will be highly optimized (and to a large degree shared.) I think the MPG is ~ 55, but I am not sure yet how much battery energy is used for the 22 miles.

 

[SageBrush]

Follow up of post #125...

Toyota expects a combined city/highway EV consumption of 120 MPGe, which works out to 280 Wh/mile. This includes charging losses.
So starting from 1000 gram C02/kWh at the power plant, the car emits 280 grams CO2 per mile when run on coal. Well actually higher because transmission losses have not been accounted for, but it should be quite clear that coal cannot beat a petrol hybrid, all else being equal since the same car run on petrol has LCA emissions of ~ 205 grams/mile.

 

[dhrivnak]

I think the transmission losses are accounted for as the EPA figures for an EV includes charging losses and most power companies report KWh sold. And I was comparing the more efficient Leaf to the Priusnot the Model S which is a rather large car.

 

[omgwtfbyobbq]

GREET willl give you a lifecycle analysis in terms of CO2. If you start from the C02 in combusted petrol (~ 20 lbs/gallon,) you can then calculate the upstream extraction and processing fraction.

However, the argument that NG and electricity is "wasted" by continuing the oil economy is a false accounting. We know that more energy is retrieved than spent, so all that matters is the cost of that net energy in $ and environmental terms. By similar reasoning, we don't complain that PV is "only" 15% - 20% efficient.

Addendum ...

WtW by GREET is ~ 17%

I don't think anyone's saying the NG is currently wasted. Examining the energy requirements of hydrocarbon fuel creation was I believe done to counter the claim that we didn't have the energy to power a fleet of EVs.

The basic idea is that when we don't create a gallon of gasoline, we free up some energy (mostly NG) that can power EVs. This energy appears to be enough to power an EV for ~10-15 miles at the US average, and probably twice that in places like CA, which is really neat, because it implies that switching to EVs can reduce GHG emissions by ~50-80+% compared to ICEs there.

In terms of GREET, WtW is ~17% of the total, and ~25% of the Carbon emissions (2.31kg from the gallon of gas and .59kg from upstream extraction, refining, and transportation) of a gallon of gasoline (~36+kWh).

 

[SageBrush]

In terms of GREET, WtW is ~17% of the total, and ~25% of the Carbon emissions (2.31kg from the gallon of gas and .59kg from upstream extraction, refining, and transportation) of a gallon of gasoline (~36+kWh).

Sorry, I'm not following your meaning here. Could I see it more schematically perhaps ?

As an example, when I say that WtW is 24 lbs of C02 per gallon petrol, I mean the following:
4 lbs from well to car
20 lbs from car

Since C02 is proportional to energy content, and a gallon of petrol has 33.7 kWh, it follows that the source had 24/20 more energy, or 24*33.7/20 = 40.44 kWh. Therefore 40.4 - 33.7 = 6.7 kWh (energy, NOT electricity) was expended in going from well to car.

This gives us some context to answer your claim that an electric fleet could have simply been run on the energy input (assuming it was all NG) since we know that 6.7 kWh was 'invested' in order to retrieve 40.4 kWh, for a "ROI" of ~ 5.0. Unless the NG can be used close to or more than 5x times more efficiently than oil the claim does not pass the sniff test.

In CA NG is converted to electricity at ~ 45% thermo efficiency, then
~ 7% is lost to transmission,
then ~ 15% is lost to charging,
then 3% is lost from battery to gearing,
For a total NG to car drivetrain of 45*0.93*0.85*0.97 = 34.6% utilization of source NG energy

Compare that to a Prius which combusts the petrol directly in the range of 30-35% thermo (45 - 55 MPG) utilization*.
----
At the risk of beating a poor dead horse ..
You can take 6.7 kWh of NG, convert it to 2.3 kWh electricity and travel about 6.9 miles in a Tesla Model S; or perhaps 9 miles in a LEAF. Or you can

Take the 6.7 kWh NG , make a gallon of petrol for a Prius and travel 50 miles.

*I use utlilization in place of thermo efficiency in hopes of clarify at the expense of unit accuracy.

 

[jerry33]

At the risk of beating a poor dead horse ..
You can take 6.7 kWh of NG, convert it to 2.3 kWh electricity and travel about 6.9 miles in a Tesla Model S; or perhaps 9 miles in a LEAF.

That seems somewhat low for the Model S. 2300 Wh is not quite nine miles.

 

[SageBrush]

That seems somewhat low for the Model S. 2300 Wh ...

The calc is stated above, but to recap:

Start at 6700 Wh
45% power plant efficiency (55% losses)
7% transmission losses
15% charging losses
3% battery discharge loss

I'm pretty confident of the arithmetic since I copy/pasted from a calculator ;-)
If you want to check, the expression is 6700*0.45*0.93*0.85*0.97

 

[jerry33]

The calc is stated above, but to recap:

Start at 6700 Wh
45% power plant efficiency (55% losses)
7% transmission losses
15% charging losses
3% battery discharge loss

I'm pretty confident of the arithmetic since I copy/pasted from a calculator ;-)
If you want to check, the expression is 6700*0.45*0.93*0.85*0.97

Using that calculation I get 9.36 miles.

6700*.45 = 3015.00

3015.00*.93 = 2803.9500

2803.9500*.85 = 2383.357500

2383.357500*.97 = 2311.85677500

2311.85677500/247 = 9.35974402834008097165

 

[SageBrush]

2311.85677500/247 = 9.35974402834008097165

If your use is 247 Wh/mile, sure.
It seems that 3 miles per kWh (333 Wh/mile) is a more typical reported consumption though for the Model S. If you are saying 4 miles per mile for the LEAF that sounds about right, and what I calculated earlier as well.

 

[omgwtfbyobbq]

Sorry, I'm not following your meaning here. Could I see it more schematically perhaps ?

As an example, when I say that WtW is 24 lbs of C02 per gallon petrol, I mean the following:
4 lbs from well to car
20 lbs from car

Since C02 is proportional to energy content, and a gallon of petrol has 33.7 kWh, it follows that the source had 24/20 more energy, or 24*33.7/20 = 40.44 kWh. Therefore 40.4 - 33.7 = 6.7 kWh (energy, NOT electricity) was expended in going from well to car.

This gives us some context to answer your claim that an electric fleet could have simply been run on the energy input (assuming it was all NG) since we know that 6.7 kWh was 'invested' in order to retrieve 40.4 kWh, for a "ROI" of ~ 5.0. Unless the NG can be used close to or more than 5x times more efficiently than oil the claim does not pass the sniff test.

In CA NG is converted to electricity at ~ 45% thermo efficiency, then
~ 7% is lost to transmission,
then ~ 15% is lost to charging,
then 3% is lost from battery to gearing,
For a total NG to car drivetrain of 45*0.93*0.85*0.97 = 34.6% utilization of source NG energy

Compare that to a Prius which combusts the petrol directly in the range of 30-35% thermo (45 - 55 MPG) utilization*.
----
At the risk of beating a poor dead horse ..
You can take 6.7 kWh of NG, convert it to 2.3 kWh electricity and travel about 6.9 miles in a Tesla Model S; or perhaps 9 miles in a LEAF. Or you can

Take the 6.7 kWh NG , make a gallon of petrol for a Prius and travel 50 miles.

*I use utlilization in place of thermo efficiency in hopes of clarify at the expense of unit accuracy.

I think RUG is 36.6kWh and E10 is 33.7kWh.

http://www.hrt.msu.edu/energy/pdf/heating value of common fuels.pdf

And combined-cycle gas plant efficiency is ~47% in CA.

http://www.energy.ca.gov/2014publications/CEC-200-2014-005/CEC-200-2014-005.pdf

If we have (.59kgC upstream/2.31kgC per gallon) * 36.6kWh/gallon, that's ~9.35kWh in upstream energy. At 47% generating efficiency (I'm guessing it would be a smidge higher than this, but w/e) and 97% transmission/distribution efficiency, that's 4.26kWh of electricity at someone's home.

We can compare the most efficient hybrid to less efficient EVs, but I think the most efficient EV (i3 at 270Wh/mile EPA including charging losses) is a closer comparison. In that case, the i3 would be able to travel ~16 miles using just the (mostly) NG energy inputs required to create a gallon of gas. In someplace like CA, where it take more energy to create HC fuel, the i3 could probably travel closer to ~30+ miles.

Putting it another way, on FFs, a Prius goes ~52 miles and emits ~2.9kgC. An i3 travelling the same distance would need ~(52/16)*.59=1.9kgC, so ~2/3rd the Carbon. The i3 can also use renewable electricity and would probably encourage the addition of more renewable generation. Even if the 2ZR-FXE has high enough thermal efficiency to get it close to the efficiency of using nat gas to charge EVs, the energy required upstream is enough to push Carbon emissions up by ~50% compared to an efficient EV. In states like CA, where the nat gas for extraction alone is closer to ~9kWh, that difference is greater.

 

[SageBrush]

I think RUG is 36.6kWh and E10 is 33.7kWh.

I hadn't thought about RUG, but the difference in heat content is ~ 3.3%, while 36.6/33.7 is 1.086. Can you explain the difference ?
I'll have to double check to be sure, but I think that the EPA value of 17% Well-to-car losses is for E10.

2. I just looked up the BMW i3 at fueleconomy.gov and see 290 Wh/mile combined cycle.
If we want to compare best EV to best ICE then the ECO Prius is 56 MPG combined cycle. Personally I think the best comparison is Plug-in Prius EV Vs ICE mode. Then we are not comparing a $40k USD Carbon Fibre to a $24k USD more vanilla car.

3. Transmission losses are nationally estimated at ~ 7%

4. NG power plant efficiency: This report from the CA ARB 2014 says overall weighted efficiency is 40%, but I think (and they comment) that the screwy values ascribed to CHP plants mess up the final calculation. For our purposes we can probably ignore the CHP plants since I doubt they ramp with demand but I was too lazy to calculate without them.

For all these reasons above, I think your final estimate of a California fueled i3 by NG has 33% less CO2 emissions than a Prius is significantly over-estimated, but overall I am fine with a rule of thumb that says that EV from NG is about comparable to a good hybrid. I only get fussy when people say that a coal fired EV is preferable to a good hybrid in terms of CO2 emissions.

I agree with you completely with regards to EVs and e.g PV. That is exactly my intent, in no small part because I live in coal country.

 

[omgwtfbyobbq]

That is odd, I bet the 33.4kWh amount is for E10 or E15 with anti-smog additives blended in. The i3 REX has lower mpge, which might be what you're seeing? The i3 BEV uses 27kWh/100 miles on fueleconomy.gov.

Compare Side-by-Side

Average T&D losses for the US were 5% in 2014. I'm guessing CA is better than that, but it might be worse.

How much electricity is lost in transmission and distribution in the United States? - FAQ - U.S. Energy Information Administration (EIA)

You can also use 40% efficiency for natural gas plants in CA, which includes generation from aging/peaker plants, but I don't think that's realistic. We'd probably use load following combined cycle plants since they're ~30-40% more efficient than old/peaker plants and would probably cost less.

Combined-Cycle 19,676 38.7% 87,361 67.3% 50.7% 7,205
Aging 15,851 31.2% 7,589 5.5% 5.5% 11,413
Peaker 7,418 14.6% 3,310 2.6% 5.1% 10,268

 

[SageBrush]

The i3 REX has lower mpge, which might be what you're seeing? The i3 BEV uses 27kWh/100 miles on fueleconomy.gov.

Compare Side-by-Side

Cross my heart, I saw 120 (or was it 119?) MPGe and 29 kWh/100 miles!
Now I see the figures you quoted LOL

Re: NG Power plant Efficiency in California (same link as before)

As a hopefully reasonable marginal use case, I take the weighted CC, aging and peaker plants:
(7,205*67.3+5.5*11,413+2.6*10,268)/(67.3+5.5+2.6) = 7617 btu/kWh = 44.7%
I used 45% in my earlier calculations.

I'm unconvinced that you should use 36.6 kWh in your calculations.
E.g., fueleconomy.gov reports 209 WtW grams per mile LCA for a 52 MPG Prius.
That works out to 0.209*52 = 10.87 Kg per US Gallon, or 23.91 Lbs LCA CO2 per gallon.
I used 24 lbs in my calculations.

T&D losses: The EIA says 6%

 

[SageBrush]

I think we are pretty close to agreement on the values to use for the LCA comparison of an ECO Prius and a BMW i3, so here are the calcs:

Prius
LCA CO2 for petrol is 24 lbs/US_gallon, equal to 40 kWh source energy
That works out to 24/56, = 0.429 lbs CO2 per mile or 195 grams per mile.


i3
Using the 2011 GREET publication by Wang et al,
I eyeball the 20 year NGCC Conventional gas at 825 grams/kWh
0.27 of that per mile in an i3, thus 222 grams CO2 per mile.
Shale gas is lower, and IIRC is about 15 - 20% of NG stock
I'm feeling lazy, so I'll guesstimate 800 grams/kWh weighted --
then 800*0.27 = 216 grams CO2/mile,
but divide by 0.94 to account for T&D losses, so 230 grams/mile

 

[artsci]

There will be a time, and it can't come soon enough, that coal will no longer be burned to make power. As we progress toward that goal any Tesla will become more environmentally friendly by the day.

 

[Skotty]

I don't know why this always has to be an argument. As an exercise, lets accept the notion that climate change is bad and we need to greatly reduce and possibly eliminate the use of fossil fuels. Lets also accept the notion of the long tailpipe and it's actually cleaner to drive an ICE car.

So what, then, do we do?

1) Accept defeat. I would assume that is what most contrarians think is the right approach. Give up and accept our fate.

Okay, why don't we NOT be a bunch of loser quitter aholes. What's next?

2) Well, I guess you have to clean up power pants. That would eliminate a lot of the fossil fuel emissions problem. But wait a minute, once that's done, cars will still have emissions from fossil fuels. Oh, guess what, you still need EVs (or more precisely, something that is net emissions free). So why is anyone arguing the long tailpipe argument to begin with if we end up needing EVs or something similar eventually anyway? I'll be nice and say it's because these people just weren't thinking through the problem well enough.

So anyone who argues the long tailpipe is either:

1) A loser quitter ahole.
2) Hasn't thought through the problem well enough.

If you are #1, we don't need you, you are a detriment to society. if you are #2, think it through a little more -- we need the EVs anyway. Whether we do it first, second, or at the same time as the other parts doesn't matter so much in the long run.

On a related note, who gives a $#*$% what the emissions are in manufacturing clean technology? Yes, that's part of the problem we are trying to fix. Don't tell me we can't fix a problem because of the very problem you are telling me we can't fix.