Are coal-powered electric cars really better for the environment?

I imagine for me, yes.

For you, definitely not. Every mile you power your car is a mile you could have been on your bicycle.

 

Touche.

 

If the data in Llewelynn's video is remotely accurate, gas powered cars are CO2 belchers ...

http://priuschat.com/forums/other-cars/93119-another-fun-video-about-benefits-electric-vehicles.html

He claims a Roadster EV 'produces' 40 g CO2 / km even if run 100% off coal, and that figure includes everything from mining/transport and producing the electricity.

The same oil/gas well to gas station to wheels emission would 450-500 g CO2/km for gas cars.

That's a big difference. How accurate is it?

Of course there are all the other things that come from burning fuels - CO, etc...

 

I bet people who drive advanced tech cars are much more likely to bike or walk, weather permitting, than those who haven't a thought in the world about cutting back on energy use.

I use a Specialized Sequoia bicycle for some runs to the store.

 

Not even remotely.

May I suggest you verify this yourself with a little arithmetic and googling ?

 

Well, not even remotely accurate...

Without going into long calculations, consider this:
CO2 emissions of 1 kWh produced in coal fired PP - 850 to 1000 g. Up-stream coal (mine to PP) adds about 6%. O.K. let's take 900 g total.
The Tesla is doing what: 5km/kWh? O.K. let's take 7.
That's 128 g/km running emissions.

Gasoline up-stream emissions (well-to-pump) are estimated about 15%, so a Prius with 89 g/km running emissions is actually 102 g/km well-to-wheels.

Enjoyed the video though.

Giora.

 

Tesla publishes this (part of a) table on their website:



Look at the last column, cycledrum. You can ignore the units because they are the same, and just look at the ratio. A higher number is better. Tesla makes *very* complimentary assumptions slanted towards the EV for this analysis by using the most efficient NG plant available, and can only decrease Prius CO2 emissions by 50%.

Llewyn's starting point of UK coal is close to 4x the carbon emission as Tesla's starting point with best available NG reactor. If you want more proof that even this table is hopelessly skewed towards EV, notice that the EV is rated at 170 wh/mile. Their own data earlier in the page I took this table from estimated 250 wh/mile at 65 mph.

I leave the remainder of the math to you.

 

But it takes 7 kWh of electricity to refine oil to one gallon of gasoline... If you can take the electricity used to make the gas and go just as far in an EV as the gas would take you in an ICE, how can the CO2 emissions be higher for the EV?!

Something isn't adding up with this math...

 

DarkStar,
Look at Tesla's table in post #127. The column labeled "well to station" includes the processing you mention.

Column #3 times column #5 = column #6.

If you want to play around with the units --
1 kwh = 3.6 MJ
1 km = 0.62 miles

Anyway, to point out the error in your logic --
You are ignoring the kwh spent to make the electricity.

-----
Carbon intensity of Coal Vs Petrol:

Coal: 670 grams carbon per 28.47 MJ = 7.9083 kwh
Combustion 30% -> 2.3725 kwh out of the plant
6% transmission losses to home, 15% losses to battery, 85% to wheels:
````` 1.61 kwh energy at the wheels from 1.474 pounds of coal carbon
---- or 1.1 kwh electricity at the wheels per pound carbon

Petrol:
6/7 of weight is carbon
gallon weighs 6.7 pounds, and so contains 5.743 pounds of carbon
18% of oil lost in refining to petrol, so 7 pounds of carbon is 33.4 kwh of petrol in tank
tank to wheels in Prius is 30-35%, or 7 pounds for (10 - 11.7) kwh per 7 pounds carbon.
--> (1.43 - 1.67) kwh per pound carbon from oil.

This calculation does not consider energy consumption at the wheels, only the *delivery* to the wheels.

Same car, EV vs Petrol: Coal emits 40% more carbon a mile than petrol.


Addendum: DOE says coal combustion efficiency is 33% and not 30% used above. so 1.1 kwh/pound should be 1.21 kwh/pound, and coal emits 28% more carbon a mile than petrol, rather than 40% as originally calculated.

References:
http://en.wikipedia.org/wiki/Coal#Hilt.27s_Law
MW of carbon = 12, H = 1
Hydrocarbons are ~ CH(2)
Coal combustion efficiency per US DOE

 

Just to be accurate, the US electricity consumption is from 45% coal, not 80%+ like you are suggesting.

 

"To achieve significant reductions in GHG emissions, PHEVs and BEVs must
recharge from a generation mix with a large share of nonfossil sources (e.g.,​

renewable or nuclear power generation)."

"BEVs can virtually eliminate the use of petroleum​

fuels for each vehicle mile traveled on electricity."

http://www.ipd.anl.gov/anlpubs/2010/06/67242.pdf

This was linked earlier.

 

But don't you still need to add the coal used to make the electricity that is used to make the gasoline to the total to the emissions caused by burning gasoline?

 

The first problem is the reasoning not the math. Is the only pollutant carbon dioxide? Do we care that conventional sources of crude are running down? Do point sources of pollution other than carbon dioxide matter? Do electric cars have a coal chut but refineries run on clean electricity? The last is the prius should be compared to the fleet of cars but an ev must only be compared to the prius. Once you get passed that you don't really need to worry about some bad math assumptions.

Let's first specify that marginal gasoline doesn't come from West Texas Light Sweet crude but Canadian oil sands. Let's see how much co2 a 50mpg car like the prius produces.

First how much CO2 is produced when changing sands to oil
Oil Sands Producers Cut CO2 Emissions | Oil Blog - Oil & Gas Company Analysis, Oil Traders, Energy Companies, Gas Companies, Energy Consultants

123 kg per barrel. The conversion from barrels to gallons is not straight forward we only get less than 20 gallons of gasoline from one, but lets say it is cracked and we get 42 gallons of gasoline without out producing carbon dioxide, that makes 2.9kg/gallon.

It takes 7 kwh of electricity to produce a gallon of gas from sweet crude, and although it is more for this oil sands, lets say 7kwh at the marginal grid rates. The doe assumes all natural gas. The epa uses 2007 actual marginal power.

Green Power Equivalency Calculator Methodologies | Green Power Partnership | US EPA

We get 0.691 kg per kwh x 7 kwh = 4.84
And we get 8.92 kg per gallon x 1 gallon = 8.92

So adding up we get 2.9 + 4.84 + 8.92 = 16.66 kg per gallon gasoline from oil sands. Remember this is a low estimate. If we take 50 mpg we get

0.33 kg carbon dioxide per mile in a prius type hybrid.

Now lets look at a similar electric car the leaf it gets 0.34 kwh/mile. But there are transmission losses lets divide by 90%

0.34x0.691/90% =

0.26 kg carbon dioxide per mile in a leaf type electric.

THe electricty going into these electrics is cleaner than the marginal grid and getting cleaner, and I underestimated for the oil sands marginal gas, but these should be more ball park figures. Bottom line is both are much better than the 20.4 mpg fleet. A prius does not really produce much more CO2 than a leaf, but it does not produce less unless you put the leaf in a poor location. A tesla is California or Texas does produce significantly less carbon dioxide than a porsche, but I don't think we really need to go there.

Part of the problem is oil sands are easier to make into asphault and diesel so they only account for it partially. Then they count the energy mainly as natural gas not coal to produce gasoline. The grid is not coal, and though marginal is slightly dirtier than the grid as a whole it is a very bad assumption.

 

The tar sands link was informative, thanks.
A barrel is 42 gallons, so each gallon syn-crude requires 6.44 pounds of CO2 to produce. The marginal increase should be the difference between 6.44 and production of average world oil, along with any processing differences from oil -> petrol between the two products.

Just going by the 6.44 pounds, tar sand derived petrol is about 1/3rd more carbon intensive than liquid oil. As I showed above, a LEAF run on coal is 28% more carbon intensive than a Prius run on liquid fuel, so a coal-LEAF is just a tad less carbon intensive than a tar-sands-Prius.

Answer: tax carbon, conservation will decrease demand below threshold where tar sands are economically viable. To me your argument is not in favor of EV, it is simply a demonstration of a corrupted market economy that ignores externalized costs.

Yes. When the DOE says that 18% of oil energy is expended converting it to petrol they are telling you energy costs, not source fuel of the energy.

 

Well, if you're going to use tar sands as the comparison, perhaps there are a few other things to factor in. The operation uses huge quantities of natural gas and water that could both be put to better use. Also, ground water is polluted by a perverse practice called fracking.

To my way of thinking, the logic of finding the nastiest poisons we can, and then spreading them as far and wide as possible through air, water, and soil, would render any mathematical exercise utterly moot.

 

That is a good take away. The other part of the take away should be an understanding that our marginal gasoline is getting dirtier and the government figures do not account for this. Finally looking forward, the marginal fuel on the grid is natural gas not coal so these numbers will move further in the EVs favor, but carbon dioxide is not a good reason to buy an EV.

IMHO there are very good reasons for EV but carbon dioxide savings versus hybrids are not one of them. I was simply trying to put out better figures about where our gasoline will be coming from in the future, so that we can have a more intelligent discussion.

The only way to reduce gasoline from tar sands is to reduce total consumption of gasoline. A carbon tax in the United States will simply mean the oil is refined in Canada and we import the distillates instead of the syn crude. Just like the wind fall profits tax did not reduce oil prices, it just shifted profits to foreign countries and reduced us oil production. These energy companies are very good at shifting production to react to tax changes. If you want the tax to have any effect it needs to be on all gasoline.

For the electrical grid these production shifts do not work. A carbon tax or cap and trade can work. Congress did a poor job designing the cap and trade plan, but I prefer cap and trade with the retirement of grandfathered pollution - ie. better regulation. But I would like a carbon tax more than the last cap and trade bill which was a big giveaway to certain corporations.

 

These are what I believe are the realities of the stiutation and they greatly outweigh the carbon dioxide pollution.

 

Is coal mining becoming more carbon intensive ?
Is the non-CO2 pollution getting worse as lesser quality coal becomes profitable ?

I do not know details, but it seems rather obvious that the same dynamics that opened up tar sands will operate on coal.

 

This thread can go for ever...

I think we can all agree on:

The grid must be cleaned, no matter if electricity is used to refrigerate our food, to operate a TV set or for transportation.

Apart from CO2, the tailpipe of a conventional vehicle emits pollutants that affect our health and quality of life. Any attempt to reduce these pollutants and clean the streets of our cities is blessed.

Crude oil should be used for better purposes (like plastic industry) rather than just burned.

Giora.

 

"Better" plastics industry ?

<<shudder>>

Spawn of the devil.