How much electricity to produce gasoline?

[Norbert]

...and I think the reason he arrives at 6 kWh per gallon gas, instead of Nissan's 7.5 kWh, is that he uses 85% efficiency (arbitrary number between 83.3% and 87.7% mentioned earlier in my post Feb 2011), and the EPA energy equivalent of 33.7 kWh instead of Wiki's 36.6 kWh.

So where Nissan probably calculated (a while ago): (36.6 / 83 * 100) - 36.6 = almost 7.5 kWh
the "Electric Mini" blog post calculated: (33.7 / 85 * 100) - 33.7 = almost 6 kWh

EDIT: A simpler (and more common) form to write this is: 33.7 * (100/85 - 1).

 

[Norbert]

AutoblogGreen article based on the "Electric Mini" blog:

How gas cars use more electricity to go 100 miles than EVs do

 

[VolkerP]

One problem with Elon's statement is that some of the energy used to refine gasoline is generated on site from petroleum by products and NG. Now we'd probably get more mileage if a barrel of oil were refined less and burned in a generating plant to charge EV's, but then we're still using petroleum for transportation.

It's still a statement to confront those people with, that keep saying EVs will increase overall energy consumption, will increase pollution, will overload the grid, and so on.

 

[Norbert]

It's still a statement to confront those people with, that keep saying EVs will increase overall energy consumption, will increase pollution, will overload the grid, and so on.

And whichever way the refineries use that energy, be it external electricity, petroleum or NG, (AFAIK) does produce CO2, and does consume fossil fuels (counting NG as fossil fuel), which is the subject of that discussion.

 

[vfx]

One problem with Elon's statement is that some of the energy used to refine gasoline is generated on site from petroleum by products and NG. Now we'd probably get more mileage if a barrel of oil were refined less and burned in a generating plant to charge EV's, but then we're still using petroleum for transportation.

Since the 2nd largest user of electricity in CA is the refineries I would ask how much? They are not a generating powerplant by any mean.

If you shut them (the refineries) down and augmented that amount with coal, NG, or wind/solar, at least then the importing stops.

 

[JRP3]

There was 43,019,000,000 kwh's of electricity purchased by US refineries in 2009. Big Oil Electricity Conspiracy
If we knew how many barrels of oil were processed in the US in 2009, and how much of that was turned into gasoline, we could figure out how much purchased electricity was used for each gallon of gas. Sort of. Because as that chart shows there is also coal and steam purchased by refineries, which involves electricity.

 

[stopcrazypp]

There was 43,019,000,000 kwh's of electricity purchased by US refineries in 2009. Big Oil Electricity Conspiracy
If we knew how many barrels of oil were processed in the US in 2009, and how much of that was turned into gasoline, we could figure out how much purchased electricity was used for each gallon of gas. Sort of. Because as that chart shows there is also coal and steam purchased by refineries, which involves electricity.

I've done a similar analysis before, just with older (2006) data.
http://www.teslamotorsclub.com/showthread.php/4884-More-anti-ev-gibberish?p=63031#post63031

Basically 128 million gallons of gasoline made in 2006, and 39353,000,000 kWh electricity purchase by US refineries in 2006. Works out to 0.31kWh of purchased electricity per gallon.

 

[Norbert]

But why would you be interested only in external electricity? The other forms of energy may be processed with even worse negative effects.

 

[JRP3]

If we are talking about the load on the grid of EV's then only grid purchased electricity goes towards compensating the load of EV's. This is specifically in reference to Elon saying that if we stop refining oil we have enough electricity to power EV's. You can't use the figure of 5-7kwh per gallon to make that claim.

 

[Norbert]

In the case of NG, if the same NG is used in a power plant, it may be processed more effectively. I'd consider that the likely case. I wouldn't interpret anything in this context needlessly literally, as it is as complex as you want it to be... if you consider more and more details. But that would't make it more accurate.

 

[stopcrazypp]

But why would you be interested only in external electricity? The other forms of energy may be processed with even worse negative effects.

I don't think refineries have to report internal electricity use (self generated), plus the grid probably doesn't see it, as JRP3 mentions. The closest thing you can do is to take all the inputs (natural gas and coal, etc.) to the refinery and calculate how much electricity can be made from that.

But no matter how you do the calculation, the 6-7.5 kWh number can't be used directly as the electricity number. That is only the "energy" number, which doesn't include generation losses. If you assume 40% conversion efficiency to make electricity, you end up with 2.4-3 kWh.

 

[Norbert]

I don't think refineries have to report internal electricity use (self generated), plus the grid probably doesn't see it, as JRP3 mentions. The closest thing you can do is to take all the inputs (natural gas and coal, etc.) to the refinery and calculate how much electricity can be made from that.

That's what I'd think Argonne National Laboratories have already done in their report.

EDIT: Well, not exactly, but then you have other things like nighttime electricity etc. You can't get the calculation right by pulling just one spaghetti from the plate, even though if you actually do it, you will eventually have the whole mess.

 

[Norbert]

I got a bit distracted. My point regarding JRP3 would be that counting only external electricity isn't enough (not even regarding Elon's statement, as opposed to regarding a CO2 calculation).

 

[Norbert]

If you assume 40% conversion losses to make electricity, you end up with 2.4-3 kWh.

By which calculation ? Assuming the total energy inefficiency is 6 kWh (refining only), and a part of that is already external electricity, you'll have more than 4 kWh.

 

[Norbert]

Personally, I think 83.3 % efficiency is the number to use (since we want to get away form oil in general, those "less desirable" products are probably not really something we want, referring to the ANL report). Using 33.6 kWh per gallon as energy equivalent, this results in about 6.7 kWh. If 2 kWh of that is eternal electricity, and if 40% conversion loss is correct, the result would still be 4.8 kWh.

 

[stopcrazypp]

Personally, I think 83.3 % efficiency is the number to use (since we want to get away form oil in general, those "less desirable" products are probably not really something we want, referring to the ANL report). Using 33.6 kWh per gallon as energy equivalent, this results in about 6.7 kWh. If 2 kWh of that is eternal electricity, and if 40% conversion loss is correct, the result would still be 4.8 kWh.

Sorry, it should be 40% conversion efficiency, not 40% conversion loss (post edited to reflect this). I'm taking this from average efficiency of natural gas plants in the US.

 

[Norbert]

Sorry, it should be 40% conversion efficiency, not 40% conversion loss (post edited to reflect this). I'm taking this from average efficiency of natural gas plants in the US.

Your calculation would still be missing the fact that part of it is already (external) electricity. The low 40% conversion *efficiency* (it said *loss* in your original post) is probably the result of having old plants. It seems new modern plants would/could indeed achieve 60% efficiency:

Fossil-fuel power station - Wikipedia, the free encyclopedia

One type of fossil fuel power plant uses a gas turbine in conjunction with a heat recovery steam generator (HRSG). It is referred to as a combined cycle power plant because it combines the Brayton cycle of the gas turbine with the Rankine cycle of the HRSG. The thermal efficiency of these plants has reached a record heat rate of 5690 Btu/(kW·h), or just under 60%, at a facility in Baglan Bay, Wales.[5]

So we are back to 4.8 kWh (unless the assumed 2 kWh external electricity is too high).

 

[vfx]

I really don't care if the numbers are precise or not.

If I tell someone I want my electricity back and blame the oil companies for taking it (which they do) it make the other person think.

Let the oil companies make the convoluted arguments about energy, electricity, and KWh.

I have already won the message with a short thought provoking opener. A math argument will loose every time with the general public.

 

[stopcrazypp]

Your calculation would still be missing the fact that part of it is already (external) electricity. The low 40% conversion *efficiency* (it said *loss* in your original post) is probably the result of having old plants. It seems new modern plants would/could indeed achieve 60% efficiency:
Fossil-fuel power station - Wikipedia, the free encyclopedia
So we are back to 4.8 kWh (unless the assumed 2 kWh external electricity is too high).

The external electricity, as I pointed out doesn't make a huge difference (0.31 kWh per gallon or ~5% of the total energy 6 to 7.5kWh losses from refining). The reason I use 40% average for natural gas is to keep in the spirit of the analysis (which looks at refining efficiency nationwide, not just the newest, most efficient refineries in operation).

Average efficiency of fossil fuel plants in the US (2009):
Coal - 32.8%
Petroleum - 31.2%
Natural Gas - 41.8%
http://www.eia.doe.gov/cneaf/electricity/epa/epat5p3.html
(efficiency in percentage can be figured by dividing 3,412 by the associated heat rate in the link above; see link below for details)
http://www.eia.gov/tools/faqs/faq.cfm?id=107&t=3
Notice natural gas has been steadily improving, while coal and petroleum plants have stayed the same; seems to reflect the trend that most new plants built are natural gas plants.

The ANL link I gave should have most of the necessary data to figure out the total electricity that can be made from all the feedstocks to make gasoline. The only missing data is the conversion from the feedstock to electricity. I've tried to do a rough analysis (back when I first posted that ANL link) taking into account the external electricity, and also the electricity that can be made from the natural gas, steam, and coal feedstocks, but ended up with only about 1kWh.

 

[Norbert]

The external electricity, as I pointed out doesn't make a huge difference (0.31 kWh per gallon or ~5% of the total energy 6 to 7.5kWh losses from refining).

I missed that you already had a number for that, and didn't expect it to be that low. (I didn't follow those previous discussions at that level of detail since, I think, at that time I already thought it would be better to use solar energy in combination with EVs as the more valid scenario. Recent price developments in solar seem to confirm that view. See also my post from Nov 18, 2009 in this thread).

But, if you go that far, why do you stop at that point (at refineries) instead of going further and including electricity that is available in the night (off peak), for example?

The reason I use 40% average for natural gas is to keep in the spirit of the analysis (which looks at refining efficiency nationwide, not just the newest, most efficient refineries in operation).

I don't see why you would think that using averages including old plants would be more in some "spirit". If 60% efficiency to process that NG is possible, then I don't see a reason not to actually do this. The idea isn't to keep wasting the energy except to use it for EVs. I'm talking about the possible future reality, not about a restricted thought experiment.

Average efficiency of fossil fuel plants in the US (2009):
Coal - 32.8%
Petroleum - 31.2%
Natural Gas - 41.8%
http://www.eia.doe.gov/cneaf/electricity/epa/epat5p3.html
(efficiency in percentage can be figured by dividing 3,412 by the associated heat rate in the link above; see link below for details)
http://www.eia.gov/tools/faqs/faq.cfm?id=107&t=3
Notice natural gas has been steadily improving, while coal and petroleum plants have stayed the same; seems to reflect the trend that most new plants built are natural gas plants.

As far as I can tell from the ANL study right now, coal isn't used, but very much something called "still gas"...

The ANL link I gave [...]

That's the same or similar one I referred to in Nov 2009 in this thread.
In my Feb 27, 2011 post in this thread I added a link to the updated 2010 version of that report.

[...] should have most of the necessary data to figure out the total electricity that can be made from all the feedstocks to make gasoline. The only missing data is the conversion from the feedstock to electricity. I've tried to do a rough analysis (back when I first posted that ANL link) taking into account the external electricity, and also the electricity that can be made from the natural gas, steam, and coal feedstocks, but ended up with only about 1kWh.

I'm not sure what you refer to as 1 kWh at the end, but I can now see how you would arrive at 2.4 to 3 kWh, even though I would still arrive at a larger number (probably closer to 4% than to 3%, at least if "still gas" could be processed as effectively as NG).

BTW, if the average of US NG plants is 40%, I'm wondering whether the older ones should be upgraded to 60% as soon as possible.

And once more, it should be pointed out that the long tail pipe argument is most often mentioned in the context of CO2 production, and in that context, the number of around 6.7 kWh for the amount in refineries which corresponds to CO2 production of electricity for EVs, still seems the closest estimate.