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How much electricity to produce gasoline?

Discussion in 'Energy, Environment, and Policy' started by Brent, Aug 24, 2007.

  1. Brent

    Brent Member

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    Every long tailpipe argument I've heard revolves around the idea that electrical generation for EVs emits pollution, perhaps nearly as much as burning gasoline. These arguments may ignore the amount of electricity that the production of gasoline itself requires. I don't know. I've yet to see a study that itemizes the total energy costs of putting a gallon of gasoline into a tank.

    One site* -- with self-described apples to oranges comparisons -- puts the electrical usage at about 12kW per gallon. Could this number be correct? If so, it would seem that the long tailpipe argument fails right there: 12kW will probably propel an EV at least as far as a gallon of gasoline would an ICE, while with an EV the extra carbon emissions of burning the gasoline are avoided.

    *Emissions
     
  2. TEG

    TEG TMC Moderator

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    I tend not to get too involved in the math of these figures because there are plenty of published reports and such.

    But with that said, here are some things off the top of my head:

    Electric motors are far more efficient. Typically EVs get the equivalent of over 100MPG, so when you do comparisons you have to keep in mind that the EVs make better use of the energy they get.

    The Tesla Roadster stores a bit more than 50kWh in the pack, and can go a bit more than 200 miles on that charge. That works out to about four miles per kWh.

    I have heard that 50kWh is approx energy equivalent of 2 gallons of gasoline.
    So a gas powered Roadster getting maybe 30MPG would only be able to go about 60 miles on the same amount of energy as the Roadster uses.

    That suggests that the Tesla Roadster is over 3 times more efficient than an equivalent ICE only car based on their use of their stored energy.

    The math done that way matches up simply with Tesla's quoted 135MPG equivalent as compared to a gas car with only 30-40MPG.

    So, an EV is likely to have a big energy use advantage even if it took more energy to get the electricity than it took to get the gasoline.

    I have heard some disturbing quotes as to how much oil it takes to find, extract, refine, and transport a gallon of gas to your car. I think it is a rather wasteful process.

    If you look at Wind or Solar power, the cost associated with it is more of a one time expense to mine the materials, build the power generating system, transport it and install it. Once it is in operation you then get basically "free" power for the useful life of the generator. Some people will argue that it takes a substantial amount of oil to actually get the materials and make a full solar system capable of running a house and/or powering an EV. The best data I have seen seems to suggest that a solar system will easily make more electrical energy in its lifetime than the resources used to create it in the first place, but I am sure some people will continue to debate that.
     
  3. Brent

    Brent Member

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    #3 Brent, Aug 24, 2007
    Last edited: Aug 24, 2007
    Thanks, TEG.

    I haven't been successful in finding a good reference to how much energy it takes to put a gallon into one's tank, but whatever it is, it seems to be significant:

    Allegation without backup reference.

    In 1997, petroleum extraction (not refining) used 1.5 percent (3,700GWh) of total electrical usage in California.


    Refining used 7.9 percent of Norway's energy (including natural gas, I'd think) output in 2000.

    By contrast, oil refining may use electricity less than aluminum smelters.

     
  4. TEG

    TEG TMC Moderator

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    By the way, I think I heard that pumping water around the state is the biggest single use of electricity.
     
  5. tonybelding

    tonybelding Active Member

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    Aluminum is a bit of a special case. You never find aluminum metal in nature, it's only aluminum oxide (in bauxite). To separate out the aluminum metal requires an electrical process similar to producing hydrogen with electrolysis. (This is also true of titanium metal, I'm pretty sure.) The process is reversible, so you can actually create a battery that oxidizes the aluminum to produce electricity, much the same way a fuel cell produces electricity from hydrogen.

    This is why aluminum recycling has been so successful. Melting down metallic aluminum and reshaping it requires a lot less energy than producing new aluminum from ore. It doesn't require breaking any strong molecular bonds.

    Somebody a while back floated a plan to ship energy over the ocean in the form of aluminum ingots. Say your country has lots of clean hydro and geothermal energy -- like Iceland, for example. You could use it to create aluminum ingots, load them on a ship, and sail them to NYC. There they could be "burned" in aluminum batteries to produce electricity for the grid. Then the ship load of aluminum-oxide sludge could be sailed back to Iceland for recycling into fresh metal ingots.

    It was an interesting idea, but I'm pretty sure the economics of it didn't add up.
     
  6. Cobos

    Cobos S60 owner since 2013

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    Do keep in mind that for most of the oilplatforms in the North Sea they've produced a lot of CO2 while they are extracting the oil. I'm not including the resource cost of actually building the huge concrete and metal structure. For most of our oil-only platforms any LNG is burned off in a generator that produces all the power the platform needs. The problem is usually that there is not enough LNG to make it worthwhile to "produce" LNG, but they need it removed to get to the oil.Thus the platform burns off or release the excess LNG into the atmosphere. Just that should be enough to increase the energy consumption in producing oil quite a bit. Unfortunately I can't find any exact figures.

    Cobos
     
  7. malcolm

    malcolm Active Member

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    Refinery energy consumption

    I felt this was worth posting as a separate thread:

    EV WORLD: America's Irrational Petroleum Dependence

    I'm not sure about the accuracy of these figures but the gist is why use energy to refine oil into gasoline (or urine into hydrogen) when EVs allow you to cut out the inefficiencies inherent in any fuel-making step.

    Using the figures above, the Roadster could travel about 10 miles on the energy diverted from the pointless refining of one US gallon.
     
  8. vfx

    vfx Well-Known Member

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    Would be nice to have this as an accurate number handy.

    We have been looking for this number for a while now.

    How much energy does it take to produce a gallon of gasoline?
    Well to wheel?
    Refinery only?


    And on a secondary note that came up in biofuel discussions:
    How much water is used to make a gallon of gasoline?
     
  9. Brent

    Brent Member

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  10. vfx

    vfx Well-Known Member

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    Last paragraph:

    That just raw kWhr to gasoline conversion a *some* MPG rating. What about adding in all the other MPG vs Electric transportation efficiencies as well?

    I would also like proof of that last statement.
     
  11. Tdave

    Tdave Member

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    #11 Tdave, Jul 11, 2009
    Last edited: Jul 11, 2009
    12.5 kWh consumed just to process/refine a gallon of gas represents $1.375 of the cost for that gallon of gas (assuming 11 cents per kWh). That seems far too high to me.

    I've seen figures that say refining adds 27 cents to the price of a gallon of gas. At 11 cents per kWh, that would translate to 2.45 kWh for refining. Rough estimate by working backwards.
     
  12. Palpatine

    Palpatine Banned

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    Large commercial customers of electricity pay less than the standard residential rate. They operate 24 hrs per day so they use a lot of off peak electricity also.

    I don't claim to know the numbers or anything. But that could account for part of the difference.
     
  13. Tdave

    Tdave Member

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    #13 Tdave, Jul 12, 2009
    Last edited: Jul 12, 2009
    You're absolutely right. Using the average 6.84 cents per kWh industrial electric rate from that table...

    And a Google search tells me that refining costs could be 27, 33, or 48 cents ...

    27 cents for refining / 6.84 cents per kWh = 3.9 kWh for refining.
    48 cents for refining / 6.84 cents per kWh = 7.0 kWh for refining.

    The 12 kWh figure still seems to be about twice reality.

    Still, with 7 kWh, we can go 25 miles in our Teslas, on just the electricity used to refine the gallon of gas that a combustion engine car uses to go the same distance.

    That's a great sound bite!
     
  14. Brent

    Brent Member

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    It really eviscerates the long tailpipe argument, which was my hope all along...
     
  15. BBHighway

    BBHighway Member

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    It also completely destroys the argument that the gird can't possibly handle electric cars. If there's enough electric power to run all the refineries, then there is enough to handle all the electric cars.
     
  16. DRM

    DRM Roadster #619

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    The problem here is that the grid must distribute that power. I don't think there's ever been an argument that electrical generation was insufficient to charge electric vehicles, only that the distribution system (the grid) wasn't up to the task (especially during peak hours). The new 2010's should represent the first step in a system-level solution for smart-grid EV charging .... I'm really looking forward to seeing how this plays out.

    //dan.
     
  17. vfx

    vfx Well-Known Member

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    No one will believe us...


    eeyore.jpg
     
  18. Palpatine

    Palpatine Banned

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    If everyone just switched to CFL bulbs it would reduce electricity consumption by 20%. That is almost enough to cover everyone recharging an EV at night.

    There are numerous ways to reduce electricity consumption with no loss in quality of life. I don't consider EVs load on the grid to be an issue at all.
     
  19. BBHighway

    BBHighway Member

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    I have seen many arguments that electric cars will overload the grid. Typically the argument is that we already have rolling brownouts and blackouts and having cars plugged in will only make it worse. Most people don't differentiate between electricity generation and distribution, they just worry that there is not enough extra power available for plug in cars.

    In reality, since it will take many years for electric cars to become a significant portion of the vehicles on road there will be plenty of time for the electric grid to adapt. Being able to say that there will be no net increase in electric power consumption could help alleviate people's fears.
     
  20. Brent

    Brent Member

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    Here's an intriguing response I picked up from the Climate Progress blog when I posed the same question:

    My WorldChanging “Attention Grant” — David MacKay’s “Sustainable Energy — Without the Hot Air” « Climate Progress
     

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