Diesel vs. Hybrid

Discussion in 'Gen 2 Prius Fuel Economy' started by briloop, Aug 30, 2007.

  1. Jonnycat26

    Jonnycat26 New Member

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    <div class='quotetop'>QUOTE(IsrAmeriPrius @ Sep 3 2007, 01:50 PM) [snapback]506353[/snapback]</div>
    I didn't realize they had one. :)

    I'm just saying that all things being equal, the Jetta TDI isn't built for economy. It achieves its milage despite the disadvantages it has, not because of any advantages VW engineering have given it.
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    <div class='quotetop'>QUOTE(Jonnycat26 @ Sep 2 2007, 09:07 PM) [snapback]506149[/snapback]</div>
    That's pretty close in weight. VW must be using just as much lightweight materials (or the weight is for a stripped out version).
     
  3. Jonnycat26

    Jonnycat26 New Member

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    <div class='quotetop'>QUOTE(Tideland Prius @ Sep 3 2007, 02:04 PM) [snapback]506363[/snapback]</div>
    Not really... and not sure where the Jetta #s came from. According to Edmunds, the Jetta weighs 3230 and the Prius weighs 2932. That's nearly 300 pounds difference, which is like carrying a full sized adult and a half dozen bowling balls in a Prius at all times.

    Jetta Specs:
    http://www.edmunds.com/new/2008/volkswagen...4386/specs.html

    Prius Specs:
    http://www.edmunds.com/new/2007/toyota/pri...7218/specs.html
     
  4. patsparks

    patsparks An Aussie perspective

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    <div class='quotetop'>QUOTE(IsrAmeriPrius @ Sep 4 2007, 03:20 AM) [snapback]506353[/snapback]</div>
    You have got to be kidding??
    Volkswagen are doing their best to create a reputation for UNreliability. VWs appear on several lines of the least satisfied vehicle owners cars while Toyota and particularly the Prius appear at the point end of the most satisfied owners survey results. I think VW are trading on their German car reputation even for the models that are made outside of Germany.

    These figures you quote are most likely coming from very same people who gave us the Prius uses more energy than a Hummer crap. If this was true wouldn't exxon be loving the stuff?
     
  5. donee

    donee New Member

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    Hi Madler,

    You might be right on soy beans. But I doubt it. I read one place that Rape-Seed biodiesel production yeilds three times the energy as put into it. Are you considering that the non-oil parts of soy are still used for food ? On corn and ethanol, at one time there was less than a 1.0 energy yield, but most likely now they are a little beyond 1.0, with distilation energy recovery and probably other techniques (geothermal, and waste power plant heat for distilation energy).

    But, even if you were right, Soy Beans would be planted anyway. For two main reasons since long before bio-fuels craze. It breaks up the insect cycle when rotated with corn. And Soy re-fertilzes the soil in the cheapest way possible. Soy nitrogen fixes atmospheric nitrogen into the soil. If it was not rotated with corn, that nitrogen would come from petro-chemical fertilizers.
     
  6. IsrAmeriPrius

    IsrAmeriPrius Progressive Member

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    <div class='quotetop'>QUOTE(patsparks @ Sep 3 2007, 03:32 PM) [snapback]506444[/snapback]</div>
    I was. I thought that the sarcasm of my remark was obvious.

    B)
     
  7. patsparks

    patsparks An Aussie perspective

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    <div class='quotetop'>QUOTE(IsrAmeriPrius @ Sep 4 2007, 09:08 AM) [snapback]506478[/snapback]</div>
    Thankyou, just some people post like that and they are serious. Unfortunately we live in a world full of silly people. I count myself as one and I think a few here count me as one too. So I don't agree with everyone here, what is it the yanks keep going on about, the second ammendment or some such? You know the law you have to quote if you want to speak freely.
     
  8. donee

    donee New Member

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    Hi again Madler,

    Ethanol in fuel was never intended to be an energy source. This is a perversion of the original benefit of Ethanol for political purposes. Ethanol is there as a chemical to improve oxidation. And its an expensive one too.

    It would be better to replace all the Ethanol with a higher fraction of Butanol. Energy content would be similar to gas, and the energy yeild from the bio source would be higher for similar inputs. The only issue is the amount of oxidative capability would decrease per bushel of corn (or other bio matter). But, it should pay for itself, unlike Ethanol.
     
  9. IsrAmeriPrius

    IsrAmeriPrius Progressive Member

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    <div class='quotetop'>QUOTE(patsparks @ Sep 3 2007, 04:45 PM) [snapback]506485[/snapback]</div>
    Close but no cigar. The Second Amendment allows us to arm ourselves silly. The First Amendment permits us to make fools of ourselves.

    Just in case you are curious, here is our Bill of Rights:
     
  10. patsparks

    patsparks An Aussie perspective

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    Thanks, the second was another argument I was having.
    Twas the first one
     
  11. madler

    madler Member

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    <div class='quotetop'>QUOTE(donee @ Sep 3 2007, 04:24 PM) [snapback]506469[/snapback]</div>
    Yes, rapeseed may work -- you can get more biodiesel per unit land from than than soy. I have seen figures of 2:1 to 3:1, though those figures are from the biodiesel proponents. I have not seen an independent analysis for the energy benefit of rapeseed.

    That study did in fact consider that (the reference is linked in my post). However proponents argue that that study did not count enough of the input energy towards the soybean meal and glycerin, and counted too much to the biodiesel. Accounting is often tricky when two or more things benefit from the same source.

    I sure hope so. I eat and drink a fair bit of the stuff. The question is whether you start growing more soy because the demand for biodiesel makes it economically worthwhile. If the energy balance is in fact negative, then it can only be worthwhile if the government subsidizes it. That's the part that worries me, since that's exactly what they're doing with the ethanol from corn.
     
  12. madler

    madler Member

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    <div class='quotetop'>QUOTE(patsparks @ Sep 3 2007, 03:32 PM) [snapback]506444[/snapback]</div>
    Um, no, the figures are coming from a professor at Cornell that is in the business of analyzing the energy requirements of food production. It was a small step to analyze the energy required to make biodiesel, as compared to it's energy output. The link to the reference is in the post.

    The motivation is that of an environmentalist that doesn't want to see the situation made worse by something that sounds like a good idea, but for which the calculations haven't been done thoroughly enough. So I don't get the Hummer connection.

    I also can't figure out your Exxon comment. Loving what stuff why?
     
  13. patsparks

    patsparks An Aussie perspective

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    <div class='quotetop'>QUOTE(madler @ Sep 4 2007, 10:13 AM) [snapback]506520[/snapback]</div>
    If energy in was greater than energy out wouldn't Exxon be promoting biofuels to increase energy consumption therefore increase their bottom line? Even if the energy used is not oil it would increase demand for energy in general driving up the demand and price of oil. More profit for oil companies!

    How do the numbers stack up with canola oil biodiesel and sugar cane ethanol? These are the green products being used in Australia. Maybe it's a case of the negative effect until the technology advances to a greener state. You know, like how early Prius when considering developement energy consumption was more energy hungry than a Hummer. :~
     
  14. coloradospringsprius

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    <div class='quotetop'>QUOTE(Jonnycat26 @ Sep 3 2007, 06:08 PM) [snapback]506436[/snapback]</div>
    Thanks for providing that link, which shows that the Jetta is now rated at only 29 mpg on the highway - only 64.4 percent of the Prius' 45 mpg highway rating. Funny how those 300 extra pounds and wider tires cause a 35.6 percent decrease in mpg!

    But that's going from the Prius to the Jetta. Using the Jetta as the baseline, the Prius gets 55 percent better mpg on the highway than the Jetta. I think that fulfills the requirements of an apples-to-oranges comparison. Obviously no one would use the Jetta as an example of a car that gets comparable mpg to the Prius.

    And that's highway mpg. If one wanted to make the comparison really ugly, one could use the city mpg ratings.
     
  15. Jonnycat26

    Jonnycat26 New Member

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    <div class='quotetop'>QUOTE(coloradospringsprius @ Sep 3 2007, 10:58 PM) [snapback]506583[/snapback]</div>
    That's the non-diesel jetta. :(

    I thought you'd read that bit... the 2008 diesel jetta hasn't been rated yet, but it's supposed to have better mileage than the older TDI, and the weight should be similar to the 2.5.
     
  16. RobH

    RobH Senior Member

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    <div class='quotetop'>QUOTE(madler @ Sep 2 2007, 09:19 PM) [snapback]506158[/snapback]</div>
    This argument holds if you are producing diesel with diesel. It breaks down when you produce a different product than the original.

    Consider the hypothetical example of putting 1000 units of dyno-diesel in, and getting 800 units of biodiesel back. A dirty fuel has been converted to a clean fuel, and that 20% energy loss is the same magnitude that we already pay for pollution control equipment.

    Next consider the example of putting 1000 units of ocean wave energy into a process that yields the same 800 units of biodiesel. The ocean wave energy was useless in its original form, but valuable as the liquid fuel biodiesel.

    In Prius terms, the energy return from regenerative braking is quite inefficient. But the alternative is to lose all of the energy, instead of just a portion.

    In general, energy lost in a conversion is worthwhile if the result of the conversion is a more desirable product. It's just the cost of producing the final product.

    ...

    The energy cost of imported oil products is understated. For example, the cost of our military presence in Iraq is cost shifted from oil prices to general taxes.

    Our oil wars should be financed with gas taxes.
     
  17. madler

    madler Member

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    <div class='quotetop'>QUOTE(patsparks @ Sep 3 2007, 05:55 PM) [snapback]506527[/snapback]</div>
    Ah, I see. No, Exxon would not invest in something that will turn out to be a net energy loss, since they can't keep the wool pulled over everyone's eyes forever. Instead Exxon is working on biofuels that could possibly turn out to be net energy winners, since they plan to make money off of successful biofuels -- not dead-end biofuels. A company with that much money is planning for several alternate futures, including one in which their oil gets too expensive, or futures with heavy carbon emission penalties, or both. They're not stupid you know.

    Sugar cane ethanol is a loss. Though another poster indicated that the purpose of the ethanol was not to just produce energy, but to better burn the gas it's mixed with by providing a little oxygen. I don't know if that effect counters the energy inefficiency of the sugar cane source.

    Canola oil (rapeseed) may be a win with claims of 2:1 to 3:1 energy out to energy in, but I haven't seen an independent study of that.
     
  18. madler

    madler Member

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    <div class='quotetop'>QUOTE(RobH @ Sep 3 2007, 08:39 PM) [snapback]506602[/snapback]</div>
    Huh? You burned 1000 units of the dirty fuel when you could have instead burned 800 units of dirty fuel by skipping the biodiesel step. Either with or without emission control, you're behind the game on all pollutants. There is no way that burning the 800 units of biodiesel will suck any of the 1000 units of pollutants back out of the atmosphere.

    If the ocean wave energy was useless in its original form, then how did the biodiesel farmer use it? Why couldn't someone else have used that energy instead, resulting in less carbon dioxide emission from a power plant? Unless you have a carbon-free energy system, someone somewhere is emitting carbon dioxide in order to let you use that energy to instead make biodiesel at a net energy loss (i.e. no benefit from the solar energy that the crop is collecting). I'm not seeing how this can be a win.
     
  19. jweale

    jweale Junior Member

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    <div class='quotetop'>QUOTE(RobH @ Sep 3 2007, 11:39 PM) [snapback]506602[/snapback]</div>
    Biodiesel is not an inherently cleaner fuel compared to a modern low sulfer diesel. The particulate and NOx emissions are inherent to the diesel engine's operation. Even with biodiesel you have the same high temperature lean operation that both produces NOx and soot and results in O2 in the exhaust that sacrificially protects the NOx from catalytic reduction. And a catalytic converter can't touch elemental carbon - that pretty much has to be mechanically filtered. Diesel pollution control equipment, such as soot filters, carries a significant back pressure efficiency penalty. And the NOx spewing high temperature operation is integral to the diesel's high cycle efficiency potential.

    Bio-diesel is great stuff, but once it has been generated I've never heard of it being categorically cleaner at the final tailpipe. A bit lower soot but higher NOx. Eggheads are certainly cranking to make it better, but the same is true of dino formulations.

    If it were cleaner at the tailpipe and offered the benefit of centralized combustion of the diesel allowing better source pollutant capture, ala' electrical power plants treating exhaust better than a million individual cars, then a 1:0.8 input dino-diesel:eek:utput biodiesel might be a win. Unfortunately, it's not cleaner at the tailpipe, nor is the production consumption of dinodiesel cleaner (actually, biofuel consumes diesel in poorly controlled off-road farm vehicles, with regulated emissions significantly worse than burning it in a Hummer).

    More optimistically, it certainly looks like biodiesel can be made in a net energy positive cycle. It's just not a no-brainer to do so. Check out Brazil for a real bio-fuel success story; around a third of their auto fuel comes from a very net-positive sugar to ethanol industry.
     
  20. patsparks

    patsparks An Aussie perspective

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    Why do you call it dino diesel when it comes from fishes and things like that not dinosuaurs?
     
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