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Detroit, 12:13 PM
Tue Nov 24
24 posts in the last 24 hours

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  • posts about #wheels more →

    Study Says Air Cars Are Inefficient

    Group Wants Government to Jump-Start the E.V. Revolution

    A Battle in Canada Over Idling at Drive-Throughs

    Graham Nearn, Founder of Caterham Cars, Is Dead

    Auto Dealers Challenge California's Tailpipe Climate Regulation

    Audi to Build e-tron Electric Supercar

    Design Firm Known for Exotics Turns to Hybrids and Hatchbacks

    E.P.A. Says M.P.G. for Electric Cars and Plug-in Hybrids Are a Work in Progress

    New App Connects iPhone to In-Dash GPS

    Alcohol Interlocks Are Gaining Traction
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    Dsmvwl  Admin  Promote to frontpage Approve user Ban user ×
    Image of Flathead Smith Flathead Smith
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    Let's see here, the change in internal energy of a system, measured from state one to state two, is equal to:

    ΔU=αRn2T2- αRn1T1=αR(n2T2- n1T1)

    At the same time, the work done by the pressure-volume changes as a result from this process, is equal to:

    W= ∫ P dV

    Since the process is not adiabatic......

    Dammed that 2nd Law of Thermodynamics,… who ever it was that invented that, needs to come up with something more useful. I'm going to write the President and Congress and ask them to have it outlawed.
     Reply
    Flathead Smith was starred Flathead Smith was unstarred
    Image of Van Sarockin, rogue trebuchet Van Sarockin, rogue trebuchet
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    But in breaking news, what will stew your goat, is that Tesla is readying an IPO.
     Reply
    Van Sarockin, rogue trebuchet was starred Van Sarockin, rogue trebuchet was unstarred
    Image of pres pres
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    Breaking: the snozzberries taste like snozzberries.
     Reply
    pres was starred pres was unstarred
    Image of DoctorNine DoctorNine
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    It's dead as a primary energy store. We've known that for years. This is hardly news. Where it shines though, is kinetic energy recapture. Particularly on heavy vehicles.

    As usual, Berkeley points its beady little eyes at the tail of the snake sticking out of the hole, and pronounces that it is passing small, and therefore may be disregarded.

    Aren't they cute?
     Reply
    Edited by DoctorNine at 11/20/09 4:07 PM DoctorNine was starred DoctorNine was unstarred
    Image of Van Sarockin, rogue trebuchet Van Sarockin, rogue trebuchet
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    Maybe so, but I'm glad some folks are giving it a try.
     Reply
    Van Sarockin, rogue trebuchet was starred Van Sarockin, rogue trebuchet was unstarred
    Image of Elhigh Elhigh
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    I've read it before, that for capacity vs weight, compressed air isn't that good. If I could point to one thing that kinda makes up for the lack, the exhaust air is actually cooler than ambient temperatures, so right there you've got AC.
     Reply
    Elhigh was starred Elhigh was unstarred
    Image of weatherman weatherman
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    I thought compressed air was supposed to be very efficient for energy storage. The article only points to a figure of energy density, which is apples-to-oranges. As for being more or less efficient than electric, it seems to me that efficiency isn't the only issue - there's also cost, infrastructure, and weight issues, for instance. I'm sure this kid knows what he's talking about - having an engineering degree from Berkeley I would certainly hope he does, but from what I've read and seen about these vehicles there are a lot of advantages.
     Reply
    weatherman was starred weatherman was unstarred
    Image of nataku8_e30 nataku8_e30
    11/20/09

    @weatherman: I would think that compressed air is pretty inefficient, and if you're using an electrical air compressor - you're comparing the efficiency of the compression stage (lots of heat generated here) and then the expansion stage (some energy lost here as well, since the "exhaust" air is moving pretty quickly, and all of that energy is inefficiency) vs. the efficiency of a battery, which is really pretty good these days. The other issue is going to be weight savings - is the air system going to be substantially lighter than a similar range electric system? That could offer some major efficiency gains.
     Reply
    weatherman promoted this comment nataku8_e30 was starred nataku8_e30 was unstarred
    Image of weatherman weatherman
    11/20/09

    @nataku8_e30: you're probably right about generating the pressure. I guess I was only thinking of storing and releasing the energy. As for the weight issues though, all the stuff I've seen on these air cars suggests that the engines are very light and the weight of the "fuel" is about the same as a gasoline engine. Now, it won't take you near as far as gas, but I think for the same range on battery you'd need something weighing 2-4x as much.

    #tips
     Reply
    weatherman was starred weatherman was unstarred
    Image of skierpage skierpage
    11/20/09


    @nataku8_e30: Right. You have to remove the heat during the compression stage, otherwise your hot high pressure tank cools to have all the stored energy of a farting balloon; this takes energy (and/or time). Also the cooling as the air rapidly expands in the car is wasted energy unless you run the air through some kind of intercooler. In theory you can use the heat from pumping up (to warm the bathrooms in air car pump stations?) and use the cooling from the engine as air conditioning, but overall the efficiency kills.

    The badly-written Wikipedia article cites claims that compressed-air cars are at best 14% efficient, and that a 5-minute re-pump would require a 1 MegaWatt compressor. It's hard to overcome over the inefficiency, even if batteries weigh 500 pounds.

    MDI has an AirPod car putt-putting around France and still claims Tata Motors will use the technology.
     Reply
    skierpage was starred skierpage was unstarred
    Image of nataku8_e30 nataku8_e30
    11/20/09

    @skierpage: There is one big advantage to this, though. With a decent regulator, I'd have all the air I need to run my spray gun, vacuum pump, impact wrench, sand blaster, or any other air tools i end up buying. My 2hp compressor kind of blows.

    (sorry)

    #tips
     Reply
    nataku8_e30 was starred nataku8_e30 was unstarred
    Image of smalleyxb122 smalleyxb122
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    If by "relatively inefficient", he means "incredibly inefficient", I agree with his findings.
     Reply
    smalleyxb122 was starred smalleyxb122 was unstarred
    Image of KeyserSoze KeyserSoze
    11/20/09

    @smalleyxb122: Now you're just splitting hairs... :-)
     Reply
    DoctorNine promoted this comment KeyserSoze was starred KeyserSoze was unstarred
    Image of that ain't the way to have fun, son that ain't the way to have fun, son
    11/20/09

    In reply to Study Says Air Cars Are Inefficient
    Yep, just like ethanol, it's less-efficient than good ol' dead dinosaurs.

    While the ICE is only 'bout 20% efficient, +/-, but it's still better than most anything else which gives similar range/performance.

    Now where's my Mr. Fusion?!
     Reply
    that ain't the way to have fun, son was starred that ain't the way to have fun, son was unstarred
    Image of KeyserSoze KeyserSoze
    11/20/09

    @that ain't the way to have fun, son: Doc Brown's borrowing if for a while. He'll be back last week.
     Reply
    AmishJohn promoted this comment KeyserSoze was starred KeyserSoze was unstarred
    Image of Xelmon Xelmon
    11/18/09

    In reply to Group Wants Government to Jump-Start the E.V. Revolution
    Yeah... As long as there is oil and greed on this planet, it's likely not going to happen. =\
     Reply
    Xelmon was starred Xelmon was unstarred
    Image of AynRandian AynRandian
    11/18/09

    @Xelmon: Oil and greed? Are you sure you didn't mean good economic sense?
     Reply
    Xelmon promoted this comment AynRandian was starred AynRandian was unstarred
    Image of Xelmon Xelmon
    11/18/09

    @AynRandian:
    Eh? ...
    *reads*

    Oh wait what!? The big guys are saying that the gov't should do something??

    Err, my bad, that's different. That may actually go somewhere!
     Reply
    Xelmon was starred Xelmon was unstarred
    Image of skierpage skierpage
    11/12/09

    In reply to A Battle in Canada Over Idling at Drive-Throughs
    Just restrict the drive-through lane to cars with a stop-start feature, hybrids, and battery-electric vehicles. It's in the bible - "Idling cars are the devil's playthings"!

    Or as @GreenN_Gold: says, put a slope in the lane so everyone can coast through (banging into the rear bumper of the car in front). #wheels
     Reply
    skierpage was starred skierpage was unstarred
    Image of GreenN_Gold GreenN_Gold
    11/12/09

    In reply to A Battle in Canada Over Idling at Drive-Throughs
    If I'm expected to turn my engine off while in the drive through, then I expect the drive through to be downhill. Seems like a reasonable trade off. Call me when all the drive throughs are downhill. #wheels
     Reply
    GreenN_Gold was starred GreenN_Gold was unstarred
    Image of that ain't the way to have fun, son that ain't the way to have fun, son
    11/12/09

    In reply to A Battle in Canada Over Idling at Drive-Throughs
    But with the engine off, you don't have no heat, eh....

    Take off.... #wheels
     Reply
    that ain't the way to have fun, son was starred that ain't the way to have fun, son was unstarred
    Image of powermatic powermatic
    11/12/09

    In reply to A Battle in Canada Over Idling at Drive-Throughs
    Hope this doesn't draw needed resources from The Great Moose War. #wheels
     Reply
    powermatic was starred powermatic was unstarred
    Image of Maymar Maymar
    11/12/09

    In reply to A Battle in Canada Over Idling at Drive-Throughs
    I sometimes turn my car off sitting in the drive-through lane. Of course, that's because it's an overheating piece of shit. #wheels
     Reply
    Maymar was starred Maymar was unstarred
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