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Re: [evworld] Digest Number 536

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  • Rick Woodbury
    ... No it doesn t. If a vehicle were 60% efficient and traveled 60 miles on a charge for example, as it became 100% efficient it would go 100 miles. That would
    Message 1 of 3 , Jul 31 11:08 AM
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      Al Zelicoff, MD wrote:

      > 5. Yet, the MDI is advertised as being able to travel about 200
      > kilometers on an air-charge. Given that it is no more aerodynamic than
      > battery powered cars (although it is less weighty) and that electric
      > motors are, for all intents and purposes nearly 100% efficient in
      > converting on-board energy into movement, this suggests that the MDI is
      > 20 to 30 times more efficient yet. That just doesn't make sense.

      No it doesn't. If a vehicle were 60% efficient and traveled 60 miles on a
      charge for example, as it became 100% efficient it would go 100 miles. That
      would mean no heat loss from friction, no aerodynamic drag, or any other
      factors, i.e., impossible. Obviously 20 to 30 times more efficient is 20 to
      30 times impossible.

      There was an electric motor company in China advertising that their motor
      was so efficient that it could get several times the range of a conventional
      motor. Obviously they were smoking the same stuff. Current electric motors
      are 85% efficient or more, meaning that there is very little heat loss. If a
      motor were 100% efficient (absolutely impossible since there is always some
      friction and other losses) it could go 15% further on a charge. Obviously
      range must be increased by carrying more energy not so much through
      efficiency gains. A lithium-ion pack can carry many times the energy per
      weight and volume of lead acid. That makes sense.

      Thanks for doing the energy calculations for compressed air. I've always
      thought it was highly suspect, but never took the time to disprove it. I
      know that it takes a 6 hp air compressor to run a 1 hp or less air tool and
      the compressor can't keep up at that. There is a lot of loss in heat when
      the air is compressed too.

      A compressed natural gas car can get a 200 mile range using all of the
      energy in the gas itself from a 5,000 psi cylinder. A home compressor works
      for many hours to reach that pressure. To think you could throw away the
      energy in the gas and run 200 kilometers on the pressure is ludicrous.

      It's hard to get 200 Wh/mi with an electric car with it's highly efficient
      motors. How can one expect to get the same or better efficiency out of a
      reciprocating engine. An internal combustion engine is about 13% efficient.


      Rick Woodbury Phone: (509) 624-0762
      President, Commuter Cars Corporation Toll-free: (800) 468-0944
      Doubling the capacity of freeways Fax: (509) 624-1466
      Quadrupling the capacity of parking Cellular: (509) 979-1815
      Zero to 60 in under 4 seconds
      715 E. Sprague Ave., Suite 114 Email: rick@...
      Spokane, WA 99202 Web: http://www.commutercars.com
    • murdoch_1998
      Rick, et. al.: Lord knows I have to defer to your judgment and other experts in an EV-making discussion. But, with respect, on this more general science
      Message 2 of 3 , Jul 31 12:19 PM
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        Rick, et. al.:

        Lord knows I have to defer to your judgment and other experts' in an
        EV-making discussion.

        But, with respect, on this more general science issue, I want to try
        to understand something here about this relationship between energy
        efficiency and mileage. I do not think there is necessarily a
        linear relationship between the percentage energy efficiency and
        miles per unit energy. My reasoning is something along these lines.

        Theoretically, in the ideal, one can get an infinite distance from a
        miniscule energy input. "A body in motion stays in motion unless
        acted upon by an outside force".

        So, if we had an ideal car on a non-friction surface and no
        resistance (wind or otherwise), after the original "impetus" of
        energy, the car should go forever. The distance traveled would be
        infinite.

        Now, if we include real-world performance issues of acceleration and
        deceleration, wind resistance, etc. then do we come closer to a
        linear mathematical correlation between energy efficiency and
        mileage?

        I don't know the upper limits on mileage per MegaJoule, given
        idealized thought experiments or alternatively given some defined
        real-world constraints (a certain weight to a vehicle, some internal
        friction, acceleration and decelleration, wind resistance, etc.).
        I've just always wondered about this question as to what we mean
        when we say "energy efficiency" and relate it to mileage.

        It seems to me I have read once or twice articles about college-type
        contests where teams shoot for the most awesome mileage they can get
        and throw away virtually every other consideration. The speed
        traveled, the number of possible passengers, etc. etc... these
        factors are all subordinated to mileage. And in those contests I'm
        pretty sure the mileage figures attained have been astounding, I
        think well into the hundreds of miles per gallon (but I could be
        wrong... haven't seen this data for years).

        In any event, I'm not sure how I should view this issue of mileage
        and energy efficiency.


        --- In evworld@yahoogroups.com, Rick Woodbury <rick@c...> wrote:
        > Al Zelicoff, MD wrote:
        >
        > > 5. Yet, the MDI is advertised as being able to travel about 200
        > > kilometers on an air-charge. Given that it is no more
        aerodynamic than
        > > battery powered cars (although it is less weighty) and that
        electric
        > > motors are, for all intents and purposes nearly 100% efficient in
        > > converting on-board energy into movement, this suggests that the
        MDI is
        > > 20 to 30 times more efficient yet. That just doesn't make sense.
        >
        > No it doesn't. If a vehicle were 60% efficient and traveled 60
        miles on a
        > charge for example, as it became 100% efficient it would go 100
        miles. That
        > would mean no heat loss from friction, no aerodynamic drag, or any
        other
        > factors, i.e., impossible. Obviously 20 to 30 times more efficient
        is 20 to
        > 30 times impossible.
        >
        > There was an electric motor company in China advertising that
        their motor
        > was so efficient that it could get several times the range of a
        conventional
        > motor. Obviously they were smoking the same stuff. Current
        electric motors
        > are 85% efficient or more, meaning that there is very little heat
        loss. If a
        > motor were 100% efficient (absolutely impossible since there is
        always some
        > friction and other losses) it could go 15% further on a charge.
        Obviously
        > range must be increased by carrying more energy not so much through
        > efficiency gains. A lithium-ion pack can carry many times the
        energy per
        > weight and volume of lead acid. That makes sense.
        >
        > Thanks for doing the energy calculations for compressed air. I've
        always
        > thought it was highly suspect, but never took the time to disprove
        it. I
        > know that it takes a 6 hp air compressor to run a 1 hp or less air
        tool and
        > the compressor can't keep up at that. There is a lot of loss in
        heat when
        > the air is compressed too.
        >
        > A compressed natural gas car can get a 200 mile range using all of
        the
        > energy in the gas itself from a 5,000 psi cylinder. A home
        compressor works
        > for many hours to reach that pressure. To think you could throw
        away the
        > energy in the gas and run 200 kilometers on the pressure is
        ludicrous.
        >
        > It's hard to get 200 Wh/mi with an electric car with it's highly
        efficient
        > motors. How can one expect to get the same or better efficiency
        out of a
        > reciprocating engine. An internal combustion engine is about 13%
        efficient.
        >
        >
        > Rick Woodbury Phone: (509) 624-
        0762
        > President, Commuter Cars Corporation Toll-free: (800) 468-
        0944
        > Doubling the capacity of freeways Fax: (509) 624-
        1466
        > Quadrupling the capacity of parking Cellular: (509) 979-
        1815
        > Zero to 60 in under 4 seconds
        > 715 E. Sprague Ave., Suite 114 Email: rick@c...
        > Spokane, WA 99202 Web:
        http://www.commutercars.com
      • Mage
        I would have to posit that with energy efficiency as with most endeavors 2 simple rules apply: The 80/20 rule and the logrithmic slope of perfection. With the
        Message 3 of 3 , Aug 1, 2004
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          I would have to posit that with energy efficiency as with most endeavors 2
          simple rules apply:
          The 80/20 rule and the logrithmic slope of perfection.

          With the 80/20 you could say that 80% of energy conversion can be had with
          20% of the effort both technological as well as energy input. Whereas the
          last 20% of energy conversion nirvana would take 80% of the effort. But of
          course as has been pointed out perfect energy conversion is impossible and
          this is where the second rule kicks in. As one approaches higher and higher
          energy conversion efficiencies the effort to attain such efficiency becomes
          logrithmically more difficult and expensive. Resulting in the last tenth of
          the last percent effectively requiring an infinity of effort.

          With this in mind, economically, one should never attempt to recover the 81%
          of any task. The ROI just isn't there. One would be better off finding an
          alternative task to attempt, a different conversion mechanism to invest in.

          Just a thought,
          Dave Cline
          -----Original Message-----
          From: Rick Woodbury [mailto:rick@...]
          Sent: Saturday, July 31, 2004 12:09 PM
          To: evworld@yahoogroups.com
          Subject: Re: [evworld] Digest Number 536


          Al Zelicoff, MD wrote:

          > 5. Yet, the MDI is advertised as being able to travel about 200
          > kilometers on an air-charge. Given that it is no more aerodynamic than
          > battery powered cars (although it is less weighty) and that electric
          > motors are, for all intents and purposes nearly 100% efficient in
          > converting on-board energy into movement, this suggests that the MDI is
          > 20 to 30 times more efficient yet. That just doesn't make sense.

          No it doesn't. If a vehicle were 60% efficient and traveled 60 miles on a
          charge for example, as it became 100% efficient it would go 100 miles.
          That
          would mean no heat loss from friction, no aerodynamic drag, or any other
          factors, i.e., impossible. Obviously 20 to 30 times more efficient is 20
          to
          30 times impossible.

          There was an electric motor company in China advertising that their motor
          was so efficient that it could get several times the range of a
          conventional
          motor. Obviously they were smoking the same stuff. Current electric motors
          are 85% efficient or more, meaning that there is very little heat loss. If
          a
          motor were 100% efficient (absolutely impossible since there is always
          some
          friction and other losses) it could go 15% further on a charge. Obviously
          range must be increased by carrying more energy not so much through
          efficiency gains. A lithium-ion pack can carry many times the energy per
          weight and volume of lead acid. That makes sense.

          Thanks for doing the energy calculations for compressed air. I've always
          thought it was highly suspect, but never took the time to disprove it. I
          know that it takes a 6 hp air compressor to run a 1 hp or less air tool
          and
          the compressor can't keep up at that. There is a lot of loss in heat when
          the air is compressed too.

          A compressed natural gas car can get a 200 mile range using all of the
          energy in the gas itself from a 5,000 psi cylinder. A home compressor
          works
          for many hours to reach that pressure. To think you could throw away the
          energy in the gas and run 200 kilometers on the pressure is ludicrous.

          It's hard to get 200 Wh/mi with an electric car with it's highly efficient
          motors. How can one expect to get the same or better efficiency out of a
          reciprocating engine. An internal combustion engine is about 13%
          efficient.


          Rick Woodbury Phone: (509) 624-0762
          President, Commuter Cars Corporation Toll-free: (800) 468-0944
          Doubling the capacity of freeways Fax: (509) 624-1466
          Quadrupling the capacity of parking Cellular: (509) 979-1815
          Zero to 60 in under 4 seconds
          715 E. Sprague Ave., Suite 114 Email: rick@...
          Spokane, WA 99202 Web: http://www.commutercars.com



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