6003Re: [rootsradicals] Re: The Energy Cost of Electric and Human-Powered Bicycles
- Aug 8, 2008Sorry Morgan - didn't really mean to offend, but obviously the post was
written in an offensive manner. I will clean up my act, because this is an
interesting topic and I think it's worth discussing (I guess I'm a mental
masturbator, eh?) ;-)
My main counter-argument is that, when talking about a bicycle, regardless of
power source (human, motor, or a combination thereof), you cannot exclude the
energy cost of the vehicle's operator. Even if the operator isn't doing any
motive work (i.e. a pure motorcycle application), there is some energy cost
inherent to keeping the bike upright and steering it.
Thus, comparing the energy cost of the electric motor looks only at a portion
of the total energy requirement needed for the bike to qualify as a vehicle
(instead of a paperweight). It excludes the energy cost of the human balancing
and steering it, even if that person is doing little or no motive work.
Therefore the electric vs. human comparison as presented is not "apples and
apples", but rather "apples and oranges." You can't exclude the caloric cost
of balancing and steering just because both scenarios require it, because
doing so inaccurately under-reports the true energy cost of the hybrid or pure
motorcycle application and then incorrectly compares it against the total
energy cost of the human powered application.
So, even excluding questions about the efficiencies of the motor, batteries
and electrical / food source(s), the comparison as presented is misleading and
That's all I was trying to say, sorry for ruffling feathers and being a jerk.
---------- Original Message -----------
From: "Morgan" <mcgurme@...>
Sent: Fri, 08 Aug 2008 12:19:22 -0000
Subject: [rootsradicals] Re: The Energy Cost of Electric and Human-Powered
> Since we're getting snippy and claiming something is "bunk"
> (ok, actually, you claimed it was "masturbation"):
> For a given power input level to the bike, if the electric
> is doing more, then the human is doing less. And vice versa.
> Conservation of energy and all that thermodynamic stuff.
> So if the electric has twice the efficiency as the human, then the
> most efficient way to ride is electric-only.
> But, assuming that you'd like to pedal also (I do), then this means
> there is more total power going into the bike. The result? Faster
> speed, shorter travel time, and less energy expended by the human
> overall (though complicated by the fact that friction is not linear
> with velocity).
> When you come up with a paper that solves the equations balancing
> power from a human-electric hybrid drivetrain, and the various types
> of friction at a given velocity, and use that to show somehow that
> the human is more efficient than the electric, then your claim of
> "mental masturbation" may hold merit. Until then? Not so much.
> And BTW, my e-bike is absolutely more efficient than I am. I charge
> it by solar. Excepting the fixed (and already expended) costs of
> generating the solar panels, it requires zero additional carbon or
> other resource inputs to power the electric portion of my bike. Not
> true of my legs.
> Yet still I choose to pedal. How inefficient of me!
> --- In firstname.lastname@example.org, "surfimp" <steve@...> wrote:
> > --- In email@example.com, "Mighk Wilson" <mwilson@> wrote:
> > >
> > > Carl referenced:
> > >
> > > >>A paper entitled: "The Energy Cost of Electric
> > > and Human-Powered Bicycles " By Justin Lemire-Elmore 2004<<
> > That 'paper' is quite the exercise in intellectual masturbation. Sadly
> > the author of the paper forgot that the creature riding the e-bike is
> > not powered by Li-Ion chemistry... LOL! The real energy cost of riding
> > the bike is actually his "human power" cost (or at least some
> > percentage thereof) + the electrical power cost... the human powered
> > bike wins hands down when the 'new math' is excluded ;)
> > Regardless, if anyone likes their e-bike for whatever reason, great,
> > it's one less car as plenty of others have noted. But please, no
> > half-baked theses that they're somehow more "eco friendly" than a
> > purely human powered vehicle. That's just silly :)
> > Steve
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