[SGVLUG] [OT]Hybrids and trains (was fuel prices and the dollar)

[David Lawyer]

On Wed, May 14, 2008 at 09:13:13AM -0700, Matt Campbell wrote:
> Hi David, Dan,
> 
>  
> 
> Thanks for speaking up, more people need to do that.  I have heard other
> information than what you provided in your letter on a number of occasions.
> Can you provide references for the data you based your statements on?

Look at a BSFC map such as
http://mae.ucdavis.edu/Courses/Spring07/EME163/introduction_3_29_07.pdf
Slide 1 (Engine performance map on p. 10)

>  
> 
> 'Hybrids use internal combustion engines no more energy-efficient than the
> engines on non-hybrids.'.
> 
> It was my understanding that hybrid motors run in their efficient mode for a
> much larger portion of their operating time than non-hybrid motors which is
> where they get their efficiency.
Correct, unless you drive with a lot of coasting.
> See the difference between running a
> Atkinson motor http://en.wikipedia.org/wiki/Atkinson_cycle vs. a standard
> internal combustion motor http://en.wikipedia.org/wiki/Four-stroke_cycle.
> Don't forget the energy savings from regenerative breaking.
You save even more energy if you coast to a stop and are going very
slow when you finally apply the brakes.
> 
> 
> 'They also waste a lot of energy converting the gasoline motor power to
> electricity, charging a battery, and then withdrawing energy from the
> battery'.

> Ok, this was an eye opener for me.  What I found was 'The
> coulometric charging efficiency of nickel metal hydride batteries is
> typically 66%, meaning that you must put 150 amp hours into the battery for
Do you have a reference for this?  Sounds reasonable.
> every 100 amp hours you get out.'.  I know that electric motors and
> generators as well as batteries have seen huge improvements in efficiency
> over the last 20 years, so I assume you are right in that there is a major
> power loss here.  Anyone else have comments?
Not sure that there have been major efficiecny improvements in
electric motors.  They still use copper and iron and the copper losses
are still i^2r, etc.  Make them bigger and they'll be more efficient
but cost and weigh more.
> 
> 
> 'As for trains vs. airplanes, it turns out that they are about equally
> energy efficient'.
> 
> As Samuel Clements noted there are three types of lies:  lies, damn lies and
> statistics.  Depending on your criteria you can make statistics for just
> about any argument.  In what way are planes as efficient as trains?

In passenger-miles per gallon of fuel.
> 
> Dan, 'Toyota Prius . push the air past the front of the vehicle  . and it
> has one of the largest drags thereof'.  What I find is: 'Wind resistance is
> reduced by a drag coefficient
> <http://en.wikipedia.org/wiki/Automobile_drag_coefficients>  of 0.26' which
> is lower than most other vehicles.
But you could design other vehicles with 0.26 also and perhaps have
the frontal area lower than the Prius which would result in less
aerodynamic drag.
> 
>  
> 
> Now if you were talking about the environmental impact of the manufacturing
> and disposal of the batteries compared to the pollution saved in running the
> Prius..
> http://en.wikipedia.org/wiki/Battery_%28electricity%29#Environmental_concern
> s 
Good point.  My letter was already too long but still couldn't cover
the topic adequately.

> 
>  
> 
> And don't forget: 'Advocates for the blind warn that the Prius is so quiet
> it could be hazardous to blind pedestrians and others accustomed to engine
> noise to warn of a nearby vehicle'.
> 
>  
> 
> In the end I get twice the mileage from our Prius as from my car, and nearly
> 10 times as from my truck.  No matter how 'false' the energy savings is in
> the Prius it seems to be working.
True, but if you had a small car that was designed for coasting, etc.
and signals were designed to tell you how many seconds to turning red,
then with very skilled driving and a BSFC map you might do just as well.  
> 
> Matt
			David Lawyer