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

Wed May 14 09:13:13 PDT 2008

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?

'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.  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.

'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
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?

'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?

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.

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 

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.

Matt

From: sgvlug-bounces at sgvlug.net [mailto:sgvlug-bounces at sgvlug.net] On Behalf
Of Dan Borne
Sent: Wednesday, May 14, 2008 8:12 AM
To: SGVLUG Discussion List.
Subject: Re: [SGVLUG] [OT]Hybrids and trains (was fuel prices and the
dollar)

I applaud your letter, I think it is a good thing to say especially since
the only thing I hear about conservation of any sort is people driving a
Toyota Prius (which is a quite flawed method of "conservation" when one
considers that around 70% of the energy a car produces is used to push the
air past the front of the vehicle and it has one of the largest drags
thereof) . I am still confused thought how a plane is more efficient than a
train; doesn't a jet engine burn 10, 11 gallons of fuel a second.

2008/5/13 David Lawyer <dave at lafn.org>:

I've submitting the following letter to the editor of the LA times.
Not sure they will print it.
                       David Lawyer
=======================================================================
Re: "Civilization's last chance", May 11

The implication that hybrid autos and trains (instead of airplanes)
could make much of a difference in global warming is simply wrong.

Hybrids use internal combustion engines no more energy-efficient than
the engines on non-hybrids.  They also waste a lot of energy converting
the gasoline motor power to electricity, charging a battery, and then
withdrawing energy from the battery to power an electric motor to move
the car.  All this energy conversion wastes energy and adds to the
weight of the car.  The reason hybrids get good mileage is not because
they are inherently efficient, but because people don't know how to
efficiently drive a non-hybrid and because laws and car design, etc.,
impede one from efficiently driving it.

To efficiently drive a non-hybrid, one needs to get a "brake specific
fuel consumption map" for their engine, which the auto companies don't
supply.  Then use the map to apply the optimal amount of torque at any
given rpm, but autos have no torque meter.  Efficient driving will
mean doing a lot of coasting but coasting in neutral is illegal.

As for trains vs. airplanes, it turns out that they are about equally
energy efficient, and we don't save energy by taking the train.  See
the U.S. Dept. of Energy's "Transportation Energy Data Book": edition
26, table 2.14, and account for the fact that about 15% of fuel for
passenger aircraft goes to transport freight in the cargo hold.  For
details see my "Fuel-Efficiency of Travel in the 20th Century"
http://www.lafn.org/~dave/trans/energy/fuel-eff-20th-3.html#air_eff
<http://www.lafn.org/%7Edave/trans/energy/fuel-eff-20th-3.html#air_eff> 

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