London Banter - View Single Post - Electric or Hybrid Card or something car, suggestions?

Sales! · April 2nd 04, 04:51 PM posted to uk.rec.cars.misc,uk.transport.london

Apparently on date Fri, 2 Apr 2004 14:20:07 +0000 (UTC),
(D.P.Round) said:

Table four merely plucks the two figures out of the air. It doesn't derive them
or explain how it came to these figures, it just says "88%" versus "15%".

Fair comment but it is the best data I could find in a hurry. We since
have a figure of 34% for a 'Prius engine so I suspect that they have
not tried hard to present ICE in the best possible light. Still the
*efficiency* of the EV concept is similar as the losses are not large.

Efficiency in this case is very misleading. An electric motor has few losses,
primarily because the energy loss has already been paid converting the fuel,
(mostly oil or coal) into electrical energy in the first place. Petrol is not
an energy source that you can use to run a computer or power light bulbs, it is
a combustible fuel that you can burn to produce heat, firelight, or drive an
internal combustion engine that can then make a car go forward. The
"efficiency" in that case, is obviously not as meaningful when converting the
"fuel" into intrinsic "contained energy value" and talking about which engine
converts it into motion with fewer losses.

There are hidden factors, an ICE engine produces heat that is used to keep the
passenger compartment warm while the engine is running. Try keeping the car
warm, dry or for that matter cool in summer, using your battery power source
instead of the combustion engine's mechanical or heat energy and suddenly
there's a whole extra load on the alternative power source that is not at all
easy to incorporate.

I might say how much motion does the electric motor manage to produce per litre
of petrol. To be more efficient, it has to use the same fuel. To use an
inherently more useful energy source is cheating, like comparing a steam
engine, with lower calorific wood fuel with a petrol engine.

To take an extreme example, an electric motor runs almost forever on a
kilogramme of electricity, mainly because it weighs almost nothing. That's
obviously not a sound basis for comparison.

One of the issues I have with the comparison is it ignores things like vehicle
range and carrying capacity.

A point that cannot be argued with and the true reason that EVs are not
practical. Efficiency is not the issue. Batteries are very poor compared
to petrol and are not getting better that quickly.

I don't think they can become equivalent, based on the nature of "a battery".
Of course, an energy cell may be invented, e.g. something with a core fissile
energy supply, that can have a lot more energy in it than petrol, kilo for
kilo. But, that's not what I mean by a rechargeable battery.

You can get more from nicads, if you don't mind the fact that you are utilising
a fairly expensive and polluting metal Cadmium, you can bump this up to maybe 1
MJ

Why no NiMH? No Cadmium and a higher energy density again. Currently based

AFAIK they're much the same, maybe 35% more energy but less power output, if
that matters and it probably doesn't. Either way, the same situation applies to
both sorts, and also to anything under development to the best of my knowledge,
which isn't catholic.

on AA size (which may not be a useful comparison for a great many reasons)
the achievable energy density seems to be something like four times that
on NiCads. Again for small batteries Li poly do much better than NiMH and
far more than twice NiCads. This doesn't tally with your data. Do you
know why? Regardless it will not get close to petrol anytime soon.

I didn't study the figures, just got some examples off the web, Duracell as I
recall. They ought to be in favour of battery use, though, so I feel they are
reliable enough.

80% of my annual milage is done in stop-start slow driving with total
journey length of around 20 miles. This is achievable for an EV.

I couldn't travel 16 miles in stop-start driving. As the average speed in stop
start driving is supposed to be approximately 4 mph, that is a four hour
journey, I'd buy a bicycle. Alternatively, 80% of your *time* is stop start,
and it is probably more correct to say you do 2 miles of stop start and 18 at a
moderately constant speed. But, I don't know. And there are journeys where
electric motors would make more sense, no doubt about that, just they are the
exception, not the rule.

Add an engine for long trips (hybrid) and the result should be really
useful. I guess there must be snags or we would all have one since
I am sure that my requirements are not unusual.

Hybrid is a good technology for certain types of driving. On a steady journey
you can see why running an engine to make power that you convert into
electricity and then use to drive the wheels, is inherently inefficient when
you could drive the wheels using the power output directly. The hybrid scheme
really comes into its own when you couple a fuel cell or portable nuclear plant
with electric motors, these power sources can constantly produce power to
charge the batteries, which can then carry only what is needed for driving the
car at that moment. Thus, the car has plenty of power to accelerate, and can
cruise at a steady rate with modest required power output, retaining some
energy for overtaking in bursts. When you park it, the batteries recharge from
the nuclear plant so it is ready to use again when you want to go home.

If you drive it all day, the car loses power and slows down, until you are
using the output power directly, which means you never get stranded, but you
can't always dash about flat out.

It's an expensive, out of date concept that
is only popular among those who do not understand the situation and is intended
to solve a problem that no longer exists in any serious extent, which is the
emission of nitrous oxides and incomplete combustion products by passenger
vehicles in city environments, i.e. the reduction of smog. Modern cars in
roadworthy condition produce almost no smog even in cities.

Perhaps though it doesn't seem that was in a traffic jam.

Ten years ago, motorways began to smell bad when you were parked in a huge
traffic jam. I have to say, that this is no longer the case and I recall
sitting in a jam near Heathrow last year with outside temperature over 40
centigrade, the air conditioning was managing to keep the car cool and dry, and
there was no smell of smog or smoke from the other vehicles. It is the case
that diesel buses still pump out fairly sizable clouds of smoke, I have noticed
that. An old "Atlantean" double decker pointed this out to me a year or two
back, reminded me what things used to be like, in fact.

You can monitor the air quality, people have done this and the old smog issues
have basically gone away. You're free to do your own study.