In article ,
The Natural Philosopher wrote:
Predicting the future is risky. And we've been promised cheap electric
cars since I was a kid. But for every development of these we get
similar improvements with IC engines.

No you do not. Electric motirs have wlayws been vastly more efficient
than IC engines for sound theoretical reasons.

I'm not disagreeing with that, but you've got to look at the whole picture.
The efficiency of the actual motor makes little difference if the
generation/storage of the power needed is wasteful.

IC engines have got beter by tuning te fuel air mixtures, and increasing
peak pressures, but you cannot escape the laws of phsyics. Only if you
go to extremely high temperatures with e.g. a gas turbine can you get
efficenices even approaching 40-50%. Or fit condenser to the exhaust..

You can do all that in a generating set, but its TOO HEAVY in a car.

Trouble is that with 50% generator efficiency and then storing that
electricity to drive a 90% efficient motor you're getting dangerously
close to even the 30% of an IC engine using the same fuel. Add in the
heating required for much of the year for the inside of the car and it can
become worse in practice.


The issues are safety, cost, and recharge times.

And, of course, how you generate the electricity to charge them. That
is the big fly in the ointment since charging any battery is an
inefficient process.

Its not. Abou 90% efficient. If you do it right

Again, the most efficient way of charging a battery may not be the best
way for long life. And these type of batteries will always be expensive -
perhaps half the total cost of the car.

As I said before Drivel is usually wrong, but in this case randomly,
he is not.

Excuse me? He reckoned there were existing batteries that weighed the
same and had the same energy capacity as a tank of petrol. This is
just plain nonsense.


well I have him plonked, so I can't say what he said originally.

Well that was what I was replying to. It's as well to read that first. ;-)

Ther are batteries in existence that will enable electroic cars to
compete in performance and range with a comparable wieght of petrol
powertrains...lets leave it at that..

I'd be willing to bet there aren't. They'll fiddle all sorts of things to
get this result. Extra low friction tyres and bearings etc. Low vehicle CD
and weight. Then compare it to a bog standard car - the worst they can
find, probably too.

However you need to do an overall analsyis of the whole vehicle power
train- looking at one or another compnonet leaves a false impression.
You are as guilty of that as Drivel.

I'm trying to analyse the whole use of energy for a vehicle, likely
running costs and life. You should try that too. ;-)

--
*Does fuzzy logic tickle? *

Dave Plowman London SW
To e-mail, change noise into sound.