On Fri, 24 Jul 2009, Basil Jet wrote:

Andy wrote:

Just to be clear, I wasn't arguing for air conditioning to be fitted,
but I still think you are mis-estimating the effect of regeneration on
the total energy consumption and heating for the new trains. The whole
point of regeneration is to reuse the energy which used to be 'wasted'
in resistor banks on the trains (with the original rheostatic train
brakes). My understanding is that little of the recovered energy goes
back to the lineside equipment, if the current rails are not receptive,
then the spare energy goes to resistors, like in older stock. The extra
big lineside equipment is purely because more current is needed in the
first place.

What happened to the test of trackside rotating cylinders designed to
store the energy from regenerative braking?

That was just spin.

tom

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Tom Anderson wrote:
On Fri, 24 Jul 2009, Basil Jet wrote:

Andy wrote:

Just to be clear, I wasn't arguing for air conditioning to be
fitted, but I still think you are mis-estimating the effect of
regeneration on the total energy consumption and heating for the
new trains. The whole point of regeneration is to reuse the energy
which used to be 'wasted' in resistor banks on the trains (with the
original rheostatic train brakes). My understanding is that little
of the recovered energy goes back to the lineside equipment, if the
current rails are not receptive, then the spare energy goes to
resistors, like in older stock. The extra big lineside equipment is
purely because more current is needed in the first place.

What happened to the test of trackside rotating cylinders designed to
store the energy from regenerative braking?

That was just spin.

ROFSE!

John B wrote:
...
IANAelectrical engineer, but I just don't understand why it it
would
make economic sense to switch to traction types that are
inherently
less efficient.

Capital vs. Revenue is one reason I can think of. The financial
model for train operators must be very complicated - so a simple
Net Present Value and Payback Period calculation may not be
possible. The model used may show that in the short-to-medium
term, it's more profitable to use AC. Long-term savings aren't
relevant to a franchise that may only be seven years long, if the
savings aren't realised until after year 15, for example.

--
MatSav

In message
,
gunsmith writes
Perhaps you should consider the case for the reduced heat generation
by considering the average total power used by the whole opperational
fleet; not just one train. When a train is regenerating it is
effectively drawing negative energy.

Perhaps you might like to give us a clue what you're responding to?
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)

Peter Masson wrote:


"Tom Barry" wrote

And without Boris trumpeting them as meeting a manifesto commitment,
to boot. If they'd only had aircon...

Among the problems with aircon on the tube lines is - where do you dump
the heat? Presumably on, say, the Central or Piccadilly lines it would
be possible to devise a system whereby the heat was retained on the
train until it got to the open air, and then dumped, but Victoria Line
trains stay underground all the time they are in service. No use cooling
the trains if you just heat the tunnels even more.

Peter

AIUI, however, the new rolling stock is going to have some sort of new
venting system that will make journeys cooler.

Right?

Andy wrote:
On 23 July, 16:17, "Recliner" wrote:
"Peter Masson" wrote in message



"Tom Barry" wrote
And without Boris trumpeting them as meeting a manifesto commitment,
to boot. If they'd only had aircon...
Among the problems with aircon on the tube lines is - where do you
dump the heat? Presumably on, say, the Central or Piccadilly lines it
would be possible to devise a system whereby the heat was retained on
the train until it got to the open air, and then dumped, but Victoria
Line trains stay underground all the time they are in service. No use
cooling the trains if you just heat the tunnels even more.
That's why the plan is to cool the stations, not the trains, but of
course there's less to see with that approach.

And the regenerative braking on the new 2009 stock will also mean less
heat released into the stations and tunnels in the first place.

Is there no regenerative breaking on the current rolling stock? What
bout on other lines?

Peter Masson wrote:


"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?

Add to that the congestion relief works at Victoria and the more
frequent service, there'll be more passengers pumping kilowatts into the
system.

Perhaps the Victoria Line needs to be extended into the open air, at
least so the piston effect of trains can add ventilation into the
tunnels, and ideally so that the next generation (49 stock) can have
aircon that takes heat out of the system and dumps it in the open air.
Take over Chingford from National Rail? Quadruple Northumberland Park to
Cheshunt, with a extended Victoria Line running the local service?

Peter

Wasn't there talk about building a station around Northumberland Park?

Tom Anderson wrote:
On Fri, 24 Jul 2009, Peter Masson wrote:

"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some
seriously hefty cooling gear to cool stations. Gear that itself draws
power ... maybe more than the entire train regenerated power is taken
up by air- con ?

Add to that the congestion relief works at Victoria and the more
frequent service, there'll be more passengers pumping kilowatts into
the system.

Perhaps the Victoria Line needs to be extended into the open air, at
least so the piston effect of trains can add ventilation into the
tunnels, and ideally so that the next generation (49 stock) can have
aircon that takes heat out of the system and dumps it in the open air.

How about putting in some crossovers at Finsbury Park and running some
trains from Cockfosters into the Vic core? It's probably too far from
the Picc portal to Finsbury Park for this to really help.

Could you get a piston effect with some more ventilation shafts with
valves attached? Shafts would come in pairs, with a one-way valve on
each, so passing trains would push up one and suck it down the other.
Integrate some of the shafts with the Lea and New River for
water-cooling of the incoming air.

tom


Different signalling and train-operating systems between the two lines
would make that difficult.

On Sun, 26 Jul 2009, wrote:

Peter Masson wrote:

"Tom Barry" wrote

And without Boris trumpeting them as meeting a manifesto commitment, to
boot. If they'd only had aircon...

Among the problems with aircon on the tube lines is - where do you dump the
heat? Presumably on, say, the Central or Piccadilly lines it would be
possible to devise a system whereby the heat was retained on the train
until it got to the open air, and then dumped, but Victoria Line trains
stay underground all the time they are in service. No use cooling the
trains if you just heat the tunnels even more.

AIUI, however, the new rolling stock is going to have some sort of new
venting system that will make journeys cooler.

Right?

Right. it's basically just much better ventilation. Someone posted a study
by some physicists a while back that suggested it would make the insides
of the cars a few degrees cooler. Not an awful lot, but significant.

tom

--
She got destiny, she got supremacy, she got everything ever from A to Z.

On Jul 25, 11:36*am, D7666 wrote:
On Jul 25, 4:38*am, Andy wrote:

*A more powerful modern traction system doesn't
necessarily generate twice as much heat just because it has twice as
much power at its disposal.

I^2*R still applies.

Power (w) = Volts (V) x Amps (A)

Same 630 V voltage applied, double the power = double the current.

Double the current and the heating effect in all conductors goes up 4
times.


Any what is the resistance of said conductors in a 2009 stock train
compared to a 1967 stock? Plus the effect of the 750V power supply
which you've already mentioned. You seem to keep thinking that the
innards of the 2009 stock will be the same as the 1967 stock.

That is one of the laws of electricity.

Either you are continuing to suggest - as I have already commented -
the laws of phyiscs are suspended or you just plain do not understand
it.


NO, you are the one who doesn't understand, you seem to be fixated on
the current consumed. Power is not the problem, current is not the
problem. How much of the energy consumed goes to waste heat, rather
than moving the train is the problem. You don't seem to grasp the idea
that electrical machines in general have got considerably more
efficient in the last 40-45 years.

The current used by the system is NOT the amount of waste heat
generated by the train. You keep mentioning the power consumption, but
this has nothing directly to do with the amount of waste heat
generated by the trains (for a given design it will be related of
course, but not between designs). I have never said that the trains
will be consuming less power, just trying to point out that the power
will be used much more efficiently in a modern electrical system than
it was in a 1960s design.

You need to recognise the difference between nominal power rating of
the motors (the kW consumed) and the amount of that power which is
converted into kinetic energy by the drive train? Can you say what
the electrical efficiency of the 2009 stock is compared with the 1967
stock, if you can't then your power ratings are useless when looking
at energy wasted. I'm willing to bet that the 2009 stock is
substantially more electrically efficient than the 2009.

All this is on top of the difference in heat generation between the
rheostatic brakes on the 1967 stock compared to regenerative brakes on
the 2009 stock. The Victoria line should be good for regeneration, as
the service is frequent and so braking trains will usually find the
line receptive to the energy being produced, with another train
accelerating out. Indeed the constant constant current AC motors will
be much better in this regard than the DC motors.

I give up.