It seems odd that as LUL attempts to cool down the tube, it is introducing
giant electric projectors at many stations, along with the illuminated
moving panels on the escalators. The stories in Railway Herald this week,
page 5 about cooling down, and page 6 about the heat producing equipment,
seem to show a lack of joined up thinking!

What might be more sensible is for equipment at every sub surface station to
be reviewed and every heat producing item examined to see how its heat
output could be reduced or eliminated. Every little bit might help!

MaxB

Batman55 wrote:
It seems odd that as LUL attempts to cool down the tube, it is introducing
giant electric projectors at many stations, along with the illuminated
moving panels on the escalators. The stories in Railway Herald this week,
page 5 about cooling down, and page 6 about the heat producing equipment,
seem to show a lack of joined up thinking!

What might be more sensible is for equipment at every sub surface station to
be reviewed and every heat producing item examined to see how its heat
output could be reduced or eliminated. Every little bit might help!

MaxB


According to TfL, the heating effect arises because of the incremental
heating and cooling caused by each passing train's energy consumption.
The frequency of trains means the cooling of the tunnel walls is that
little bit less than the heating, so over the years the ground heats up
because it never gets a long enough break between trains. This is
rather borne out by the original Bakerloo Line claim that it was an
nice, cool way to travel in the heat of the summer - it was decades
before the effect was realised. Presumably if you could shut the tube
for a few years you could reverse it, but I can spot a couple of
problems with that idea.

I suspect, therefore, that things like lighting and electronics in
stations (which are better ventilated than the tunnels anyway) are of
minute benefit compared with reducing the heat produced in the tunnels
by each train by a little bit. Indeed, one of the ideas being looked at
is blowing cold air over the brakes of trains standing at stations, so
they don't take the heat into the tunnel when moving off. Obviously
this merely transfers it to the station, whence it can be removed
somewhere. Regen braking has a place here, too, if you can shove the
heat from the necessary resistors outside.

Tom

What surprised me was an item on the TV a while back saying that some
shaft extraction fans on I think the victoria line were being brought
back into use. Only now?? And why the hell were they out of use in the
first place?? Also I'd be interested to know the power consumption of
the most recent tube stocks compared to the old stocks since all power
used eventually ends up as heat. I wouldn't be surprised if like the
new 3rd rail surface stocks they use considerably more power overall
than older stocks and so contribute to the problem.

B2003

In article ,
(Tom Barry) wrote:

Batman55 wrote:
It seems odd that as LUL attempts to cool down the tube, it is
introducing giant electric projectors at many stations, along
with the illuminated moving panels on the escalators. The stories
in Railway Herald this week, page 5 about cooling down, and page
6 about the heat producing equipment, seem to show a lack of
joined up thinking!

What might be more sensible is for equipment at every sub surface
station to be reviewed and every heat producing item examined to
see how its heat output could be reduced or eliminated. Every
little bit might help!

According to TfL, the heating effect arises because of the
incremental heating and cooling caused by each passing train's
energy consumption. The frequency of trains means the cooling of
the tunnel walls is that little bit less than the heating, so over
the years the ground heats up because it never gets a long enough
break between trains. This is rather borne out by the original
Bakerloo Line claim that it was an nice, cool way to travel in the
heat of the summer - it was decades before the effect was realised.
Presumably if you could shut the tube for a few years you could
reverse it, but I can spot a couple of problems with that idea.

I suspect, therefore, that things like lighting and electronics in
stations (which are better ventilated than the tunnels anyway) are
of minute benefit compared with reducing the heat produced in the
tunnels by each train by a little bit. Indeed, one of the ideas
being looked at is blowing cold air over the brakes of trains
standing at stations, so they don't take the heat into the tunnel
when moving off. Obviously this merely transfers it to the
station, whence it can be removed somewhere. Regen braking has a
place here, too, if you can shove the heat from the necessary
resistors outside.

If it's regen braking, rather than rheostatic, the heat goes as energy to
other trains and not into resistors.

--
Colin Rosenstiel

On 1 Jul, 22:01, (Colin Rosenstiel) wrote:
Regen braking has a
place here, too, if you can shove the heat from the necessary
resistors outside.

If it's regen braking, rather than rheostatic, the heat goes as energy to
other trains and not into resistors.

Ish. On AC, absolutely right; on DC, you need banks of resistors as
well because putting it back to the grid if there isn't a conveniently
placed train to take it is Too Bloody Hard. However, given the traffic
density on LUL, most of the time there'll be someone accelerating
while you're breaking so it should work out OK...

--
John Band
john at johnband dot org
www.johnband.org

John B wrote:
On 1 Jul, 22:01, (Colin Rosenstiel) wrote:
Regen braking has a
place here, too, if you can shove the heat from the necessary
resistors outside.
If it's regen braking, rather than rheostatic, the heat goes as energy to
other trains and not into resistors.

Ish. On AC, absolutely right; on DC, you need banks of resistors as
well because putting it back to the grid if there isn't a conveniently
placed train to take it is Too Bloody Hard. However, given the traffic
density on LUL, most of the time there'll be someone accelerating
while you're breaking so it should work out OK...


Yes, that's what I was getting at. In mitigation, I hadn't read Cap'n
Deltic's latest screed in MR at that point, which suggests that
receptivity in DC networks is higher than previously thought, so you
might not need as much resistance capacity and associated cooling around
the place.

What's the effect of the suggested upping of the voltage to 750v DC on
some lines? Being a concrete'n'steel type engineer (manqué) I don't
understand electricity as well as I should.

Tom

On 1 Jul, 23:34, Tom Barry wrote:
John B wrote:
Ish. On AC, absolutely right; on DC, you need banks of resistors as
well because putting it back to the grid if there isn't a conveniently
placed train to take it is Too Bloody Hard. However, given the traffic
density on LUL, most of the time there'll be someone accelerating
while you're breaking so it should work out OK...

[hangs head in shame at 'braking' typo]

Yes, that's what I was getting at. In mitigation, I hadn't read Cap'n
Deltic's latest screed in MR at that point, which suggests that
receptivity in DC networks is higher than previously thought, so you
might not need as much resistance capacity and associated cooling around
the place.

My last bout of crazy-travelling-about-the-place ended just before the
latest edition came out, so I've only seen the preview email. Bring on
the next train voyage...

What's the effect of the suggested upping of the voltage to 750v DC on
some lines? Being a concrete'n'steel type engineer (manqué) I don't
understand electricity as well as I should.

transmission losses [hence, here, heat gains] = current^2 / resistance

Since resistance is ~constant and power delivered to the train =
current * voltage, increasing the voltage from 630V to 750V reduces
the current required to provide the same power by 16%, which reduces
transmission losses by 29%.

This ignores the effect of almost everything real-world (especially
the fact that you're dealing with two rails at +420 and -210 rather
than a single rail at +630), but you get the idea.

--
John Band
john at johnband dot org
www.johnband.org

On Tue, 1 Jul 2008, John B wrote:

On 1 Jul, 22:01, (Colin Rosenstiel) wrote:

Regen braking has a place here, too, if you can shove the heat from
the necessary resistors outside.

If it's regen braking, rather than rheostatic, the heat goes as energy to
other trains and not into resistors.

Ish. On AC, absolutely right; on DC, you need banks of resistors as well
because putting it back to the grid if there isn't a conveniently placed
train to take it is Too Bloody Hard.

But there are places to send it other than the grid, surely? Supercaps?
Pumped storage? Flywheels? A giant laser firing into space?

tom

--
.... which may end up with the women in your office cornering you at the
office xmas party and taking turns at jamming their bootclad feet into
your genitals. This is what is known as the Wrong Kind of Footsie. --
Lord Foom

In message , at
00:07:52 on Wed, 2 Jul 2008, Tom Anderson
remarked:
on DC, you need banks of resistors as well because putting it back to
the grid if there isn't a conveniently placed train to take it is Too
Bloody Hard.

But there are places to send it other than the grid, surely? Supercaps?
Pumped storage? Flywheels? A giant laser firing into space?

How about a plant that's generating hydrogen by electrolysis. That
wouldn't need a steady flow of current, and could simply absorb whatever
was available from one second to the next. Then use the hydrogen to
power those buses they have. Or did that experiment end now?
--
Roland Perry

"Tom Barry" wrote in message

Regen braking has a place here, too, if
you can shove the heat from the necessary resistors outside.

Quite apart from the fact that the resistors aren't likely to be needed
much in the central underground sections where there are lots of other
accelerating trains, I assume they put out no more heat than the
friction brakes would have done. They're more likely to be needed on the
extremities of the network where there may not be many other trains
around to absorb the power.