In article ,
Phil Richards wrote:

On Sun, 10 Aug 2003 22:36:16 +0100 Stuart
said...

Victoria Line platform - like an oven (it has always seemed to me to be
the hottest line on the network for no obvious reason)

Agree, possibly apart from the depot at Northumberland Park, the who line
is underground. Consequently the trains are more "stuffy" than other
lines even in the winter months. Wonder how often the trains get to
surface?

Air conditioning seems to be a no, no (& there is no need for any one to
explain the reasons why), perhaps Victoria Line stock (now the oldest
tube stock running on the system) can at least be fitted with forced air
ventilation as a compromise.

First, reduce the amount of train braking energy dissipated into deep
tunnels in the form of heat by upgrading as much of the rolling stock as
possible with regenerative brakes as opposed to rheostatic brakes.
Braking energy from rheostatic brakes accounts for a large proportion of
tunnel heating.

Second, equip all rolling stock with heat pumps instead of electric
convection heaters (part of the space requirement can be met by the
removal of the heaters). The heat pumps can be used in winter to extract
and concentrate warmth from the outside air and transfer this to the car
interiors (as a marginal benefit, this would cool the tunnels slightly);
conversely in the summer, the heat pumps can be used to provide comfort
cooling. For deep tunnel trains, the heat pumps can be combined with
'coolth reservoirs' (carried under the non-traction cars) so that the
heat pumps can be switched off while the train is below ground; this
avoids the problem of increasingly hot tunnel air reducing heat pump
efficiency. A 'coolth' reservoir uses a compact well-insulated body of
fluid (perhaps a eutectic salt) kept constantly at around freezing
point; energy (latent heat) is transferred into and out of the reservoir
during the solid / fluid phase change. While the train is in the open
(typically at each end of the line) its heat pumps are used to extract
as much energy as possible from the train's 'coolth' reservoirs,
freezing the reservoir fluid. Then, when the train goes underground, it
relies on the stored 'coolth' to continually cool a transfer medium
(water) for use in carriage comfort cooling. The 'coolth' reservoirs
would be sized to yield up all of their latent energy during the tunnel
part of the journey. When the train is back in the open, the process is
repeated.

To keep the cooling load and space requirements to a minimum, multiple
small-scale 'fan-coil' units could be fitted within carriages at high
level; a conservative performance objective might be to cool the top 30%
of carriage air to around 21-23 degrees C. Cool air would circulate
downwards into a less comfort critical zone while becoming warmer; this
vitiated air could then be vented at foot level and, if still cooler
than the ambient external air, used to cool the heat pumps as it is
expelled ('coolth' recovery). The chilled water loop supplying the
fan-coils would be continuous between carriages, since not all cars may
have space to accommodate heat pumps and / or 'coolth' reservoirs.

Given the extent of refitting required, it may be more efficient to
commission new rolling stock. Looking at the state of underground rail
design world-wide, most new air-conditioned rolling stock seems to
consist of established designs fitted with commercial off-the-shelf
cooling units; fully integrated bespoke cooling systems would almost
certainly yield much better space economy and performance.

From a national 'green' energy accounting point of view, the total new
energy load from active cooling could be offset by investing in
renewable source energy generating plant, such as wind turbines or tidal
barrages. It may be possible to make the system carbon neutral.

The financial cost of the system, which, including generating plant and
partial upgrading of the LU power supply, would certainly be
substantial, should also be considered at a national level. Millions of
citizens spend a significant portion of their lives using the tube. It
doesn't matter how much they may or may not be compensated in their jobs
- there is no way that private citizens can bring about a cooler tube.
Only government can do this.

Regards ;-)

C.

"Charlie Whitaker" wrote in message
news:charlie-
First, reduce the amount of train braking energy dissipated into deep
tunnels in the form of heat by upgrading as much of the rolling stock as
possible with regenerative brakes as opposed to rheostatic brakes.
Braking energy from rheostatic brakes accounts for a large proportion of
tunnel heating.


Regen braking has been tried previously on both the underground and other
railways. Where it has fallen down in the past is having somewhere for the
regenerated electricity to go and be used at the moment is it being
generated, i.e. as one train is braking for a station another needs to be
accelerating away.

In article , Charlie
Whitaker writes

Second, equip all rolling stock with heat pumps instead of electric
convection heaters (part of the space requirement can be met by the
removal of the heaters). The heat pumps can be used in winter to extract
and concentrate warmth from the outside air and transfer this to the car
interiors (as a marginal benefit, this would cool the tunnels slightly);
conversely in the summer, the heat pumps can be used to provide comfort
cooling. For deep tunnel trains, the heat pumps can be combined with
'coolth reservoirs' (carried under the non-traction cars) so that the
heat pumps can be switched off while the train is below ground; this
avoids the problem of increasingly hot tunnel air reducing heat pump
efficiency. A 'coolth' reservoir uses a compact well-insulated body of
fluid (perhaps a eutectic salt) kept constantly at around freezing
point; energy (latent heat) is transferred into and out of the reservoir
during the solid / fluid phase change. While the train is in the open
(typically at each end of the line) its heat pumps are used to extract
as much energy as possible from the train's 'coolth' reservoirs,
freezing the reservoir fluid. Then, when the train goes underground, it
relies on the stored 'coolth' to continually cool a transfer medium
(water) for use in carriage comfort cooling. The 'coolth' reservoirs
would be sized to yield up all of their latent energy during the tunnel
part of the journey. When the train is back in the open, the process is
repeated.

To keep the cooling load and space requirements to a minimum, multiple
small-scale 'fan-coil' units could be fitted within carriages at high
level; a conservative performance objective might be to cool the top 30%
of carriage air to around 21-23 degrees C. Cool air would circulate
downwards into a less comfort critical zone while becoming warmer; this
vitiated air could then be vented at foot level and, if still cooler
than the ambient external air, used to cool the heat pumps as it is
expelled ('coolth' recovery). The chilled water loop supplying the
fan-coils would be continuous between carriages, since not all cars may
have space to accommodate heat pumps and / or 'coolth' reservoirs.

Given the extent of refitting required, it may be more efficient to
commission new rolling stock. Looking at the state of underground rail
design world-wide, most new air-conditioned rolling stock seems to
consist of established designs fitted with commercial off-the-shelf
cooling units; fully integrated bespoke cooling systems would almost
certainly yield much better space economy and performance.

From a national 'green' energy accounting point of view, the total new
energy load from active cooling could be offset by investing in
renewable source energy generating plant, such as wind turbines or tidal
barrages. It may be possible to make the system carbon neutral.

The financial cost of the system, which, including generating plant and
partial upgrading of the LU power supply, would certainly be
substantial, should also be considered at a national level. Millions of
citizens spend a significant portion of their lives using the tube. It
doesn't matter how much they may or may not be compensated in their jobs
- there is no way that private citizens can bring about a cooler tube.
Only government can do this.

Excellent idea. Have you submitted it on the TfL website? Could be built
into the new stock if the maintenance was easy enough for the depot
crews.
--
Andrew
Electronic communications can be altered and therefore the integrity of this
communication can not be guaranteed.
Views expressed in this communication are those of the author and not
associations or companies I am involved with.

"Charlie Whitaker" wrote in message
...

Regen braking has been tried previously on both the underground and
other
railways. Where it has fallen down in the past is having somewhere for
the
regenerated electricity to go and be used at the moment is it being
generated, i.e. as one train is braking for a station another needs to
be
accelerating away.

The LU web site:

http://tube.tfl.gov.uk/content/faq/t...dOnly=menu6&si
deMenu=menu6option7

says that the 1995 / 1996 stock uses regenerative braking. I assume this
is also true for the 1992 stock. Although I am not an electrical
engineer, my understanding is that control systems are now sophisticated
enough to monitor the DC rail 'receptivity' and adjust the amount of
current fed back to the rail during regenerative braking. It doesn't
seem possible to completely eliminate rheostatic braking (the train will
still need to carry some resistors) but it is possible to reduce it.
Friction braking at low speeds will also generate some heat.

LU has trialled the Urenco flywheel energy-storage system as a way of
storing surplus energy and/or smoothing the demand of energy from the grid.
It can reduce energy consumption by 25-40% with regenerative braking. See:

http://www.uptenergy.com/en/traction/Railway.pdf
http://tube.tfl.gov.uk/content/about...nt/climate.asp

Also it was in Modern Railways a couple of years back.

Charlie - I take it you're going to submit this proposal of yours to LU in
the 100k competition? I must admit to working with some mates on an
alternative proposal...

Angus

In article ,
"Angus Bryant" wrote:

"Charlie Whitaker" wrote in message
...

Regen braking has been tried previously on both the underground and
other
railways. Where it has fallen down in the past is having somewhere for
the
regenerated electricity to go and be used at the moment is it being
generated, i.e. as one train is braking for a station another needs to
be
accelerating away.

The LU web site:

http://tube.tfl.gov.uk/content/faq/t...dOnly=menu6&si
deMenu=menu6option7

says that the 1995 / 1996 stock uses regenerative braking. I assume this
is also true for the 1992 stock. Although I am not an electrical
engineer, my understanding is that control systems are now sophisticated
enough to monitor the DC rail 'receptivity' and adjust the amount of
current fed back to the rail during regenerative braking. It doesn't
seem possible to completely eliminate rheostatic braking (the train will
still need to carry some resistors) but it is possible to reduce it.
Friction braking at low speeds will also generate some heat.

LU has trialled the Urenco flywheel energy-storage system as a way of
storing surplus energy and/or smoothing the demand of energy from the grid.
It can reduce energy consumption by 25-40% with regenerative braking. See:

http://www.uptenergy.com/en/traction/Railway.pdf
http://tube.tfl.gov.uk/content/about...nt/climate.asp

Also it was in Modern Railways a couple of years back.

That looks like an elegant solution.

Charlie - I take it you're going to submit this proposal of yours to LU in
the 100k competition? I must admit to working with some mates on an
alternative proposal...

Angus

I did send them the proposal in pretty much the same words as I posted
here, yes. I suspect that there will be more than a few 'thermal
flywheel' proposals in the bag for them to consider. The difference
might be that I haven't done any sums :-).

Although 100K would be useful, I did worry a bit about the ethics of
trying to justify that kind of prize in exchange for a written proposal
of 500 words or fewer. I suspect that there are no 'breakthrough' ideas
for cooling the tube - it may require careful application of a
combination of established techniques, a lot of cash and a lot of
persistence.

But what the hell ...

Regards,

Charlie

"Charlie Whitaker" wrote in message
...
In article ,

Charlie - I take it you're going to submit this proposal of yours to LU
in
the 100k competition? I must admit to working with some mates on an
alternative proposal...

I did send them the proposal in pretty much the same words as I posted
here, yes. I suspect that there will be more than a few 'thermal
flywheel' proposals in the bag for them to consider. The difference
might be that I haven't done any sums :-).

Although 100K would be useful, I did worry a bit about the ethics of
trying to justify that kind of prize in exchange for a written proposal
of 500 words or fewer. I suspect that there are no 'breakthrough' ideas
for cooling the tube - it may require careful application of a
combination of established techniques, a lot of cash and a lot of
persistence.

I reckon that one wouldn't see much of the £100k personally - most of it
would be used to research and develop the idea in greater depth.

Whatever emerges from the competition should be interesting though!

Angus