"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