On 8 May, 10:07, wrote:
On Thu, 7 May 2009 19:19:48 +0100

Paul Terry wrote:
It would be daft to develop Crossrail in the hope that adequate battery
technology would be available by the time the trains have to be
ordered. However, battery trains have been used for suburban rail -
Dublin to Bray between 1932 and 1950. In .uk a battery MU operated
between Aberdeen and Ballater in the early 1960s, while battery locos

Probably lines with very light traffic and low top speeds.

have been used to haul engineering trains on LU in the dead of night
when the power's een switched off.

They still are AFAIK.

Although I agree with the basic premise, battery technology is becoming
increasingly impressive - parts of the new Rome trolleybus system
currently run on battery power for some miles, and Alstom's trams for
Nice also run on batteries in the city centre. These are vehicles
capable of carrying a large number of passengers in heavy traffic,
although probably not on the scale required for the far reaches of
Crossrail.

Theres a big difference between accelerating a 20 ton tram to 20mph and
a 200 ton train to 60mph quickly enough so it keeps to the timetable.
Moreover when the batteries are not being used you're hauling around
god knows how many tons of dead weight - hardly enviromentally friendly.
Plus most EMUs these days seem to be pretty lardy anyway. I suspect if
batteries were thrown into the mix axle loads could become a serious issue.

hmm - some numbers.

E = 1/2 200,000kg x 30^2 = 100MJ = 30KWhrs.

That's about 200kg of Li-ion battery, for the energy load. But the
power requirement is much tougher - you would need some of these fast
charge batteries, which actually have less energy storage. Without
looking up the W/kg figures, I'd guess a few tons.

Hybrid technology is certainly useful for trains, but you'd probably
want to use ultra caps to capture the braking energy.