Playing it cool

John B wrote:
> On 1 Jul, 22:01, rosenst...@cix.co.uk (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

In message <Pine.LNX.4.64.0807020003010.17290@urchin.earth.li >, at
00:07:52 on Wed, 2 Jul 2008, Tom Anderson <twic@urchin.earth.li>
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