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Re: Bio-diesel 159

"John B" <spam@johnband.org> wrote in message
news:34a4e7f2-58f9-4778-adca-a538176a2161@79g2000hsk.googlegroups.com...
> On Aug 12, 2:37 pm, "Stephen" <newsmai...@ntlworld.com> wrote:
>> But is electrification any more environmentally friendly?
>> At the source of traction its certainly cleaner, and can produce more
>> power
>> to weight, but its just moved the pollution from the train to the power
>> station. Plus there's all the transmission losses to consider which, when
>> generating electricity from fossil fuels, makes this less efficient and
>> creates more pollution.
>
> No - transmission losses are sub-5%; while the energy saving from
> regen braking is 10-20%. On that basis alone, electricity is more
> environmentally friendly - that's before you take into account the
> chance to improve generation mix over the train's lifetime, and the
> weight savings from not lugging your own power plant around with you.
>
The only problem with not lugging the powerplant around is that the
decreased weight is usually put to good use with increasing acceleration and
power to go faster cutting minutes off the timetable. So the power use is
quite often more.

As for regenerative braking to me its not that significant in this country
as compared with somewhere like Switzerland. After all if the trains are
driven for passenger comfort then there shouldn't be too much braking
(signals willing!) but more coasting, as we don't have the hills.

Also what isn't taken into account is the generated electricity that's lost
as you can't just switch on and off a power station using fossil fuels or
even nuclear power for that matter. You can, of course, switch hydro on
quite quickly. So to cater for the big peaks some power stations are brought
up to load quite a long time before the peak occurs and then take time to
wind down with all the excess electricity generated going to waste. Well not
all, as there is a type of hydro station called pumped storage as this pumps
the water up with the turbines in reverse during times that excess
electricity is being produced but can then revert to normal in about 10mins
to generate electricity. I believe that some are now being built to
supplement the couple we have (Wales & Scotland).

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