On Dec 21, 1:30*am, Bill Wright wrote:
Neil Williams wrote:
On Dec 20, 2:49 pm, Bill Wright wrote:

Anyway what's green about running a bus on batteries?

Because you can put energy back into them when braking,

And how much energy will that provide? The energy wasted when braking is
very small. Most fuel is used combating rolling resistance and wind
resistance. London is not the sort of place where buses drop down long
hills on their brakes.

If the driver anticipates properly very little energy is wasted in
braking for traffic conditions. Better to start a bonus scheme where the
driver's pay is linked to his fuel consumption. That's the scheme all
the self-employed are on, and believe me it works.

just like a lot of modern trains put energy back into the overhead wire (assuming
something is there to consume it) when they brake.

That's different because the infrastructure and engineering are already
there, so don't add weight and complexity. Even if that only wins back a
few percent it's probably worthwhile. But diesel buses? Give over!



I don't believe there is any plan to charge the batteries overnight,
the diesel engine will do that.

So given that the process of generating electricity, storing it in
batteries, and then using it to drive motors is highly inefficient, how
is this going to save diesel? Don't forget the weight of the batteries
has to be lugged around as well. Bonkers!

Bill

Both batteries and electric motors have moved forward hugely in the
efficiency stakes. Also, the electronic control sytems are typicallly
better than 95% efficient.
About town most losses are due to braking. Aerodynamic drag is low
and friction is low with modern engines and lubricants.
On the motorway most losses are aerodynamic, the big one varies with
the square of speed.
ie twice as fast = four times the losses.