Boltar wrote:

On Jul 7, 7:26 am, Paul Terry wrote:

They are branded in quite large letters front and rear:

http://www.busandcoach.com/featureStory.aspx?id=640

"The diesel engine is set to run constantly - unlike some hybrid
systems where it shuts down for periods."

So how does that help pollution or fuel economy if the bus is crawling
along in some endless jam? I thought the whole point of hybrids is
they can switch the engine off and crawl on electric power om traffic?


Another point with hybrid drive is actually that the engine can run on
most fuel-efficient rpm when it runs, in this case all the time. This
does not matter practically, a small engine can be compensated with
running it constantly and using a larger battery pack, which is what I
think they have done here.

The problem with direct-driving diesel engines is that they need to be
large and are very fuel-consuming while they accelerate, such engines
are not capable of providing enough torque in any other way, while
eletrical motors are used to what they are best for, that is providing
enough torque from still standing while they would not be efficient for
keeping speed once the vehicle has accelerated. Diesel engines are on
the other hand good at providing constant amounts of energy over longer
time so they are best used for generators and for direct-driving the bus
once it has enough speed. ...and the battery pack is used to even out
the electrical power consumption over time.

In shorter words, the engine, battery pack and electrical motors are
used to what each of them are doing best.

"TfL expects that the battery packs will have to be replaced every
three years, at a cost of around £3,000."

So thats 400 kgs of batteries down to the tip every 3 years not to
mention the new set that has to be manufactured? Oh very green.


I am in most cases looking forward with great interest to inovative
experiments on making fuel-efficient transport solutions but this one
surprises me somewhat. Instead of expensive large battery packs,
wouldn't it be better to build a trolley-bus network with trolley buses
with regenerating brakes? Larger initial investment costs probably but
it would surprise me if trolley-buses would not turn out cheaper after a
few years.

It should be said though that with this kind of battery cells it is as
far as I have understood it possible to use large parts of the materials
in the process of building new ones, but still, the batteries need to be
replaced and in other aspects the buses still need at best the same
amount of maintenance as traditional diesel buses, if not even more.

--
Olof Lagerkvist
ICQ: 724451
Web: http://here.is/olof