Taxi on electrical power
 

Just saw on flightglobal.com. Quite promising, isn't it?

VIDEO: L-3 and Lufthansa get moving with e-taxi demonstrator

Very interesting, I wonder what the limitations would be in regard to aircraft weight/ KVA demand.

Isn't it more efficient to use ground based systems like jetTRACS?

Attaching electrical motors to the MLG increases ac weight.
This is reducing efficiency during flight.

Furthermore, visibility for pilot is limited when going backwards, even
when using a camera systems.

True - but if sufficient fuel is saved during the taxy out then you wouldn't have to load that fuel load to begin with.

We used to reverse taxy in confined spaces on Vanguards - but only under the supervision of a Marshaller.

Extra fuel is gone after taxi and before going airborne, but motor is still there.

Also true - but you only have to buy the motor once.
You'll consume extra fuel at about 4% of the weight of the motors per hour of flight. The maths shouldn't be too difficult.

So you have to stop somewhere approximately 2 minutes taxi time from the runway to start your engines. Then when one doesn't start eco taxi back to the ramp to get maintenance to have a look before having another go. Meanwhile everyone else in the queue is fighting over when to stop and start engines.

For some overcrowded hubs at rush hour this may be ok but can you imagine being in the 40 minute taxi queue at JFK only to have to taxi back in with a problem?

For all the other times when your taxi is less than 10 minutes this just will never pay for itself. A ground based solution is a much better idea as it adds no extra weight.

But when you're driven by a tech company trying to sell stuff and confused by illogical "green" arguments I guess you'll give anything a go.

When I was at school, energy could not be created or destroyed, merely converted from one form to another, and undesirable losses normally occurred during the conversion processes.

I am not a physicist, but surely the conversion chain from chemical to electrical then to kinetic is a longer and more wasteful one than chemical to kinetic. Then as mentioned above, the carriage of motors, cabling and coolant would be very wasteful over time.

The green argument is looking a little thin.

I disagree for light aircraft with 60/90 kva generators.

It is only an experiment in a early phase. Keep cool....
And as far as i know, they replace 2 of the 4 brakes by an motor which can also be used as a eddy current brake (in the future).

How is that relevant?

A light aircraft flying short legs (as fitted on an A320) could from my perspective save money. Large aircraft requiring heavier systems over a long flight may experience more fuel burn due to the added weight.

The miniscule saving wouldn't warrant the extra ground cost in my opinion.