this is great news. can't wait to hear about any data, etc. that they gain from this.

I don’t see the news in this. Aren’t all trains made as serial hybrids? The only new thing about this train is that they use a lithium battery. It used to be NiCd batteries for this kind of application. Correct me if I am wrong.

Henrik:
I think the power units on most current train tractors are direct serial diesel/electric with no intermediate battery storage; makes sense to store electricity in batteries as a power buffer to fill in the poor low rpm characteristics of the ICE when extra power is required and to recovery some energy with regen.

I think Lad is right in his basic points. There are two ways in which a hybrid train would differ from a conventional diesel-electric locomotive:

1. Substantial battery storage.
2. Regenerative braking.

In fact, conventional diesel-electric locomotives often employ an "everything-but" form of regenerative braking -- they can slow their trains by engaging the drive shaft and spinning the electric motor, which generates current. But then they run the current through what is essentially a large toaster coil and vent the waste heat.

Regarding Lad's low-RPM point -- I don't see how that particularly follows. Since the diesel engine in a conventional locomotive runs an electric generator, which then powers the wheels, you can run the diesel at whatever RPM you want and use the electric drive as an infinitely variable transmission system.

Hybridity makes sense in that you recapture braking energy, and you do get to smooth-out peaks in power demand (and engine output), even if you already have the ability to constrain the operating range to a favorable RPM band.