genset and hybrid

whats the differance between genset and hybrid locomotives?

Here's how I understand it:

A genset unit is powered by 2 or 3 smallish (400 HP? or so) engine/generator units. The individual units are started/stopped in response to actual drawbar power demand.

The advantage is you run smaller engines only as required, and run each at or near it's fuel economy/emissions "sweet spot". Also when standing a genset runs only a single genset unit as needed to keep air up and charge the starting batteries - otherwise all the engines shut down completely.

A hybrid OTOH employs two sources of power - typically a single small engine/generator and a storage battery bank. The engine/generator runs at constant speed/load near it's fuel ecomony "sweet spot". And it charges the battery when the locomotive power demand is less than the engine output. The battery then supplements generator output when bursts of high power are needed - eg. for acceleration.

Also a hybrid utilizes regenerative braking - ie. using the traction motors as generators to charge the batteries with kinetic energy otherwise wasted by regular brakes when decelerating.

What FarmallBob said is correct. The genset switchers currently being built by NRE employ either two or three 700 HP engines. The two-engine version is called 2GS14B (2 Gensets, 1400 HP, B trucks); the three-engine version is called 3GS21B (3 Gensets, 2100 HP, B trucks).

Doesn't NRE make a "Railpower" locomotive, with three Deutz engines, each worth (667) horsepower?

Railpower Technologies is the name of the company that makes the "Green Goat" hybrid switchers.

NRE's genset switchers (2GS14B, 3GS21B, et al.) are marketed under the "N-ViroMotive" name.

I came across a photo of the builder's plate on an NRE 3GS21B:

http://www.rrpicturearchives.net/showPi ... ?id=755801

Note the section that says "Engine Type: QSK19" -- the QSK19 is a very popular Cummins engine used in many different applications, ranging from construction and mining to farming and marine. There are three QSK19s in this unit.

Wow, a hundred horsepower is wasted before it turns into traction power.

Hmmm... genset - sounds like a GE center-cab switcher.

nessman wrote:Hmmm... genset - sounds like a GE center-cab switcher.

Yeah - pretty much. Stick today's solid state electrical control hardware and computerized engine/alternator management systems into a 40's era GE centercab and you'd have yourself a 2 engine genset.

Peter Radanovic wrote:Wow, a hundred horsepower is wasted before it turns into traction power.

That's not really unusual. The GEVO-12 in its current incarnation produces over 4500 horsepower, but GE rates the ES44AC and ES44DC as having 4400 horsepower for traction. EMD locos are probably similar.

MEC407 wrote:That's not really unusual. The GEVO-12 in its current incarnation produces over 4500 horsepower, but GE rates the ES44AC and ES44DC as having 4400 horsepower for traction. EMD locos are probably similar.

I suspect 4,500 gross HP for the GEVO V12 prime mover installed in a locomotive is significantly understated!

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Consider the following published energy conversion efficiencies. (These incidentally represent "best case" efficiencies for top of the line components):

- Main alternator – 96%
- Traction motors – 93% (this is for an AC traction motor; DC traction motors might be a % or two LOWER).
- Electrical power controls (rectifiers, inverters, etc) - 95%

Combining the above gives an overall engine-to-drawbar transmission efficiency of ~85% (= .96 x .93 x .95)

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What's this mean? It says for 4,400 HP to show up at the drawbar, 5,187 HP (= 4,400 / 85%) must be supplied to the main alternator by the diesel engine.

Next consider a locomotive's “parasitic losses”, ie. the power required to run the locomotive auxiliaries. Items like radiator cooling fans, intercooler blower, traction motor blowers, the air brake compressor, aux alternator (ie. the control/lighting/battery charging generator), etc. all consume power. Combined these easily represent another 100 HP, probably much more.

Finally there's the power required simply to move the locomotive itself - 180 or so tons of locomotive deadweight has gotta be kept rolling before the drawbar can apply any horsewpower to pull a train. Depending upon the speed there's another 100 - 200 HP is "lost" to that activity.

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Bottom line: For 4,400 HP to show up at the drawbar and be available for pulling a trailing load, well in excess of 5,000 HP must be developed by the locomotive's prime mover.