Forums

[Ham549]

[:D]I have been reading about this "new" hybrid car technology. This "new" technology is really something the cars engine always runs at its most efficient speed to get best fuel economy the engine turns a generator that makes electric power for the car to run on so you can very your speed while having your engine keep running at its most fuel efficient RPM. The "new" technology gets better they have regenitive breaking which slows your car down while making electricity! I wonder when the railroads will adopt this technology? [;)]

[CSSHEGEWISCH]

Except for the regenerative braking, the Green Goats already make use of this technology. It works best in yard applications because of the widely varying load demands in the average yard job.

[Ham549]

I guess no one gets the joke. Come on everyone here is supposed to know some about trains. The Joke is for all of you who don't know trains, is that locomotives have been using hybrid technology from pretty much day. A "diesel" locomotive has a diesel engine turning a generator just like a hybrid car has a engine turning a generator. Also locomotives have had regenerate brakes for years they are called dynamic brakes. The fact that people call this technology new is a joke because the railroads have been using the technology for years.

[Anonymous]

Gee, I'm glad I don't stick around here much.

[chad thomas]

QUOTE: Originally posted by Ham549

I guess no one gets the joke. Come on everyone here is supposed to know some about trains. The Joke is for all of you who don't know trains, is that locomotives have been using hybrid technology from pretty much day. A "diesel" locomotive has a diesel engine turning a generator just like a hybrid car has a engine turning a generator. Also locomotives have had regenerate brakes for years they are called dynamic brakes. The fact that people call this technology new is a joke because the railroads have been using the technology for years.

Not quite. They are not the same thing. A traditional diesel electric is a straight diesel engine that uses a electrical transmission. It conveys the power from the crankshaft to the axles (minus it's inefficiency in electromagnetic coupleing and mechanical friction) or if the unit has dynamics it can work in reverse and couple the axles to the load. The load is a resistor grid that converts that energy to heat that is wasted. There is nothing hybrid about that. It is simply an electric driveline (although with ser/par shunting can be a torque multiplier)

A gas-electric hybrid system is different. The combustion engine is coupled to an electric motor/generator through a planetary gear much like the rear end in a NON-positract.
The combination of the two move the car. The brain of the car decides how much power each puts to the wheels. The advantage comes from the regenerative brakeing canceling out the extra energy requirements of accelerating back to speed from a stop. When you begin to decelerate (brake) the engine speed drops to it's minimum causeing an equal increase of rpm on the electric motor (now a generator). That energy is converted to electricity and stored in a battery. Then when you start to accelerate the electricity is converted back to mechanical propulsion. As you use up the energy you stored the combustion engine takes back over. In a constant speed situation like on the freeway there is no advantage in a gas-electric hybrid (except you might recover some energy from going down a steep hill but on most grades the wind resistance will suck up enough energy to keep you from brakeing).

A gen-set hybrid is entirely different. It basicly is a straight electric running on internal batterys with on board generating capacity. That generating capacity is far less then what the peek demand for the loco would be but sience it's duty cycle is usualy much less it evens out in switching service. One advantage to doing this is you can build your generator to run at one speed and you design the generator for peek efficiency at that speed.

[Ham549]

It is a hybrid. The whole point of connecting the diesel engine to a generator instead of strength to the wheels is that the engine can run at its most efficient speed that way you can run the locomotive at any range of speed and still have the fuel efficiency. Also regenerative brakes and dynamic brakes are the same thing it doesn’t matter what’s at the other side of the brakes a generator or a battery so it’s not hi-tech to say “hey lets put a battery on the other side of this braking system” thought I am a bit surprised that dynamic brakes aren’t used to help charge a locomotives batteries until recently. I wonder why they just use a on the charge a capacitor with the brakes? That would give you the boost of power you need to start off from a dead stop

[chad thomas]

You lost me.
Your saying that a deisel-electric was a hybrid from day one (if I understand you right).
Thats not true. As to the genset-hybrid I am not disagreeing with you.

Dynamic and regenerative brakes are not the same thing. Dynamics can in no way store energy. All they can do is convert electrical energy to heat, after the traction motors convert kinetic energy to electrical energy. The only thing they have in common with regenerative brakeing is the traction motors. The reason they haven't used regenerative brakeing in the past is battery (capacitor) technology was not practical for this application. You can thank NASA for pushing the battery technology to where it is today. Not to mention the simiconductor technology to controll the high voltage / current used in these hybrids did not exist till recently.

[CSSHEGEWISCH]

Diesel-electrics exist primarily because that's the best transmission for the horsepower and duty cycles involved. Straight mechanical designs with a clutch won't hold up in those power ranges and various torque-converter and other hydraulic-based designs have faded out worldwide except in a few speicalized roles. Diesel-electric drives are also used in large off-road trucks such as those used in open-pit mines for the same reasons. Until recently, fuel efficiency was not really a factor.

[Ham549]

I am learning a lot here. But still saying “Dynamic and regenerative brakes are not the same thing. Dynamics can in no way store energy.” Well that’s not entirely true they could if you attached them to a battery or capacitor. The only difference between locomotives dynamic brakes and a hybrid car’s brakes is what they do with the energy they generate.

[chad thomas]

Well I guess it's all in how you look at it. Your right that it boils down to what you do with the energy. A dynamic brake is just a resistor, All be it a HUGE resistor, which is a very simple single electronic componet. A regenerative brakeing system requires big simiconductors and complex circuitry (read microprocessors) to controll the flow of energy both in and out of the storeage medium (a battery in this case) and a storeage meidum that can handle it. In the case of the gensets it's lots of big high tech batteries that can handle these HUGE loads (pulling a long cut of cars).

The reason i saY storeage medium instead of battery is that there are mechanical means of storeing energy that could be more economical in certain applications. One of them is flywheels. A flywheel in a vaccume is efficient at storeing energy and is better suited for quickly storeing or dissipateing large amounts of energy. Unfortunatly they are more bulkey for railroad application. I did see a design for a commuter engine with a flywheel based regenerative brakeing system in Railway Age about 12 years ago though.