Green Way to Haul Freight

I don't get it. I started an engineering project with my college along the same lines, except I tossed out the idea of batteries a long time ago because unless you line the entire train with batteries they will not be able to hold the current of an entire train maintaining safe speed going down a long hill.

I found a thesis where the author describes one train making over 900kw going down one hill. The avg for the hill was about 500kw with about 80 trains. That is a great deal of energy, but why attempt to put it in a few batteries? Even if they attached one car behind the locomotive that was at capacity with nothing but batteries it wouldn't hold that much juice.

My plan is to use a catenary wire overhead that the trains connect to so the electricity can be transmitted over a grid. My next problem is to figure out how to clean up the voltage efficiently and make sure the trains work on the correct htz for a commercial power grid.

My system would have 2 huge advantages over batteries, it will have the capability of recovering all of the energy of a braking train, and can provide electricity to the train during the uphill or accelerating leg of the journey. After all, no matter how efficient the diesel engine is, a power-plant still makes the same electricity the locomotive traction motors use better. My main drawback is the cost of a catenary system, but you only have to buy it once, maintenance should be still cheaper than loads of batteries, not to mention the hazardous waste manufactured creating and disposing of those batteries.

Drew

Drew, The cost of building/running the infrastructure to do that I suspect would be much greater than any benefit gained if reclaiming the braking energy was the only reason.

Electric trains already do put their energy back into the grid when going down hill, and are significantly more efficient than running diesels on high capacity lines.

There are some electric trains that use the grid (for power and regen). But all of the ones I was able to find were done to cut pollution in urban areas, and they did it because of an ordinance.

I just don't see how it can be cheaper to do what G.E. is doing with this hybrid. The article mentions some savings, but does not say how much energy the batteries will hold, I doubt it will come close to the amount of a train using regenerative brakes on a long slope. I am not talking about wiring up the entire rail system, only areas of heavy dynamic brake use.

So far I have been unable to find out how much a catenary line system will cost.

Drew

I think the entry level price is over $1 million per mile, but in practice rather higher.

Most surface rail electrification systems in UK and Europe were originally installed for economic reasons - not air quality. However pollution control ordinances did drive electrification in New York.

The safety and reliability of returning retard energy to the Cat/ Con is at best questionable. This is why locomotives are equipped with retard resistor grids. In recent years electric passenger trains have been able to return part of the energy to the Cat/ Con provided the deceleration is kept within strict limits.

For a minerals traffic train with installed loco traction power of 15 MW or more the retard effort can be as high as 45MW. In an electrified system, Propel is cut by the magnet switches at section isolators etc and the train just coasts on through, but this isn't advisable for retard. Retard must be available at all times. Without the ability to divert the energy by a hard connection retard becomes unstable and the massive energy available can burn the conductor of the Catenary / Conductor system. The problem is acute as speed lowers and each length of conductor is heated longer, the localised heat causes soft spots to develop in the conductor which is a hard drawn copper strip in an I shape.

For a hybrid system such as what GE are working on, excess energy is diverted to the retard grid. This would need to happen on an electrified section too.

For diesel electric trains the DC link voltage is about 1500 VDC. Assuming a modern AC loco there are 6 inverters hanging off this DC link, one for each axle. In retard the traction motors operate as induction alternators and return power to the DC link via the antiparallel diodes in the inverters. The DC link voltage must be controlled closely to prevent catastrophic failure. This is currently done by the retard grids and the choppers coupled with the rate of frequency decrease in the inverters. To get this level of power off the machine would require a very large extra inverter and a power transformer to raise the voltage to 25kv AC single phase. The problems I have described for the electric locos above then come into play.

A 1500v to 2000v battery system is much simpler, more reliable and on non electrified lines, the only option.

There is a lot involved in the design or electrified rail systems which I won't add now, but be assured hybrid capability will assist electrified systems as much as Diesel Electric systems.

Wont it be better to use flywheels to store the braking energy, flywheel on grid or on the train, and then use that juice at the next acceleration ? (www.vyconenergy.com). I suppose flywheels provide better power density and last 15-20yrs, without the usual dead cell issues associated with batteries. On the flip side, power available from flywheels is for instantaneous use only.

I have a thesis written by a civil engineer who suggested that too. He was getting about 70% loss going to and from the flywheel. Additionally, in his plan it would require coupling and uncoupling the flywheel car costing too much time for some high priority trains and thus not be feasible for those trains.

In the thesis the author studied the section of rail known as Cajon Pass, he described an average of 80 trains per day averaging 915 kWh each, that is 73200 kWh of electricity over 82 miles every day. Do you think that would be worth putting up a catenary line?

The thesis was written in 2006, I doubt there is less freight passing through there now and until there is a better way to transport cargo over long distance, I doubt that will decrease.

Drew

Oh dear the pedant in me will come out...
Sorry but surely Diesel-electric is already a hybrid, the clue is in the name?
Mr P Dantic (Harlow Essex)

Sort of...true hybrids use batteries to augment the hp of a generally smaller ic engine.

Trains use electric motors so they can use dynamic braking where kinetic energy is released as heat through a resistor grid slowing the train without wasting friction brakes. This train is using batteries to store some of the dynamic brake energy in it's batteries and then use it as extra hp when accelerating only.

Drew

Oh dearie me no...if you look up the deffinition of hybrid, there is no mention of batteries, it just means a mix of more than one type of anything.
Lets have no sloppy language here!
Mr Sam Antics

You are absolutely correct Del, diesel-electric locomotives were hybrids before hybrid cars were even a twinkle in an inventor's eye! More power to GE if they think they can improve this already-existing hybrid system, but I would not put my money on them. Not much stop and go driving involved with a freight train; quite the contrary, once you get that behemoth going, you sure don't want to stop! Makes you wonder whether the complexity of batteries would be worth it, to recapture regenerative braking in an application where braking is as limited as possible. Rayzer