Savannah Station Questions (For the Technical Folks)

[xyzzy]

Alright, now that we've dispelled the notion that the weight of the diesel prime mover is a drag, it's only the weight of the fuel that you're concerned about. 5000 gallons is typical for a fuel tank on a road locomotive. 5000 gallons of diesel fuel weighs approximately 35,000 pounds (7 pounds per gallon) or 17.5 tons. Let's suppose four fully-fueled locomotives are assigned to pull a coal train of 100 cars, each weighing 100 tons. The incremental weight of the fuel in the 4 tanks adds 70 tons to what is a 10,850 ton train (the 100 cars plus the dry weight of the four locomotives at 212.5 tons each). In other words, we're talking about a fuel weight penalty of 0.6%. That's not much, and bear in mind that it falls as the fuel is consumed.

 

[Ryan]

No, the weight penalty of the diesel prime mover and diesel fuel is not a factor. The locomotive must be ballasted anyway in order to get enough weight on the axles to avoid slipping. Besides, the inevitable transformer and high voltage components in a pure electric are not lightweight, either. Between electrical equipment and ballast, the GG1 (which was highly successful in freight service) weighed 475,000 pounds.

You seem to be contradicting yourself here.

Alright, now that we've dispelled the notion that the weight of the diesel prime mover is a drag, it's only the weight of the fuel that you're concerned about.

We have? I must have missed that part.

 

[xyzzy]

My point is, an unballasted electric can suffice for passenger service (although an AEM-7 is prone to slip as it comes out of the Hudson River tunnels). But put an unballasted electric on a freight and you'll slip all day.

Guest_Nathanael argued that the weight of the prime mover and the weight of the fuel are problems. The weight of the prime mover isn't for reason of reaching the necessary weight. The weight of the fuel isn't a significant consideration, either.

 

[Devil's Advocate]

A diesel locomotive is a fairly efficient electricity generator.

Compared to what?

It could well be that the saving by using shore based power ws so small it was not worthwhile.

With Amtrak routinely trumpeting their "green" image it's odd to see them running parked locomotives simply because being less wasteful wasn't "worthwhile" enough for them to bother with. Here in San Antonio they plug in the ground based HEP but still leave the Texas Eagle locomotives running all night long anyway. That's around eight hours each night or almost 250 hours a month, or nearly 3,000 hours each year. Or a minimum of 60,000 hours during the lifespan of a locomotive. I wonder how many gallons of diesel it takes to keep a locomotive running for 60,000 hours or more. Oh well at least petroleum is still cheap right.

By the time you consider line losses between power plant and user using oil or gas to power a central generating plant, I would suspect that it would prove ridiculous.

To a man with only a hammer, every problem resembles a nail. To a railroad with nothing but diesel electric locomotives every problem just needs more diesel thrown at it. Which is fine when petroleum is cheap. When it becomes more expensive there's no easy way to mitigate the costs. Which is why rail shipment invoices now come with perpetual fuel surcharges.

Most people agree that nuclear is cheaper than coal or oil.

Cheap nuclear sounds great until you start researching the issue. Last I checked here in the US nothing is cheaper than using coal when deployed nationwide. If you add up the full costs of designing, building, fueling, maintaining, and decommissioning nuclear power plants, including the costs and liabilities born by the US taxpayer, the cost of nuclear is in reality surprisingly high. Modern nuclear power plants can easily reach tens of billions of dollars just to license and build. Not to mention that the fuel still needs to be mined, transported thousands of miles via specialized shipping, heavily refined and processed, constantly protected, carefully loaded, constantly monitored, even more carefully removed, slowly cooled in specialized pools, sealed in specialized caskets, transported thousands of additional miles to be stored away from natural resources, prying eyes, and terrorists for anywhere from thousands to millions of years.

So far as I can tell the myth of cheap nuclear comes from a unique sequence of events whereby the original builders of the nuclear plants eventually succumbed to the debts incurred in building and maintaining their own plants. Other companies that did not build and were not liable for the debts were able to come in and buy the plants for pennies on the dollar. Thanks to agreements already in place from as early as the 1950's the US taxpayer remained on the hook for much of the legal liability and storage costs from plants built prior to the 1980's. As a result the new plant owners were able to leverage this rather unique situation into a great money making business. Unfortunately it only works for the middlemen. The original owners who built the plants got burned, just like the US taxpayer will eventually get burned as the first bills for decommissioning hundreds of plants and their fule for millions of years of highly secure storage must be paid. Good luck when that day comes.

 

[cirdan]

A diesel locomotive is a fairly efficient electricity generator. It could well be that the saving by using shore based power ws so small it was not worthwhile.

Disagree.

A diesel locomotive is a fairly efficient generator of electricity when under load. Maybe in the region of 40 to 100 percent of its nominal output.

When below 15 or even 10 percent of load, its efficiency is rather dismal.

Its a bit like you never driving your car at speeds above 10 mph and then being surprised you aren't doing the mpg the manufacturer claims.

 

[cirdan]

Most people agree that nuclear is cheaper than coal or oil. There's an argument these days about whether nuclear is cheaper than natural gas. Duke Power in the southeast just withdrew its plans for additional nuclear because natural gas is so attractive. Nuclear is not cheaper than hydro, in terms of hydro that is already in place.
That said, the losses from transporting the electricity after it has been generated are substantial -- regardless of the source of the electricity. It's why the conducting cables in high-voltage transmission lines are often 250 degrees in temperature. If you can generate electricity where it is needed with reasonable efficiency and safety, you will almost always do better than importing your electricity from several hundred miles away -- such are the lengths of transmission lines that an electrified railroad in the western states would face -- even if generation is as cheap as hydro.

I agree that LNG is very cheap right now. That is largely due to new fields having been opened up. But such are the laws of economics and the market that that low price will doubtlessly attract new users and new customers and new applications and demand will rise to the point that supply cannot keep up and the price will rise again until a new price equilibrium is established.

Yes, there are losses on electricity transmission lines. But there are also losses in transporting coal or LNG. A coal train uses diesel fuel, an LNG pipeline needs pumping stations. Diesel fuel also needs to be transported. Furthermore, all that steel needed to make a pipeline requires energy to make it, more energy than a transmission line (when broken down by thermal units over useful economic lifetime). Thermal unit for thermal unit, source to sink losses in electricity are actually in the same ballpark as losses in running a diesel or LNG generator. The exact figures will depend on the precise situation, so you cannot really draw up a general rule here. It's all in the laws of thermodynamics and you cannot get something for nothing and if you save something at one point in the chain, you will almost certainly pay the penalty at another point.

The great advantages of electric locmotives lie in fewer moving parts, less vibrations and being cleaner which translates into lower maintenance costs, plus a greater power denisty, ie, more hp per ton, meaning better accelerations and hence better line utilisation, more trains per unit of time for the same track geometry. Those advantages only really come into their own for very busy routes. Possibly there are a handful of freight corridors where these advanatages would apply. But trains don't normally start where the corridor starts but come from and continue to other destinations, and so you would need engine changing facilities and the logistics of that would soon outweigh the cost savings.

 

[Nathanael]

No, the weight penalty of the diesel prime mover and diesel fuel is not a factor.

Yes. Yes, it is.

The locomotive must be ballasted anyway in order to get enough weight on the axles to avoid slipping.

Well, if you want to use an inefficient hauling method. If you use sufficiently distributed power, it's not an issue. There's always enough weight on the axles, it's just a question of how many powered axles you have.

Your statement that only the Milwaukee removed electric is incorrect. There are many examples of de-electrification such as the Great Northern (74 miles in mountainous territory). Wikipedia has a good list at http://en.wikipedia.org/wiki/Railroad_electrification_in_the_United_States

The short-term benefit from scrapping the capital was the main motivator for several of these -- which is not good management, and is only done in an industry which is collapsing. The engine change penalty was the main motivator for the rest (these were merely short electrified mountain districts, not fully electrified lines). Very few places had a fully electrified line, the Iowa Traction Railroad and the South Shore Line being exceptions... both still electrified.

 

[NE933]

What he said.
Don't worry about all the n00b questions, that's what we're here for. It's a pleasant distraction from arguing about Amtrak cost allocations. Again. And again. And again.

You mean you don't like fighting about how much a plastic spoon from the Cafe, or a roll of toilet paper, costs?!

 

[Nathanael]

But trains don't normally start where the corridor starts but come from and continue to other destinations, and so you would need engine changing facilities and the logistics of that would soon outweigh the cost savings.

This is, to be fair, a good reason for not electrifying. What we've heard about the famous recent BNSF electrification study (the one which concluded that BNSF should not electrify at current prices, but should at some undisclosed higher fuel price) was that it concluded that it only made sense to electrify the entire BNSF network at once, never less than that.

 

[cirdan]

But trains don't normally start where the corridor starts but come from and continue to other destinations, and so you would need engine changing facilities and the logistics of that would soon outweigh the cost savings.

This is, to be fair, a good reason for not electrifying. What we've heard about the famous recent BNSF electrification study (the one which concluded that BNSF should not electrify at current prices, but should at some undisclosed higher fuel price) was that it concluded that it only made sense to electrify the entire BNSF network at once, never less than that.

I have some difficulty envisaging that. BNSF must have thousands of miles of track that are surviving on minimal to no maintenance and maybe seeing just a handful of seasonal freights per year. Freight cars also need to be switched into and out of factories and other customer facilities, so you would still need diesels for that. A 100% electrified rail system is difficult to envisage. Even countries like Switzerland, which have electrified all their passenger mileage still have some marginal bits of freight line that require diesels. Some of their switching engines are even dual mode, being able to run both off electrics mosty while using diesel for pulling cars out of factory tracks and such. I suppose you could say Amtrak has some engines like that too, even though the context is totally different.

 

[dart330]

I do remember a few years back BNSF was proposing allowing a major electrical transmission line to be placed in the right of way along the transcon in exchange for electrifying it. I'm on my phone or I would try and post the article.

 

[VentureForth]

An interesting point was made near the beginning of this thread. Why not have 480V on the opposite spur for PV? Savannah is certainly a destination where someone would be interested in parking their PV overnight or two or three.

Then again, with most of the station activity being between 7 PM and 8 AM, perhaps it's NOT the best idea...