Fuel Cost For A Station Call?

[bangyuk]

Anyone know or prepared to estimate how much fuel it would cost for, say, a 3 car DMU to stop at a station (and then start again) that it would otherwise have passed straight through. Probably easiest to assume the track is level and the line speed is 60mph.

I have found two schools of thought: it costs virtually nothing; it costs a lot . . . .

 

[90019]

It will cost more, because momentum and energy are lost when braking, so more fuel is used to gain them again after stopping compared to the constant energy and momentum of the one staying at a constant speed, which uses a relatively small amount of fuel in comparison.

Actual cost though? I can't begin to guess.

 

[bangor-toad]

Anyone know or prepared to estimate how much fuel it would cost for, say, a 3 car DMU to stop at a station (and then start again) that it would otherwise have passed straight through. Probably easiest to assume the track is level and the line speed is 60mph.

I have found two schools of thought: it costs virtually nothing; it costs a lot . . . .

Oooh, I shoud resist but I can't

OK, 60mph is 1 mile per minute or 1600meters per min or about 27meters per second.

A 3 car DMU. Each carriage is about 35 tons. Total weight is 105 tons or 105,000kh.

The kinetic energy of the train is E= 1/2 m v2.

So the total kinetic energy of the train at 60mph is 0.5 * 105,000 * 27 *27
This is 38,272,500 Joules.

Looking it up, the energy content of diesel is about 38MJ / litre.

So in pure energy terms, it would appear you would only need a 1 liter of diesel.
But, and it's a big one...

No engine is 100% efficient. A good diesel engine can optimistically turn 30% of the chemical energy into usable work. Allow for a well used train engine and you're probably looking at about 20% actual efficiency.

So, the extra fuel to slow down and then speed back up will be about 5 litres.

Of course, this might be complete rubbish but it seems plausible!
Cheers,
Jason

 

[bangyuk]

Jason,

Thanks, that looks like a reasonable estimate. Broadly speaking, perhaps a fiver per stop. It would be better for electrics with regen braking, or, indeed, a hybrid like my Prius!

 

[90019]

Oooh, I shoud resist but I can't

OK, 60mph is 1 mile per minute or 1600meters per min or about 27meters per second.

A 3 car DMU. Each carriage is about 35 tons. Total weight is 105 tons or 105,000kh.

The kinetic energy of the train is E= 1/2 m v2.

So the total kinetic energy of the train at 60mph is 0.5 * 105,000 * 27 *27
This is 38,272,500 Joules.

Looking it up, the energy content of diesel is about 38MJ / litre.

So in pure energy terms, it would appear you would only need a 1 liter of diesel.
But, and it's a big one...

No engine is 100% efficient. A good diesel engine can optimistically turn 30% of the chemical energy into usable work. Allow for a well used train engine and you're probably looking at about 20% actual efficiency.

So, the extra fuel to slow down and then speed back up will be about 5 litres.

Of course, this might be complete rubbish but it seems plausible!
Cheers,
Jason

Having not done this stuff for over a year, I'm not completely certain, but that does look about right.

 

[Peter Mugridge]

You can easily see why the Parry is so efficient on short shuttles can't you?

I wonder if it's possible to put a flywheel into an ordinary DMU to capture some of the braking energy to assist the re-start, or would the benefit be lost by having to lug the weight of the flywheel around once the train has regained speed?

 

[tbtc]

Another question (related, but different) would be the cost to the TOC (e.g. if slowing down, stopping, doors opening, doors closing, accelerating) added three minutes to the journey then this would cost the TOC 'x' in additional resources...

(plus the cost of stopping at a station?)

 

[455driver]

Plus the extra wear and tear on the brakes, gearboxes etc.

As for your (supposedly) environmentally friendly Prius, have you looked into the whole life costs for the car, I will stick to my fully depreciated (non turbo) diesel that returns a real world 62mpg thank you.

 

[b0b]

I thought I heard once that the average cost for an HST station call was in the region of 100 quid. Not sure what that figure includes though.

 

[90019]

Plus the extra wear and tear on the brakes, gearboxes etc.

As for your (supposedly) environmentally friendly Prius, have you looked into the whole life costs for the car, I will stick to my fully depreciated (non turbo) diesel that returns a real world 62mpg thank you.

Run it on used veg oil, and it's even cleaner and cheaper

Most people don't seem to realise that the majority of emissons produced by a car come from the production and disposal.

The Prius is a sham. The current one isn't so bad as it's actually a half decent sized family saloon, but as an eco car, it's pretty useless.

 

[Peter Mugridge]

The Prius is a sham. The current one isn't so bad as it's actually a half decent sized family saloon, but as an eco car, it's pretty useless.

I'm consistently getting 50+ mpg on the combined cycle from a 12½ year old Suzuki Swift automatic. That's something which is completely pre-electronics, is an automatic ( automatics are supposed to gobble more fuel than manuals ) and it's matching and bettering the hybrids...

 

[90019]

I'm consistently getting 50+ mpg on the combined cycle from a 12½ year old Suzuki Swift automatic. That's something which is completely pre-electronics, is an automatic ( automatics are supposed to gobble more fuel than manuals ) and it's matching and bettering the hybrids...

They do use a bit more than the equivalent manual, but it's not a huge difference.

 

[LE Greys]

Here's an extra stage to the question.

Does the fare paid by a passenger from Berney Arms to Norwich (return) justify the cost of stopping a 156 there twice?

 

[TheWalrus]

I was told £100 for a hst, but have since heard differently

 

[bangyuk]

The £100 might include a station access charge to the station operator - sounds a bit much for fuel alone?

As for the Prius mpg, I'm not really a car person, but it gets 30% more mpg than my last car, a diesel, it does me nicely and its a nice colour.

 

[455driver]

Run it on used veg oil, and it's even cleaner and cheaper

Used to use a 20% mix in my old corsa diesel , haven't had this one long enough to start mucking about yet, wont be long though

The Prius is a sham. The current one isn't so bad as it's actually a half decent sized family saloon, but as an eco car, it's pretty useless.

Agreed, a hybrid that is no more economical (in the real world) than a normal car is a complete waste of time and is only there to massage peoples ego.

 

[90019]

Agreed, a hybrid that is no more economical (in the real world) than a normal car is a complete waste of time and is only there to massage peoples ego.

And they're currently extremely polluting to produce and dispose of.

 

[Ivo]

I would have thought that it would be kinder to the environment to buy something like a Focus than a Prius because the production line emissions (where it is so much more active) would be less per unit? Throw in the fact mileage differences, and that even a Prius still contributes some pollution...

 

[455driver]

Re the Toyota Prius-

As for your (supposedly) environmentally friendly Prius, have you looked into the whole life costs for the car, I will stick to my fully depreciated (non turbo) diesel that returns a real world 62mpg thank you.

And they're currently extremely polluting to produce and dispose of.

One of the most expensive bits environmentally is the costs of making and disposing of the batteries.
Which ties in with what I wrote in post 8 above.

 

[90019]

I would have thought that it would be kinder to the environment to buy something like a Focus than a Prius because the production line emissions (where it is so much more active) would be less per unit? Throw in the fact mileage differences, and that even a Prius still contributes some pollution...

The most environmentally friendly car you can buy is a second hand diesel running on used veg oil.
You remove the emissions from producing a new car and disposing of the second hand one, as well as for producing diesel.

 

[Ivo]

Could always build one's own electric car, like I intend to one day.

Or buy one of these (good luck!)...

 

[O L Leigh]

Hydrogen fuel cells are a blind alley. Ask yourselves this simple question. Why are the leaders in developing hydrogen fuel for cars oil giants like BP and Shell?

If you can't make the leap from that one simple question alone, look up details on how commercial quantities of hyrdogen gas are refined.

O L Leigh

 

[bangyuk]

Honestly, if I'd wanted your prejudices about the Prius I would have posted to the Top Gear forum or asked Mr. Clarksod. As it is, the answers which kept to the topic have been useful and informative, thanks!

 

[ainsworth74]

if I'd wanted your prejudices about the Prius I would have posted to the Top Gear forum or asked Mr. Clarksod.

Its not prejudice. Take the battery for instance, the nickle is mined in Canada (and the mine has turned its surroundings into a polluted wasteland) shipped to Europe for refining before heading for China for more processing and finally making its way to Japan for assembly before the car is then sent to wherever!

Hybrids make a person feel better about their green credentials, but honestly its not that much better than an ordinary car if you look at the whole life of the vehicle.

 

[jon0844]

Hybrids aren't particularly good when you want to drive on a motorway, having to lug all the extra weight from those batteries. May as well get an electric-only vehicle and stick to town driving, and even then I'd wait until battery AND charging technology improves.

I'd say that an electric vehicle is the future, once the range improves and we can charge them in minutes, not hours. Then, like electric trains, you have the advantage of having many options on how you generate the electricity in the first place - as well as removing the pollution from the roads.

Suffice to say, if you want to take it to extremes then you ditch ALL motor vehicles and all take to two-wheels, or walk! Better still, we work to reducing all the journeys we don't need to do right now (such as driving miles to/from work if you don't NEED to be in an office 5 days a week) and other things like that.

 

[moonrakerz]

or, indeed, a hybrid like my Prius!

Which cost twice as much as my 1.6 petrol Ford which gives me over 50mpg on a long run !!

 

[b0b]

The £100 might include a station access charge to the station operator - sounds a bit much for fuel alone?

my understanding was that it included wear & tear on a 30 year old trainset as well as the fuel cost of accelerating to speed from a stop. It might include the charge, I don't remember.

 

[O L Leigh]

Honestly, if I'd wanted your prejudices about the Prius I would have posted to the Top Gear forum or asked Mr. Clarksod.

No-one would have mentioned the Toyota Pious if only you hadn't introduced yours into the discussion. However, as an aside, the Clarkson is correct. As much as his on-screen persona is to appear to be an arse and as offensive as possible, wider research shows that he is actually very well-informed.

The key to increasing fuel mileage has been well understood for very many years, and the answer lays in reducing weight, aerodynamic and mechanical drag, and in using highly efficient power plants. Hybrids are not a very good option because although they provide some efficiencies (e.g. by taking advantage of the different characteristics of petrol and electric motors), they are needlessly heavy and complicated machines and are consequently outperformed by conventional cars such as VW's Bluemotion range.

While I'm on a rant, I mentioned before about the blind alley offered by hydrogen fuel cells. Today I had to take my bike into the shop for a bit of fettling and, while I was waiting, I dived into an old copy of Bike magazine that was lying around in the waiting area. Contained within this publication was an article on an experimental Suzuki Burgman scooter that used a hydrogen fuel cell.

Now, I have already hinted at one of the reasons why it is a very bad idea but this article contained another very good reason, and that is efficiency. This article quotes an expert who states that refining, storing and transporting hydrogen requires so much energy that less than a quarter of the energy required to get hydrogen fuel into the customers vehicle would be available at the wheel. However, if this energy was put into the National Grid instead and used to charge up a battery electric vehicle approximately two thirds would be available at the wheel. This makes battery electric vehicles three times as efficient and only a third as polluting to run as equivalent vehicles powered by hydrogen fuel cells. This is an appalling statistic and certainly should make people think twice before proclaiming hydrogen fuel cells as being "zero emissions" or even the solution to the impending energy crisis.

But to bring this post back to the topic, the lessons learnt by the car industry should be understood also by the rail industry. For greater efficiency we need lighter and more aerodynamically efficient trains that take full advantage of efficient power and propulsion systems. We also need to be driving ahead with rail electrification in order that more of the network can be run from renewable energy such as wind power that is completely carbon neutral. Storage of kinetic energy using flywheels or battery banks to be fed back in as part of the acceleration phase does need to be considered, but only if the penalty in weight and complexity makes it sufficiently advantageous. Rail travel needs to be at the forefront of "green" transportation and to show it.

O L Leigh

 

[jon0844]

I wish I'd had the time to write even part of that!

Just out of interest, even with lighter trains (which must be possible by using more expensive, but lighter, materials) people are getting bigger and heavier - and more people are travelling. And more people are travelling carrying their whole life in a suitcase, as if they're never planning to go home.

How does this impact?

 

[Greenback]

But to bring this post back to the topic, the lessons learnt by the car industry should be understood also by the rail industry. For greater efficiency we need lighter and more aerodynamically efficient trains that take full advantage of efficient power and propulsion systems. We also need to be driving ahead with rail electrification in order that more of the network can be run from renewable energy such as wind power that is completely carbon neutral. Storage of kinetic energy using flywheels or battery banks to be fed back in as part of the acceleration phase does need to be considered, but only if the penalty in weight and complexity makes it sufficiently advantageous. Rail travel needs to be at the forefront of "green" transportation and to show it.

An excellent post sir! Although with our fragmented industry and cahs strapped government it's difficutl to see who would take the lead...