Steam v.s Diesel v.s Electric?

[MCR247]

1000 miles without re-fueling? You sure?

 

[moonrakerz]

Indeed it's not.
But you also have to take into account fuel used whilst a diesel is idling as well, and I would say electrics are likely to be more efficient than a diesel overall.

Indeed -the diesel is probably idling to to keep the heating/air-con/lighting going, which an electric would have to do as well, but at night the diesel is shut down. At night the power station is kept running so that the power is instantly available for the morning rush hour.
"Efficiency" is notoriously difficult to define and calculate.

A diesel train carries its own fuel with it - for which there will be a penalty. A diesel train undoubtedly has much higher maintenance costs, but fuel supply costs are small.

An electric train picks up its "fuel" as it needs it. That fuel at the trackside is made from some other type of fuel: gas, coal, nuclear, wind, tidal - to convert that fuel into electricity incurs a penalty. Then to transfer that electricity many miles to the train also incurs a further penalty. Much less maintenance (and simpler) on an electric train, but "fuel" supply costs are enormous and bring their own problems as we have seen of late.

I am not "in favour" of either type, completely open minded - but I would like to see a proper comparison on the true costs of each type of motive power - it seems to be written in stone that electric is "better" - but is it ?
I seem to remember that the prediction that the Himalayan glaciers would all have melted by 2035 was also written in stone.....................AND - many years ago it was stated that nuclear generated electricity would be so cheap that it wouldn't be worth the trouble of metering it ..............dream on !

 

[jopsuk]

With effective fuel efficiency, figures aren't always very "true". for example, there's attempts to to put the consumption of power by electric cars in terms of mpg, based on the generation and tramission and use of the electricity. Howver, fuel consumption figures for petrol/diesel cars don't take into consideration the extraction, production and transportation of the fuel- I think once those are factored in you effectively have around one-third of the quoted fuel efficiency. I may have this figure wrong

There's a lot of misinformation about energy effiency- a friend has been trying to put together an internal website for his work with simple facts, and has found it very very frustrating trying to find well sourced reliable data.

 

[sprinterguy]

1000 miles without re-fueling? You sure?

I don't know about 165s, but I do know that HSTs can manage about 1,200 miles on one tank of fuel, and a 37 with extended fuel tanks can manage about 800 miles. So 1,000 miles for a DMU which has a much smaller engine than a loco sounds reasonable.

 

[Royston Vasey]

I don't know about 165s, but I do know that HSTs can manage about 1,200 miles on one tank of fuel, and a 37 with extended fuel tanks can manage about 800 miles. So 1,000 miles for a DMU which has a much smaller engine than a loco sounds reasonable.

Don't forget the HST range is on two tanks of fuel, not one. There is also much more space on the underframe of a power car to put a big fuel tank than an underfloor-engined DMU.

 

[sprinterguy]

Don't forget the HST range is on two tanks of fuel, not one. There is also much more space on the underframe of a power car to put a big fuel tank than an underfloor-engined DMU.

Yeah, I was keeping those facts in mind. A 165 has a much smaller fuel tank, but also a much smaller engine size, so should manage a better mpg figure. And remember that a 165 has 2 or 3 engines per unit, in the same way that a HST has two, but has much less weight to haul around.

 

[90019]

At night the power station is kept running so that the power is instantly available for the morning rush hour.
"Efficiency" is notoriously difficult to define and calculate.

Actually, they're not. Only the ones that are needed to generate enough power are kept running. It is a huge waste to generate electricity that isn't needed as it can't be stored on the national grid. What they have is people watching the time, the day, what's happening on tv, what other events are happening, then predicting the amount of power that will be needed, so that power stations aren't running unnecessarily and wasting power. There are also a few around the UK that can be powered up within a couple of minutes for an instant increase in power when needed.

 

[LE Greys]

If we look at straightforward thermal efficiency, I believe that the best passenger vehicle in the country is rather surprising, the IC 225. Having only four motors probably helps. I can't remember the figure, but I think it's about 37%. An MTU-powered HST is about 32%, while a 9-car Meridian is about 28%. Duke of Gloucester with 10 MkIs comes in around 25%.

If anyone has better figures, please pass them on.

 

[moonrakerz]

Actually, they're not. Only the ones that are needed to generate enough power are kept running. It is a huge waste to generate electricity that isn't needed as it can't be stored on the national grid. What they have is people watching the time, the day, what's happening on tv, what other events are happening, then predicting the amount of power that will be needed, so that power stations aren't running unnecessarily and wasting power. There are also a few around the UK that can be powered up within a couple of minutes for an instant increase in power when needed.

Actually - they are.............

I was going to mention that because I was half expecting that response - I saw that programme on BBC 4 as well ! Interesting but rather simplistic - all you need is a copy of the TV Times.......

"Steam" power stations (the overwhelming majority) have to be kept "hot". You cannot start one up from cold in a few minutes - it takes hours/days.
More power stations than are needed are kept running (not all generating - if there is no load you cannot actually produce much electricity - nowhere for it to go) overnight, perhaps on half load ("spinning or generating reserve") so that full output can be ramped up fairly quickly in response to expected demand.
A turbo generator is kept spinning on low load, as the load increases (ie: more output required) it is physically harder to turn the rotor, so more steam is fed to the turbine, which obviously requires more gas/oil/coal to be burnt - this all takes time, the whole generating loop HAS to be kept hot. If the steam cannot keep pace with the demand the generator will start to slow down. As it slows the frequency will drop, this is the critical feature, not the voltage. Voltages can vary by as much as 10%, frequency is normally kept to within 0.4%.
Because of their design, nuclear reactors are not as flexible as most other types of power station, so are kept on as high an output figure as possible - supplying a large percentage of the base load.

Facilities like Dinorwig are used for large short term surges (such as everyone making a cup of tea when England go three nil down to The Faroe Islands at Wembley), not for standing load. Dinorwig is an amazing place, it can produce 1800MW; from zero to full output in less than a couple of minutes - BUT after 5 hours the lake is empty, it then takes longer than that to re-fill it, and that can only be done when there is spare generating capacity available elsewhere.
The conventional power stations are supplying power to Dinorwig to pump water back up into the lake (overnight) - Dinorwig actually uses about one third more electricity than it ever produces - not very efficient at all, but it was built for a specific purpose which it fulfills admirably. The "green" lobby certainly cannot hold Dinorwig up as an good example.

They used to do tours of Dinorwig, don't know if they still do - worth a visit, an Amazing place.

 

[90019]

Actually - they are.............

I was going to mention that because I was half expecting that response - I saw that programme on BBC 4 as well ! Interesting but rather simplistic - all you need is a copy of the TV Times.......

Fair enough, I was just going on what I've been told before, as well as the documentary, which was certainly interesting to watch


I remember hearing about an incident a few years back with a mix up of instructions I think it was, leading to 2 nuclear power stations being shut down for maintainance at the same time rather than one. Apparently they came within about an hour of having blackouts becuase of it.

They used to do tours of Dinorwig, don't know if they still do - worth a visit, an Amazing place.

Yeah, I've been round Cruachan a few years ago and Torness as well, but that was a few years ago. I'm going to find out about Cruachan again sometime, and find out if you can still see Torness.

 

[LE Greys]

"Steam" power stations (the overwhelming majority) have to be kept "hot". You cannot start one up from cold in a few minutes - it takes hours/days.
More power stations than are needed are kept running (not all generating - if there is no load you cannot actually produce much electricity - nowhere for it to go) overnight, perhaps on half load ("spinning or generating reserve") so that full output can be ramped up fairly quickly in response to expected demand.
A turbo generator is kept spinning on low load, as the load increases (ie: more output required) it is physically harder to turn the rotor, so more steam is fed to the turbine, which obviously requires more gas/oil/coal to be burnt - this all takes time, the whole generating loop HAS to be kept hot. If the steam cannot keep pace with the demand the generator will start to slow down. As it slows the frequency will drop, this is the critical feature, not the voltage. Voltages can vary by as much as 10%, frequency is normally kept to within 0.4%.
Because of their design, nuclear reactors are not as flexible as most other types of power station, so are kept on as high an output figure as possible - supplying a large percentage of the base load.

As I understand it, nuclear reactors are self-regulating because a decrease in steam demand causes an increase in reactor core temperature. This attenuates the neutron flux, reducing the reaction rate and thus the temperature in the core. Nuclear-powered ships use this to avoid having to drop the control rods into the core when running slowly. It's a very useful feature.

 

[RobShipway]

I am for electric, however the electricity is from either nuclear powered or coal powered stations so it is possibly as I think has been discussed here before just as much fumes going into the air from Electric trains as there is from Diesel trains.

 

[TGV]

Oh dear. Did we all get it wrong?

 

[Daimler]

If we look at straightforward thermal efficiency, I believe that the best passenger vehicle in the country is rather surprising, the IC 225. Having only four motors probably helps. I can't remember the figure, but I think it's about 37%. An MTU-powered HST is about 32%, while a 9-car Meridian is about 28%. Duke of Gloucester with 10 MkIs comes in around 25%.

If anyone has better figures, please pass them on.

I'm no expert on these things, but the 5AT project website would appear to suggest that efficiency for steam engines is rather lower:

I remember reading - some time back - an extensive comparison between different forms of traction, but unfortunately I can't remember the exact figures. Suffice to say, steam was significantly less efficient than other forms of traction (and I seem to remember that even electric traction struggles to beat 40% efficiency).

The 5AT project website has some interesting figures for steam locomotive efficiency, which would appear to suggest that a standard steam locomotive such as those preserved today would struggle to achieve as much as 8% efficiency, since this is the figure quoted for the advanced (for steam as a mode of traction in general) Chinese 'QJ' class.

However, those involved in the 5AT project seem to think that a 'modern' steam locomotive (as opposed to Tornado, which in the most part is a replica of a 1940s steam locomotive) might be able to achieve as high as 16% efficiency - which might seem very poor, but is already a tremendous improvement!

Apologies for shamelessly quoting my own post!

EDIT: Here's the relevant page on the 5AT project website.

 

[LE Greys]

I'm no expert on these things, but the 5AT project website would appear to suggest that efficiency for steam engines is rather lower:



Apologies for shamelessly quoting my own post!

EDIT: Here's the relevant page on the 5AT project website.

Interesting. Looks like my figures must have been calculated differently - probably from the standard BR power curve, although that referred to mean effective pressure rather than thermal efficiency.