Electrification - Back to Square One

[Joseph_Pestell]

I have a horrible vision of all of the streets set up like a dodgem car ride.

Or worse - like a trolleybus system.

[The Stationmaster]

"normal" fuel consumption was reckoned as a gallon a mile on average for most diesel locos when I was at Ipswich in the 80s. Ok, we didn't have Deltics but that was how we reckoned it for our locos

 

Andi

 

The standard allowance in loco diagramming (officially, for all except Class 60s) in BR days was an average of 1 gallon per mile for mainline diesels.  Class 60s were individually assessed according t the turn they would be working but the outcome wasn't much different.  Overall I think dmus used a bit less per mile than locos.

[rodent279]

Don't forget the thermal efficiency of even the best diesel engines struggles to reach 50% (for the average steam loco, it's more like 8%, and that'd be a good 'un). In other words, half of the enrgy stored in a tank of diesel gets wasted as heat.

So, if you're looking at this purely from an "energy stored in a tank of diesel/used on a tour of duty", vs "energy stored in a battery/used in a tour of duty".......don't forget that at best half of the energy stored in a tankful of diesel is wasted, and does not contribute to the useful work done by the engine.

I'd hope that the internal losses in a traction battery, and the losses in the control system would be far smaller, and that the overall efficiency from "energy stored" to "work done" would be much higher.

[Trog]

My point is that this is a brand-new (approx. 3 year old) concrete crossover which replaced a 35-year old timber layout that we managed to keep in good order and SAFE (sometimes straying onto Very Poor as far as track geometry was concerned) for years and years - desperate for it to be renewed and not knocked out of the renewal plan again for another year - now it has been done and they've managed to cock it up and break it within a very short space of time - all the IBJ's around this new x-over are sat in patches of wet-beds etc.

 

Sounds like the installation may have been more than a bit lacking, even with poor maintenance track done properly including drainage if required should not go to wet beds in three years.

[Edwin_m]

Don't forget the thermal efficiency of even the best diesel engines struggles to reach 50% (for the average steam loco, it's more like 8%, and that'd be a good 'un). In other words, half of the enrgy stored in a tank of diesel gets wasted as heat.

So, if you're looking at this purely from an "energy stored in a tank of diesel/used on a tour of duty", vs "energy stored in a battery/used in a tour of duty".......don't forget that at best half of the energy stored in a tankful of diesel is wasted, and does not contribute to the useful work done by the engine.

I'd hope that the internal losses in a traction battery, and the losses in the control system would be far smaller, and that the overall efficiency from "energy stored" to "work done" would be much higher.

 

I saw some calculations some years ago which suggested that the "well to wheel" efficiency of electric and diesel were not much different, once the efficiency of the power station was taken into account (this is around 50% maximum, and losses in the power transmission must also be considered).  The losses in charge and discharge of a battery are probably somewhere around 30% so a battery train could be less energy efficient than a diesel. 

 

However, more recently regenerative braking has become universal in new electric units, and battery units should be able to regenerate into the battery unless it is fully charged already.  This typically reduces consumption by 15-20%.  Also a diesel engine can only use diesel, which has to come from fossil sources or biofuel.  Electric or battery trains can make use of power from any source including renewables and nuclear, so even if the overall efficiency is lower overall electric/battery may still be the way to go. 

[rodent279]

I saw some calculations some years ago which suggested that the "well to wheel" efficiency of electric and diesel were not much different, once the efficiency of the power station was taken into account (this is around 50% maximum, and losses in the power transmission must also be considered).  The losses in charge and discharge of a battery are probably somewhere around 30% so a battery train could be less energy efficient than a diesel. 

 

However, more recently regenerative braking has become universal in new electric units, and battery units should be able to regenerate into the battery unless it is fully charged already.  This typically reduces consumption by 15-20%.  Also a diesel engine can only use diesel, which has to come from fossil sources or biofuel.  Electric or battery trains can make use of power from any source including renewables and nuclear, so even if the overall efficiency is lower overall electric/battery may still be the way to go. 

 

Yes, that'd be about right. The best conventional power stations I suspect can edge over 50%, but not by much. I would imagine efficiency of transmission & distribution systems is in the mid to high 90's, so still probably better than straight diesel-electric, though again, not by a long way.

 

I believe Chapelon argued that the overall efficiency from burning the coal in the power station to using electricity in a 1500 V D.C. locomotive, using the technology of the 1930's & 1940's, wasn't appreciably higher than burning coal in the firebox of one of his most advanced steam locos.

 

But of course, as you say, electric traction, whether traditional via 3rd rail or OHL, ov via battery, can be powered by renewables and/or nuclear, and regen braking can feed back into the grid.

 

(And you have to remember that the thermal efficiency figures are the best achievable, which is usually under a steady load. In a power station, it's easier to run the prime mover at a steady load, with little or no fluctuation, whereas a diesel engine in a vehicle is constantly going through load cycles, from idle to maximum, to part load, back to idle, & so on.)

Edited July 28, 2017 by rodent279

[jim.snowdon]

Yes, that'd be about right. The best conventional power stations I suspect can edge over 50%, but not by much. I would imagine efficiency of transmission & distribution systems is in the mid to high 90's, so still probably better than straight diesel-electric, though again, not by a long way.

 

I believe Chapelon argued that the overall efficiency from burning the coal in the power station to using electricity in a 1500 V D.C. locomotive, using the technology of the 1930's & 1940's, wasn't appreciably higher than burning coal in the firebox of one of his most advanced steam locos.

 

But of course, as you say, electric traction, whether traditional via 3rd rail or OHL, ov via battery, can be powered by renewables and/or nuclear, and regen braking can feed back into the grid.

 

(And you have to remember that the thermal efficiency figures are the best achievable, which is usually under a steady load. In a power station, it's easier to run the prime mover at a steady load, with little or no fluctuation, whereas a diesel engine in a vehicle is constantly going through load cycles, from idle to maximum, to part load, back to idle, & so on.)

It would have to be questioned as to whether Chapelon was quoting the best achievable results for his steam locomotives, or what could be achieved on a typical day by a typical fireman and driver, who could not be relied upon to work the locomotive to its optimum, o rindeed whether the locomotive itself was in good condition. Nonetheless, I think you will find that a coal powered generating station, using pulverised coal in a stationary boiler that is free from the constraints of a locomotive, will yield a higher efficiency in terms of energy in to energy out.

 

Regenerative braking on trains has a positive benefit, although the proportion recoverable is generally reckoned to be only about 20% on average - stopping trains will achieve better than long distance trains, as most of the energy used by the latter goes in overcoming train resistance and is lost as heat. The recoverable energy is really limited to the kinetic energy of the train. The presumption has to be that the regerated energy can be fed back into the traction supply and used elsewhere, otherwise it has to be dissipated as heat in on-board resistors. It is possible to regenerate into a battery, but the significant limitation is the rate at which the battery can convert that energy into stored charge - in practice this is relatively low, so most of the energy still has to be dumped. Super-capacitors may be a more viable alternative, but I haven't seen these applied to anything larger than trams so far, and even there they remain a relative novelty, intended more as a means of operating for short distances without overhead (so as not to spoil the appearance of the historic town square, etc.).

 

Jim

[jjb1970]

The interesting thing about the changes we are seeing in energy conversion is that the old assumption that inefficiency = more fuel in = more emissions out = worse for the environment is no longer necessarily true. If you have a genuine low carbon, renewable form of energy conversion such as wind, tidal, wave then poor energy efficiency is much less of a concern. That means you can look at generating hydrogen from sea water as a transport fuel for example. Yes it's inefficient, but you're not making pollution at the point of energy conversion (clearly, there is still an environmental impact from construction and decommissioning). So for an electric railway (which could be electric by virtue of wires, or by batteries, or fuel cells) it may not really matter if you have losses in generation and transmission.

Something to keep in mind is that when looking at efficiencies it is important not to compare apples with pears. Yes, a modern diesel engine can achieve 50% efficiency (a lot more with energy recovery) but that is at it's design point at stable loads. At high turn down ratios and if binary loading that nominal efficiency won't be achieved. A power plant on the other hand tends to run at or near its design point at a stable load and so can actually be expected to achieve its nominal efficiency in a way that diesel engines in transport applications generally don't.

That said, the efficiency of a power plant depends on a lot of factors, a combined cycle gas turbine plant is much more efficient than a coal fired steam plant, just as a combined heat and power plant is much more efficient than a straight power plant. A supercritical coal plant without CHP will probably achieve about 45% (the ones we currently have are less than that), a CCGT CHP can go about 80% with the right heat balance.

The thing that I think should really favous electricity is pollution (carbon perhaps excepted) and operating costs. Even if we took the diesel engine efficiency at a nominal efficiency then that engine needs a lot of maintenance in terms of hr/KWhr relative to a power plant, it uses expensive oil fuel instead of cheap gas or free wind (admittedly, you can run modify trains to use LNG fuel) and emissions abatement is nowhere near as effective as the systems used in power plants.

If considering steam locomotives, then I don't think there is any way you could argue they are competitive in terms of efficiency regardless of where you draw the system boundary.

[Joseph_Pestell]

Don't forget the thermal efficiency of even the best diesel engines struggles to reach 50% (for the average steam loco, it's more like 8%, and that'd be a good 'un). In other words, half of the enrgy stored in a tank of diesel gets wasted as heat.

So, if you're looking at this purely from an "energy stored in a tank of diesel/used on a tour of duty", vs "energy stored in a battery/used in a tour of duty".......don't forget that at best half of the energy stored in a tankful of diesel is wasted, and does not contribute to the useful work done by the engine.

I'd hope that the internal losses in a traction battery, and the losses in the control system would be far smaller, and that the overall efficiency from "energy stored" to "work done" would be much higher.

That depends how you obtain the electricity that you are using. If via the National Grid, you have transmission losses that are roughly equivalent to that inefficiency of the diesel engine.

[david.hill64]

That depends how you obtain the electricity that you are using. If via the National Grid, you have transmission losses that are roughly equivalent to that inefficiency of the diesel engine.

Really? National Grid quotes nationwide transmission loss at about 1.8%. Most of this will be in the low voltage transmission within cities, not in high voltage lines which could include the railway 25kV system. I have been trying to find out at what voltage electricity is sent from wind arrays as I never see high voltage lines from them and suspect that they are busy warming the earth through buried cables.

[jim.snowdon]

That depends how you obtain the electricity that you are using. If via the National Grid, you have transmission losses that are roughly equivalent to that inefficiency of the diesel engine.

Power lost in transmission is proportional to the square of the current, times the impedance. Power transmitted is voltage times current, so if you increase the voltage, the current is reduced proportionately, and the power loss by the square of that reduction.

 

That's why the National Grid core network runs at 400kV (and 800kV was looked at a while back), supported by a second tier network at 264kV. The Regional Electricity Companies take over at 132kV.

 

Translated into a railway context, in simple terms, it's why the tird rail network is all about not many volts but lots of amps, whereas the AC network is all volts and not many amps.

 

Jim

[Edwin_m]

In the next few decades we will need a lot more power generation to power electric cars, at the same time as coal and older nuclear stations are being shut down and new nuclear capacity will only appear slowly.  Renewables help up to a point but most forms aren't reliably available at the times they are needed, but if they are backed up by energy storage then the power they produce when nobody wants it becomes a valuable resource and won't be used for processes like generating hydrogen which are only worthwhile if the energy is free.  With all these considerations I'd suggest that energy efficiency will still be an important consideration in the electrified railway network for the foreseeable future. 

Edited July 29, 2017 by Edwin_m

[jim.snowdon]

In the next few decades we will need a lot more power generation to power electric cars, at the same time as coal and older nuclear stations are being shut down and new nuclear capacity will only appear slowly.  Renewables help up to a point but most forms aren't reliably available at the times they are needed, but if they are backed up by energy storage then the power they produce when nobody wants it becomes a valuable resource and won't be used for processes like generating hydrogen which are only worthwhile if the energy is free.  With all these considerations I'd suggest that energy efficiency will still be an important consideration in the electrified railway network for the foreseeable future. 

It doesn't appear to have dawned on the politicians (not that that is novel), that if they replace internal combustion engined vehicles by electric ones, (a) the energy currently stored in all the petroleum products that these vehicle use as fuel will still need to be found from somewhere, ie more power stations, and (b) given the rather more limited range of electric vehicles, either the populus will have to clump together in ever bigger cities, or the railways will need expanding to allow the goods and materials to be got to the customer - in a way, back to the pre-WW1 era, when it was the railways (and canals) that got everything moved round the country. Long distance travel by road will largely become a non-starter, simply because once a refuelling stop has to be factored in, the time it takes to re-charge a decent sized battery will become a large part of the whole journey time.

 

Jim

[pH]

 Long distance travel by road will largely become a non-starter, simply because once a refuelling stop has to be factored in, the time it takes to re-charge a decent sized battery will become a large part of the whole journey time.

 

 

This may apply to small, densely-populated countries like the the UK, but there is no way it can be applied to large, thinly-populated countries like (for example) the US, Australia or Canada. And I think it illustrates that there isn't a "one size fits all" solution here. 

 

I am going to be driving 650 km across BC this week. I will be carrying items my son and daughter-in-law have bought online from stores local to us here. (Not the main point of the journey, but "Since you are coming anyway, could you bring ...) . There is absolutely no way that I could do that journey by train - the nearest station to our destination is 250 km away, and I don't know of any public transit between it and our destination. There is a bus service, 50% slower than by car and more expensive than what it will cost me in gas (yes, I know I've already absorbed fixed costs, but it's surprisingly more expensive) or flights which are even more expensive, and would require a car trip at the end to get to our destination, anyway. 

 

EVs over that distance, with 'refuelling' stops, would stretch the journey to about what it was 50 years ago when the road was nothing like what it is today. And there aren't many towns (i.e fuelling stations) on the way. It's not too difficult to run out, and you don't want to be caught out on that road in anything but good weather. (Basic rule - if you don't know a road well, when the gas gauge hits "1/2 full", stop at the next gas station and fill up.)

 

I could be wrong, but I don't see 'battery' vehicles of any size (car, bus, truck etc.) working in the countries I mentioned for long distances. Trains are just not an option in large parts of these countries. Hybrids road vehicles are possiblilities, though, where they are not totally dependent on electrical power.

[rodent279]

Another factor to consider with electric cars is how good will they be at towing? We go camping with a small trailer rammed with camping gear, and are thinking of going for a trailer tent. If you start adding trailers, caravans, boats etc, you'll drain the battery quicker. Since, love 'em or hate 'em, a lot of people tow caravans etc, if an electric car isn't suitable for towing, they're not going to buy one.

Clever politicians haven't thought thought of that have they?

[david.hill64]

Another factor to consider with electric cars is how good will they be at towing? We go camping with a small trailer rammed with camping gear, and are thinking of going for a trailer tent. If you start adding trailers, caravans, boats etc, you'll drain the battery quicker. Since, love 'em or hate 'em, a lot of people tow caravans etc, if an electric car isn't suitable for towing, they're not going to buy one.

Clever politicians haven't thought thought of that have they?

Getting caravans off the road? A hidden benefit!!!

 

Seriously though electric vehicles have higher torque and therefore potentially really suited to towing but will consume energy in doing so.

Edited July 30, 2017 by david.hill64

[jjb1970]

It doesn't appear to have dawned on the politicians (not that that is novel), that if they replace internal combustion engined vehicles by electric ones, (a) the energy currently stored in all the petroleum products that these vehicle use as fuel will still need to be found from somewhere, ie more power stations, and (b) given the rather more limited range of electric vehicles, either the populus will have to clump together in ever bigger cities, or the railways will need expanding to allow the goods and materials to be got to the customer - in a way, back to the pre-WW1 era, when it was the railways (and canals) that got everything moved round the country. Long distance travel by road will largely become a non-starter, simply because once a refuelling stop has to be factored in, the time it takes to re-charge a decent sized battery will become a large part of the whole journey time.

 

Jim

 

The government proposal does not outlaw IC engines, range extender arrangements such as PHEVs will still be allowed. A 300 mile+ range is already practical from pure batteries and it is going up. The recharge times are coming down. Energy is increasingly moving away from large centralised generation towards distributed power and more localised distribution. I think that very soon most of us will become "prosumers". I really don't see the high profile recently announced target as being particularly ambitious and see no real technical arguments against it.

[JJGraphics]

Another factor to consider with electric cars is how good will they be at towing? We go camping with a small trailer rammed with camping gear, and are thinking of going for a trailer tent. If you start adding trailers, caravans, boats etc, you'll drain the battery quicker. Since, love 'em or hate 'em, a lot of people tow caravans etc, if an electric car isn't suitable for towing, they're not going to buy one.

Clever politicians haven't thought thought of that have they?

 

 

Are there actually any Clever Politicians? If so, they are strangely invisible.

 

John

[jim.snowdon]

Are there actually any Clever Politicians? If so, they are strangely invisible.

 

John

Not in the UK there aren't, at least in terms of having any real function in government. There are, though, too many at the top who are clever at scheming ways to ensure that they hold the strings of power, eeven if they don't know what to do with them.

 

Jim

[Mark Saunders]

Are there actually any Clever Politicians? If so, they are strangely invisible.

 

John

 

They are being clever by not being seen then when it goes wrong they blame someone else!

 

The real beauty of this is that in many cases Central Government passes decisions down to County Council level!

 

Mark Saunders

[phil-b259]

They are being clever by not being seen then when it goes wrong they blame someone else!

 

The real beauty of this is that in many cases Central Government passes decisions down to County Council level!

 

Mark Saunders

 

Quite so

 

hence the retort from ministers when questioned about congestion charging / financial penalties for drivers of fossil fuelled cars has been met with the "we believe its up to local people to decide whats best for their area" While this sounds all very noble such statements usually ignore the fact that insufficient funding has been passed down to local authorities to implement such changes or that the funding is conditional upon local authorities doing unpopular things.

[rockershovel]

Not in the UK there aren't, at least in terms of having any real function in government. There are, though, too many at the top who are clever at scheming ways to ensure that they hold the strings of power, eeven if they don't know what to do with them.

 

Jim

Clever politicians are quite common, well advised ones of sound judgement, committed to their supposed roles and duties, rather less so.

 

This isn't new. The late, great A P Herbert brought us this snippet from Mr Justice Cocklecarrot;

"Mr Haddock, I have listened to your submission to this bench for some time now, and I am none the wiser"

"As your Lordship says; however, you ARE now, somewhat better informed"

[number6]

Clever politicians are quite common, well advised ones of sound judgement, committed to their supposed roles and duties, rather less so."

You get the politicians you deserve, they are a reflection of our society and if they aren't clever...

[APOLLO]

Quite so

 

hence the retort from ministers when questioned about congestion charging / financial penalties for drivers of fossil fuelled cars has been met with the "we believe its up to local people to decide whats best for their area" While this sounds all very noble such statements usually ignore the fact that insufficient funding has been passed down to local authorities to implement such changes or that the funding is conditional upon local authorities doing unpopular things.

 

Several years ago up here in Wigan we were given a vote whether or not to accept congestion charging in the Greater Manchester area (of which Wigan is a part). The overwhelming vote was NO throughout Greater Manchester, and I suspect in any future votes (if ever given) the same result will occur.

 

Wigan does not have serious congestion issues, Manchester City (and a few adjoining areas) does. Why should I pay for those, unless visiting there ?

 

Brit15

[rodent279]

Are there actually any Clever Politicians? If so, they are strangely invisible.

 

John

 

Yes, there are many very clever politicians. They are very clever at passing the blame onto others, and at devising devious schemes that benefit themselves and their vested interests, while at the same time hoodwinking large sections of the voting public into thinking that they are acting in their best interests.

 

You get the politicians you deserve, they are a reflection of our society and if they aren't clever...

 

Never a truer word was spoken.

Edited July 30, 2017 by rodent279