Why we shouldn't electrify more of the UK

[najaB]

Only possible with a Diesel-Electric transmission of course. Big resistor banks on the roof to dump the load (e.g. Voyagers, Meridians)

Or a more environmentally friendly option would be to shove it into batteries either for providing ETH or for traction.

The problem again being one of peakedness - if you've got batteries large enough to take the several megawatts being thrown at them during heavy braking, then they're probably too big (ie. heavy) for the job.

 

[swaldman]

The problem again being one of peakedness - if you've got batteries large enough to take the several megawatts being thrown at them during heavy braking, then they're probably too big (ie. heavy) for the job.

Yeah, this is where flywheels or supercapacitors, offering high-power short-period storage, might become worthwhile. By building a "hybrid" diesel train like this, where the energy lost when braking can be reused to accelerate, I suspect that the energy required for a commuter route could be reduced substantially - and maybe even the required engine size decreased, depending on the length of gradients on the route.

 

[Spod]

The problem again being one of peakedness - if you've got batteries large enough to take the several megawatts being thrown at them during heavy braking, then they're probably too big (ie. heavy) for the job.

What would prevent supercapacitors being used to take the sudden influx of energy and trickle it out to the batteries (or skip the batteries and run systems directly off the supercapacitors)?

 

[Bletchleyite]

The problem again being one of peakedness - if you've got batteries large enough to take the several megawatts being thrown at them during heavy braking, then they're probably too big (ie. heavy) for the job.

You'd think, but on a smaller scale isn't this how the Toyota Prius and similar non-plugin hybrids work?

 

[gallafent]

Or a more environmentally friendly option would be to shove it into batteries either for providing ETH or for traction.

Oh yes, definitely. Are there any trains that do this (yet) though?

 

[gallafent]

You'd think, but on a smaller scale isn't this how the Toyota Prius and similar non-plugin hybrids work?

Yes (Toyota's Hybrid Synergy Drive is a particuarly clever way to do this). Lifting off the accelerator, and light braking, charge the battery. Once the maximum charge rate is reached, conventional mechanical braking is blended in to provide the desired level of retardation. Likewise when the power demand of maintaining/increasing speed is below a certain level the power is all drawn from the battery and fed through the electric drive to the wheels. Once power demand exceeds battery/motor capacity, the internal combustion engine starts to chip in. Big fuel economy rewards for smooth driving (unless you're too smooth, so the discs rust up .

 

[najaB]

You'd think, but on a smaller scale isn't this how the Toyota Prius and similar non-plugin hybrids work?

It is, but as you say on a *much* smaller scale. Kinetic energy goes up linearly with mass and as the square of velocity - both of which are typically much higher for a train than a Prius.

Edit: As an example, a Class 390 at cruising speed (225km/h) has about 6000 times the kinetic energy of a Prius at cruising speed (100km/h).

 

[gallafent]

It is, but as you say on a *much* smaller scale. Kinetic energy goes up linearly with mass and as the square of velocity - both of which are typically much higher for a train than a Prius.

Acceleration and deceleration of a Prius (thus power required/generated per mass) are at much greater rates than trains too though, so the difference in power transfer requirements aren't as great as that might suggest … aside from the substantially larger motor/generators, and batteries, on trains, … time for a bit of arithmetic to see if putting some Prius drivetrains (one per axle?) under some D-stock might be a goer

In other words, it's the differential of kinetic energy that's the relevant quantity …

 

[AM9]

Or a more environmentally friendly option would be to shove it into batteries either for providing ETH or for traction.

Probably super-capacitors would be better to absorb short bursts of braking, giving support to subsequent acceleration.

 

[najaB]

time for a bit of arithmetic to see if putting some Prius drivetrains (one per axle?) under some D-stock might be a goer

Class e230?

 

[reddragon]

In China, some 350,000 Electric buses charge up via super-capacitors in very short bus stop calls, so in a basic form it works.

The move to rail will happen, certainly before 2040 on passenger trains but the tech for heavy freight is not there, unless maybe wagons are powered too? FeMUs?

 

[xotGD]

Doesn't that logic lead to an intractable eggchicken situation (unless of course a programme is put in place through which the lines, and the (vast majority of the) trains, are upgraded to be electric, or bi-mode, at the same time)? … but surely the DfT could never make that happen

It has actually happened in reverse. When an increased proportion of the cross country route network was electrified (Doncaster - Scotland), they switched to an all diesel fleet.

 

[K.o.R]

Watering points for steam locos typically had to deliver enormous volumes in a very short time during station stops. In order to do this, they had to have large tanks which were replenished from local sources slowly between trains. Similarly, charging points for on board supercapacitors can be equipped with their own large battery bank that can be recharged slowly between trains from normal local mains supplies that could not otherwise be expected to meet the surges on their own. Storage changes everything.

Hmm, on that note, could you have a small pumped-storage system to generate the power? Probably nowhere near big enough, but the "water tower" comment made me wonder.

 

[K.o.R]

In China, some 350,000 Electric buses charge up via super-capacitors in very short bus stop calls, so in a basic form it works.

The move to rail will happen, certainly before 2040 on passenger trains but the tech for heavy freight is not there, unless maybe wagons are powered too? FeMUs?

I do wonder if small motors on all wheels wouldn't be a very good idea for freight.

 

[snowball]

Class e230?

Vivarail sem to be prepared to consider a wide range of power sources, but still use the name Class 230 for all of them.

 

[mark-h]

Our grid is now dominated by Renewables (solar / wind etc) & nuclear and NR has always been contracted to Nuclear historically (not sure about now).

Gridwatch has live data on the UK power supply. Currently the supply is dominated by CCGT (47%).

 

[birchesgreen]

I do wonder if small motors on all wheels wouldn't be a very good idea for freight.

"Freight multiple units" based on the same platform as the Windhoff MPV do exist.

https://en.wikipedia.org/wiki/CargoSprinter

 

[InTheEastMids]

The problem again being one of peakedness - if you've got batteries large enough to take the several megawatts being thrown at them during heavy braking, then they're probably too big (ie. heavy) for the job.

It's the power electronics that are the main issue - and the next generation of fast chargers will charge at up to 350 kW, whereas something like a Nissan Leaf has a max output of around 100 kW, so your average EV will soon be set up to charge faster than it can discharge.

Yes (Toyota's Hybrid Synergy Drive is a particuarly clever way to do this)

I'm a little bit surprised train manufacturers have not really tried something this, because it's efficient compared to not hybridising and is very reliable - that's why a lot of Prius are used as taxis.

Gridwatch has live data on the UK power supply. Currently the supply is dominated by CCGT (47%).

It feels like there's a big debate about the electricity system on here, as it relates to rail electrification, every 6 months or so...

NR electricity consumption is apparently 3.2 TWh in a GB electricity system that consumed 319 TWh in 2017 (that's 1%) and forecasts a similar level in 2030 (Source: 2018 National Grid Future Energy Scenarios). The lights are not going to go out because NR did, or did not electrify some bits of railway. To put it another way: This uncertainty is much, much less than other uncertainties around industrial demand, electric cars, electric heating and so on that the electricity industry manages.

Hypothecating any new demand for electricity to the marginal or dirtiest generator on the system is to misunderstand how the electricity system works. It's either a technical question of "system level" efficiency (i.e. how many TWh of electricity were produced from TWh fuel ), which you can do over a year or half-hourly if you like your spreadsheets with >17500 rows. Or you can follow the money, see that NR buys from EDF and must conclude that the overwhelming majority of rail power comes from nukes.

The electricity system is decarbonising rapidly, so if CO2 is your thing, then the rate of decarbonisation is really material. For this thread, then for some notional CP7/CP8 electrification, then 2017's value (266 gCO2/kWh) isn't very helpful. Instead, some sensitivity testing with the 2030 values in each of the National Grid scenarios seems like a better idea..

 

[yorkie]

hydrogen trains may be coming our way soon. it may be pointless to electrify

How 'soon' do you predict the technology will be affordable and widely available?

 

[superkev]

For the hydrogen brigade there's an interesting YouTube comparing overall power station to wheel hydrogen (~20%) and battery efficiency (~70%). It also quotes grid efficiency of around 85% so even the dreadnought class GW electrification is probably a great deal cheaper and has a long life. See

K

 

[marko2]

For the hydrogen brigade there's an interesting YouTube comparing overall power station to wheel hydrogen (~20%) and battery efficiency (~70%). It also quotes grid efficiency of around 85% so even the dreadnought class GW electrification is probably a great deal cheaper and has a long life. See

K

This very much depends on how the hydrogen is produced - it's a good use for surplus renewables providing there is large amount of storage for the periods when there isn't any surplus at all. The idea is often sold on the basis of small plants consuming locally generated solar energy - although this is much more viable in sunny countries.
Right now a lot of hydrogen is produced from petrochemicals - which is possibly better than electrolysis powered by fossil-fuel generated electricity.

What is entirely missing is the hydrogen distribution network if it is to be produced centrally. There may also be legitimate safety concerns about large-scale hydrogen storage in residential areas - for instance at depots.

On the trains themselves, there are also practical storage problems it's apparently difficult to achieve within the UK loading gauge for low-power applications, let alone high speed trains. As with battery technology, has applications for discontinuous electrification.

 

[najaB]

There may also be legitimate safety concerns about large-scale hydrogen storage in residential areas - for instance at depots.

There's much more energy in an equivalent amount (mass or volume) of petrol or LPG and people seem comfortable with storing both in and around their homes.

 

[AM9]

There's much more energy in an equivalent amount (mass or volume) of petrol or LPG and people seem comfortable with storing both in and around their homes.

I don't think that "comfortable" is the way that people feel about petrol storage nearby. The explosion at Buncefield was a wake-up call (sorry about the pun, - it went up at 06:05 on a Sunday), for safety and human error. It's been said many time that if petrol was to be launched as a general fuel source today, even ignoring its environmental and public health damaging effects, it wouldn't get approval on pure safety grounds.

 

[swaldman]

There's much more energy in an equivalent amount (mass or volume) of petrol or LPG and people seem comfortable with storing both in and around their homes.

Hydrogen has more energy in the same mass. Less in the same volume, and that's more relevant because H2 ain't terribly dense (even at high pressure).

In the long run, Hydrogen trains might be a good alternative to diesel. Other renewably-sourced fuels might also win out, e.g. methanol or ammonia produced from spare electricity.
None of these is a good alternative to electrification, in scenarios where electrification makes sense because you're still keeping every disadvantage of diesel except for the pollution: you're still carrying engines and fuel around (motors and fuel if running from fuel cells) and you're probably accepting a lower system efficiency.

 

[InTheEastMids]

n the long run, Hydrogen trains might be a good alternative to diesel.

This. Given the Climate Change Act 2008, DfT should be factoring in an ever increasing CO2 price, which should drive diesel off the rails (even if that CO2 price doesn't arise in the market) in favour of *something^ that is low carbon.

None of these is a good alternative to electrification,

Actually, they might be excellent alternatives to electrification, in situations where the increased operating costs from the inefficiencies that you mention (and those in the video in Post #110) are outweighed by the avoided upfront tangible and intangible costs of electrification.

The sweet spot for H2 (if there ever is one) are, to me, long-distance low-density routes
Short-distance, low-density will probably go battery
Anything with high-intensity service ends up with OHLE

Issue is that, particularly as a network, there are substantial blurry areas (e.g. what is "high density" in this context? The answer is basically in terms of average kW of power demand for each bit of network but no idea what that value would be where electrification "wins" against alternatives)

An obvious intervention that DfT should have explicitly made already is "no new diesel-only fleets". If you TOCs are planning to run a train under the wires, it'd better be capable of using them.

 

[swaldman]

Actually, they might be excellent alternatives to electrification, in situations where the increased operating costs from the inefficiencies that you mention (and those in the video in Post #110) are outweighed by the avoided upfront tangible and intangible costs of electrification.

Yes, that's why I said that hydrogen is not a good alternative for electrification, in scenarios where electrification makes sense.
As you note, for routes with low traffic there will be some threshold at which electrification would be silly. I do accept that that threshold might be slightly different when comparing against different fuels.

An obvious intervention that DfT should have explicitly made already is "no new diesel-only fleets". If you TOCs are planning to run a train under the wires, it'd better be capable of using them.

I could see an argument for diesel-only fleets where they're not going to be running under wires - e.g. Scotrail services north of the central belt. I do wonder whether it would be sensible to say "If you're building a diesel-only fleet, it must be diesel-electric and capable of being converted to bi-mode in the future" - no need to pay for OHL equipment now, but make sure it can be added if the trains are repurposed in the future. But I don't know enough about diesel engineering to know if that's a silly provision.