Time to electrify... the motorways?

[BayPaul]

So assuming we go for low voltage DC, say 750v. How many lorries will be in a section and what power will they draw? This matters because you have to set the circuit breakers at an ampage so they dont keep tripping. But the higher the ampage, the bigger the risk if there is a shorting incident. And if there are loads of trucks in the section, how will the trucks cope with the voltage losses?
Will trucks regen into the overhead? Will they have a failsafe thing so the other brakes come on in case the line suddenly cant take their regen power?
And anyway, regen will have limited use, because the trailer brakes wont regen so lots of energy will still be wasted (unless we have loads of special trailers to allow regen)

Regen is probably not all that relevant - driving on a motorway it is pretty rare to need to use brakes other than for the final bringing to a stop in traffic.

 

[Ken H]

Regen is probably not all that relevant - driving on a motorway it is pretty rare to need to use brakes other than for the final bringing to a stop in traffic.

but we have engine braking (in a car) My diesel car slows down quite a lot if I take my foot off the gas pedal

 

[BayPaul]

but we have engine braking (in a car) My diesel car slows down quite a lot if I take my foot off the gas pedal

True. Thinking about it, the obvious place to put that energy would be in onboard batteries anyway, rather than feeding it back into the mains

 

[HSTEd]

So assuming we go for low voltage DC, say 750v. How many lorries will be in a section and what power will they draw? This matters because you have to set the circuit breakers at an ampage so they dont keep tripping. But the higher the ampage, the bigger the risk if there is a shorting incident. And if there are loads of trucks in the section, how will the trucks cope with the voltage losses?

Sections could be extremely short if necessary, and with modern SCADA you can potentially do with far fewer DC circuit breakers and do most control with controlled rectifiers or trip the (much cheaper) AC side circuit breakers to isolate a fault.

Given that lorries are going to have auxiliary power sources for off-wire use anyway, you can also design a much more aggressive voltage-controlled power limiting curve so the voltage simply sags to the level where the power of the rectifier(s) is matched to the power of the lorries in section.

Will trucks regen into the overhead? Will they have a failsafe thing so the other brakes come on in case the line suddenly cant take their regen power?

Well the obvious solution is, no? It's going to be an enormous headache and is not strictly necessary in such light vehicles, many of which will have traction batteries (be they hybrids or pure electrics)

Worth noting that engine braking is not regenerative - it is simply dispersing kinetic energy in the engine rather than the brake pads

 

[341o2]

I'm not sure if I'm a fan of the idea. I hate visible cables and what happens if one breaks? It could be quite damaging to other road users.

That was the reason for closing the joint trolleybus route between Walsall and Wolverhampton - due to the possibility of wires being blown onto the motorway M6

 

[BayPaul]

According to this report https://www.csrf.ac.uk/2020/07/white-paper-long-haul-freight-electrification/

• They are looking at 7500km - that sounds like basically the Strategic Road Network (SRN)
• This would cover 65% of HGV KMs, with most of the rest being able to be covered by batteries
• The cost would be around £19.3 BN. Even assuming that this is a significant under estimate and the cost should be doubled, it seems pretty good value compared to any nationwide rail-based scheme
• The infrastructure pay back period would only be 15 years, based just on the profit on electricity sales - again optimistic, but even if it was much longer that isn't a massive issue. For the hauliers, the vehicles would pay for themselves in 18 months
• They reckon 2 years to fit the M20, M25, M4, M1, M6 (to Preston), M62, M180, M18, A14, M8 and a few other roads at a cost of £5.5 BN, then 5 years to complete the network in 2 further phase

 

[Factotum]

I await the development of an app, that enables you to change your supplier in transit. (facetious again)

I have a friend in Texas who tells me that he pulls a trailer with a motor-generator set so that he can recharge his EV on the road.

 

[SouthernR]

I have a friend in Texas who tells me that he pulls a trailer with a motor-generator set so that he can recharge his EV on the road.

Is the EV towing the trailer (creating a hybrid), or is the EV on the trailer (used as a secondary vehicle)?

 

[Meerkat]

And anyway, regen will have limited use, because the trailer brakes wont regen so lots of energy will still be wasted (unless we have loads of special trailers to allow regen)

Regen would go to the batteries. Assuming the cable/connections between trailer and cab arent a big issue then the availability of the batteries to take the regen might make electric brakes on the trailer viable, helping keep the batteries up and reducing brake wear??
Sainsbury’s have got some refrigerated trailers that use a Dynamo on the axles to charge batteries tha power the fridge rather than a diesel.
I would be a bit worried that lorries would refuse to move out of the electric lane - i can think of at least one junction where I regularly had to rely on kind truck drivers or not get onto the motorway!
If this gets allowed I would hope the railways come back and ask for similar leeway on electrification safety standards!

 

[PeterC]

I would be a bit worried that lorries would refuse to move out of the electric lane - i can think of at least one junction where I regularly had to rely on kind truck drivers or not get onto the motorway!

I must admit that that concerns me as well.

 

[LSWR Cavalier]

The Knights of the Road would not need to move over (can be hazardous or impossible) to make space for joining vehicles if they were keeping a proper distance from the vehicle in front.
..
The €€highway near Luebeck is so short, it does not go through any junctions.

 

[Bald Rick]

Sainsbury’s have got some refrigerated trailers that use a Dynamo on the axles to charge batteries tha power the fridge rather than a diesel.

Where do the axles get their power from?

 

[stj]

Would be best using synthetic carbon neutral fuel instead of going down the electric route even for cars and aviation

 

[BayPaul]

Would be best using synthetic carbon neutral fuel instead of going down the electric route even for cars and aviation

Does such a fuel practically exist though? Hydrogren and Ammonia are the two that I have seen studies into, and the standard way of making both is far from being carbon-neutral. Hydrogen's low energy density probably doesn't make it very suitable for aviation, not sure about lorries but pretty borderline, and I know it has no chance for long distance maritime applications. Ammonia may have more potential, certainly for marine, but I suspect it just isn't a good enough fuel to be suitable for aviation.

 

[Meerkat]

The Knights of the Road would not need to move over (can be hazardous or impossible) to make space for joining vehicles if they were keeping a proper distance from the vehicle in front.

They have to move over or slow down. Truck drivers really don’t want to do the latter.

Where do the axles get their power from?

I was responding to someone doubting that trailers would be fitted for regen, so I was pointing out that it is effectively already being done (for another reason, and one that doesn’t involve a power connection to the cab.)

 

[stj]

Does such a fuel practically exist though? Hydrogren and Ammonia are the two that I have seen studies into, and the standard way of making both is far from being carbon-neutral. Hydrogen's low energy density probably doesn't make it very suitable for aviation, not sure about lorries but pretty borderline, and I know it has no chance for long distance maritime applications. Ammonia may have more potential, certainly for marine, but I suspect it just isn't a good enough fuel to be suitable for aviation.

Its being developed by Porsche, uses CO2 from atmosphere and Hydrogen which is synthesised into a liquid fuel which is used in conventional engines

 

[class ep-09]

Where will you set the contact wire height. The clearance between a HGV and a motorway bridge soffit is very tight.
How will HGV's overtake each other? An empty HGV will want to overtake a full one on a hill.
How much more will an empty bi-mode HGV weigh? Thats payload gone.

There may not be a need for overtaking as there should not be a " slower " or "faster " lorry going up the hill .

Electrical motors can easily keep up with the permitted speed in given location , with loaded or empty trailer .

 

[Meerkat]

There may not be a need for overtaking as there should not be a " slower " or "faster " lorry going up the hill .

Electrical motors can easily keep up with the permitted speed in given location , with loaded or empty trailer .

The lorries will have to overtake the annoying people who go slower than the lorry speed limit (who should be banned from the motorway IMO……apart from the fact there is no practicable way of doing that!)

 

[class ep-09]

The lorries will have to overtake the annoying people who go slower than the lorry speed limit (who should be banned from the motorway IMO……apart from the fact there is no practicable way of doing that!)

I agree .
I should add to my post that overtaking will take place anyway, but I wanted to comment another post , specifically in relation to lorries overtaking other lorries up the hill(s) .

 

[BayPaul]

I agree .
I should add to my post that overtaking will take place anyway, but I wanted to comment another post , specifically in relation to lorries overtaking other lorries up the hill(s) .

I don't see it as a major issue - the lorry wanting to overtake indicates out and moves from their lane in the normal way. Presumably the automatic pantograph monitoring system detects once the lorry has moved far enough from the centreline and auto-drops it (or as someone suggested earlier, activating the indicator could also do this), with the vehicle instantly switching to battery power. Once the manoeuvre has been completed, the driver hits a button to redeploy the pantograph, which checks that it is correctly aligned, and then raises, switching the vehicle back to mains power. I would imagine there would be a 'Overhead power available' alarm that would 'ping' to remind the driver to deploy the pantograph - this could probably be automated, but for my mind this would be the option that is least risk.

Once nice thing is that there is an incentive to the driver to not do the manoeuvre if there is marginal benefit, so reducing the likelihood of elephant racing.

 

[Meerkat]

I don't see it as a major issue - the lorry wanting to overtake indicates out and moves from their lane in the normal way. Presumably the automatic pantograph monitoring system detects once the lorry has moved far enough from the centreline and auto-drops it (or as someone suggested earlier, activating the indicator could also do this), with the vehicle instantly switching to battery power. Once the manoeuvre has been completed, the driver hits a button to redeploy the pantograph, which checks that it is correctly aligned, and then raises, switching the vehicle back to mains power. I would imagine there would be a 'Overhead power available' alarm that would 'ping' to remind the driver to deploy the pantograph - this could probably be automated, but for my mind this would be the option that is least risk.

Once nice thing is that there is an incentive to the driver to not do the manoeuvre if there is marginal benefit, so reducing the likelihood of elephant racing.

This seems to rely a lot on lorry operators‘s maintenance regimes….
A more complicated pantograph system, more joining from the side, and a lot lot more pantographs in use than on the railway - hoW many dewirements are they expecting? At least a lorry would stop much quicker after knackering less length of wire, and access for repair teams will be much easier.
They will need to ensure they can isolate short enough lengths to not leave loads of lorries needing a charge.
The idea of live wires flapping around a motorway amongst speeding cars and bikes is a bit scary. Would it trip out immediately or is there also a risk of live wires (and vehicles) with uncontained passengers wandering about once things come to a stand?

 

[BayPaul]

This seems to rely a lot on lorry operators‘s maintenance regimes….
A more complicated pantograph system, more joining from the side, and a lot lot more pantographs in use than on the railway - hoW many dewirements are they expecting? At least a lorry would stop much quicker after knackering less length of wire, and access for repair teams will be much easier.
They will need to ensure they can isolate short enough lengths to not leave loads of lorries needing a charge.
The idea of live wires flapping around a motorway amongst speeding cars and bikes is a bit scary. Would it trip out immediately or is there also a risk of live wires (and vehicles) with uncontained passengers wandering about once things come to a stand?

This is certainly the weakness of the system, but it seems to be working ok on the trial sections in Germany and Sweden. Presumably the system is beefed up a bit vs the equivalent would be on the rail network, and the much lower speeds presumably help a lot. I would also assume that pantograph design could help - an arrangement designed to allow for joining from the side would make sense (i.e. with downward curving horns to ensure there is no chance of the pan going above the wire). As you say, the biggest weak point is probably the operator's maintenance - if a pantograph doesn't auto-drop then it could easily bring wires down. I would assume that auto-trip would be simple enough, so that if things start crashing down they wouldn't be live, and short sections also would seem an obvious design feature. Sorry for this ramble from an interested observer, rather than someone who knows the detail of the system - I'm just thinking about how I would design it

 

[Meerkat]

This is certainly the weakness of the system, but it seems to be working ok on the trial sections in Germany and Sweden.

The trials will be with select, highly trained, operators.
Not the sort who’s wheels fall off and drive into bridges!
Would autotrip work? Someone above seemed to imply the current needed might make earth trips tricky??

 

[Western Lord]

Surprised to see the Swedes doing this, doesn't the Swedish Air Force use stretches of motorway as emergency airfields? That would make a mess of the wires. There's even been recent talk of the RAF doing the same over here.

 

[BayPaul]

The trials will be with select, highly trained, operators.
Not the sort who’s wheels fall off and drive into bridges!
Would autotrip work? Someone above seemed to imply the current needed might make earth trips tricky??

To be fair, our road system works pretty well with the current level of training and maintenance. It always surprises me that you can drive for thousands of miles around the UK and never see an incident. Although adding OHLE would increase the risk of an incident happening, it probably isn't more likely that a lorry will bring down the wires than it will hit the barriers, or have a collision, or otherwise have an incident that causes risk of death/injury, and/or blocks the motorway.
For the autotrip, it is getting well above my level of electrical knowledge, but I would have assumed that even if it isn't possible to auto-trip on the electrical side, it would be possible to have sensors to do it on the physical side - e.g if cable supports started breaking. I guess that wouldn't provide quite such instantaneous protection, but probably sufficient, given that any discharge of current is likely to be through a vehicle to earth, rather than through a person (motorbikes being the obvious exception).

 

[Factotum]

Is the EV towing the trailer (creating a hybrid), or is the EV on the trailer (used as a secondary vehicle)?

EV towing trailer.
Toyota call this system a "self charging electric vehicle" not an hybrid.

They have to move over or slow down. Truck drivers really don’t want to do the latter.

It might be practical to incorporate some control system into the wires so that the distance between and speed could be controlled.

 

[Meerkat]

It always surprises me that you can drive for thousands of miles around the UK and never see an incident. Although adding OHLE would increase the risk of an incident happening, it probably isn't more likely that a lorry will bring down the wires than it will hit the barriers

Seen plenty of lorries wandering out of lane over the years (though you would hope an OHLE lorry would have some kind of lane keeping). One only just swerved round a worker in a digger on the hard shoulder.
Hitting things is driver controlled, he has less control over the pantograph operation working properly

 

[SouthernR]

The infrastructure required to maintain the lorries, particularly the pantographs and the OHLE detection equipment, will not be trivial. (I haven't seen how the latter works.) It might be necessary to have test tracks scattered round the country.

The white paper suggests that installation will be quick (2 years for phase 1, plus 5 years for phases 2 & 3), with little disruption. How long have smart motorways taken?
This project needs to be right first time.

 

[Ken H]

Just re-looked at the pic in the guardian article in the first post. It looks like they are special pantographs designed to pick up from 2 parallel wires. like trolleybuses had 2 trolley poles. That will be because there is no way for return current through the rails, cos there are none. So already its becoming more complicated. There will have to be some good technology to keep the trucks in exactly the right line. Why not rails......?????!

 

[LSWR Cavalier]

Rails?!

There is an electrified railway line parallel to and crossing the test route by Reinfeld where trains carrying dozens of trailers pass by many times a day, on the way from Luebeck-Skandinavenkai to the marshalling yard at Maschen, or for all I know going straight to Italy or Spain.