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Author Topic: Green Roads  (Read 3431 times)
rogerw
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« Reply #15 on: August 02, 2020, 09:03:09 pm »

Have they explained how lorries will overtake other vehicles?  Or is that a question they hoped would not be asked
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ellendune
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« Reply #16 on: August 02, 2020, 09:36:51 pm »

I was wondering how much it would cost to raise all those bridges for the OLE (Overhead Line Equipment, more often "OHLE").
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stuving
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« Reply #17 on: August 02, 2020, 10:07:58 pm »

Have they explained how lorries will overtake other vehicles?  Or is that a question they hoped would not be asked

Yes. Drop the pantograph(s), drive round, or across the junction, or into and out of where you take our break, then reconnect. What's the problem?
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Trowres
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« Reply #18 on: August 02, 2020, 11:01:05 pm »

And as to the issues of sizing the power supply, its feeds, its protection, and how to earth a lorry for safety - look elsewhere.

How do trolleybuses meet electrical safety requirements?
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rogerw
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« Reply #19 on: August 03, 2020, 08:25:45 am »

Have they explained how lorries will overtake other vehicles?  Or is that a question they hoped would not be asked

Yes. Drop the pantograph(s), drive round, or across the junction, or into and out of where you take our break, then reconnect. What's the problem?

What is the return path for the current with a single contact wire and a pantograph? Works fine when running on rails but rubber tyres and tarmac roads have very high electrical resistance. Trolley buses worked ok with twin wires and trolleys but required controlled switches at all junctions. Worked OK in an urban environment with its lowers speeds. Can't see trolleys working too well at the higher speeds on motorways. Road vehicles do not stay on a rigid line, unlike those on rails, and although the picture on the BBC» (British Broadcasting Corporation - home page) looks impressive I can forsee multiple cases of dewiring and wires down
« Last Edit: August 03, 2020, 08:34:15 am by rogerw » Logged

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Oxonhutch
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« Reply #20 on: August 03, 2020, 08:55:29 am »

Road vehicles do not stay on a rigid line, unlike those on rails, and although the picture on the BBC» (British Broadcasting Corporation - home page) looks impressive I can forsee multiple cases of dewiring and wires down

I would foresee something more like existing mine haul trucks as described here.



I have seen these things working and they are very impressive. They accelerate tremendously once they contact the overhead wires.
« Last Edit: August 03, 2020, 09:02:03 am by Oxonhutch » Logged
Bmblbzzz
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« Reply #21 on: August 03, 2020, 09:14:35 am »

All the photos I've seen show double overhead wires, on long straight roads such as motorways. So those earthing and overtaking questions are not a big issue.
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stuving
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« Reply #22 on: August 03, 2020, 10:45:49 am »

Have they explained how lorries will overtake other vehicles?  Or is that a question they hoped would not be asked

Yes. Drop the pantograph(s), drive round, or across the junction, or into and out of where you take our break, then reconnect. What's the problem?

What is the return path for the current with a single contact wire and a pantograph? Works fine when running on rails but rubber tyres and tarmac roads have very high electrical resistance. Trolley buses worked ok with twin wires and trolleys but required controlled switches at all junctions. Worked OK in an urban environment with its lowers speeds. Can't see trolleys working too well at the higher speeds on motorways. Road vehicles do not stay on a rigid line, unlike those on rails, and although the picture on the BBC» (British Broadcasting Corporation - home page) looks impressive I can forsee multiple cases of dewiring and wires down

I'm sure this would use two supply wires, like trolleybuses - but different. The safety point is just that there is a question, and what's involved is likely to involve things that are not obvious. And it's not unknown for something that was safe enough fifty years ago to now need extra precautions, or be declared too risky by the liability lawyers.

Probably more relevant are the latter-day trolleybuses, or trams on rubber tyres. I don't think their commercial failure and (in France, at least) replacement by proper trams had anything to do with safety or earthing, but I'm not sure I'd know if it did. It would be surprising if they required a safety earth to a conducting road, but possibly some form of earth leakage protection is now needed. Fault current protection of low-voltage DC (Direct Current) overhead supplies is in any case difficult, calling for complicated switchgear and often for limits on the current demanded. Trains, and trams to a lesser extent, can be eaisly prevented from all starting up at once. Lorries on a road would naturally all want to do that.

And then there's the commercial/legal stuff about who's liable if it breaks. A short section without power isn't a problem - the lorries are all self-powered, after all. But for a longer section they might be unable to reach their destination, which would raise a lot of questions. And then there's national resilience ...
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stuving
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« Reply #23 on: June 30, 2022, 08:23:43 pm »

Here's someone else having a tilt at this turbine - Tevva. They have just launched a battery truck with a hydrogen fuel cell range extender (it was unveiled last September).
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The Tilbury-headquartered scale-up, which has so far raised $140m in funding, will unveil its hydrogen electric vehicle alongside its latest full-battery electric HGV at the Road Transport Expo in Warwickshire.

Hydrogen has been used safely in buses and other vehicles in more than twenty countries for many years and has a higher energy density than lithium-ion batteries or even diesel. Because of these properties, it is particularly attractive for use in larger, commercial vehicles.

By adding a hydrogen fuel cell system to its battery-electric HGV design, Tevva is delivering zero-emission solutions that will work for the overwhelming majority of fleet operators across a range of industries and sectors. The fuel cell system tops up the battery, extending the vehicle’s range and allowing the truck to carry heavier loads over longer distances.

One advantage of using the fuel cell as a range extender, rather than the primary source of power, is that it allows Tevva to provide smaller, cheaper and lighter fuel cells and operate these at the highest possible efficiency.

Tevva’s 7.5-tonne hydrogen electric truck comfortably meets (and exceeds) demanding duty cycles for nearly all urban and extra-urban use cases. Tevva’s innovation means that its customers can drive for longer (with a range of up to 310 miles or 500 kilometres) and will have reassurance because of the technology’s reliability and safety.

Crucially, hydrogen refuelling typically takes a similar time to diesel truck refuelling (5-20 minutes) and the dual-use of both battery electric and hydrogen energy sources futureproofs Tevva and its customers as the transition away from fossil fuels and the decarbonisation of the transport industry continues.
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broadgage
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« Reply #24 on: July 01, 2022, 01:01:12 pm »

I remain doubtful as to the merits of hydrogen fuel cells.
The fuel cells are expensive, bulky, and the hydrogen fuel is bulky, dangerous, and problematic to handle.

I am in favour of trolley buses and trolley trucks on motorways and in some urban areas. A lithium battery would be required to permit of running for say 25 miles on roads not electrified.
I cant see anything involving ground level conductor rails being approved on public roads, overhead should be enough of a challenge.

If any such system is to be adopted, we need a national standard, and preferably international, for interoperability. BEFORE each town, city, or district adopts its own bespoke system.

The climate emergency is now getting a bit last year, but the recent increase in diesel prices should concentrate minds somewhat. The war in Ukraine also shows the perils of being reliant on potential enemies for fuel.
« Last Edit: July 04, 2022, 11:36:52 am by broadgage » Logged

A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU (Diesel Multiple Unit) is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
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