Boundaries of Tram Operation Extended Beyond the Catenary
July 8th, 2009 | 11 Comments
Alstom's STEEM system, under testing in Paris, will allow vehicles to run between stops without a catenary.
In January, Bombardier announced the development of a new traction system called Primove that will allow trams to receive power wirelessly by communicating with circuits buried underneath the track. The implementation of this technology would allow streetcars to travel through cities at moderate speeds without requiring the construction of overhead catenaries, whose wires are often seen as the major downside of modern electric rail transit. With its new STEEM system, competitor Alstom may be able to offer the same advantages through battery power storage — at a far lower cost.
Primove has a major advantage — the fact that its power devices are buried — over a similar Alstom system currently being used in the city of Bordeaux, which relies on an exposed third rail that is only activated as a tram passes over it. This means that Primove could theoretically be used in colder, wetter climes, places where the Alstom third rail system is likely to run into trouble. But both of these technologies are significantly more expensive to build and implement than traditional catenary, meaning that they're only likely to be used in the most historically-sensitive areas where overhead wires are seen as too distracting.
If implemented, Alstom's new STEEM system*, on the other hand, will require less catenary wire and no underground construction; it simply requires the upgrading of existing tram vehicles. Trains will be equipped with large batteries connected to their motors that will be charged each time the vehicle brakes, much like the way a Toyota Prius hybrid refills its battery. In addition, the trams will be able to benefit from charging during 20-second station dwell times, where trains will benefit from a catenary; theoretically, the system wouldn't require the use of the catenary between stations.
Alstom's technology is a major advance, and it could cut down investment costs in light rail projects significantly in areas where stations are close enough to ensure that trains can move between them without running out of power. In short, it means that transit agencies could install tracks without the relatively expensive overhead catenaries between stations, putting them only above stops, where they'll serve as recharging units alone. This is a bigger advance than Bombardier's more exciting announcement earlier this year because it will result in less expensive construction and operations costs.
Though the city of Nice in the south of France already has a first generation version of this system, allowing trains to run without catenaries in the city's central square, STEEM allows for quick recharging and use throughout a vehicle's journey, something not previously possible. The system will undergo testing on two sections of Paris' T3 light rail line, at first using one vehicle that will simply retract its pantograph in the testing sections and operate autonomously even as the other trains on the line continue to use the catenary there.
Alstom's technology is not yet advanced yet to work on fast-moving American light rail systems, which typically have station stops up to a mile apart, likely too far for its battery capacity to handle. Whether the system can handle the incredible wastefulness of air conditioning — something not present in Paris — is a different question. But it could be particularly useful for streetcar networks, such as the one planned in Washington, D.C., where a congressional ban on overhead wires is still in effect — something that could likely be circumvented if the wires were only present at stations. In cities like Portland where light rail stations downtown are just blocks apart, the technology could mean the ability to get rid of overhead wires in central sections of the network.
* Système de tramway à efficacité energétique maximisée (maximized energy efficiency tramway system)
By Yonah Freemark on July 8th, 2009 | Listed: Paris, Streetcar, Vehicles | 11 Comments
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8 July 2009 at 14:05 · Reply
The problem I continue to worry about is the weight of the vehicle when batteries are loaded on. Is this going to be an issue?
Dave in KY
The benefits for rail are big,
but the huge winner in this technology could be trolleybuses, which might be able to out-compete hybrid buses at their own game. Futhermore, it would be a natural for TBRT (TrolleyBusRapidTransit). You peg the buses to stations with at-floor level loading, where the bus is charging, then the bus can use the entire street grid to get to the next stop.
Daniel M. Laenker
Even better for STEEM in Washington is that WMATA has done a great deal of business with ALSTOM before. So it shouldn't be too much of a stretch.
That said… no air conditioning? Surely you must know what DC is like in the (humid subtropical) summer. Ugh!
In passenger cars, the majority of energy, I believe about 80%+, is spent on driving; air conditioning, radio, etc., count for only a small percentage of energy consumption.
29 December 2009 at 09:04 · Reply
I've got a question so hopefully someone knows the answer.
I was under the impression that one of the reason light rail lines are so expensive to construct at grade is that they require utilities to be diverted so that the rails can act as an 'earth' line (I have no gret knowledge of electrics so bear with me if I murder the terminology). If LRVs are storing their power in batteries do they need to be earthed and if not, do utilities need to be moved?
Ocean Railroader
I remeber hearing that the Richmond streetcars did have to have ground wires put in near the tracks. The reason why most utilities are moved is the size and load of the train and it's tracks uselly.
I could see this system being tried out in Washingtion DC no wire zone but I think catenary will still be around in that it's not that bad to build wires and the trains get power 100% of the time vs have to watch a battery that could run out. I wonder though could a streetcar take on power under a catenary section and then use the power in the areas that don't have catenary or are not aloud to have ait.
EngineerScotty
Streetcars conduct power to ground through their wheels, and don't need utilities to be moved, just tracks in the pavement.
I'm with OR; it's the size and weight of the vehicles that inhibit utilities under the roadbed.
Max Wyss
Actually, that system kind of reminds me of the Gyrobus concept from the fifties of the last century, where buses were equipped with flywheels, and got "recharged" at the station stops.
An alternative to batteries are supercapacitors, which can be charged way faster than batteries, and may also be lighter, although the capacity may be lower.
It depends on the underground, but in most cases, the rails can act as ground return. There are places, where a dedicated conductor is used for the ground return (such as some lines of the London Underground). This conductor may also be a "simple" cable.
I don't really see the problem with catenary; there are many cities having it, and even in places which are "historically sensitive".
Catenary is good in that it is cheap to intill and take care of it. It can be good looking if the poles around it have good types of glass and clay insulators around it. It is still very rare or uncommon to see catenary along railroad tracks most of the time in the US.
One other place where a dedicated conductor is used for ground return is with trolleybusses, where the rubber tires prevent current from being conducted to the ground.
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