ROLLING STOCK AND TRACTION
Inherently safe
Scott continued: “The other advantage is that your rota, the key spinning element, is then wholly composite, so in the event of a failure precipitated by any one of a number of different causes, you don’t have to ‘contain’ large metallic components.”
Imagine a steel fl ywheel, or one with large permanent magnets – if that were to fail for any reason, it has components spinning around at sometimes multiples of the speed of sound, so containing that safely is a challenge.
The technology is “superior in a number of ways” to chemical batteries, Scott said.
Although it is too early to list the specifi c tram networks likely to benefi t from rolling stock equipped with the MLC fl ywheels, Nottingham is due to take delivery of 22 Alstom Citadis trams soon as part of its tram upgrade, so could be one to watch.
Retrofi t vs new build solutions
Scott told us: “Alstom is very interested in on-board energy storage for tram systems in general. The OEMs we supply, because of the life of the capital stock of the equipment they supply, tend to see both retrofi t and new build offerings as being quite attractive.
“Retrofi t provides its own challenges, as you’ve got to integrate it with an existing system that wasn’t necessarily designed for on-board inclusion of energy storage. Depending on the weight of the tram, you’re looking at one or two units per tram, largely determined by the overall energy equations of what they’re trying to optimise versus the additional packaging
Trackside technology
It is the static, trackside version of the system that is the focus of the Williams Technology Centre in Qatar.
The stationary variant is much higher power, offers much more energy storage and is designed to operate trackside in underground metro systems and to be interfaced into the electrical infrastructure.
“It allows a metro to increase quite substantially the fraction of kinetic energy that’s recovered in a braking event,” Scott said, while also meaning the rolling stock isn’t carrying any extra weight.
“In a rush hour situation at a metro station when you’ve got trains coming in every two- three minutes, they’re dumping a signifi cant amount of electricity through a braking event.
“Often what happens is that if it can’t go anywhere – to another train on the same electrically isolated segment of track – that electricity will be burnt off in resistor banks or the friction brakes will take over. That leads to more dust and heat in the tunnel.”
He said there would be “good potential” for London Underground to make use of the system, and said it could help with the major engineering challenge of cooling the deep Tube lines (see p56 and p69 for more). But
requirement and the additional mass.
“The key principle is that when the tram needs to come to a stop, if its drive motors have been run in reverse as generators and the overhead line cannot accept the power that has been generated, it has to be burnt-off locally in resistor banks. Therefore what we can do is increase the fraction that’s captured, and then re-introduce when the tram accelerates from stop again.
“The other interesting thing that can be done is self-rescue, for example if power is lost or if the tram network is designed with gaps in the power supply – at intersections, for example, overhead catenary is quite unsightly and you can design the system so trams move on their own power across those short gaps.
“That also helps in the event that you lose all power and you have to get the tram away from shared public roads or to the nearest safe place for the passengers to alight.”
Culture gap
Above: An example of the MLC 200 fl ywheel installed at the Williams Technology Centre, Qatar.
Obviously F1 engineering and railway engineering have different ways of working and
he admitted that it is a “very challenging” infrastructure.
He said: “One way we could potentially help an installation like LU is if, for example, they wanted to put a higher frequency of train service over a particular segment of the network, or they wanted to introduce new heavier rolling stock with a higher power demand, they have to do one of two things.
“Either they have to upgrade the traction power capabilities – and that means new traction power substations and civils works and the connectivity that goes with that – or introduce localised energy storage, which can top up the power requirement when that heavier train or trains at a higher frequency go over the line.”
The Doha metro, due to open in around three years time – which Scott called “one of the most ambitious projects in the world at the moment” – is looking at using such wayside technology across its four lines and 300km route length and 98 stations.
Scott said: “What QRail [Qatar Railways Company] is proposing to do, in terms of the number of stations and amount of track in that timescale has never been done before. It’s quite an exciting project, and our intention and the trajectory is very much to work closely with them to use the technology in a new build for the fi rst time.”
different priorities.
Scott said: “Rail engineers would say that F1 engineers are very good at making very high performance things and can do that very quickly – the problem is, the rail sector would say, it tends to be hideously expensive and only needs to last for two hours on a Sunday!
“But rail needs everything to be cheap as possible and to last for 20 years – so how are you going to reconcile the two?
“That’s been a really interesting journey – where we take our skills in rapid incremental improvement and prototype engineering and refocus on optimising for cost and for life.
“You couldn’t think of two more different sectors than the rail industry and Formula 1 – that’s a really interesting aspect of this business diversifi cation.”
Damien Scott
FOR MORE INFORMATION
www.williamshybridpower.com/applications/ trams/
rail technology magazine Apr/May 13 | 49
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