David Clemow: Better electric trains start with cutting overheads

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10544653

Page 1 of 2 View as a single page 4:00AM Monday Nov 24, 2008
David Clemow

I believe a better, quicker and safer system can be put in place for the electrification of the Auckland suburban rail system.

The priority to upgrade the suburban rail service to use electric units is not only commendable, it is necessary. However, in these days of advancing technology and its implementation into use, consideration must be given to the latest system.

It needs a study of what electric trains are available that may operate without continuous electrical contact for the whole journey, rather than the present proposal to provide continuous electric lines from Papakura to Swanson.

In other words: is electrical wiring necessary? In the future, of course, extensions to electric train services to Pukekohe and Helensville would be easy to implement, and if that happened costs are reduced.

But the better alternative could be electric units where the power is provided to drive the electric motors by onboard supercapacitors. Is supercapacitor technology up to the task? Overseas indications in the past two years indicate that it may be.


Firstly, a definition of a capacitor. It is simply a device that stores electrical energy or charge by non-chemical means, in that it stores charge on two conducting plates separated by insulating material. Older motoring people would know them as condensors - they actually preceded batteries in invention.

New materials have evolved to bring them to a level where they are now called supercapacitors. They have disadvantages but their main advantages are a quick recharge time and safety.

The newer ones offer considerably better storage capacity per unit volume than the best batteries (lithium-ion batteries).

They are being proposed for electric cars which, when charged, can run the car for over 800km between charges. Quick recharging will require a high-voltage system from ground unit to onboard capacitors.

The onboard electric motors that drive the wheels would be the same but the additional item would be the capacitors that would enable a train to travel between a few stations without recharging. It would depend on distance between stations, and where it would be easy for the charging system to be installed at stations with electricity lines nearby. As soon as the train stops, contact is made with the onboard capacitors from the ground unit automatically and for the duration of the stop.

Having travelled numerous times on Auckland trains recently (thanks to the Super- Gold Card), I have found no stop shorter than 30 seconds. Busier stations have been at least a minute and at Britomart and Papakura the stop is several minutes most times - plenty of time to fully recharge the capacitors.
Eliminating the overhead lines would mean a big improvement in safety, not forgetting damage caused by wind and lightning.

The charging systems would be underground and as vandal-proof as possible, and they become "live" only when contact is made when the train is stopped. Recharging systems for electric cars in garages are being introduced this way. Forgetting to put the plug in at night to recharge an electric car happens in places overseas, so devices to automatically charge vehicles when stationary are being developed. The concept is not new.

The new Government should be careful about providing the funds for the electrical wiring system, which is their part of the deal, and the Auckland Regional Council should do likewise over buying the trains.

Train units with capacitors on board may cost more. But the overall cost saving would be significant.

The whole thing could also be in operation much earlier, even though there may be delays assessing the new technology.


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AdvertisementThe writer is not an expert in electrical matters. Therefore further comment and study by appropriate people is necessary and I hope that will be unbiased.

The bottom line should be, the best train system for Auckland.

* David Clemow of Auckland is a retired Air New Zealand pilot, a previous technical director of the Airline Pilots Association and a qualified meteorologist.

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