Greater Greater Washington

China may have figured out wireless trams

This December, wireless streetcars will start carrying passengers in Guangzhou, China. The new trams will run using supercapacitor batteries instead of overhead wires.

Guangzhou's wireless tram. Photo from China Central Television.

Cities around the world, including Washington, have been increasingly interested in wireless streetcars ever since Bordeaux, France started using them in 2003. But Bordeaux's trams use an underground third rail that's proven too expensive for widespread use.

The Guangzhou system will use batteries that automatically recharge from an underground power supply at passenger stations. One recharge takes 10-30 seconds, and powers the tram for up to 4 kilometers (2.5 miles).

And a similar system is in the works for another Chinese city, Nanjing.

That's good news for DC, where laws prohibit overhead wires at key locations near the National Mall. Streetcars like Guangzhou's could solve that problem.

It's not clear how much extra this type of wireless tram would cost. Expense doomed the Bordeaux method, so that is a serious concern. But if the price is right, the technology finally seems to be there.

Cross-posted at BeyondDC.

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Dan Malouff is a professional transportation planner for Arlington County, but his blog posts represent only his own personal views. He has a degree in Urban Planning from the University of Colorado, and lives car-free in Washington. He runs BeyondDC and contributes to the Washington Post


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This is great news -- hopefully it is fully commercialized soon. Wires are not only aesthetically detracting in a place like Washington, but more importantly they are just additional exposed infrastructure subject to severe storm damage. Too bad this type of innovative technology (which would seem to have applications for vehicles beyond just streetcars) is coming out of China, not the USA!

by Randy on Jun 20, 2014 11:17 am • linkreport

a) I have no problem with one set of wires crossing the national mall at a point where the 'view' is already destroyed by a wide road and/or parked cars along the road.

b) I think a short tunnel under the mall is also perfectly fine.

by JDC on Jun 20, 2014 11:19 am • linkreport

According to one source, the cost of a line is around 420M chinese yuan ($68M) per kilometer.

by Scoot on Jun 20, 2014 11:24 am • linkreport

This is not anything new. DC's old streetcars were wireless too (in town). Streetcars both wired and wireless are still outdated and unnecessary.

by Brett on Jun 20, 2014 11:32 am • linkreport

The recharging technology is interesting. If the costs come down, what if they did that with cars or buses at stoplights or garages?

by Randall M. on Jun 20, 2014 11:44 am • linkreport

It should be pointed out that several European manufacturers have been making supercapacitor systems for streetcars for many years, including Bombardier's MITRAC, CAF's ACR, and Siemens's Sitras HES.

The tram in Zaragoza, Spain, has about a 1.4km section (out of about 12.9km) without overhead wires except at the stations, and uses CAF's ACR supercapacitors.

Supercapacitors work by adsorption of ions onto the surfaces of electrodes; advances in the past decade have been able to pack extremely large surface areas into small volumes. Batteries rely on chemical redox reactions in the bulk of an electrolyte. As things stand today, supercapacitors can deliver much higher power than batteries can, but batteries can store much more energy.

The short, high-power bursts that supercapacitors can provide can even be of use in a conventional overhead-wire powered streetcar. Throughout a cycle of starting from a stop, accelerating, cruising, and coming to the next stop, the power demands of streetcars vary quite dramatically. By far the highest power demand is at startup. By using energy stored in a supercapacitor when starting from a stop, the streetcar doesn't have to draw nearly as much current from the wire--Bombardier estimates 30% less current. A lower power demand at startup means the system can either use smaller diameter wires, or have fewer power substations, or support more streetcars simultaneously.

In Guangzhou, apparently they've put enough supercapacitors on a single streetcar to make it all the way from one station to the next. I'd imagine the feasibility of this depends very heavily on the streetcar's power needs for things like air conditioning and lighting, which need to be functioning even when the streetcar is stopped, and whether the streetcar is running in a dedicated right-of-way, where there shouldn't be any unscheduled stoppages to contend with. Full-on air conditioning in mixed traffic, such as will be the case in DC, will be a different story.

Myself, I think the only objectionable part of overhead wires is where they cross a street, when viewed from the cross direction; wires don't diminish the view when looking down a street. The reduced current draw at startup is reason enough to fit streetcars with supercapacitors, and as long as a streetcar can connect and disconnect with overhead wires on the fly, I think using supercapacitors to avoid wires at intersections makes sense.

by thm on Jun 20, 2014 11:52 am • linkreport

DC's old streetcars were wireless too (in town). Streetcars both wired and wireless are still outdated and unnecessary.

Yes, but the technology was very inefficient (in the sense that it generated a lot of waste relative to usable power). It was also prone to failure during bad weather and was expensive. Today's prevailing technology is overhead wires and so systems that can generate locomotion at relatively low cost without wires rightly generate some news buzz.

by Scoot on Jun 20, 2014 11:54 am • linkreport

I wonder if the cost will actually be that much more. Invariably there must also be cost saving not having all the wiring.

Could possibly be cheaper? I can't find it right now but the company below once mentioned their wired/wireless mixed Tram was 30% cheaper.

by Tom S. on Jun 20, 2014 11:58 am • linkreport

Kudos on the technology. Now, let's hope they figured out how to make them last more than 2 years before they have to be junked and replaced.

by spookiness on Jun 20, 2014 12:14 pm • linkreport


I don't doubt things have improved in the last 100 years. However, without a dedicated lane, a streetcar in traffic, whether wired or wireless, still is more limited than a bus, and just as efficient or inefficient depending on your perspective.

by Brett on Jun 20, 2014 12:46 pm • linkreport

For the US contexxt, the real problem with the Bordeaux system wasn't expense, although that is an issue, but differences in weather conditions, specifically snow. For that reason, Alstom has never been interested in trying to bring the method to the US.

by Richard Layman on Jun 20, 2014 1:43 pm • linkreport

have the battery chargers run on solar power!

by asffa on Jun 20, 2014 7:29 pm • linkreport

It should be pointed out that several European manufacturers have been making supercapacitor systems for streetcars for many years, including Bombardier's MITRAC, CAF's ACR, and Siemens's Sitras HES.
A Korean(Doosan?) company also has electric buses that charge their capacitors through the pavement at bus stops.

Not enough power, unless you covered the entire street

by Richard B on Jun 21, 2014 6:40 pm • linkreport

If these battery things don't work out, we can always go back to pulling them with horses.

by Zeus on Jun 22, 2014 3:49 pm • linkreport

The problem with overhead wires on Benning Road is the hundreds of poles holding the wires up. Wires could be done more tastefully like in Europe or even like H Street but DC has this stick-it-in-their-face attitude.

Even the ones on H are probably illegal but breaking the law is fine to some.

by Tom Coumaris on Jun 23, 2014 3:47 am • linkreport

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