Friday, December 18, 2015

Trolleys without the trolley wire

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Trolleys without the trolley wire

Off-wire light rail? Time was, not so long ago, that when I heard that phrase I immediately envisioned a light rail car that had accidentally got its trolley pole or pantograph off the overhead electric contact wire.

Nice tramway place GaribaldiNowadays, of course, as many rail transit professionals and advocates know, “wireless” light rail transit (LRT) systems (especially slower-moving streetcar lines) with “off-wire” capability are all the rage, and the technology has advanced to make that commercially possible. The ability to design light rail systems partially or even totally free of the conventional overhead contact system (OCS, the technical term for the overhead wires) has afforded planners a significant new dimension of flexibility—as new systems in cities as diverse as Nice (pictured), Bordeaux, Dubai, and Dallas have been demonstrating.

Dual-power LRT systems (mostly electrically powered under wire, but able to run from onboard internal-combustion engine power over non-electrified segments) have operated in a handful of locations for several decades. However, the new “wire-free” systems are typically all-electric, and generally fall into two categories:

• External power provided beneath the railcar (rather than above it). Alstom’s APS (alimentation par sol, “ground power”) system is probably the most widely used example so far.

• Onboard Energy Storage (OES) systems. Most common are either battery-based or supercapacitor-based, although hydrogen fuel cell systems (which require an onboard tank of hydrogen gas) are also being offered.

As you might imagine, all these leading-edge “wire-free” technologies were hot topics of conversation, presentation and discussion at 13th National Light Rail Conference, co-sponsored by the American Public Transportation Association (APTA) and U.S. Transportation Research Board (TRB) in Minneapolis Nov. 15-17, 2015. As usual, some of the most enlightening news and insights came out of APTA’s Streetcar Subcommittee, which met Nov. 15, with “wire-free” developments a major focus.

For me, a key takeaway is that the working concept today mostly involves hybrid implementations of these new technological developments. OES (such as with batteries or supercaps) is often combined with sections fed by external power (OCS or ground-based).

Example: According to Mark Hill, director of business development for Alstom, a new 28-km/17-mile LRT system for Rio de Janeiro will be totally “wire-free”, powered by a combination of OES supercaps and Alstom’s proprietary APS (a central third rail between the running rails, energized only when a train passes over it). Hill cited a recharging time of as little as 20 seconds (from OCS at the recharging points). While APS installation is reported to cost more than OCS, Hill predicts that maintenance will be lower.

Another example is the new 1.6-mile streetcar line connecting downtown Dallas with the city’s Oak Cliff section on the west side of the wide Trinity River flood plain, using a venerable historic viaduct that officials wanted to keep “wire-free”. Brookville Equipment Corporation’s newly designed, U.S.-built Liberty streetcar, using a lithium-ion battery system, fit the need. So far, it allows cars to run one mile off-wire, the remainder under OCS. (See First-of-its kind streetcar arrives in Dallas.)

Wire-free LRT obviously meets a demand, especially where OCS would present expensive engineering challenges or a scenic disruption. But there are drawbacks. For instance, batteries currently need replacing about every five years, at a cost of roughly $200,000 per car.

Ground-level power systems like APS seem to entail a significantly higher cost premium. And the extra equipment for OES means a hefty cost hike for every single car in the system. And how will the average cost of installing and maintaining OES charging stations compare with OCS costs?

Another issue is performance. Most OES-dependent LRT systems seem to be slower-speed streetcar/tramway lines with relatively frequent station stops. But what happens if an initial streetcar operation is later expanded into a higher-speed LRT system with stations more widely spaced, somewhat like the regional systems in San Diego, Denver, St. Louis, Portland and Dallas? Could OES support running trains at 50-65 mph with full passenger loads plus air conditioning? Currently, that’s considered unlikely.

Obviously, there are lots of tradeoffs that must be reckoned with, and the jury is still out, waiting for adequate data from actual operating experience of these new systems. Nevertheless, it’s clear that “wireless” capability offers important flexibility that may help make the case for LRT in some situations where OCS might be a dealbreaker.

Lyndon Henry

Lyndon Henry is a writer, editor, investigative journalist, and transportation consultant currently based in Central Texas. He holds a Master of Science in Community & Regional Planning, with a focus in Transportation, from the University of Texas at Austin, 1981. From 1973 to 1989 he was executive director of the Texas Association for Public Transportation, and presented the original proposals and feasibility studies for light rail that led to the inclusion of rail transit in the Austin-area planning process.. From 1981 to 1985 he served as a transportation consultant to the Hajj Research Centre at King Abdul Aziz University, in the Kingdom of Saudi Arabia. He has also served as a transportation planning consultant on several other transit projects in the USA. In 1983-84 he was a member of the Austin-Travis County Transit Task Force which recommended a transit authority for the Austin area. That agency, eventually named Capital Metro, was created in 1985. From 1989 to 1993, Mr. Henry served as a board member and vice-chairman of Capital Metro. From 1990 to 1992 he was an Adjunct Faculty member at St. Edwards University, teaching a course in public policy. Since 2000 he has served as a technical consultant to the Light Rail Now Project, and from 2002 to late 2011 he served as a Data Analyst for Capital Metro in Austin. He is also a member of APTA’s Streetcar and Heritage Trolley Subcommittee and Light Rail Transit Technical Subcommittee.

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