04/04/2007 05:50 PM

Trains of the Future

Is France's Energy-Guzzling TGV Prototype the Right Answer?


As Tuesday's record-breaking TGV run in France illustrates, trains are traveling faster than ever before. But at what point will ever-increasing speeds make high-speed rail unsafe and environmentally unfriendly?

The record-breaking TGV V150: Frivolously advanced train technology

The record-breaking TGV V150: Frivolously advanced train technology

Trains will never travel as fast as commercial air planes -- that's a certainty. But certainty can be challenged -- as French train company SNCF has consistently demonstrated.

On Tuesday, SNCF set a new world speed record on rail when a special TGV train barrelled down new tracks east of Paris, reaching a top speed of 574.8 kilomters (357 miles) per hour. The previous record of 515.3 kilometers per hour had also been set by a French TGV train.

The aim of the record high-speed train trip on Tuesday, according to an official statement by French TGV manufacturer Alstom, was to demonstrate the "highly promising future in the domain of very high-speed rail transport." But more than anything else, the lightning-fast race down the tracks merely illustrated just how frivolously advanced train technology can be put to use. No railway company in the world is seriously considering putting trains that travel at such high speeds into regular passenger service.

The French spent no small amount of money on the spectacle. The electricity required to operate the train strained the rail line's power grid almost to the breaking point. The overhead electrical lines and a large part of the train's propulsion system "can for all intents and purposes be junked" after a trip like Tuesday's, an engineer at the German train manufacturer Siemens claims.

A costly joyride

All told, the conspicuous high-speed trip is believed to have cost Alstom, SNCF and train track owner RFF about €30 million ($40 million). For the trip, the French built a customized TGV with strengthened end cars and extra power that came from underfloor engines in the middle wagon. The total output of about 20 megawatts is more than twice that of the most powerful trains currently in use. Of course, there's a basic law of physics at play here: When speed doubles, drag quadruples -- and energy consumption rises accordingly.

The energy-devouring high-speed train is symptomatic of France's relationship to railway technology, which is shaped less by an ecological conscience than by sheer faith in technological progress.

When SNCF introduced the first high-speed trains back in 1981, it had a head start on German national railway Deutsche Bahn -- which only started service on its ICE trains a decade later. The introduction last month of new tracks connecting Paris with Strasbourg in eastern France has extended the French high-speed rail network to a total length of almost 2,000 kilometers. By comparison, Germany -- where numerous low mountain ranges and the bureaucratic jungle that comes with the country's federalist system obstruct railroad planning -- has only about 1,000 kilometers of high-speed tracks, leaving the country with a network that is far from complete.

This often makes Deutsche Bahn and train-builders Siemens and Bombardier look a bit shabby compared to Germany's western neighbor. Indeed, many in the German industry looked to Tuesday's record-breaking trip with a corresponding degree of displeasure. Ansgar Brockmeyer, who is responsible for trainsets at Siemens, takes snipes at the project, noting that "only protoypes or specially equipped test vehicles" were used.

The transportation division of German-based engineering and electrical engineering giant Siemens does at least hold its own world record -- in the area of serially produced trains. The Velaro E, an updated version of the most recent Intercity Express (ICE) train, achieved a top speed of 403.7 kilometers per hour about six months ago. When it goes into service, it will travel between Madrid and Barcelona at maximum speeds of 350 kilometers an hour -- a world record for scheduled passenger service.

The Velaro is equipped with 8.8 megawatts of propulsive capacity, 10 percent more than the sister model ICE3, which is in use in Germany. This propulsive capacity allows the Velaro to travel the 625 kilometer distance between Madrid and Barcelona in two-and-a-half hours. Air travel will likely end soon on this route as has happened when travel times have been massively reduced between other major cities by high-speed rail, like Berlin and Hamburg -- to the benefit of both the environment and the climate.

Siemens estimates that the train, assuming it is carrying an average load of passegners, will emit only 30 kilograms of carbon dioxide per passenger. The figure for air travel along the same route is 85 kilograms per passenger.

But how much faster can trains travel before they lose their benefits for the environment? Aerodynamics experts at the German Aerospace Center (DLR), the country's space agency, believe the acceptable limits of technical viability are reached at a speed of about 400 kilometers per hour.

The Perils of High-Speed Train Design

That figure is the benchmark, in any case, for a research project that Sigfried Loose, a Göttingen-based DLR aerodynamics expert, is working on together with Canadian train manufacturer Bombardier. The project is called "Next Generation Train" and it is meant to set the stage for the train of the future. That train will be "faster, lighter, safer and at the same time quieter," pledges DLR chairman Johann-Dietrich Wörner. Of course, he knows well that the goals he is announcing tend to be mutually exclusive in physics.

Loose's main goal consists in eliminating so-called "show stoppers" -- serious problems whose solution is an absolute precondition for further speed increases. The greatest problem is the danger of crosswinds, he says.

At the very latest, the recent gale-force winds of the storm " Kyrill" that forced Deutsche Bahn to suspend train travel in some regions, showed German people that one of the major factors of fear of flying also applies to train travel. Up until now, the only cases of trains being blown off the tracks have happened with lighter commuter trains. Narrow-gauge trains have even been known to topple over while standing still, but usually without causing any serious harm to people.

A complete ICE train weighs more than 800 tons. It's not likely to be knocked over by wind blasts -- at least not while standing still. But things change when a train is traveling at 350 kilometers per hour. At those speeds, the head of the train is exposed to considerably less gravitational pull and could actually topple if hit by an abrupt crosswind. Aerodynamics experts have already calculated this effect in models: It could lead to a train disaster of a similar magnitude to the 1998 ICE crash in Eschede, Germany that killed 101 and injured 105.

Safety measures

A number of safety precautions are in place to prevent such a disaster from happening. High-speed train tracks are lined with wind-protection fences in especially critical areas. And SNCF has set up a warning system along the southern Marseille-bound route, where strong mistral winds lurk, so that such strong winds can be noticed in time and train speeds reduced if necessary.

In addition, safety authorities like Germany's Federal Train Agency require train manufacturers to prove that their trains are resistant to crosswinds of a pre-defined force when traveling at maximum speed. Resistance to crosswinds moving at 28.8 meters (94.5 feet) per second -- the equivalent of wind force 11 on the Beaufort scale -- is considered the standard.

Modern high-speed trainsets "are already reaching their limits in this regard," says Alexander Orellano, the leading aerodynamics expert at train manufacturer Bombardier. In the trainsets for the most recent ICE models in Germany, the engine is distributed underfloor along the length of the train and there are no separate locomotives at the train ends. This makes the head of the train even more sensitive to gusts.

But the advantages the motorized trainsets bring with them -- better traction and considerably higher passenger capacity -- are pushing all major train manufacturers to develop them. Even Alstom -- a company that swore by conservative and robust locomotive trains up until now – will soon present its first motorized train sets in the form of TGV's successor, the AGV. But no information has been unveiled yet about the new train's aerodynamic characteristics or wheel load.

Designing the train of tomorrow

ICE manufacturers still resort to the solution of applying steel plates to the ends of the train in order to make them heavier. It's a simple solution -- and one that contradicts DLR's goal of reducing overall train weight. Loose envisions a train that is 30 percent lighter than today's trains while still resting stably on the tracks.

Model trains the size of those produced for train fans by German toy company Märklin and DLR's wind tunnels are the tools he uses in his research. The model trains are sometimes specially produced by him and sometimes purchased in toy shops and subsequently re-worked until they have the shape needed. The wind tunnels are among the best facilities in the world and use extreme refrigeration and compression to make air so dense that even model tests yield realistic results.

The physicist wants to present a first train model towards the end of the year. It will probably be equipped with spoilers not unlike those found on the front of race cars. As far as the basic shape of the head of the train is concerned, a number of very different variants are being discussed. Loose needs to bear in mind an additional phenomenon that train producers largely disregarded until now: the sonic boom in tunnels.

Trains thrust into tunnels like the piston of a bicycle pump, creating a pressure wave that races ahead of the vehicle at the speed of sound. This can lead to a thunderlike sound at the end of the tunnel, similar to that caused by planes traveling faster than the speed of sound. In Japan, where homes are often built close to train tracks, this phenomenon has caused windows to shatter.

Furthermore, part of the pressure wave returns into the tunnel with negative pressure and then races past the passengers in the approaching train. The acoustic effect, similar to that of a slap in the face, becomes all the more painful the faster the train's speed and the narrower the tunnel.

But tunnels are becoming narrower: For security reasons, only single passageway tunnels are being dug out, and the cross section has decreased from 90 square meters to 60. As Loose says: "That will be unbearable for passengers traveling in today's trains even at a speed of 300 kilometers an hour."


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