SIEMENS

Trains are an indispensable part of any sustainable mobility concept. Commuter trains, subways, and streetcars help to prevent cities from drowning in traffic. Commuters can't get by without them, and they are an environmentally-friendly alternative to cars and airplanes for trips between major cities. New technologies have turned this traditional mode of transportation into the environmental choice for travelers around the world.

With its Velaro, a fourth-generation high-speed train that uses only 0.33 liters of fuel per 100 km per seat—a figure no carpool can match—Siemens is sending a particularly frugal and fast entrant into the fray for long-distance rail service. Velaro gets its passengers from A to B very quickly. The standard version of the train reaches a speed of 320 km/h, and some models, such as the one used in Spain, hit 350 km/h and more. Velaro thus represents serious competition for airliners. “On routes of up to about 1,200 km, passengers travel faster in the Velaro,” says Ralf Mayer of Siemens Mobility. “This is assuming that the train connects the downtown areas of the departure and arrival cities directly, so that travel to and from airports and associated waiting times are obviated.” In addition to saving time, the train is also a big plus for the environment. According to Mayer, a Velaro trip in Spain generates only around 14 g of carbon dioxide per person and kilometer, compared to 140 g for an airliner.

Such efficiency doesn't just happen by accident. A range of technologies help Velaro to systematically save energy and minimize carbon dioxide emissions. Take the train's on-board energy management system, for instance, which only activates the next power supply block when power reserves drop below a defined threshold. This enables just two of four active power supply blocks to provide all the energy required for operation. Nearly all the fans on board are speed-controlled or can operate at two different speeds. As a result, the volume of air flowing through the train isn't greater than is actually required.

When the train is at rest, most electrical consumers are turned down as far as possible or even switched to standby mode. “The result of all of these measures is that the Velaro is very economical in terms of energy use,” says Mayer.

Low Drag. A train's aerodynamics are crucial for high speeds, and here the Velaro also represents a major advance compared to its predecessors. Previous trains had a variety of structures protruding from the roof, such as air conditioning units, which cause turbulence when the train is moving at high speeds. “The latest Velaro has a smooth, high roof that largely prevents turbulence,” says Mayer. “Its new contour also enabled us to reduce the mass of air that a train pushes ahead of it and which causes substantial drag particularly in tunnels and when passing other trains.” Development engineers were able to reduce the train's drag by about 15 %, resulting in an energy savings of between 6 and 8 %.

The engineers' ingenuity also carried over to the interior. Light-emitting diodes (LEDs) have replaced the halogen spots previously used for lighting. LEDs consume much less electricity at the same level of brightness and also generate less waste heat, reducing the load on the air conditioning system and saving even more energy. And when the Velaro has to be braked, the train turns into an electrical generator. Almost all of the roughly 8,000 kW of power at the wheels can be fed back into the electrical system during generative braking. In practice, up to 30 % of the energy consumed can be reused.

Driver assistance systems in the Velaro prevent unnecessary braking and acceleration; their instructions to the train engineer help to achieve energy savings of about 6 %. Technology alone is not enough, however. As with driving a car, the human factor also plays an important role in a train's energy consumption. And with an increasing number of freight-forwarders training their truck drivers to drive more fuel efficiently, rail service operators in countries such as Germany, Austria, France and Switzerland are training their train engineers to drive economically, which can yield a good 10 % in additional energy savings. “If the train engineer stops accelerating about two kilometres before the crest of a hill, the train's speed remains relatively constant due to its momentum, and the downward slope on the other side allows the train to continue on its way unabated,” explains Mayer.

Environmentally Optimized. In addition to energy consumption, another important factor is use of resources. The wood used in the Velaro's interior comes from sustainably managed forests; the coolants—such as esters rather than mineral oil in the transformers—are certified to be environmentally safe; and 98 % of the plastic used can be recycled.

Velaro's steadily growing list of customers demonstrates that it has not only been optimized for the environment, but is also a very economically-competitive product. It has been operating between Madrid and Barcelona since 2006; China followed in 2008; and it has been operating under the name “Sapsan” (Russian for “peregrine falcon”) between the Moscow and St. Petersburg since mid-2009. Velaro is scheduled to begin operation in Germany in December 2011.

With its four (electrical) system technology, the Velaro can operate throughout Europe, which doesn't have a standardized grid voltage for trains. The Velaro D can handle direct current at 1.5 or 3 kV as well as alternating current at 15 or 22 kV. It is also equipped for the train protection systems used in different European countries. These systems work with different communication protocols and even require installation of different antennas.