Green SelTrac CBTC
Smart train control yields major energy savings
Metro and urban rail networks are the backbone of urban transportation systems, providing smooth, low-carbon journeys for more than 40 billion passengers every year. Rail is highly energy efficient and its environmental impact is modest – trains produce around three times less CO2 per passenger kilometre than cars.
Rail networks are nevertheless major energy users. To put this in context: the amount of traction energy used by a metro train during a typical 25-minute journey is enough to power a family home for more than a month. Faced with pressure to reduce costs and enhance their green credentials, many operators are now asking: could rail be made even more efficient?
Thales’ Green SelTrac® CBTC is a pioneering and complete solution that reduces energy consumption by up to 15% on networks that use Thales’ SelTrac® communications-based
Green CBTC helps the environment and reduces customer costs
Energy savings are
achieved through a combination
of intelligent scheduling and new
approaches to real-time supervision.
train control. Energy savings are achieved through a combination of intelligent scheduling and new approaches to real-time supervision.
“Green CBTC helps the environment and reduces customer costs,” says Kevin Tobin, Chief Software Architect, Thales Canada. “To achieve this, our approach is to bring together strategies and algorithms that improve train control and save energy.”
Energy efficient control
Optimising energy performance means minimising energy-intensive stop/start cycles and maximising opportunities for coasting – cutting the power at a pre-determined point and allowing the train to continue running under its own momentum.
These opportunities are identified using sophisticated simulation tools which take into account both the physical attributes of the route, such as gradients and speed restrictions, and the technical characteristics of the train. This information is used to create driving profiles – computerised instructions that determine how the train will be driven throughout its journey.
As well as an energy-optimised baseline profile, it’s also possible to create profiles that allow faster and more energy-intensive running to assist in schedule recovery. Different train loading conditions are also taken into account. That’s important, because the weight difference between a crush-loaded train and one that’s empty can be 40 tonnes or more.
Automatic Train Supervision (ATS) also plays a critical role in delivering energy efficiency. ATS looks beyond the level of the individual train, ensuring that every operational decision takes into account the needs of the wider network – in short, making sure that solving one problem doesn’t create another.
One way intelligent supervision helps to save energy is by adapting
train performance to avoid stops between stations: keeping a train moving, even at low speed, is far more efficient that stopping it and then starting again.
Global supervision also allows operators to constrain peak energy demand. That’s important, because in many cities, electricity suppliers penalise operators if a pre-determined peak threshold is exceeded. ATS applies peak power constraints – reducing the number of simultaneous train starts that cause power demand to spike.
Energy-efficient planning tools also allow operators to visualise the consequences of scheduling decisions and profile choices, both at the offline timetable planning phase and during operations.
As well as optimising energy consumption, Green CBTC also supports regenerative braking: the process by which a train’s kinetic energy is turned back into electricity when the train slows down. To work efficiently, there needs to be another train nearby ready to accelerate.
“Most railways can re-use their energy locally when trains are braking,” says Mr Tobin. “One of the optimisation strategies that we use both at the planning level and at the supervision level, is to coordinate the departure and arrival of trains.”
Because braking energy is turned into electricity rather than heat, regenerative braking also helps to keep temperatures down in deep-level tunnels, creating a cooler and more comfortable environment for passengers and staff.
Thales’ ability to deliver solutions such as Green CBTC builds on the company’s leadership in the development of communications-based train control, which it first implemented more than 25 years ago. And it underlines a continuing commitment to meeting real business needs through innovation.
|GREEN SELTRAC® CBTC AT A GLANCE|
• Efficiency gains – 15% reduction in energy consumption
• Increased passenger satisfaction – fewer stops in tunnels
• Smoother operations – reduced wear on track and trains
• Energy control – eliminate peak energy demand spikes
• A clearer picture – visualise predicted energy costs
Download brochure: SelTrac® CBTC communications-based train control for urban rail