How intelligent control systems could reduce energy consumption in public transport
In order to expand public transport as quickly as possible, concepts are needed that make do with existing capacities – above all infrastructure, but also available energy.
One promising approach is the development of intelligent control systems that efficiently link the operation and control of traction power networks. Rail travel protects the climate. This is another reason why public transport should be further expanded. Until now, the expansion scenarios that have been drafted have primarily focused on rail capacity. The concepts are therefore based primarily on the assumption that the lack of tracks is the limiting factor.
Energy-efficient speed profiles
If more trains are to run on the rails, more frequent services are needed. However, industry, research, and transport companies have long been aware that there is another influencing factor without which expansion is not possible: energy. Rail transport has always been one of the largest consumers of electricity in Germany: the industry requires around 11 billion kilowatt hours per year.
Energy saving concepts have therefore been around for many years – for better climate protection and for cost reasons. They are based primarily on the realization that energy consumption can be significantly reduced through energy-efficient speed profiles.
Initial development stage
These concepts focus exclusively on the energy-saving potential of individual vehicles. For example, driver assistance systems provide drivers with speed recommendations, particularly for starting and braking. However, this approach, like the incentive systems introduced later, did not produce the desired results. Train drivers implement the recommendations too infrequently and inconsistently.
Next stage of expansion
It no longer considers just a single vehicle, but several vehicles and the rest of the route, for example a slower train ahead or a red signal. In addition, an automatic system, such as an Automatic Train Operation (ATO) system, takes over control of the train to regulate speed and for starting and braking.
For example, it regulates the acceleration of a train and thus phases of maximum speed as well as phases in which a vehicle travels at a slightly reduced speed over a longer distance. It also controls coasting phases and makes extensive use of opportunities in which trains do not consume energy. This control system determines the best energy profile for the specified arrival and departure times of all trains.
Avoiding peak loads
However, these solutions cannot save the electricity required for the higher frequencies currently planned. The capacity of the existing electrical networks is insufficient, especially during peak loads. This will not change in the medium term. Industry, research, and transport companies are therefore currently working on control systems that link the entire operational management with the control of the traction power networks. One of the key issues is the energy required for departure.
This is because it is particularly high and therefore also particularly expensive. Peak loads have a significant impact on the amount of electricity companies have to pay. For this reason, mathematical formulas are being developed that take all other influencing factors into account in order to reduce the number of simultaneous departures.
Synchronization of arrivals and departures
Another focus is on synchronizing arrivals and departures so that the energy released during the braking process of a train entering the station can be fed back into the power grid and used immediately to accelerate a departing train. To achieve this, trains must brake and start up at exactly the same time. If transport companies combine energy-optimized train operation, reduce simultaneous departures across the entire network, and always schedule arriving and departing trains so that braking energy is used for starting energy, they could not only expand their services but also save energy costs at the same time.
Current research projects and outlook
Current research projects also suggest that transport companies can save considerable energy and immense costs simply by adjusting timetables by a matter of seconds – imperceptibly to passengers – and by using driver assistance systems for real-time train control. This requires the development of algorithms that enable control systems to respond quickly and reliably to disruptions in everyday operations. The fact is that, up to now, traction power control and operational management have been carried out in two separate worlds – and thus also in separate control centers.
However, the future will require that the organizationally independent areas within the transport company grow together and create a holistic system by linking existing data and using artificial intelligence.
Against this backdrop, Peak Mobility plans to develop an intelligent control system that optimally coordinates and controls the operational management and control of the entire electrical infrastructure. For all sub-areas—systems for public transport, control of traction power networks, and artificial intelligence—the manufacturer can draw on proven solutions and will create valuable synergies for customers in the future.
Operational efficiency and energy efficiency in harmony
The expansion of public transport services can only be achieved with intelligent systems that take a holistic view of and control the operational and energy-related framework conditions. Experts agree that it will be crucial to use the remaining degrees of freedom in timetable planning to balance the load on the traction power network and to take into account all aspects of operational activities in real time, in addition to energy-saving concepts.
