Public transport takes a leading role in the efforts of increasing the transport sector’s energy efficiency. Current solutions are already able to recover braking energy from light rails and open up the existing rail infrastructure for other electric vehicles to use. The challenge is to adapt and coordinate the components for the respective case. A holistic control approach is needed to take the options and restrictions into consideration. In addition, grid stability services shall be supported in order to facilitate the increased usage of renewable energies.

The GUW+ project consortium is developing a concept for the shared energy supply of electric buses and light rails that enables the integration of energy storage units to offer grid stability services in DC substations with bidirectional power supply. The energy supply of charging stations for electric buses will be electrically isolated from the rail’s energy supply. Existing legal conditions are thereby taken into consideration and possible needs for adaptation in this context will be identified.


The Novel GUW+ Supply Concept

 GUWPrinzipskizze EN s



GUW+‘s overall objective is to actively support the market launch of electromobility in the field of road-bound public transport.

By the shared use of existing municipal infrastructure, the procurement costs of charging infrastructure for buses are reduced significantly. After their on-board use, bus batteries undergo a second stationary use, resulting in a considerable reduction of the life cycle costs of electric buses.

 Cost-efficient bus charging by integration in existing municipal infrastructure

The light rail infrastructure is structured similar to the necessary infrastructure for electric bus charging stations (building, power supply, power electronics). Investment costs are reduced by the shared use of existing infrastructure in GUW+ and the simplified design of the required power electronics components.

Support of public transport electrification (buses) by second use of batteries

Life cycle costs of electric buses are reduced by means of a closed second-use concept for the cost-intensive traction batteries (approx. 30% of a standard electric bus) in GUW+, i. e. within the same operation. Procurement of electrical buses thus becomes more attractive. The battery storage unit integrated in the substation provides various amortization options, such as consolidating the discontinuous power supply, storing braking energy, offering grid stability services as well as maintaining the power supply for public transport during a blackout.

► Securing sustainability and transferability of the overall concept for other cities

By integrating the GUW+ demonstrator in the existing infrastructure of project partner ÜSTRA AG, the abovementioned scenarios can be demonstrated in regular service of electric light rails and buses. During the one-year test operation, the design tools required for a future widespread impact can be validated.