SaxHybridPLUS

Electromobility is regarded as the future of both public and private transport. Although the first vehicles are already on the market and in regular use, there are still some barriers impeding the overall introduction of electromobility. One reason for this is the still very limited range of fully electric vehicles. In public transport, this problem is intensified by the high energy demand of buses as well as long and challenging routes which are difficult to cover with the fully electric vehicles available today.

The project SaxHybrid^PLUS is one of 50 projects funded by the Federal Ministry of Transport and Digital Infrastructure (BMVI) within the program Schaufenster Bayern-Sachsen ELEKTROMOBILITÄT VERBINDET (»Bavaria-Saxony »ELECTROMOBILITY CONNECTS« Showcase Programme «). The main objective was the development and testing of core technologies for plug-in hybrid buses. Thanks to the hybrid approach, several disadvantages of present-day electric vehicles were compensated, which helps electromobility on its way to acceptance in public transport. Much emphasis was put on a systemic approach in the interaction of vehicle, charging infrastructure and network infrastructure. In addition, the project also addressed issues regarding the integration of plug-in hybrid bus charging infrastructure into the urban space. Furthermore, technologies for high energy efficiency of hybrid buses have been developed.

Partners

The following partners participated in the SaxHybrid^PLUS project:

• Vossloh Kiepe GmbH (adaptation of power electronics and control, development and installation of the battery)
• Lex & Hesse GmbH (lightweight construction)
• Dresdner Verkehrsbetriebe (DVB) AG (implementation partner)
• Leipziger Verkehrsbetriebe (LVB) (implementation partner)
  
• Fraunhofer IVI (self-learning energy and power management system, integration of recharging function)
  

For the testing of the technologies developed in the project, an 18-meter articulated bus was equipped as a technology carrier. This vehicle is designed as a plug-in hybrid bus, but it can also be converted and used for the evaluation of other core technologies in electrified public transport, such as fully electric operation.

The SaxHybrid^PLUS bus has a serial plug-in hybrid propulsion. It is equipped with two electric traction machines, a diesel generator, an electric energy storage unit and a fast charging facility (docking station). With this propulsion system, the bus can be operated fully-electrically without restrictions for up to 15 kilometers. Thanks to the diesel generator, the bus does not depend on charging stations and can be used flexibly, even without any recharging.

Both hybrid and plug-in hybrid buses require an operational strategy adapted to the respective route (energy and power management) in order to achieve high fuel and energy efficiency. Thus, one of the most important novel elements of the vehicle is its self-learning operational strategy, which permanently adjusts the vehicle functions to the route, traffic situation, number of passengers and outside temperature (by air conditioning). With the help of this self-learning and adaptive energy and power management, the driver can operate the bus as easily as a diesel bus. The transport company does not have to cope with any installation or programming efforts either. Even for the first-time use on additional routes in the transport network, no preparations are necessary. The bus »gets to know« the route during the first trip and keeps optimizing the interaction of fully electric operation, recharging at charging stations and efficient use of the diesel generator with each tour taken.

The goal is to minimize the diesel consumption and to reduce emissions and noise pollution, especially in sensitive areas, for instance at bus stops, in the city center as well as in residential and recreational areas. Sections with fully-electric operation can be defined in advance and integrated into the operational strategy.

The Fraunhofer IVI has been working in the field of electromobility for many years. The institute’s employees have acquired a wide range of competencies in all relevant areas. In the SaxHybrid^PLUS project, the institute is responsible for the operational strategy of the bus and for the fast charging station. 

• »DockingPrinciple«
• Fast-Charging Electric Bus
  

Since March 21^st, 2016, the transport company Dresdner Verkehrsbetriebe AG and the Fraunhofer IVI have been running a field test of the plug-in hybrid bus in regular operation. The test is carried out on bus route 61, which is topographically challenging as it features various route elevation profiles and varying passenger demand and thus offers ideal (pre)conditions for testing the energy and power management system. An expansion of the field test to other bus routes is planned.

The installed battery has a nominal energy content of 48 kWh and can be charged with up to 330 kW. With its usable energy amount of 38 kWh, the bus can be operated fully electrically for up to 15 km. At that point, the diesel propulsion will join in. The bus is therefore especially well-suited for use on bus routes passing through sensitive urban areas. At the same time, the bus features the technological freedom of a diesel bus.

The articulated bus by Swiss manufacturer Carrosserie Hess AG is equipped with a high-performance battery and power electronics by Vossloh Kiepe GmbH. Recharging is carried out at the depot Dresden Gruna using a pantograph system by manufacturer Schunk.

Regular service on DVB’s bus route 61

Recharging

Recharging of the energy storage is performed using three recharging concepts:

• Pantograph contact system: fast-charging, max. 330 kW, 250 kW permanently, time for contact closure < 1s,
• Plug: 35 kW
• Recuperation

Energy storage unit

• Lithium-titanium-oxide batteries: power 240 kW, energy content 48 kWh (2 modules of 24 kWh each), 38 kWh usable

SaxHybrid^PLUS – energy storage systems for hybrid buses with qualified energy management – projekt of the Schaufensters Elektromobilität Bayern – Sachsen (Showcase electromobility Bavaria – Saxony); 2013 – 2016; commissioned by: Federal Ministry of Transport and Digital Infrastructure (BMVI); contact: project management organization VDI/VDE (phone: +49 30/ 3100780); adaptive energy and performance management system for plug-in hybrid buses, test of a plug-in hybrid bus in Dresden and Leipzig

Testing program of the Federal Ministry for the Environment, Nature Conservation and Building (BMU) »Analysis of efficiency, costs and deployment for the regular operation of diesel hybrid buses«; 2014 – 2015; commissioned by: VCDB as contractor of the BMU; contact: Mr. Jürgen Lange (phone: +49 351/ 4823124); route analysis and recommendations for optimized regular operation of hybrid buses on the basis of different operating conditions; demands made of driving staff and analysis of driver influence on vehicle efficiency

Scientific and technological accompaniment of the long-term testing of a hybrid bus in comparison; 2014 – 2015; commissioned by: ViP Verkehrsbetrieb Potsdam GmbH; contact: Mr. Oliver Glaser (phone: +49 331/ 66141000); recording of the operating data of a hybrid bus in comparison; assessment in terms of energy efficiency; acceptance of hybrid bus technology with driving staff

Accompanying research »Hybrid buses for more environmentally friendly public transport«; 2010 – 2012; commissioned by: VCDB GmbH as contractor of the Federal Ministry for the Environment. Nature Conservation and Building (BMU); contact: Mr. Jürgen Lange (phone: +49 351/ 4823124); assessment of hybrid technology regarding energy efficiency; recording of operating data in the transport association RegioHybrid; acceptance of hybrid bus technology; recommendations for operation in the transport association RegioHybrid

Professional accompaniment of the introduction of different hybrid bus types in Munich; 2011; commissioned by: MVG; contact: Mr. Franz Fendt (phone: +49 89/ 21914210); assessment of hybrid technology regarding energy efficiency and costs; comparative recording of operating data of different hybrid and diesel bus types, survey on the acceptance of hybrid bus technology with drivers and passengers

Professional accompaniment of the introduction of a Solaris articulated hybrid bus in Dresden; 2008 – 2009; commissioned by: DVB AG; contact: Mr. Mino Weber (phone: +49 351/ 8571454); assessment of hybrid technology regarding energy efficiency and costs; comparative recording of operating data of a hybrid bus and a diesel reference bus, optimization of the hybrid bus with regard to diesel consumption, recommendations for regular operation

Professional accompaniment of the introduction of a Solaris articulated hybrid bus in Hannover; 2008 – 2009; commissioned by: üstra; contact: Mr. Jens Ernsting (phone: +49 511/ 16682685); assessment of hybrid technology regarding energy efficiency and costs; comparative recording of operating data of a hybrid bus and a diesel reference bus

Implementation Concepts for Hybrid Trolleybuses

ELIPTIC – coordinated by Free Hanseatic City of Bremen; 2015 – ongoing; commissioned by: European Commission; contact (Senate of the Free Hanseatic City of Bremen): Mr. Michael Glotz-Richter (Tel.: +49/421/3616703); Use case Eberswalde: simulation and assessment of three articulated bus routes in Eberswalde regarding hybrid trolley bus operation

E-Bus Skorpion – hybrid trolley buses on articulated bus routes in Leipzig – projekt of the Schau-fenster Elektromobilität Bayern – Sachsen (Showcase electromobility Bavaria – Saxony); 2013 – 2016; commissioned by: Federal Ministry of Transport and Digital Infrastructure (BMVI); contact: project management organization VDI/VDE (phone: +49 30/ 3100780); assessment of the articulated bus lines in the Leipzig urban area regarding their suitability for the operation of hybrid trollex buses on the basis of detailed energy balance calculations

ElektroHybridBus Esslingen; 2013 – 2016; commissioned by: municipal transport service Esslingen am Neckar; contact: Mr. Harald Boog (phone: +49 711/ 35123223); simulation and assessment of articulated buses regarding hybrid trolley bus operation

Vehicle simulation of an electric bus on LVB route 70; 2012; commissioned by: Verkehrs-Consult Leipzig (VCL) GmbH; contact: Mr. Wolfgang Schütze (phone: +49 341/ 9642429); simulation and assessment of articulated bus route 70 in Leipzig regarding hybrid trolley bus operation

Use of storage systems in the trolley buses of the city of Eberswalde; 2011; commissioned by: Barnimer Busgesellschaft mbH; contact: Mr. Frank Wruck (phone: +49 3334/ 52250); technical layout of storage units for a trolley bus with an energy storage system for improved energy recuperation and partially catenary-free operation; accompaniment of measuring campaigns