Analysis of Hybrid Buses in Regular Service

From 2006 to 2009 the first prototypes of hybrid city buses were introduced to the public by various bus manufacturers. Already in 2006 Solaris Bus & Coach S.A. delivered a close-to-production vehicle to the Transport operators of Dresden (DVB AG) and Leipzig (LVB GmbH) which is equipped with a power split hybrid propulsion system developed by Allison Transmis-sion. The second generation vehicle with a smaller diesel engine, driven third axle and with an improved power train cooling system is in daily use by the üstra Hannoversche Verkehrsbetriebe AG. When ordering further hybrid buses environmental and economic facts have to be considered. Fuel-saving, wear reduction and lower maintenance costs have to amortize additional procurement costs. To provide an objective evaluation of hybrid buses, the vehicles in Dresden, Leipzig and Hannover were compared to conventional diesel buses in exten-sive field campaigns.

In order to obtain representative results, the acquired data of both test vehicles were recorded and evaluated in daily regular service by the Fraunhofer Institute for Transportation and Infrastructure Systems. The evaluation periods lasted for
12 months in all cases; thereby the vehicles were in regular service use for 16 to 18 hours every day.

The lines for parallel services were chosen according to the expected fuel saving potentials of the hybrid buses. The lines were split up into track sections, characterized by passenger demand, altitude profile and distances between stops.

Additional evaluations based on requested time intervals, such as holiday season, trade fair dates, rush hour or times with low traffic have been carried out, too.

Using a real time controller, all available state variables of the on-board data bus (CAN) and the passenger counting system, as well as the GPS-position for every way- and time point, could be recorded exactly (cf. Fig-ure 2). The parameter fuel consumption was verified by measurements with a fuel-flow-sensor and has been equilibrated with the refuelling data of the operators.

The acquired data, from which it is possible to generate acceleration-, track-, velocity-, power-, and fuel-consumption-profiles for every vehicle and for every period of time, were saved in a database. Developed software ensured a fast and secure conditioning and evaluation of the raw data.

It is possible to provide substantiated comparisons of buses with different propulsion systems using test-drives on public transport lines as well as stan-dardized test cycles on testing areas. The comparisons also serve for the optimization of drive trains.

The data acquired in regular service can be evaluated by the Fraunhofer IVI regarding to the average fuel consumption per track section, per time interval as well as in dependence on the number of passengers, the average speed and the deviation from sched-ule. The advantage of this measure-ment method is based on the exact localization of potential sections for energy saving.

Cost-benefit-analyses consider all costs for procurement, equipment, training, maintenance and service occurring in a testing period as well as costs which are expected in normal future opera-tion. Scenarios for cost developments of the vehicle, spare parts, diesel and operating fluids as well as the lifetime of the batteries and their costs form the basis for cost-benefit-analyses. Such analyses identify the conditions under which the additional procurement costs of hybrid buses can be amortized.

Simulations and calculations allow conclusions on fuel saving potentials caused by further technological developments. For instance it is possible to determine fuel savings using a start-stop-automatic, a mechanical decoup-ling of the peripheral equipment, the use of a predictive energy management and downsizing of the diesel en-gine. Furthermore it is possible to predict the fuel consumption on other lines or to evaluate possible influences of modifications of the line-characteristics on fuel consumption.

The acceptance by drivers, maintenance staff and passengers is important for the successful introduction of hybrid buses. With the help of comprehensive surveys, the operability, the driving characteristics, the maintainability as well as the interior design of the vehicles can be evaluated.

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

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

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

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: 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

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

Hybrid Trolleybuses

ELIPTIC – coordinated by Free Hanseatic City of Bremen; 2015 - 2017; 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 articu-lated 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