First experiences of ethanol hybrid buses operating in public transport
2011 (English)Conference paper, Presentation (Refereed)
With the ambitions to further increase its share of renewable fuels and to reduce the amount of local carbon dioxide emissions and noise, Stockholm Public Transport (SL), together with bus manufacturer Scania and bus operator Nobina, hosted a one year project to evaluate the performance of ethanol hybrid buses. Six ethanol hybrid buses were operating in regular public transport between June 2009 and June 2010. During this period the buses were operating at three different suburban routes. The purpose was to accumulate experimental data and to validate the robustness of the ethanol hybrid system and its components. In addition, in order to obtain comparable data, standardized duty cycle tests were performed. Furthermore, with the objective to assemble experimental data during heavy traffic and low mean velocity conditions, two urban routes were selected for staged tests with one ethanol hybrid bus.
The purpose of this paper is to evaluate the energy efficiency of the electrified driveline and hybrid components of the Scania ethanol hybrid bus based on experimental data.
The bus is a series hybrid vehicle with regenerative braking. A start/stop software to avoid idling was optional. The key components of a series hybrid are internal combustion engine, generator, energy storage, electric engine and resistor. The energy storage was commercially available super capacitors. The components of the electric powertrain were developed and delivered by Voith Turbo. A bus with identical exterior properties, an ethanol internal combustion engine coupled to a conventional automatic gearbox but without a hybrid system was used as a reference throughout the project. The measurement equipment was installed in the hybrid system to capture energy flows in and out of key components. Parallel logging of GPS coordinates generated a velocity profile which coupled with energy flow data constitute to the foundation of the analysis.
The main results are presented as Sankey diagrams visualizing the energy flow through the electrified powertrain and determines the energy efficiency for each of the different traffic situations. The initial experimental results indicate that the reduction of fuel consumption benefits from routes with low mean velocity and a high number of stop. At such favorable conditions the fuel reduction are in the order of 30 %. The potential additional fuel savings of the start/stop software has been simulated and adds another 5-10 % fuel reduction. Not all of the hybrid system’s components are not yet robust enough and need further development. The super capacitors work consistent and are suitable as energy storage for this application.
Place, publisher, year, edition, pages
Ethanol hybrid bus, Series hybrid, Duty cycle, Urban public transportation
IdentifiersURN: urn:nbn:se:kth:diva-107424OAI: oai:DiVA.org:kth-107424DiVA: diva2:575874
World Renewable Energy Congress, May 8-13 2011, Linköping, Sweden
QC 201305272012-12-112012-12-112015-09-16Bibliographically approved