| 1. |
- Wikström, Martina, et al.
(författare)
-
Analysis of the fuel economy improvement potential of ethanol hybrid buses
- 2011
-
Ingår i: Proceedings of the 24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2011. - : Nis University. - 9788660550165 ; , s. 2220-2229
-
Konferensbidrag (refereegranskat)abstract
- With the ambitions to further increase its share of renewable fuels and to reduce the amount of carbon dioxide emissions, local emissions and noise, Stockholm Public Transport (SL) hosted a one-year project to evaluate the performance of ethanol hybrid buses. An important part of the project was the duty cycle tests according to SORT - Standardised On-Road Tests cycles (developed by the International Association of Public Transport, UITP). The duty cycle tests generated experimental data, on which this paper’s discussion is based upon. The purpose of this article is to evaluate the potential of energy-efficiency improving measures on the powertrain. The ethanol hybrid bus is a series hybrid vehicle with regenerative braking. A start/stop software to avoid idling was optional. A bus with similar exterior properties, but with the ethanol internal combustion engine coupled to a conventional automatic gearbox instead of a hybrid powertrain was used as a reference throughout the project. Based on both experimental data and simulations, several measures to increase the overall energy-efficiency may be proposed. Assessed measures to increase the energy-efficiency include size optimization of powertrain components, such as energy storage and electric motor, and internal combustion engine (identified by using Sankey diagrams), adjustment of the super capacitors energy management system and utilisation of engine start/stop functionality. Analysis shows that the size of the energy storage is well attuned if applied as urban transport. It would be possible to downsize the ICE, from approximately 200 kW to approximately 150 kW, without losing substantial performance. Using the start/stop software reduces the fuel consumption with 15 % in the standardized city duty cycle but has the potential for even further fuel economy improvements in real traffic with more idling.
|
|
| 2. |
- Wikström, Martina, et al.
(författare)
-
First experiences of ethanol hybrid buses operating in public transport
- 2011
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
