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Real life testing of a hybrid PEM fuel cell bus
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. (Energiprocesser, Energy Processes)
Lund Univ, Dept Ind Elect Engn & Automat.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. (Energiprocesser, Energy Processes)ORCID iD: 0000-0002-0635-7372
Lund Univ, Dept Ind Elect Engn & Automat.
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2003 (English)In: Journal of Power Sources, ISSN 0378-7753, Vol. 118, no 1-2, 349-357 p.Article in journal (Refereed) Published
Abstract [en]

Fuel cells produce low quantities of local emissions, if any, and are therefore one of the most promising alternatives to internal combustion engines as the main power source in future vehicles. It is likely that urban buses will be among the first commercial applications for fuel cells in vehicles. This is due to the fact that urban buses are highly visible for the public, they contribute significantly to air pollution in urban areas, they have small limitations in weight and volume and fuelling is handled via a centralised infrastructure.

Results and experiences from real life measurements of energy flows in a Scania Hybrid PEM Fuel Cell Concept Bus are presented in this paper. The tests consist of measurements during several standard duty cycles. The efficiency of the fuel cell system and of the complete vehicle are presented and discussed. The net efficiency of the fuel cell system was approximately 40% and the fuel consumption of the concept bus is between 42 and 48% lower compared to a standard Scania bus. Energy recovery by regenerative braking saves up 28% energy. Bus subsystems such as the pneumatic system for door opening, suspension and brakes, the hydraulic power steering, the 24 V grid, the water pump and the cooling fans consume approximately 7% of the energy in the fuel input or 17% of the net power output from the fuel cell system.

The bus was built by a number of companies in a project partly financed by the European Commission's Joule programme. The comprehensive testing is partly financed by the Swedish programme "Den Grona Bilen" (The Green Car). A 50 kW(el) fuel cell system is the power source and a high voltage battery pack works as an energy buffer and power booster. The fuel, compressed hydrogen, is stored in two high-pressure stainless steel vessels mounted on the roof of the bus. The bus has a series hybrid electric driveline with wheel hub motors with a maximum power of 100 kW.

Hybrid Fuel Cell Buses have a big potential, but there are still many issues to consider prior to full-scale commercialisation of the technology. These are related to durability, lifetime, costs, vehicle and system optimisation and subsystem design. A very important factor is to implement an automotive design policy in the design and construction of all components, both in the propulsion system as well as in the subsystems.

Place, publisher, year, edition, pages
2003. Vol. 118, no 1-2, 349-357 p.
Keyword [en]
PEM fuel cell system; hybrid bus; test; hydrogen
National Category
Vehicle Engineering Chemical Engineering
URN: urn:nbn:se:kth:diva-8316DOI: 10.1016/S0378-7753(03)00086-7ISI: 000183286600047OAI: diva2:13607
QC 20100721Available from: 2008-05-05 Created: 2008-05-05 Last updated: 2012-02-09Bibliographically approved
In thesis
1. Towards sustainable urban transportation: Test, demonstration and development of fuel cell and hybrid-electric buses
Open this publication in new window or tab >>Towards sustainable urban transportation: Test, demonstration and development of fuel cell and hybrid-electric buses
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Several aspects make today’s transport system non-sustainable:

• Production, transport and combustion of fossil fuels lead to global and local environmental problems.

• Oil dependency in the transport sector may lead to economical and political instability.

• Air pollution, noise, congestion and land-use may jeopardise public health and quality of life, especially in urban areas.

In a sustainable urban transport system most trips are made with public transport because high convenience and comfort makes travelling with public transport attractive. In terms of emissions, including noise, the vehicles are environmentally sustainable, locally as well as globally. Vehicles are energy-efficient and the primary energy stems from renewable sources. Costs are reasonable for all involved, from passengers, bus operators and transport authorities to vehicle manufacturers. The system is thus commercially viable on its own merits.

This thesis presents the results from three projects involving different concept buses, all with different powertrains. The first two projects included technical evaluations, including tests, of two different fuel cell buses. The third project focussed on development of a series hybrid-bus with internal combustion engine intended for production around 2010. The research on the fuel cell buses included evaluations of the energy efficiency improvement potential using energy mapping and vehicle simulations. Attitudes to hydrogen fuel cell buses among passengers, bus drivers and bus operators were investigated. Safety aspects of hydrogen as a vehicle fuel were analysed and the use of hydrogen compared to electrical energy storage were also investigated.

One main conclusion is that a city bus should be considered as one energy system, because auxiliaries contribute largely to the energy use. Focussing only on the powertrain is not sufficient. The importance of mitigating losses far down an energy conversion chain is emphasised. The Scania hybrid fuel cell bus showed the long-term potential of fuel cells, advanced auxiliaries and hybrid-electric powertrains, but technologies applied in that bus are not yet viable in terms of cost or robustness over the service life of a bus. Results from the EU-project CUTE show that hydrogen fuelled fuel cell buses are viable for real-life operation. Successful operation and public acceptance show that focus on robustness and cost in vehicle design were key success factors, despite the resulting poor fuel economy. Hybrid-electric powertrains are feasible in stop-and-go city operation. Fuel consumption can be reduced, comfort improved, noise lowered and the main power source downsized and operated less dynamically. The potential for design improvements due to flexible component packaging is implemented in the Scania hybrid concept bus. This bus and the framework for its hybrid management system are discussed in this thesis.

The development of buses for a more sustainable urban transport should be made in small steps to secure technical and economical realism, which both are needed to guarantee commercialisation and volume of production. This is needed for alternative products to have a significant influence. Hybrid buses with internal combustion engines running on renewable fuel is tomorrow’s technology, which paves the way for plug-in hybrid, battery electric and fuel cell hybrid vehicles the day after tomorrow.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. xii, 76 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2008:30
acceptance, analysis, auxiliary system, bus, Clean Urban Transport for Europe, concept, CUTE, demonstration, driver, drive cycle, duty cycle, energy flow, evaluation, fuel cell, heavy duty vehicle, hybrid management, hybrid vehicle, hydrogen, passenger, PEM, safety, Sankey diagram, series hybrid, sustainable, test, urban transport, vehicle simulation, acceptans, analys, hjälpaggregat, buss, Clean Urban Transport for Europe, koncept, CUTE, demonstration, körcykel, förare, energiflöde, utvärdering, bränslecell, tunga fordon, hybridsystemkontroll, hybridfordon, vätgas, passagerare, PEM, säkerhet, Sankey-diagram, seriehybrid, uthållig, hållbar, test, stadstransport, fordonssimulering
National Category
Vehicle Engineering Chemical Engineering
urn:nbn:se:kth:diva-4721 (URN)978-91-7178-940-2 (ISBN)
Public defence
2008-05-23, F3, Lindstedtsvägen 26, Stockholm, 13:00
QC 20100722Available from: 2008-05-05 Created: 2008-05-05 Last updated: 2010-07-22Bibliographically approved

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