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Fuel Cell Buses in the Stockholm CUTE Project: First Experiences from a Climate Perspective
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. (Energiprocesser, Energy Processes)
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. (Energiprocesser, Energy Processes)
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. (Energiprocesser, Energy Processes)ORCID iD: 0000-0002-0635-7372
2005 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 145, no 2, 620-631 p.Article in journal (Refereed) Published
Abstract [en]

This paper aims to share the first experiences and results from the operation of fuel cell buses in Stockholm within the Clean Urban Transport for Europe (CUTE) project. The project encompasses implementation and evaluation of both a hydrogen fuel infrastructure and fuel cell vehicles in nine participating European cities. In total, 27 fuel cell buses, 3 in each city, are in revenue service for a period of 2 years.

The availability of the fuel cell buses has been better than expected, about 85% and initially high fuel consumption has been reduced to approximately 2.2 kg H-2/10 km corresponding to 7.51 diesel equivalents/10 km. Although no major breakdowns have occurred so far, a few cold climate-related issues did arise during the winter months in Stockholm.

Place, publisher, year, edition, pages
2005. Vol. 145, no 2, 620-631 p.
Keyword [en]
fuel cell bus; climate conditions; evaluation; auxiliary systems
National Category
Vehicle Engineering Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4991DOI: 10.1016/j.jpowsour.2004.12.081ISI: 000231893300066Scopus ID: 2-s2.0-23844507950OAI: oai:DiVA.org:kth-4991DiVA: diva2:7358
Note

QC 20100721

Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
In thesis
1. On direct hydrogen fuel cell vehicles: modelling and demonstration
Open this publication in new window or tab >>On direct hydrogen fuel cell vehicles: modelling and demonstration
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In this thesis, direct hydrogen Proton Exchange Membrane (PEM) fuel cell systems in vehicles are investigated through modelling, field tests and public acceptance surveys.

A computer model of a 50 kW PEM fuel cell system was developed. The fuel cell system efficiency is approximately 50% between 10 and 45% of the rated power. The fuel cell auxiliary system, e.g. compressor and pumps, was shown to clearly affect the overall fuel cell system electrical efficiency. Two hydrogen on-board storage options, compressed and cryogenic hydrogen, were modelled for the above-mentioned system. Results show that the release of compressed gaseous hydrogen needs approximately 1 kW of heat, which can be managed internally with heat from the fuel cell stack. In the case of cryogenic hydrogen, the estimated heat demand of 13 kW requires an extra heat source.

A phase change based (PCM) thermal management solution to keep a 50 kW PEM fuel cell stack warm during dormancy in a cold climate (-20 °C) was investigated through simulation and experiments. It was shown that a combination of PCM (salt hydrate or paraffin wax) and vacuum insulation materials was able to keep a fuel cell stack from freezing for about three days. This is a simple and potentially inexpensive solution, although development on issues such as weight, volume and encapsulation materials is needed

Two different vehicle platforms, fuel cell vehicles and fuel cell hybrid vehicles, were used to study the fuel consumption and the air, water and heat management of the fuel cell system under varying operating conditions, e.g. duty cycles and ambient conditions. For a compact vehicle, with a 50 kW fuel cell system, the fuel consumption was significantly reduced, ~ 50 %, compared to a gasoline-fuelled vehicle of similar size. A bus with 200 kW fuel cell system was studied and compared to a diesel bus of comparable size. The fuel consumption of the fuel cell bus displayed a reduction of 33-37 %. The performance of a fuel cell hybrid vehicle, i.e. a 50 kW fuel cell system and a 12 Ah power-assist battery pack in series configuration, was studied. The simulation results show that the vehicle fuel consumption increases with 10-19 % when the altitude increases from 0 to 3000 m. As expected, the air compressor with its load-following strategy was found to be the main parasitic power (~ 40 % of the fuel cell system net power output at the altitude of 3000 m). Ambient air temperature and relative humidity affect mostly the fuel cell system heat management but also its water balance. In designing the system, factors such as control strategy, duty cycles and ambient conditions need to taken into account.

An evaluation of the performance and maintenance of three fuel cell buses in operation in Stockholm in the demonstration project Clean Urban Transport for Europe (CUTE) was performed. The availability of the buses was high, over 85 % during the summer months and even higher availability during the fall of 2004. Cold climate-caused failures, totalling 9 % of all fuel cell propulsion system failures, did not involve the fuel cell stacks but the auxiliary system. The fuel consumption was however rather high at 7.5 L diesel equivalents/10km (per July 2004). This is thought to be, to some extent, due to the robust but not energy-optimized powertrain of the buses. Hybridization in future design may have beneficial effects on the fuel consumption.

Surveys towards hydrogen and fuel cell technology of more than 500 fuel cell bus passengers on route 66 and 23 fuel cell bus drivers in Stockholm were performed. The passengers were in general positive towards fuel cell buses and felt safe with the technology. Newspapers and bus stops were the main sources of information on the fuel cell bus project, but more information was wanted. Safety, punctuality and frequency were rated as the most important factors in the choice of public transportation means. The environment was also rated as an important factor. More than half of the bus passengers were nevertheless unwilling to pay a higher fee for introducing more fuel cell buses in Stockholm’s public transportation. The drivers were positive to the fuel cell bus project, stating that the fuel cell buses were better than diesel buses with respect to pollutant emissions from the exhausts, smell and general passenger comfort. Also, driving experience, acceleration and general comfort for the driver were reported to be better than or similar to those of a conventional bus.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. viii, 96 p.
Series
Trita-KET, ISSN 1104-3466 ; 208
Keyword
Chemical engineering, direct hydrogen, Proton Exchange Membrane, PEM, fuel cell, fuel cell vehicle, fuel cell hybrid vehicles, on-board hydrogen storage, Kemiteknik
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-147 (URN)91-7283-978-3 (ISBN)
Public defence
2005-03-18, Kollegiesalen, Valhallavägen 79, Stockholm, 13:15
Opponent
Supervisors
Note
QC 20101020Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2010-10-20Bibliographically approved
2. 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.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:30
Keyword
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
Identifiers
urn:nbn:se:kth:diva-4721 (URN)978-91-7178-940-2 (ISBN)
Public defence
2008-05-23, F3, Lindstedtsvägen 26, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20100722Available from: 2008-05-05 Created: 2008-05-05 Last updated: 2010-07-22Bibliographically approved

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