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On direct hydrogen fuel cell vehicles: modelling and demonstration
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
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 [en]
Chemical engineering, direct hydrogen, Proton Exchange Membrane, PEM, fuel cell, fuel cell vehicle, fuel cell hybrid vehicles, on-board hydrogen storage
Keyword [sv]
Kemiteknik
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-147ISBN: 91-7283-978-3 (print)OAI: oai:DiVA.org:kth-147DiVA: diva2:7360
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
List of papers
1. Evaluating PEM Fuel Cell System Models
Open this publication in new window or tab >>Evaluating PEM Fuel Cell System Models
2004 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 126, no 1-2, 88-97 p.Article in journal (Refereed) Published
Abstract [en]

Many proton exchange membrane (PEM) fuel cell models have been reported in publications and some are available commercially. This paper helps users match their modeling needs with specific fuel cell models. The paper has three parts. First, it describes the model selection criteria for choosing a fuel cell model. Second, it applies these criteria to select state-of-the-art fuel cell models available in the literature and commercially. The advantages and disadvantages of commercial models are discussed. Third, the paper illustrates the process of choosing a fuel cell model with an example: the National Renewable Energy Laboratory's (NREL's) evaluation of two detailed stand-alone fuel cell system models. One is from Virginia Tech University, and the other is from Sweden's Royal Institute of Technology. Both models have been integrated into NREL's vehicle simulation model ADVISOR(TM) 2003 (Advanced Vehicle Simulator).

Keyword
fuel cell, proton exchange membrane, advanced vehicle simulator, fuel cell system modelling
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4986 (URN)10.1016/j.jpowsour.2003.08.044 (DOI)000188947000012 ()
Note
QC 20101019Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
2. On-Board Hydrogen Storage for Fuel Cell Vehicle
Open this publication in new window or tab >>On-Board Hydrogen Storage for Fuel Cell Vehicle
2001 (English)In: Proceedings of the 36th Intersociety Energy Conversion Engineering Conference: Savannah, GA: 29 July 2001 through 2 August 2001, 2001, 581-588 p.Conference paper, Published paper (Refereed)
Abstract [en]

Methods for onboard storage of hydrogen were evaluated for use in a fuel cell vehicle. Compressed hydrogen gas and cryogenic liquid hydrogen seem to be the two most viable options. Both these storage options were modelled, for storage of 5 kg hydrogen, to be implemented in an automotive fuel cell system simulation model. Hydrogen discharge was simulated for different values of cell stack operating pressure and temperature, using a constant rate of hydrogen release, and the power requirement for heating of the hydrogen to fuel cell stack operating temperature was calculated. The calculations show that compressed gaseous hydrogen storage requires a heating capacity of 0.72 - 1 kW for stack operating temperatures of 343-368 K. In the case of liquid hydrogen storage, heating demand for vaporisation and heating of the fuel was calculated to between 10 and 13 kW for stack operating temperatures of 343-368 K. The fuel cell stack produces surplus heat that can be used for fuel heating. Calculations show that the heat content of the cooling medium is sufficient to heat the fuel stream to approximately 20 K below stack temperature, with temperature differences in heat exchangers being the limiting factor. The radiator/compartment heating and humidifier will also extract heat from the cooling medium. However, to reach system temperature an auxiliary heat source will be required. This could be in the form of an electrical heater or a hydrogen burner. Also, for liquid hydrogen storage, a power demand arises for maintaining operating pressure inside the storage vessel during hydrogen release. This was calculated to between 13 and 28 W for the fuel cell stack operating conditions simulated, and this power demand can be supplied by directing a stream of released and heated hydrogen through a coil running inside the storage vessel.

Series
Proceedings of the Intersociety Energy Conversion Engineering Conference, ISSN 0146-955X
Keyword
Automotive fuels, Compressibility of gases, Computer simulation, Fuel storage, Heat exchangers, Radiators, Vaporization, Fuel cell vehicles, Hydrogen storage
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4987 (URN)
Conference
36th Intersociety Energy Conversion Engineering Conference (IECEC)
Note
QC 20101019 NR 20140805Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2012-02-09Bibliographically approved
3. Cold Climate Thermal Management for Fuel Cells Using Phase Change Materials
Open this publication in new window or tab >>Cold Climate Thermal Management for Fuel Cells Using Phase Change Materials
(English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755Article in journal (Other academic) Submitted
Keyword
Proton Exchange Membrane Fuel Cell, Automotive Fuel Cell System, Latent Heat Store, Phase Change Material, Thermal Management, Cold Climate
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4988 (URN)
Note
QS 20120326Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
4. The Effect of Drive Cycles on the Performance of a PEM Fuel Cell System for Automotive Applications
Open this publication in new window or tab >>The Effect of Drive Cycles on the Performance of a PEM Fuel Cell System for Automotive Applications
2001 (English)In: Proceedings, ATTCE 2001-Automotive and Transport Technology Congress and Exhibition, 2001, 417-426 p.Conference paper, Published paper (Refereed)
Abstract [en]

The purpose of this system study was to compare the performance and fuel consumption of a pure fuel cell vehicle ( i.e. with no battery included) with an internal combustion engine (ICE) vehicle of similar weight in different drive cycles. Both light and heavy duty vehicles are studied.

For light duty vehicles, the New European drive cycle, NEDC [70/220/EEC], the FTP75 [EPA] and a Swedish driving pattern from the city of Lund [ Ericsson, 2000 ] are utilised. The fuel consumption for these drive cycles was compared with ICE vehicles of similar weight, an Ibiza Stella 1.4 (year 2000) from Seat and a Volvo 960 2.5 E sedan (year 1995). For heavy duty vehicles, urban buses in this study, two drive cycles were employed, the synthetic CBD14 and the real bus route 85 from Gothenburg, Sweden.

It can be concluded that marked improvements in fuel economy can be achieved for hydrogen-fuelled light and heavy duty vehicles. The fuel consumption of a small fuel cell vehicle was 50% less than the corresponding ICE vehicle in both the NEDC and the FTP75. With proper dimensioning of the system components, e.g. the engine, further reductions in fuel consumption can be achieved. The range of more than 500 km with 5 kg of hydrogen in a 345 bar fuel tank was comparable to an ICE vehicle. If the pressure is raised to 690 bar, a driving range of 600 km could be achieved. As the auxiliary system counteracts the increase in fuel cell efficiency, raising the minimum operating voltage from 0.6 to 0.75 V in a 50 kW fuel cell system, provides only a 5% reduction in fuel consumption. A fuel cell bus operated in the CBD14 and the bus route 85, compared with diesel-fuelled urban bus of similar weight, demonstrates a reduction in fuel consumption of 33 and 37 % respectively.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4989 (URN)10.4271/2001-01-3454 (DOI)
Conference
ATTCE 2001-Automotive and Transport Technology Congress and Exhibition
Note
QC 20101020 NR 20140805Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2012-02-09Bibliographically approved
5. Effects of Ambient Conditions on Fuel Cell Vehicle Performance
Open this publication in new window or tab >>Effects of Ambient Conditions on Fuel Cell Vehicle Performance
2005 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 145, no 2, 298-306 p.Article in journal (Refereed) Published
Abstract [en]

Ambient conditions have considerable impact on the performance of fuel cell hybrid vehicles. Here, the vehicle fuel consumption, the air compressor power demand, the water management system and the heat loads of a fuel cell hybrid sport utility vehicle (SUV) were studied. The simulation results show that the vehicle fuel consumption increases with 10% when the altitude increases from 0 m up to 3000 m to 4.1 L gasoline equivalents/100 km over the New European Drive Cycle (NEDC). The increase is 19% on the more power demanding highway US06 cycle. The air compressor is the major contributor to this fuel consumption increase. Its load-following strategy makes its power demand increase with increasing altitude. Almost 40% of the net power output of the fuel cell system is consumed by the air compressor at the altitude of 3000 m with this load-following strategy and is thus more apparent in the high-power US06 cycle.

Changes in ambient air temperature and relative humidity effect on the fuel cell system performance in terms of the water management rather in vehicle fuel consumption. Ambient air temperature and relative humidity have some impact on the vehicle performance mostly seen in the heat and water management of the fuel cell system. While the heat loads of the fuel cell system components vary significantly with increasing ambient temperature, the relative humidity did not have a great impact on the water balance. Overall, dimensioning the compressor and other system components to meet the fuel cell system requirements at the minimum and maximum expected ambient temperatures, in this case 5 and 40 degrees C, and high altitude, while simultaneously choosing a correct control strategy are important parameters for efficient vehicle power train management.

Keyword
proton exchange membrane (PEM) fuel cell system, fuel cell hybrid vehicle, performance, ambient conditions
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4990 (URN)10.1016/j.jpowsour.2004.12.080 (DOI)000231893300030 ()2-s2.0-23844493581 (Scopus ID)
Note

QC 20101020

Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
6. Fuel Cell Buses in the Stockholm CUTE Project: First Experiences from a Climate Perspective
Open this publication in new window or tab >>Fuel Cell Buses in the Stockholm CUTE Project: First Experiences from a Climate Perspective
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.

Keyword
fuel cell bus; climate conditions; evaluation; auxiliary systems
National Category
Vehicle Engineering Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4991 (URN)10.1016/j.jpowsour.2004.12.081 (DOI)000231893300066 ()2-s2.0-23844507950 (Scopus ID)
Note

QC 20100721

Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved
7. A First Report on the Attitude towards Hydrogen Fuel Cell Buses in Stockholm
Open this publication in new window or tab >>A First Report on the Attitude towards Hydrogen Fuel Cell Buses in Stockholm
2006 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 31, no 3, 317-325 p.Article in journal (Refereed) Published
Abstract [en]

Surveys of the attitude towards hydrogen fuel cell buses among passengers and bus drivers were performed in Stockholm during the autumn of 2004. Another field survey of the attitude of the fuel cell bus passengers is planned towards the end of the CUTE Stockholm project, i.e. during the autumn of 2005.

The main results from the surveys are:

People are generally positive towards fuel cell buses and feel safe with the technology.

Newspapers and bus stops are where most people get information about the buses.

The passengers, furthermost those above the age of 40, desire more information about fuel cells and hydrogen.

The drivers are generally positive to the fuel cell bus project.

Although the environment is rated as an important factor, 64% of the bus passengers were not willing to pay a higher fee if more fuel cell buses were to be used.

Keyword
fuel cell buses; attitude; acceptance; survey
National Category
Vehicle Engineering Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4992 (URN)10.1016/j.ijhydene.2005.11.008 (DOI)000236294700001 ()2-s2.0-30944444575 (Scopus ID)
Note

QC 20100721

Available from: 2005-03-07 Created: 2005-03-07 Last updated: 2017-12-05Bibliographically approved

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