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17Статья поступила в редакцию 12.08.2010. Ред. рег. № 855
The article has entered in publishing office 12.08.2010. Ed. reg. No. 855
APPENDIX
From Nissan Technical Review No.59 (2006.Sep.)
INTRODUCING THE 2005 MODEL YEAR X-TRAIL FCV
Y. Ban
Nissan Motor Co., Ltd. 1, Natsushima-cho, Yokosuka-shi, Kanagawa 237-8523, JAPAN
This paper describes the 2005 model year X-TRAIL FCV that was approved by the Minister of Land, Infrastructure and Transport of Japan in December 2005. This 2005 FCV model incorporates a host of new technologies, including a fuel cell stack newly developed in-house, for a substantial improvement in cruising range and other performance attributes compared with the previous 2003 model year FCV Limited leasing of the 2005 X-TRAIL FCV to Kanagawa Prefecture and the city of Yokohama was launched in April 2006.
ПРИЛОЖЕНИЕ
Из бюллетеня «Nissan Technical Review», выпуск 59 (сентябрь 2006 г.)
МОДЕЛЬ АВТОМОБИЛЯ НА ТОПЛИВНЫХ ЭЛЕМЕНТАХ X-TRAIL 2005 ГОДА
Й. Бан
В данной статье представлена модель автомобиля на топливных элементах X-TRAIL 2005 года, которая была одобрена министром Японии по вопросам земли, транспорта и инфраструктуры в декабре 2005 г. Эта модель автомобиля на топливных элементах воплотила в себе целый ряд новых технологий, включая батарею топливных элементов, недавно разработанную самим концерном для значительного увеличения запаса хода и других эксплуатационных показателей по сравнению с предыдущей моделью автомобиля на топливных элементах, представленной в 2003 году. В апреле 2006 г. на условиях лизинга несколько автомобилей 2005 X-TRAIL FCV было передано префектуре Канагава и городу Йокогама.
Organization(s): Planning and Advanced Engineering Development Division, Advanced Vehicle Engineering Department, Advanced Vehicle Development Group, Senior Manager.
Yukimasa Ban
Introduction
Fuel cell vehicles (FCVs) are being developed as a promising means of reducing the environmental impact of vehicle use, including carbon dioxide (CO2) emissions. At Nissan, we began developing FCV technologies in 1996, and through the development of successive prototype models (Fig. 1), we have been working to resolve various issues that must be addressed
to promote real-world use of FCVs. Since 2001, we have participated in demonstration tests of FCVs in the United States and Japan. Through these tests and other efforts, we have been engaged in educational activities to familiarize the public with FCVs in an effort to advance their diffusion. This paper describes the 2005 model year X-TRAIL FCV fitted with a fuel cell stack that was newly developed in-house.
2002 FCV model
2005 FCV model
Fig. 1. X-TRAIL FCV Prototypes
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Vehicle Specifications
Fig. 2 shows the appearance of the 2005 X-TRAIL FCV, and Table gives its major specifications.
The 2005 X-TRAIL FCV is available in two types of specifications, depending on the difference in the maximum pressure of the hydrogen fueling system. A 35-MPa specification was approved by the Minister of Land, Infrastructure and Transport of Japan in December 2005. Compared with the 2003 FCV model, the 2005 X-TRAIL FCV has the same external appearance, except for the body color, and the same external dimensions, excluding the overall height. The vehicle's overall height was reduced by 55 mm by discontinuing the rear spoiler. The curb weight of the 2005 X-TRAIL FCV has been lightened to 1,790 kg (1,850 kg for the 70-MPa specification), a substantial reduction of 170 kg from the
Specification Comparison of 2005 and 2003 X-TRAIL FCV Models, for 70 MPa
2005MY 2003MY
Vehicle Overall length/width/height (mm) 4485/1770/1745 4485/1770/1800
Curve Weight 1790 (1860) 1960
Seating capacity 5
Top speed (km/h) 150 145
Cruising range (km) over 370 (over 500) over 350
Motor Type Coaxial motor integrated with reduction gear
Max. powerCkW) 90 85
Fuel cell stack Fuel cell Polymer electrolyte type
Max. power (kW) 90 63
Supplier In-house UTC Fuel Cell (USA)
Battery Type Compact Lithium-ion Battery
Fueling system Fuel type Compressed hydrogen gas
Max. pressure (MPa) 35 (70) 35
1,960-kg weight of the 2003 FCV model. As will be described later, this reduction was achieved by lightening the weight of the newly developed fuel cell system and that of the high-voltage electric powertrain system.
Fig. 2. 2005 Model Year X-TARIL FCV
Major Technologies
All of the major components of the 2005 X-TRAIL FCV were newly developed compared with the 2003 FCV model. This section describes the details of the technologies incorporated in the 2005 X-TRAIL FCV
Packaging
The in-vehicle layout of the major components is shown in Fig. 3. The fuel cell system and the high-pressure hydrogen storage system are located under the floor and the traction motor, inverter and other components of the high-voltage electric powertrain system are located in the engine compartment. This component layout is the same as that of the 2003 FCV model, but the Compact Lithium-ion Battery pack has been moved from behind the rear seatback to below the luggage area floor. This change has enhanced the
practical utility of the 2005 X-TRAIL FCV by increasing the luggage area length by approximately 400 mm over that of the 2003 FCV model. In addition, for the 70-MPa specification, the diameter of the high-pressure hydrogen storage cylinder was reduced by 20 mm from that of the cylinder used on the 2003 FCV model, thereby lowering the sitting height of the rear-seat passengers for enhanced entry/exit ease and greater rear-seat comfort. Downsizing the high-pressure hydrogen storage cylinder reduced the amount of hydrogen that can be stored in the vessel by 15% from the previous model (based on a comparison with the 35-MPa specification). However, the cruising range of the 2005 X-TRAIL FCV has been extended by 20 km over that of the 2003 FCV model by enhancing the efficiency of the fuel cell system and lightening the vehicle weight, among other improvements.
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Fig. 3. Layout of Major Components
Fuel cell stack Fig. 4 is a photograph of the fuel cell stack that was newly developed in-house at Nissan. This new fuel cell stack adopts thin carbon separators, making it possible to downsize the stack by approximately 60% compared with the fuel cell stack used on the 2003 FCV model. Nonetheless, the maximum power output of the new fuel cell stack was increased to 90 kW by improving the polymer electrolyte membrane and optimizing the method of operating the stack. That output compares with 63 kW for the 2003 FCV model stack.
Fig. 4. In-house developed Fuel Cell Stack
70-MPa high-pressure hydrogen storage cylinder The 70-MPa high-pressure hydrogen storage cylinder newly developed for the 2005 X-TRAIL FCV is shown in Fig. 5. Developed jointly by Nissan and Dynetek Industries Ltd. of Canada, this cylinder raises the charging pressure twofold over that of the previous 35-MPa high-pressure cylinder.
Fig. 5. 70 MPa Hydrogen Storage Cylinder
The higher pressure boosts the hydrogen storage capacity by 30% in the same volume compared with a charging pressure of 35 MPa. In order to raise the charging pressure to 70 MPa, it was necessary to develop anew all the constituent parts of the hydrogen fueling system, including the high-pressure hydrogen storage cylinder, hydrogen cutoff valve and the pressure regulator, among others. That made it possible to increase the hydrogen storage capacity while ensuring reliability against hydrogen leakage. A prototype FCV model fitted with the 70-MPa high-pressure hydrogen storage cylinder was tested on public roads in Canada in February 2006. An investigation was made of the effect of a temperature rise inside the cylinder during rapid charging of hydrogen and the effect of a temperature drop due to a rapid discharge of hydrogen under low ambient temperatures.
High-voltage electric powertrain system Fig. 6 is a photograph of the traction motor fitted on the 2005 X-TRAIL FCV, and Fig. 7 is a photograph of Nissan's Compact Lithium-ion Battery. The weight of the traction motor was reduced by 5% from that of the motor used on the 2003 FCV model, while at the same time increasing the maximum power output by 5 kW. A coaxial reduction gear, like that used on the 2003 FCV model, was adopted in order to use the available space with high efficiency.
Fig. 7. Compact Litium-ion Battery
The case is made of magnesium, which reduced the weight by 5% compared with that of the 2003 FCV model. The Power Delivery Module (PDM) mounted in the engine compartment comprises an inverter and a DC/DC converter and functions to provide electric power from the fuel cell stack and the Compact Lithium-
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ion Battery to the traction motor and other components. The PDM developed for the 2005 X-TRAIL FCV is 30% smaller than the unit used on the 2003 FCV model, as a result of improving the layout of its internal parts and the cooling system.
Like the 2003 FCV model, the 2005 X-TRAIL FCV is fitted with Nissan's high-voltage Compact Lithium-ion Battery consisting of laminated cells with high energy density. The controller that monitors the cell voltage was downsized and modularized, making it possible to mount the battery pack under the luggage area floor.
Vehicle Performance
Cruising range
Fig. 8 shows the progress made in improving the cruising range of Nissan's FCVs over the years. The cruising range is one of the key issues for the practical use of FCVs. The 2005 X-TRAIL FCV was developed with the aim of achieving a cruising range of more than 500 km under Japan's 10-15 emission test driving cycle. Toward that end, the 70-MPa high-pressure hydrogen storage cylinder explained earlier was newly developed to increase the quantity of hydrogen stored on-board by 30% compared with that for a charging pressure of 35 MPa. Additionally, the efficiencies of the fuel cell stack and high-voltage electric powertrain system were enhanced, the vehicle weight was substantially reduced, and the aerodynamic performance was also improved. The combined effect of these improvements extended the cruising range of the 2005 X-TRAIL FCV to 500 km, compared with 350 km for the 2003 FCV model.
Power performance Fig. 9 outlines the progress made in improving the 0100 km/h acceleration performance of Nissan's FCVs in recent years. The 2005 X-TRAIL FCV accelerates from 0 to 100 km/h in 14 sec., compared with 20 sec. for the 2003 FCV model. That improvement is the result of increasing the power output of the fuel cell stack and traction motor and substantially lightening the vehicle weight. The improved acceleration performance compares favorably with that of conventional ICE vehicles. Additionally, the 2005 X-TRAIL FCV attains a top speed of 150 km/h, up from 145 km/h for the 2003 FCV model. These figures indicate that its power performance has reached a level that is fully sufficient for real-world use.
S001 02 03 04 OS Fig. 9. Progress of Acceleration Performance of FCV
Crash performance The 2005 X-TRAIL FCV was developed to comply with the road vehicle safety standards enforced on FCVs in Japan since April 1, 2005. Fig. 10 shows scenes of the frontal and rear-end collision tests that were conducted on prototype models in-house. The results of these tests confirmed that the 2005 X-TRAIL FCV meets not only the specified occupant injury criteria, but also the standards established for hydrogen storage safety and high-voltage safety.
Fig. 8. Progress of Crusing Range of FCV
However, even though the 2005 X-TRAIL FCV attains a cruising range of 500 km, that is only the minimum level provided by conventional internal combustion engine (ICE) vehicles. It will be necessary to improve the cruising range further in future work. To accomplish that, it will be necessary to increase the quantity of hydrogen storable on-board the vehicle. With the current high-pressure hydrogen storage system, it is difficult to increase the storage capacity further because of vehicle layout restrictions. Therefore, it will be necessary to develop a new system with higher hydrogen storage efficiency.
Fig. 10. Crash Performance
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Future Issues
The 2005 X-TRAIL FCV achieves a cruising range, power performance and other attributes close to the levels of conventional ICE vehicles, but there are still many issues that need to be resolved in order to popularize FCVs. Some of these issues must be tackled through joint public-private sector efforts, such as the deployment of the necessary hydrogen supply infrastructure and the development of uniform specifications and standards. In addition to those issues, the five broad areas noted below also need to be addressed through research and development efforts at the vehicle level.
Improvement of durability and reliability Durability and reliability have been significantly improved compared with the situation at the time development work on FCVs was initiated, but the levels are still not equal to those of ICE vehicles. Further technological developments are especially needed for suppressing fuel cell degradation. Efforts are under way to develop improved materials for the electrode catalyst layer and the solid polymer electrolyte membrane, as well as control technologies for suppressing performance degradation.
Assurance of low-temperature startability Fuel cell start-up at low temperatures is now possible under certain special conditions, but low-temperature startability under all sorts of environments like that of ICE vehicles is still not assured. Technologies must be developed for preventing the freezing of product water generated in the fuel cell and for quickly thawing a frozen stack.
Size and weight reductions Simplification of the fuel cell system is also needed to reduce its size and weight, as well as for reducing the cost. One example of a technology for downsizing fuel cells is to reduce the cell thickness through the use of metal separators.
Improvement of cruising range Improving the cruising range of FCVs requires an increase in the quantity of hydrogen stored on-board. The current high-pressure hydrogen storage system is limited by the available on-board space and the weight of the system. It will be necessary to develop new hydrogen storage materials and new hydrogen storage systems such as chemical hydrides.
Conclusion
Various technologies for promoting the real-world use of FCVs have resulted from the development of FCV prototypes at Nissan. These technologies have been incorporated into the 2005 model year X-TRAIL FCV to attain a cruising range of 500 km, which has been difficult for previous electric vehicles and FCVs to achieve. The limited leasing program initiated for the 2003 FCV model has also been continued for the 2005 X-TRAIL FCV, enabling us to verify the practicability of the vehicle based on actual operation by ordinary drivers.
There are still many issues that remain to be addressed in order to promote the real-world use of FCVs. We intend to continue our efforts to develop the necessary technologies for popularizing FCVs and ushering in the hydrogen society of the future.
Cost reduction The cost per vehicle at present is extremely high because current FCVs are still at the prototype level. Even if one looks only at the material cost, the current cost level is rather high compared with ICE vehicles. In order to reduce the cost further, the fuel cell system must be simplified and the amount of platinum used for the catalysts must be reduced.
Acknowledgements The authors would like to thank the many individuals who cooperated with the development of the 2005 model year X-TRAIL FCV
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