TRANSPORTATION AND SAFETY IN JAPAN DEVELOPMENT OF THE FCX VEHICLE AT

Takashi MORIYA Wako Research Center, Honda R&D Co., Ltd.

1. INTRODUCTION In July 2002 Honda was the ducing size and weight include 1) Automobile manufacturers to- first in the world to win approval to development of an electrolytic poly- day are pursuing research and de- sell an FCV in the United States, mer membrane and 2) innovations velopment of high efficiency and also received such approval in in electrode production technology technologies. Such technologies can Japan. On 2 December 2002, the (platinum-loaded carbon). lead to cleaner exhaust emissions, Honda-developed FCV (FCX) was Each cell in a PEFC stack is which addresses the urban environ- delivered both to Japan’s Cabinet constructed of a membrane elec- mental problems that seem to grow Office and to the City of Los Ange- trode assembly (MEA) that sand- yearly, and reduce the volume of les in the United States. This paper wiches an ion-exchange membrane CO2 emissions, which are thought provides a brief introduction to the between electrodes; then in turn is to contribute to global warming. history of FCV development at sandwiched between a gas diffusion Concern about future depletion of Honda and a description of the FCX. layer and flow-path inscribed sepa- oil reserves is also growing. Honda rators (Figure 1). The stack is built began active development of fuel of layers of these cells. The voltage cell vehicles (FCV) in the mid 2. AN OVERVIEW OF FUEL of individual cells varies between 1990s, believing the technology CELLS AND FUEL CELL 0.7V and 1V depending on electri- could meet and solve the demands VEHICLES cal current generated but operate in of these three enormous social is- The fuel cells currently receiv- a range of about 0.7V at times of sues. In November 2000, the Cali- ing so much attention for their po- maximum output. Since the operat- fornia Fuel Cell Partnership tential to power both vehicles and ing voltage for the drive motor is a (CaFCP) in the United States, which homes are polymer electrolyte fuel stable 288V, the stack needs to con- includes both automobile manufac- cells (PEFC), in which great ad- tain about 400 cells for use in auto- turers and the major oil companies, vances have made in size and mobiles. began conducting real-world FCV weight reduction. Such fuel cells uti- In so far as they extract energy driving tests. Honda’s vehicles have lize the energy released when hy- by supplying fuel to trigger a chemi- logged more than 10,000 miles in drogen and oxygen are combined cal reaction, fuel cells can be con- CaFCP fleet tests and have received in a reaction generating water. Ma- sidered a kind of electrochemical government permission for driving jor technological innovations for re- engine no different than the inter- tests on public roads in Japan. nal-combustion engine. Not being subject to the limitations of Carnot efficiency that apply to heat engines, however, fuel cells can achieve an H2 O2 MEA extremely high theoretical efficiency of 83% (roughly 60% in practice). There are two principal meth- ods for supplying hydrogen in fuel cell vehicles: one where hydrogen is stored directly onboard and one where a reformer is used to convert H O 2 some liquid fuel into hydrogen. Pure hydrogen FCVs are extremely clean, E (Electron) discharging only water. Reformer- based FCVs using methanol or Separator Diffusion Layer Electrode Layer Ion-exchange Membrane hydrocarbon fuels have been con- Fig. 1 Basic cell structure sidered but they do discharge CO2

IATSS RESEARCH Vol.27 No.1, 2003 • 91 at time of conversion. There are also The FCX-V1 was an experi- MPa. Adopting a capacitor for elec- numerous technical issues to be mental vehicle based on Honda’s tricity storage, the V3 attained re- worked out concerning startup and EV-Plus electric and used a fuel sponsive and efficient energy transient responsiveness. At the cell stack manufactured by Ballard management. An FCX-V3 variant same time, evaluation of well-to- Power Systems with metal hydride incorporating a Honda-developed wheel CO2 emissions for reformer- tank for hydrogen storage. The fuel cell stack was unveiled in Feb- based FCVs shows no substantial FCX-V2, also experimental, was ruary 2001 as part of our efforts to superiority relative to hybrid ve- outfitted with methanol reformer achieve further performance im- hicles. equipment and a fuel cell stack de- provements. Believing the FCV to be the veloped by Honda. Both incorpo- In September 2001 we un- ultimate clean, efficient automobile rated Honda-manufactured 49kW veiled the FCX-V4, a further evo- and preferring to use sustainable drive motors and included batteries lution of the FCX-V3. This car fuel, since 1999 Honda has focused for electrical storage. Both vehicles incorporated a more compact fuel its development efforts on pure hy- were two-seaters as their backseat cell stack system and gained lug- drogen FCVs. areas were occupied by control de- gage space by locating the tanks un- vices and related equipment. der the floor. The pressure of the Based on the knowledge gain- hydrogen tanks was increased to 350 3. HISTORY OF FCV DEVEL- ed with the V1 and V2, we unveiled MPa and the driving range extended OPMENT AT HONDA the FCX-V3 pure hydrogen FCV in greatly from 180km to 315km. A The path of FCV development September 2000. Output for the V3 larger radiator improved cooling at Honda is outlined in Figure 2. was 60kW, a roughly 10kW im- performance and maximum speed Honda took up the challenge of provement over the V1 and V2. The was increased from 130km/h to FCV development in earnest in the V3 was equipped with a fuel cell 140km/h. Crushable zones were ex- mid1990s, resulting in the unveil- stack manufactured by Ballard panded both at the front and rear of ing in September 1999 of the FCX- Power Systems and carried its hy- the body, improving safety. V1 pure hydrogen FCV and the drogen fuel in high-pressure hy- Building on the foundation of FCX-V2 methanol reformer FCV. drogen tanks compressed to 250 these experimental , Honda un-

V1 V2 V3 V4

Fuel Hydrogen Methanol Hydrogen Hydrogen High-pressure High-pressure Storage Absorbing Alloy On-board Reformer Tank (25MPa) Tank (35MPa) Output 49kW 49kW 60kW 60kW Fuel Cell Stack Ballard Honda Honda/Ballard Ballard Number of Occupants 2244

Fig. 2 Development of Honda fuel cell vehicles

92 • IATSS RESEARCH Vol.27 No.1, 2003 veiled the FCX as a production FCV Ultra-Capacitor on 2 December 2002, delivering PCU (Power Control Unit) vehicles simultaneously both to Japan’s Cabinet Office and to the City of in the United Fuel Cell System Radiator States. Figure 3 illustrates the ex- terior and Table 1 summarizes the main specifications. The FCX achieves a more compact powertrain Humidifier Unit than the FCX-V4, with greater ef- Fuel Cell Stack ficiency and a maximum speed of Fuel Cell System Box 150km/h. Its 156.6L capacity hy- Drive Train Radiators Drive Motor Air Pump drogen tanks make possible a driv- Fig. 4 FCX packaging ing range of 355km in LA-4 mode. Further details are provided below. tanks under the rear seat while pack- 5. FCX POWERTRAIN ing the fuel cell system beneath the 4. FCX PACKAGING floor, resulting in a high level of col- SYSTEM Honda designed a custom plat- lision safety as well as a spacious Hydrogen stored in high-pres- form for the FCX to ensure that it cabin. Angling the ultra-capacitor sure tanks is, after pressure regula- would deliver the basic functional- behind the rear seat secured luggage tion, humidified and supplied to the ity and performance expected in an space while integration of the high- stack. The system ensures effective automobile. The degree of freedom pressure hydrogen tanks with a sub- and complete use of the hydrogen inherent in laying out a fuel cell sys- frame contributes to ease of in- in a circulating system. Air com- tem made it possible to locate the stallation. The front-rear weight dis- pressed by a Lysholm-type air pump high-pressure hydrogen storage tribution thereby achieved 55:45, is, after temperature regulation, hu- which is ideal for a front-wheel midified and supplied to the stack. drive vehicle and provides superb Humidification is accomplished by handling stability in combination a fully independent water-recovery with the Accord-type 5-link double- system that recycles the water va- wishbone rear suspension (Figure por generated in the fuel cell stack. 4). Recognizing that the air pump is a potential source of noise, noise-re- Fig. 3 Honda FCX exterior ducing technologies such as double floating mounts and the combina- Table 1 Honda FCX main specifications tion muffled resonator chamber and × × × × Length Width Height 4,165 1,760 1,645 intake module have been adopted Weight 1,680 kg to improve quietness. A cooling sys- Maximum Speed 150 km/h tem is needed since fuel cell reac- Cruising Range 355 km (LA-4 mode) tions generate heat. However, the Maximum Motor Output 60kW [82 PS] low operating temperature means Maximum Motor Torque 272 Nm [27.7 kgm] that the difference with the outside Maximum Fuel Cell Stack Output 78kW air is small, requiring a large radia- Energy Storage Ultra-capacitor (Honda) tor. Cooling performance is im- Hydrogen Storage 156.6L/350 atmospheres proved by supplementing the fuel

IATSS RESEARCH Vol.27 No.1, 2003 • 93 cell system radiator with two drive magnetic AC synchronous motor high-performance ultra-capacitor train radiators located on either side that Honda developed for the EV- (electrical two-layered condenser) of the front of the vehicle. Plus. A structural overhaul and im- developed independently by Honda. The energy management sys- provements to areas such as the The capacitor uses a new high- tem combines fuel cells and the ul- magnetic circuit configuration re- performance activated-carbon elec- tra-capacitor, providing a power sulted in a 60kW output even as size trode to improve electrical storage boost during startup and accelera- and weight were reduced by 20%. capacity and its electrode wrapped- tion and recovering energy during With 93% efficiency in Japan’s 10- element construction enables high- deceleration. Furthermore, while 15 mode, the FCX drive motor is density packing of electrodes out to idling an automatic idle stop sys- extremely compact, powerful and the cell casing. As a result, energy tem assures both power performance efficient. From a technical stand- efficiency is 7-10% higher than and efficiency. point, the adoption of full-range, full nickel-hydride batteries. The capaci- digital vector control and the com- tor achieves an energy density of 5.1 Fuel cell stack bination of reluctance torque with a 3.9Wh/kg (at a 2.7-1.35V discharge) Using fuel cell stacks in ve- low-loss magnetic circuit results in and an output density of over hicles not only demands that they both high efficiency over a wide 1,500W/kg, making it one of the are small and lightweight, but also range and an expanded power band. finest capacitors in the world with requires improved performance (I- In addition, rotor heat is controlled regard to charge/discharge. V characteristic) and reduced cell through the adoption of newly de- thickness. The FCX employs a com- veloped high heat resistant magnets 5.4 Energy management pact, lightweight fuel cell stack as well as magnetic partitioning that A summary comparison of manufactured by Ballard Power Sys- helps suppress the eddy currents that FCV systems is presented in Figure tems that outputs 78kW of power. generate such heat. 5. Systems can be divided into those that rely solely on the fuel cell stack 5.2 Drive motor 5.3 Ultra-capacitor and those that supplement the fuel The drive motor for the FCX As a supplementary power cell stack with an additional source further refines the 49kW permanent source, the FCX employs a new of power such as a capacitor or bat-

Basic configuration System configuration features Efficiency Power performance

High-voltage Instantaneous Capacitor-assisted Transmission efficiency Fuel cell distribution system • high-output system (FCX) Motor stack Braking regeneration • Ultra- (converter) not required ssist possible capacitor

Transmission efficiency High-voltage distribution Battery-assisted High-voltage Fuel cell (Losses in high-voltage Motor system required Output assist possible system control device stack control device) for fuel stack/battery Braking regeneration Battery •

Simple high-voltage Fuel cell Output and Fuel cell system Transmission efficiency direct-supply Motor • responsiveness depends stack Braking regeneration × system on fuel cell stack Startup device required

Fig. 5 FCV system comparison

94 • IATSS RESEARCH Vol.27 No.1, 2003 tery. A capacitor provides a power vided by the hydrogen energy in- been recognized by the EPA (Envi- boost to assist the fuel cell stack vested) of 45% in LA-4 mode (US ronmental Protection Agency) and during times of transitional response driving evaluation mode) – more adopted as its official measure for and also recovers energy, contrib- than twice that of current gasoline- fuel consumption. uting to fuel efficiency. With less powered vehicle and more than 1.5 The energy stored in 1kg of energy than batteries, capacitors au- times that of hybrid cars. hydrogen happens to be roughly the tomatically follow the voltage char- same as that stored in a gallon of acteristics of the fuel cell stack. 5.5 Measuring fuel consumption gasoline, making comparisons such Unlike batteries, capacitors do not There was no standardized test- as those in Figure 7 possible. These require high-voltage control devices ing procedure for measuring FCV values are EPA-approved and come that lead to large inefficiencies. fuel consumption comparable to that from the guidebook published by Figure 6 illustrates the output for gasoline-powered vehicles. the DOE (US Department of En- characteristics of the fuel cell and After investigating a number of ergy)/EPA listing fuel consumption ultra-capacitor system. During start- procedures we settled on the weight- for all vehicles. The FCX is the only up and acceleration, drive motor based method – a measurement of vehicle registered in the new FCV output is covered by capacitor out- the distance the vehicle can run on category created for it, though the put until the fuel cell output kicks one kilogram of hydrogen – as the future will surely bring additional in, making effective use of the most accurate (unit: miles/kg-H2). vehicles from other companies. capacitor’s ability to provide signifi- This measurement method has the cant output on demand. On the other advantages of being unaffected by 5.6 Hydrogen storage technology hand, fuel cell output is sufficient the temperature or pressure of the There are three typical meth- during gentle acceleration and cruis- gas, being free of measurement cal- ods for storing hydrogen: liquid hyd- ing. During deceleration, the drive culation errors and performed on rogen tanks, high-pressure hydrogen motor’s counter-electromotive force measuring equipment that is inex- tanks and hydrogen absorbing metal is recovered and this energy stored pensive to produce. alloy tanks. in the capacitor. In the United States, this Among them, compressed gas As a result, the FCX achieves weight-based method has been storage is the most realistic choice energy efficiency (defined as the en- adopted by the SAE (Society of Au- at the current time because of the ergy required for mode traveling di- tomotive Engineers). It has also ability to leverage existing experi- ence with CNG (compressed natu- ral gas) vehicles, particularly as concerns safety-related issues, as Fuel cell output well as the fact that fueling time

Output Motor output Speed can be limited to a few minutes. Vehicle speed The FCX employs a high-pres- sure hydrogen tank made of alumi- num liner, carbon fiber, and glass fiber. This three-layer structure pro- + vides superior strength and corro- 0 – sion resistance. Tanks can be filled to 35MPa. Two of these tanks are Ultra-capacitor output employed to achieve a 156.6L hy- drogen capacity which, combined 0 with an improved fuel consumption Fig. 6 Fuel cell and ulta-capacitor output characteristics

IATSS RESEARCH Vol.27 No.1, 2003 • 95 Drive Power Energy Efficiency Comparison Fuel Economy Comparison cell stack. Numerous technical is- 50 60 sues need to be overcome before fuel cell vehicles achieve the space 40 50 utility and ease-of-use expected in 40 30 an automobile and attain overall user

30 benefits – including cost – compa- 20 rable to current internal-combustion 20 Fuel consumption

Energy efficiency (%) engine vehicles. 10

(miles/gallon or miles/kg-H2) 10 At the same time, the issue of FCX Compact gasoline-power car Hybrid car FCX Compact gasoline-power car Hybrid car Natural gas car 0 0 hydrogen fueling infrastructure Fig. 7 FCX energy effeciency and fuel consumption needs to be considered in tandem with future FCV development. In this light, demonstration projects not only spur further development rate, produces a 355km driving testing and disaster tests carried out of FCV but also help identify hy- range when driven in LA-4 mode. in tanks have confirmed a high level drogen-supply infrastructure issues At about three minutes, filling time of safety and reliability. and provide feedback valuable for at a high-pressure fueling station is the future development of manufac- comparable to that for a gasoline- turing, transportation and storage powered vehicle. 7. FUTURE CHALLENGES methods. Future challenges for the FCX The popularization of FCVs include improved startup stability at will take time. It is too late, how- 6. VEHICLE SAFETY temperatures below freezing, further ever, to start working on technolo- The FCX package layout posi- extension of the driving range and gies only when they are needed. tions the fuel cell system box under additional endurance and reliability. Continued steady progress will be the floor and the high-pressure Cruising range improvements await required before we reach that day, hydrogen tanks beneath the rear innovations in hydrogen storage but Honda is committed to pursu- seat, completely isolating the cabin technologies. Increased pressure ing the development of the technolo- from all hydrogen and high-voltage levels for compressed gas are re- gies needed to make it a practical lines. Hydrogen sensors are located quired but a level needs to be iden- reality. throughout the vehicle to provide a tified that maintains safety. warning in the unlikely event of a Achieving improved FCV reli- hydrogen leak. Should a hydrogen ability and safety requires examina- leak occur inside the fuel cell system tion of ease-of-use feedback gained box, a forced ventilation system in both real-world use and demon- activates and, as needed, an auto- stration tests as well as in simple matic cut-off system closes the main evaluations. stop valve on the hydrogen tank or cut-off valves located along the sup- ply lines. The high-voltage lines are 8. CONCLUSION electrically floating. If grounding The FCX fuel cell system is occurs, a sensor sends a warning, and still relatively large and heavy. Pur- in the event of a collision a contact suit of continued size and weight mechanism shuts down the source reductions are needed for system power line. Repeated floodwater control devices as well as the fuel

96 • IATSS RESEARCH Vol.27 No.1, 2003