Fuel cells start to look real
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DaimlerChrysler NECAR 5 and Commander 2
DaimlerChrysler recently introduced two new prototype fuel-cell vehicles - the NECAR 5 (fifth-generation New Electric CAR), which is based on the Mercedes-Benz A-Class car, and the Jeep Commander 2 SUV. Both concept vehicles generate hydrogen fuel onboard by reforming methanol. Company engineers characterize the status of the company's current fuel-cell drive technology as "fit for practical use." In the past six years, the clean drive system has been shrunk sufficiently, so that it requires no more space than a conventional drive system.
The company expects to invest about $1 billion to develop the new drive system from the first prototype to the point of mass production. Klaus-Dieter Vöehringer, member of the company's Board of Management with responsibility for research and technology, predicted the fuel cell will be introduced into vehicles in several stages. "In 2002, DaimlerChrysler will deliver the first city buses with fuel cells, followed in 2004 by the first passenger cars," he said. Up to that time, the vehicles from the first production phase will be using liquid or gaseous hydrogen as a fuel. However, in his view, "these fuels are unlikely to see widespread use because of the high cost of the infrastructure. Nevertheless, we'll be operating test fleets in several regions of the world to gain experience with daily use of fuel cells."
 DaimlerChrysler's latest fuel-cell vehicles: the NECAR 5 (foreground) and Jeep Commander 2. |
Vöehringer does not expect high unit sales during the first three years after market introduction because there will be a limited number of hydrogen filling stations and the technology must first prove its maturity in daily use. "The development time of 10 years for a revolutionary new drive system is an extremely short period considering the enormous challenges," he stated. "And, of course, the ordinary DaimlerChrysler customer won't want to buy a test vehicle but will instead demand a thoroughly perfected and proven product." Vöehringer anticipates the breakthrough will come with the mass introduction of the methanol-driven fuel-cell car, which will allow the driver to "fill up" just like today and drive 480-600 km (300-375 mi) on a single tank.
The NECAR 5's design, which features a Ballard Mark 900 fuel-cell unit and a methanol reformer that runs at 280°C (535°F), is focused on improving packaging, according to Christian Mohrdieck, Senior Manager for Fuel-cell Systems at Liberty and Technical Affairs. In the NECAR 5, the entire fuel-cell system with methanol reformer has been accommodated within the underbody of a Mercedes-Benz A-Class model. That makes the available space comparable to a standard A-Class vehicle. At the same time, the fuel cell's weight has been substantially reduced. In addition, the efficiency of the fuel-cell system has been increased by 50% over the company's previous fuel-cell test vehicle.
"From the technological point of view, NECAR 5 is a prototype of what we may roll out in a few years," Vöehringer explained. "We'll now begin building test fleets to ready the technology for mass production. Developing the manufacturing technology for the components and reducing the related costs will be our main task."
The Jeep Commander 2 likewise operates on a fuel cell fueled by hydrogen generated from methanol in a reformer. Peak power output is supplemented by a battery. The SUV demonstrates that the use of fuel cells is by no means limited to compact vehicles. "Commander 2, which has two Ballard Mark 700 fuel-cell stacks, shows that the technology can work in a much heavier vehicle," said Mohrdieck.
 The Commander 2 is fueled by hydrogen generated from methanol in a reformer and has two Ballard Mark 700 fuel-cell stacks. Click to enlarge |
The Jeep's hybrid-electric powertrain combines the fuel-cell stack with dual front and rear ac-induction electric motors that provide full-time, four-wheel drive. A 90-kW nickel/metal-hydride battery pack is included to provide a power assist boost for acceleration and towing heavy payloads, faster fuel-cell warm-up, and regenerative brakes that capture energy normally lost upon stopping. Mohrdieck noted that the battery contributes 300 V of current for these purposes for only 18 s at a time. Commander 2, which can go from 0 to 97 km/h (0 to 60 mph) in 12 s, produces near-zero tailpipe emissions and gets 24 mpg (gasoline equivalent) in combined-cycle driving tests.
To compensate for the additional weight and cost of the fuel cell and battery system, Jeep designers incorporated DaimlerChrysler's lightweight injection-molded thermoplastic polymer body technology. Because of its low-mass body, the Commander 2 scales 2590 kg (5715 lb) - slightly more than typical full-size SUVs. This includes more than 1100 kg (2500 lb) for the hybrid-electric fuel-cell powertrain, which is 500 kg (1100 lb) more than a standard IC engine.
For the California Fuel Cell Partnership demonstration program, DaimlerChrysler introduced the California NECAR, or NECAR 4A. Unlike 1999's liquid-hydrogen-fueled NECAR 4 vehicle on which it is based, the California NECAR operates on pressurized hydrogen. With its optimized 55-kW electric drive system, it reaches a top speed of 145 km/h (90 mph). Development engineers have been able to considerably reduce the weight and volume of both the drive system and the compact fuel-cell unit, whose core comprises a Ballard Mark 900 stack; for instance, the stack weighs only about two-thirds that of NECAR 4's Mark 700 unit and takes up only half as much space. As a result, the entire occupant cell and luggage compartment can now be used to full capacity. The use of lightweight components, both in the interior and on the bodywork, reduces weight even further. Three hydrogen tanks with a maximum pressure of 35 MPa (5100 psi) are integrated into the vehicle; with a filling capacity of about 1.8 kg (4 lb) of hydrogen, the new NECAR has an operating range of up to about 190 km (120 mi).
Though DaimlerChrysler is pushing methanol, and eventually hydrogen, as its favored fuels for future fuel-cell vehicles, it is staying "fuel-neutral" by pursuing gasoline-reforming technology as well. During an 18-month cooperative research project, its partner XCELLSiS and Shell Hydrogen successfully developed and tested a prototype gasoline reformer to produce hydrogen onboard for fuel-cell applications. The result of the joint research was a 50-kW multi-fuel system with compact design for mobile and stationary use. The development of this powerplant combined DaimlerChrysler and XCELLSiS expertise in designing fuel processors and complete fuel-cell systems along with Shell's proprietary Catalytic Partial Oxidation (CPO) technology.
During intensive testing at the XCELLSiS laboratories in Nabern, Germany, the new reactor unit performed well under stationary and dynamic operating conditions. "We were very pleased with the speed in which we came to results in this research project," said Ferdinand Panik, head of DaimlerChrysler's fuel-cell project. "This is a good example of the versatility of the new fuel-cell technology. Because of the expected high costs, we will continue to work on a methanol reactor as our first priority, as this is the most advanced technology today. But we will also keep an eye on the progress the CPO reactor will make."
DaimlerChrysler and partner Mitsubishi announced in November that they may develop automotive fuel-cell technology jointly. Cooperative development of fuel-cell cars would be a key step in an expected deepening of cooperation after the German auto company took a 34% stake in Mitsubishi.
