Driving the Mercedes-Benz F-Cell in the crowded, confusing, and twisting roads around Monte Carlo, Monaco, it’s immediately clear that hydrogen fuel cells are more than science projects.
Next to the subcompacts and city cars, there’s plenty of thrust to keep up with and overtake traffic. On the highway, the hydrogen Benz ran up to 100 mph without a second thought. And from the cabin, the whole car is as natural and refined as any car on the road. To the driver, the F-Cell feels like a production-ready electric car that short circuits that issues of battery charging with a range of 285 miles and a refueling time of about three minutes as three tanks store a total of 3.7 kg of hydrogen at more than 10,000 psi.
Of course, hydrogen presents its own challenges, namely the chicken-and-egg question of which come first, hydrogen cars or hydrogen refueling stations? To motivate the refueling stations, Mercedes will launch a pilot program in spring 2010 that will place 200 F-Cell cars in the hands of customers in the U.S. and Europe. The roughly 60 cars for America will almost all be leased out to drivers in the Los Angeles area where eleven hydrogen stations already exist. A few may also make it to Washington, D.C.
The F-Cell uses a powertrain that combines two power sources, a small-capacity (1.4 kWh) battery and a hydrogen fuel cell that collaborate with a similar strategy to a conventional hybrid. From a stop, acceleration can be handled solely by the battery, while the fuel cell kicks in around 7 mph to do the majority of the work. Under hard acceleration, the electric motor can deliver 100 kW (136 hp) to the front wheels, with 80 kW coming from the fuel cell and the remaining 20 kW being provided by the battery.
The F-Cell exhibits the typical electric-drivetrain characteristics. Acceleration is best just as the vehicle leaves a stop and tapers off at speed. The absence of a transmission, however, means power response is almost instantaneous. As with a hybrid, the brakes combines hydraulic clampers with regenerative braking that spins the electric motor to act as a generator and charge the battery. There’s very little feel through the pedal, but the progression of stopping power is natural and intuitive, making modulation easy. The vehicle is also extremely quiet, with the only noises being the whine of the motor and the quiet wheeze of an air compressor. Otherwise, the F-Cell is exceptionally normal. From the interior, the only indication of the fuel cell underneath is a unique gauge cluster with a large dial indicating power. The navigation screen also shows multiple information displays including consumption and energy flow diagrams.The test cars are all based on the European B-Class, a compact hatchback that most closely resembles a Honda Fit in shape. Chosen for its unique sandwich-floor architecture, the B-Class allows Mercedes engineers to mount the fuel cell and fuel tanks below the passenger compartment. The electric motor and an air compressor are packed under the hood, while the battery is mounted below the cargo floor.
Fuel cells have an inherent efficiency and the Mercedes unit is roughly twice as frugal as an internal combustion engine. From an energy standpoint, the F-Cell consumes hydrogen at a rate equal to the amount of energy used by a diesel car returning 81 mpg on a combined U.S. test cycle. Of course, at the tailpipe, the F-Cell only emits water, and to measure the car’s true environmental impact requires knowing how the hydrogen in your tank was separated into a pure element.
While the system is quite refined in driving, Mercedes still has a handful of improvements to build into the third-generation fuel-cell system they are currently working on for 2015. Chiefly, the company wants to triple the engineering lifespan of a fuel cell from four to twelve years. Engineers say that in a customer’s hands, the current technology would likely live well past four years, but a gradual degradation of the membranes in the fuel cell may make the 80 kW output more like 70 kW. Cost also needs to be tackled, with the goal of ultimately pricing the car equal to a C-Class.
By 2015, Mercedes intends to have a full production program to sell the fuel cell cars to customers outright. That car will be a part of the family that was previewed with the BlueZero concept at the 2009 Detroit auto show. In addition to the fuel cell vehicle, the production BlueZero family will include combustion-engine, range-extended-electric, and battery-electric vehicles based on the same sandwich architecture, but wearing unique sheet metal.
source: automobilemag
