We first encountered the Mercedes-Benz BlueZERO concept vehicle platform when the it was announced in December and recently we had chance to take a closer look at the 2009 North American International Auto Show in Detroit.
The three five-seater BlueZERO variants are based on the unique sandwich-floor architecture which Mercedes-Benz introduced some ten years ago, initially for the A-Class and then for the B-Class, one of the aims being to integrate alternative drive systems. Advantages of the modified construction include the positive effect of the major drive components on the center of gravity, their space-saving design, and the fact that they are extremely well protected within the vehicle underbody.
The BlueZERO E-CELL has battery-electric drive with a 35kw/hr Li-ion battery giving a range of up to 200 km. The BlueZERO F-CELL (fuel cell) has a range of 400 km on one tank of Hydrogen. The BlueZERO E-CELL PLUS with electric drive and additional internal combustion engine as power generator (range extender). This version has an overall range of up to 600 km and can cover a distance of up to 100 km using electric drive alone with its 17.5-kWh lithium-ion battery.
All three BlueZERO variants share the same key electrical components. All three are front-wheel drive and use a 100kw permanent-magnet synchronous electric motor (BLDC) that revs to a maximum of 13,280 rpm. Peak torque is 320 Nm and as with all EVs maximum torque is available from zero rpm with torque output exceeding the figure achieved by a current V6 gasoline engine at 2500 rpm.
The BlueZERO E-CELL is a fairly conventional battery electric vehicle which will see production first in the form of the Smart EV. Mercedes-Benz has also announced plans to launch an electric version of the A-class small family car in 2010. The BlueZERO F-CELL and E-CELL PLUS are much more "concept" cars and no plans for production have been announced at this stage.
While most automakers at the Detroit show (bar Honda) seem to have stopped pushing the Hydrogen dream with the promise of "affordable" fuel cells that are always 10-15 years away, Mercedes clearly retains an interest in the technology, although the fuel cell version of the BlueZERO is still at blue-sky concept stage. The electric motor, high-voltage battery, and hydrogen tank are positioned beneath the passenger cell to save space. The system uses the most efficient energy source for the current driving situation. When parking or manoeuvering at slow speed, for example, the electric motor uses only battery power. When accelerating, both the fuel cell and the battery provide energy. When braking, the electric motor acts as a generator and charges the battery. This efficient system therefore makes use of the energy that would be converted into heat during conventional braking and stores it in the powerful lithium-ion battery. The other two versions, of course, also have regenerative braking.
For longer journeys Mercedes-Benz sees the fuel cell as one of the key technologies for zero-emission driving. The current problem is that there is no hydrogen filling station infrastructure anywhere in the world, but Mercedes believe this technology offers ideal possibilities for sustainable mobility well into the future. The hydrogen-powered fuel cell combines zero emissions with a long operating range, since electrical power is generated on board during the journey. There are no exhaust emissions whatever and no CO2 is emitted either. The BlueZERO F-CELL emits nothing more than steam. Moreover, a fuel cell drive system is almost twice as efficient as an internal combustion engine.
There is no mention of plug-in charging for the battery pack, meaning this vehicle runs on Hydrogen only, which could present a problem if there's nowhere to fill it up. The only difference between this fuel cell version and the battery EV version seems to be range. An EV with 400km range is becoming a reality with larger 53kw/hr battery packs like that found in the Tesla - which has an EPA range of 244 Miles (390km) likely being cheaper to install than an entire fuel cell system dependent on an as yet non existent hydrogen infrastructure.
A little more realistic is the third version, the BlueZERO E-CELL PLUS which is a plug in series hybrid with very similar specifications to the Chevy Volt. It has the same 1.0-litre turbocharged gasoline engine as the smart fortwo as an additional range extender. This compact three-cylinder powerplant has an output of 50 Kw at a constant 3500 rpm. If required, it can recharge the 17.5-kWh lithium-ion battery via a similarly rated alternator. A range of up to 600 kilometres is possible on a single tank. The purely electrical, locally emission-free range is up to 100 kilometres.