Hamburger Hochbahn AG has acquired four Mercedes-Benz Citaro FuelCELL Hybrids under the German “NaBuZ demo” scheme to promote sustainable bus systems for the future. Three more buses are to follow next year. (Earlier post.)
The Citaro FuelCELL Hybrid features a number of key enhancements in comparison to the fuel cell buses which went into trial operation in Hamburg in 2003: hybridization with energy recovery and storage in lithium-ion batteries; electric motors in the wheel hubs offering a continuous output of 120 kW; electrified auxiliary units; and more advanced fuel cells. The latter are designed for an extended service life of at least six years or 12,000 operating hours.
|Citaro FuelCELL Hybrid|
|Net weight||13,400 kg|
|Drive power||2 x 80 kW|
|Fuel cell power||140 kW|
|Energy storage power||250 kW|
|Energy capacity||26 kWh|
|H2 cylinders (350 bar)||7|
|H2 storage capacity||35 kg|
The fuel cell stacks of the new Citaro FuelCELL Hybrid are identical to those of the Mercedes-Benz B-Class F-CELL with fuel cell drive, which is also being deployed in Hamburg. As on the earlier fuel cell buses, the two stacks are installed on the vehicle’s roof. They are now accompanied by the lithium-ion batteries which store energy that is recovered during braking; the new hybrid is able to run for several kilometers on battery power alone.
The concept behind the new FuelCELL bus essentially corresponds to that of the Mercedes-Benz BlueTec Hybrid buses which are in service in Hamburg. A key difference is that the latter derive their electric power from a diesel generator, while in the new FuelCELL buses the fuel cells generate the electricity for the drive motors.
The improved fuel cell components and the hybridization with lithium-ion batteries result in a reduction of almost 50% in hydrogen consumption for the new Citaro FuelCELL Hybrid in comparison to the previous generation: 10–14 kg/100km compared to 20–24 kg/100 km. Overall fuel cell system efficiency has also been improved from 48–38% in the previous generation to 58–51% in the Citaro FuelCELL Hybrid. As a result, it has been possible to reduce the number of tanks from the total of nine on board the fuel cell buses deployed in earlier trials in Hamburg to seven on the current vehicles, holding 35 kg of hydrogen in all. The fuel cell bus has a range of around 250 kilometers.
According to all the forecasts, 20 to 25 years from now mineral oil and, in turn, diesel will be in short supply and too expensive to be a viable fuel for buses. From the coming decade on, Hochbahn thus aims to purchase only electrically driven zero-emission buses. Commissioning this new generation of buses represents an important step on the road to electric mobility.—Günter Elste, CEO of Hamburger Hochbahn AG
Demonstration of the Citaro FuelCELL Hybrid buses as part of the NaBuZ demo project is to take place on Hochbahn’s regular service routes. The project is integrated into the Clean Energy Partnership (CEP).
The NaBuZ project receives funding through the federal transport ministry’s National Innovation Programme (NIP). NIP is coordinated by NOW GmbH. There will also be close cooperation with the European CHIC project, in which 26 fuel cell buses are being run in five European cities.
Daimler Buses’ involvement in the NaBuZ demo project and the CHIC project follows on from the European Union’s CUTE and HyFLEET:CUTE projects which were staged from 2003 to 2009. In the course of these projects, 36 Mercedes-Benz Citaros fitted with second-generation fuel cell drives were in operation with twelve transport companies on three continents, driving over more than 140,000 operating hours covering more than 2.2 million kilometers.