The bus of the future arrived in Hamburg as quiet as a whisper and free of pollutants. Hamburger Hochbahn AG produced four Mercedes-Benz Citaro FuelCELL Hybrid buses as part of the German-funded project, "NaBuZ demo" (Nachhaltiges Bussystem der Zukunft - Demonstration [Sustainable Bus System of the Future - Demonstration]). Another three are planned for the next year. With Olaf Scholz (First Mayor of Hamburg) and Rainer Bomba (State Secretary at the German Federal Ministry of Transport) in attendance, Hartmut Schick (Head of Daimler Buses) presented two of the first buses of this new generation to Günter Elste (Chairman of the Board of Hamburger Hochbahn AG). "With these new FuelCELL Hybrid vehicles, Hamburg is once again taking a pioneering role in this area. The transport operator has already made a name for itself and gathered good experiences in Europe while testing fuel cell buses from the previous generation. Passengers and drivers were also enthusiastic," commented Hartmut Schick during the presentation.

Compared with the fuel cell buses which were tested in Hamburg in 2003, the new Citaro FuelCELL Hybrid provides several significant new features: hybridisation with energy recovery and storage in lithium-ion batteries, powerful electric motors with 120 kW of continuous output in the wheel hubs, electrified power take-off units and further enhanced fuel cells. These should achieve an extended service life of at least six years or 12,000 operating hours. The fuel cell stacks of the new Citaro FuelCELL Hybrid are identical to those of the Mercedes-Benz B-Class FCELL with fuel cell drive which is also already transporting customers in Hamburg. As with the previous fuel cell buses, the two stacks are located on the vehicle roof.

New additions there are the lithium-ion batteries which for example store recovered energy. With the power stored there the new Citaro FuelCELL Hybrid can drive several kilometres on battery operation alone. In general the design of the new FuelCELL buses is largely the same as that of the Mercedes-Benz BlueTec Hybrid buses that run in regular service; these buses also get electrical energy from a diesel generator. In the new FuelCELL buses, however, fuel cells are already generating emission-free power for the drive motors.

Thanks to improved fuel cell components and hybridisation with lithium-ion batteries the new Citaro FuelCELL Hybrid saves on almost 50 percent in hydrogen usage compared with the preceding generation. That means the number of tanks was reduced from nine (in the previously tested fuel cell buses) to seven containers holding 35 kg of hydrogen. The range of the fuel cell buses is around 250 kilometres. In addition the drive system with fuel cells is virtually maintenance-free and has a very long life. With this multitude of technical advancements, purely electric buses with fuel cells are making significant steps towards becoming energy producers in series production.

Adding his thoughts, Günter Elste, Chairman of the Board of Hamburger Hochbahn AG said: "According to all forecasts, in 20 to 25 years mineral oil and in turn diesel will become too scarce and too expensive to power buses. That is why it is a goal for HOCHBAHN to procure only emission-free buses with electric drive, starting from the coming decade. The commissioning of this new generation of buses is a key step on the road towards electric mobility."

Hartmut Schick, Head of Daimler Buses, said, "Hamburger Hochbahn AG is a very sustainable company in all aspects, with a consistent approach to everything from energy generation to sustainable usage for people. We here at Daimler Buses have firmly established sustainability as a corporate goal."

The demonstration of the Citaro FuelCELL Hybrid buses as part of the "NaBuZ demo" project will take place during HOCHBAHN’s regular service. The project is being integrated as part of the CEP (Clean Energy Partnership).
The NaBuZ project is supported by the National Innovation Programme (NIP) of the German Federal Ministry of Transport. The NIP is being coordinated via NOW GmBH. In addition there is close cooperation with the European CHIC project in which 26 fuel cell buses are being operated in five European cities.

With the commitment of the NaBuZ demo project and in the CHIC project Daimler Buses is building upon the successful CUTE and HyFLEET:CUTE projects of the European Union which were conducted from 2003 to 2009. In total 36 Mercedes-Benz Citaro buses with second-generation fuel cell drive have been optimally tried and tested at twelve transport operators on three continents. With more than 140,000 operating hours and over 2.2 million kilometres logged, Mercedes-Benz buses have proven the viability of the environmentally friendly fuel cell drive in everyday use.