For the presentation of the eCitaro fuel cell at the Global Public Transport Summit, Daimler Buses has now presented all the details of its first series-produced electric bus with a fuel cell as a range extender. Series production of the eCitaro fuel cell will start at the same time as the trade fair premiere.
Daimler Buses already provided the first key data on the drive of the new eCitaro variant at the end of May . Since then, it has been known that the eCitaro fuel cell combines third-generation Mercedes-Benz lithium-ion batteries with a fuel cell as a range extender. As a solo bus, the model has three battery packs with a total capacity of 294 kWh. As an articulated bus, there are three or four packs with a total of up to 392 kWh. In both cases, the fuel cell has an output of 60 kW – and comes from Toyota.
Daimler Buses specifies a range of up to 350 kilometers for the range extender articulated bus and up to 400 kilometers for the solo bus. In view of this range, the eCitaro fuel cell is not designed for opportunity charging on the route, but for pure depot charging with a plug with up to 150 kW. It is "the ideal supplement for transport companies with an existing battery-electric vehicle fleet that want to serve their long routes without recharging and without additional buses". Of course, to use the range extender, you also need a hydrogen source. More on that below.
With regard to the start of series production, Daimler Buses states that the articulated bus variant can be ordered from the trade fair premiere – i.e. immediately. The manufacturer has not yet made any statements about the market debut of the solo bus. The bus manufacturer has not yet mentioned prices either.
Daimler Buses provides a detailed look at the structure of the new eCitaro variant. A conscious decision was made to use a drive with a large battery capacity and a compact fuel cell in the "range of possible combinations", the manufacturer explains, pointing out, among other things, that electricity from the grid as a fuel will be significantly cheaper in the foreseeable future as hydrogen. The fuel cell of the eCitaro fuel cell is therefore not used as the main energy source, but is only used to extend the range.
With regard to the fuel cell itself, Daimler Buses now specifies that it is a "tested module" - namely a second-generation Toyota fuel cell in a heavy-duty design with a maximum output of 60 kW. In the eCitaro fuel cell, it should be operated at around 20 kW in the best point range and work in a voltage range of 400 to 750 volts. The fuel cell module is installed on the roof due to its flat and compact design. In the case of the solo bus, the module, which weighs around 240 kilograms, is placed just behind the front axle, in the case of the articulated bus at the front on the roof of the rear vehicle.
The manufacturer specifies the service life of the module as around 40,000 hours in use as a range extender, which should correspond to a service life of seven to ten years. The module receives the hydrogen (gaseous and at a pressure of 350 bar) from Type 4 tanks, which are also mounted on the roof and each have a capacity of 5 kg. The rigid bus has five tanks with a capacity of 25 kilograms of H2, and the articulated bus has six or seven tanks with 30 or 35 kilograms of H2. Refueling takes place in the direction of travel on the right above the second axle. The company states that the refueling time is "under optimal conditions and depending on the refueling infrastructure (...) in the Solobus around ten minutes".
The main energy stores on board are, of course, the battery packs based on NMC (lithium nickel manganese cobalt oxide). An intelligent control regulates how the two systems interact, with transport companies being able to choose between two different operating modes: In “Maximum range” mode, both battery charge and hydrogen are used to the maximum. The fuel cell always works in the most efficient operating range. In the “minimum H2 consumption” mode, on the other hand, the battery supplies most of the energy for the drive and ancillary consumers. The fuel cell only shoots in as much energy as is necessary to reach the previously set range.
The eCitaro fuel cell is largely based on the eCitaro with a pure battery drive. "Although extensive adjustment measures were necessary, they were not completely redesigned," says Daimler Buses. The range extender variant also adopts the ZF axle drive, which delivers 125 kW and 485 Nm in the solo bus. In the articulated bus variant, two electric axles with 125 kW each are available as an option. The layout of the passenger compartment and the driver's cockpit correspond to the usual eCitaro models. The only exception is that the bus driver has a power meter in the instrument panel instead of the usual rev counter to show the energy flow of the eCitaro G fuel cell and another display showing the percentage of fuel in the hydrogen tank.
There are major differences in other areas: the software for individual control units, for example, is new on the eCitaro fuel cell. This applies, among other things, to the heat control. The new variant can thus use the waste heat from the fuel cell to heat the vehicle interior. “As with the battery-electric eCitaro, Daimler Buses also uses the compact air conditioning system with a heat pump for the eCitaro fuel cell, but with the refrigerant R134a. In combination with the waste heat from the fuel cell, it achieves greater efficiency at low temperatures, even compared to the eCitaro’s CO₂ air conditioning system. The waste heat from the fuel cell can also be used to regulate the temperature of the batteries,” says the manufacturer.
Another plus point: The eCitaro fuel cell should be able to transport a large number of passengers thanks to the weight distribution of the batteries, fuel cell and hydrogen tanks. A three-door articulated bus with a driven axle, three battery packs and seven hydrogen tanks will offer around 128 passenger seats. "The eCitaro fuel cell thus offers even more passenger capacity than a battery-electric eCitaro with a maximum battery configuration," the company points out.
For the development of the range extender technology, Daimler Buses received 3.3 million euros in funding as part of the National Innovation Program for Hydrogen and Fuel Cell Technology (NIP). In addition to the technical aspects, Daimler Buses is also introducing new digital services with the new model variant. The focal point: the virtual data interface TiGR, which is intended to play an important role in data integration in the customer's individual software. With TiGR, the company is one of the first vehicle manufacturers in Europe to offer a data interface for remote bus monitoring that is certified according to the uniform, international ITxPT standard.
media.daimlertruck.com (start of series production), media.daimlertruck.com (fuel cell)
