- Citaro: from the low-emission bus to the zero-emission bus
- The eCitaro gets an exclusive tailored exterior
- Flexible charging technology: plug-in charging as standard, current collector as an option
- Thermal management: new methods for heating and air conditioning
- Practical range even in difficult conditions
- The future is electric: launch of an innovation initiative
It is emission-free in local use and almost noiseless. It combines the tried and tested platform of the Mercedes-Benz city bus with new technological solutions. The fully electric Mercedes-Benz eCitaro brings electromobility for city buses to a whole new level. The new eCitaro uses innovative components only now available for the first time for the eCitaro to achieve a hitherto unknown degree of energy efficiency. The performance of the eCitaro meets most of the requirements of the transport companies even at launch. It is also already prepared for the battery technology of the future. Its design allows the basic shape of the Citaro to merge with elements of the Mercedes-Benz Future Bus into a distinct visual appearance of its own. And it’s more than a city bus: Mercedes-Benz takes a holistic approach to electromobility and integrates the eCitaro into the overall system of e-mobility.
Urbanisation demands low-emission and, locally, zero-emission mobility
Metropolis, city or small town: They all face similar challenges and problems: A growing population leads to increasing mobility during the working day and leisure time. One approach is an extensive public local transport network using low-emission buses which can also run locally with zero emissions. The new all-electric-drive Mercedes-Benz eCitaro is an important element in this: In local use it runs completely emission-free and almost noiselessly.
Citaro: from the low-emission bus to the zero-emission bus
The platform for the new Mercedes-Benz eCitaro is the best-selling Citaro, which has sold over 50,000 units worldwide. With its wide range of low-emission and now locally zero-emission city buses, it provides the answer to issues surrounding environmentally friendly local public transport services. The all-electric-drive eCitaro now makes the step from the low-emission bus to the zero-emission local-use bus.
The eCitaro gets an exclusive tailored exterior
The eCitaro is a true Citaro – but a very special one. That’s because with along with its extraordinary qualities, the new Mercedes-Benz eCitaro also boasts an equally exceptional design. It’ � s based on the familiar Citaro look, but borrows elements of its design language from the revolutionary Mercedes-Benz Future Bus study.
This is particularly evident in the face of the eCitaro. The centrepoint is the Mercedes star. Decorative elements emanate from the star, to the left and right. The three-dimensional elements consist of transparent material with a PVD chrome coating on the reverse side. This produces attractive lighting effects when seen from different angles and in varying conditions of sunlight. The model insignia with its blue letter "e" discreetly and yet unmistakably indicates the fully electric drive technology.
The bumper and the model-specific three-dimensional A0 pillars neatly frame the face of the eCitaro. Another feature of the city bus is the curve of its windscreen. It sweeps elegantly up to the roof and incorporates the destination display. Visually, the windscreen smoothly transitions into the roof with dark bars on the left and right. At its centre, the roof sports an "island" in the vehicle colour, which almost seems to float – another of the design elements of the Future Bus.
The roof-mounted equipment on the eCitaro is concealed behind an elegant roof-edge ridge made of a multi-piece extruded aluminium section. The glossy black lower segment extends the generous side-window glazing of the city bus. The upper segment is painted in the vehicle colour. These optical tricks lend the eCitaro perfect proportions.
The rear corner posts end at the top in a pronounced curvature in the roof-edge ridge. Their elegant shape along with the likewise stylised island that disguises the roof-mounted equipment and the bars that connect rear window and roof take the heft off the high superstructure.
A fusion of elegant and at the same time practical design
Overall, the eCitaro sports a solid appearance with clearly drawn contours and no showmanship whatsoever. At the same time, the new eCitaro is a true practical bus. The eCitaro adopts the structure of the current model unchanged, a crucial factor in facilitating the repair of accident damage, for example. The curved windscreen comes from the Citaro Ü and is thus a common spare part. The roof-edge ridge at the sides is not only a two-part design, it is also segmented.
Interior: new coffered ceiling with high-tech lighting
In the passenger compartment, the eCitaro rings in a general update of the interior of the entire Citaro family of models. A stand-out feature in the interior is the coffered design ceiling above the centre aisle and the sweeping roof-edge flaps. They hide a new air circulation system with textile ducts in place of the current plastic air ducts. They are even easier and simpler to install.
The technology modules as connectors between the individual elements of the coffered ceiling are particularly noteworthy. They combine the interior lights and the loudspeakers in one element. With this step, the interior lights are switched to LED as standard. The lighting is ingenious: the light of the LED lamps is refracted in a way to make the technology modules appear to the observer as one homogeneous light panel.
Another new feature is the black trim on the window posts. As a result, the window posts stand out less, soothing the appearance of the side walls.
Proven electric axle, new modular battery concept
The powertrain of the new eCitaro is based on the proven and optimised ZF AVE 130 electric portal axle with electric motors at the wheel hubs. The peak output of the motors is 2 x 125 kW, while torque is 2 x 485 Nm. It is an inherent feature of such motors that this is fully available right from the start, ensuring appropriate dynamic performance even with a full complement of passengers.
Lithium-ion batteries with a total capacity of up to 243 kWh provide the power. The batteries are split between up to ten modules, each supplying around 25 kWh. The basic equipment sees two battery modules on the vehicle roof plus four fitted at the rear. Depending on customer requirements, another two or four battery modules are mounted on the roof of the eCitaro.
With the full complement of batteries, the eCitaro with standard equipment weighs around 13.44 t. In conjunction with a gross vehicle weight rating of 19.5 t, this corresponds to a payload of more than six tonnes or around 88 passengers – in line with what is needed in practice even during rush hour.
Flexible charging technology: charging at the depot as standard, optional current collector
The eCitaro's charging technology also allows it to adjust to the individual wishes and requirements of the transport operators. For the start of series production, plug-in charging is envisaged. To this end, the city bus features a socket for a Combo-2 plug above the front wheel arch on the right-hand side of the vehicle in the direction of travel.
If opportunity charging is required to extend the range, there will also be an option to charge the eCitaro via a current collector on the roof in future. This option will be gradually phased in once series production has started. There will be two possible variants: In phase 1, an integral current collector (pantograph) on the roof; in phase 2, charging rails on the roof that will allow charging via a stationary current collector at a charging station.
Thermal management: new methods for heating and air conditioning
However, the battery capacity alone provides little indication of the actual performance capability and, above all, the range of an all-electric city bus – the true measure is that of energy consumption. In the case of a city bus, this is impacted significantly by climatic conditions and the need to cool and, above all, to heat the interior.
At an outside temperature of minus ten degrees Celsius, the energy consumption of a city bus doubles compared to journeys where no heating is required. The engineers have therefore carefully considered the issue of thermal management. Compared with the current Citaro with combustion engine, the energy requirement for heating, ventilation and climate control has been reduced by about 40 percent. This exceptional energy efficiency provides the basis for the eCitaro's practical operating range even under unfavourable conditions. This is accomplished with the use of innovative components that only reached market readiness in concert with the eCitaro.
Heating featuring heat pump, networking of components
In the first instance, Mercedes-Benz cools the batteries to ensure that they remain at the ideal temperature, thereby ensuring maximum charging capacity, performance capability, and service life. At extreme outside temperatures, the passenger-compartment climate control system is used to boost the cooling of the batteries.
The passenger compartment of the eCitaro is heated in an energy-efficient manner by a heat pump. An even temperature distribution is ensured by use of the familiar sidewall fan heaters. The conventional heater at the front is equipped with a double heat exchanger.
All components that give off heat are linked together, to keep the amount of energy required for their cooling to a minimum. Since the human body also gives off heat, the heating on a bus carrying a full complement of passengers can be turned down earlier. Furthermore, Mercedes-Benz varies the output of the heating and climate control systems according to the number of passengers.
During the colder months, the roof-mounted air conditioning system is additionally used as a heat pump, so ensuring effective and efficient climate control for the passenger compartment. The use of CO2 as a coolant brings further benefits. The particularly efficient use of the heat pump is impressive, even at very cold temperatures.
Another boon: The interior can be conditioned up to and even beyond the desired temperature while the batteries are still being charged at the depot. The bus will therefore have been heated or cooled to suit the seasonal conditions before it sets off.
High efficiency: practical range even in difficult conditions
Operating range figures for all-electric-powered city buses are often difficult to compare. Mercedes-Benz prefers to consider a "worst-case scenario" and therefore takes its direction from the challenging standardised city driving cycle known as SORT2 and includes the energy requirements of the auxiliary consumers in its calculations. According to this, the Citaro achieves an operating range of around 150 kilometres in the summer. This means that even without opportunity charging, the eCitaro already covers about one third of all routes. Under ideal conditions, the eCitaro even drives around 250 km without opportunity charging.
Driver's area: familiar cockpit, power meter instead of rev counter
Benefit for the eCitaro driver: Cockpit and operating concept of the city bus are largely unchanged – except that now a power meter replaces the rev counter. It displays the current power demand and/or energy recuperation rate. The driver also receives information about the charge status of the batteries. He or she can access the range, available power and a charging indicator on the central display.
In general, the performance is optimised for maximum efficiency, without the driver having to deal with major differences from the Citaro with combustion engine. For example, in the basic setting, the bus coasts in an energy-efficient manner when the driver takes their foot off the accelerator pedal – it "sails". Alternatively, the driver can use a multi-stage electric brake lever to set a basic deceleration rate – similar to the engine braking torque or the retarder effect of a diesel bus – as the energy recovery rate.
Start of series production by the end of 2018, initial orders already received
The countdown for the new city bus bearing the three-pointed star is running at full steam: Since its world premiere for the public at the IAA Commercial Vehicles Show in Hanover, delivery of the first customer vehicles has already begun.
The future is electric: prelude to an innovation offensive
The new Mercedes‑Benz eCitaro of the year 2018 represents the launch of an innovation initiative with a clear strategy aimed at the swift and above all practical electrification of local public transport with buses in cities and population centres. The eCitaro will be able to replace almost all city buses powered by a combustion engine in just a few years.
Since the development of battery technology is progressing at a rapid pace, the eCitaro is already designed to be transitioned to the battery technology of the future. This concerns the lithium-ion batteries currently in use, for example. As things currently stand, the next generation with a larger capacity and resulting increased range will already be available for customers of the eCitaro in two years’ time. With a total capacity of up to 330 kWh, the eCitaro will then cover about 50 percent of all applications. This battery capacity also opens the door to the introduction of an eCitaro G articulated bus.
Another step already scheduled during that same period envisages the use of lithium-polymer batteries, also referred to as solid-state batteries, as an option in the future. These are characterised by a particularly long service life and high energy density. With a rated battery capacity of about 400 kWh in the solo bus and even more in the articulated bus, the eCitaro will then meet about 70 percent of all requirements without opportunity charging. The characteristics of solid-state batteries differ significantly from NMC batteries: They have a different shape, are more voluminous overall and are not suitable for quick-charging. City buses equipped with them are therefore suitable for other types of application. For this reason, the eCitaro will in future be offered with a choice of NMC or solid-state batteries.
Subsequently, the range of the eCitaro will be increased yet again by a range extender in the form of a fuel cell that generates electricity. It will be designed to allow the eCitaro to fulfil nearly 100 percent of all requirements on city buses. This technology eliminates the need for opportunity charging and the complex infrastructure required for it in almost all cases – the eCitaro will be able to replace city buses with combustion engine virtually one to one.