Curtain call for the electric Citaro

Following the yearly press round table on march 5 2018, the journalists got the opportunity to learn more about the all-electric city bus in three tech-workshops. Special highlight: an exclusive test drive in the electric Citaro.

"Today there is an exclusive presentation of the concept behind our eBus being launched this fall. And we invite you to ride along in the all-electric Citaro," says Gustav Tuschen, Head of Development Daimler Buses, in his introductory talk to get the journalists in the mood. He then starts by looking into the future: "In 2025, the number of all-electric city buses licensed was on a par with their combustion-engine counterparts. But now, in 2030, they already account for a share of 75 percent."

The combustion engine is still omnipresent today, however, so there is no possibility of an abrupt end. For this reason, the development toward locally emission-free driving must involve a gentle transformation. "On the one hand, we optimize the drive system with combustion engine. At the same time, we develop the all-electric city bus, which can gradually replace combustion-engine buses," continues Tuschen.

"The most balanced eBus overall"

Gustav Tuschen anticipates possible questions from journalists asking why Daimler Buses has not unveiled the electric city bus until this year: "As number one, we have a special responsibility toward our customers and their passengers. So it was not our goal to be the first. As market leader, our ambition is to be the best." He adds that, ultimately, the aim is to provide the best possible support for customers in the transition to electric mobility. And that the electric city bus from Daimler Buses will be the most balanced bus overall to be launched on the market.

Start of series production at the end of 2018

According to the timeline. the first series-production vehicles will arrive and go to customers at the end of the year. For Tuschen, the key modules of the technical concept are: the tried-and-tested electrically driven rear axle with motors on the wheel hubs, modular battery packs on the roof and in the rear, and standard charging via Combo 2 connector at the depot or, when on the road, via an optional current collector - either installed in the vehicle or located in a stationary position.
One key aspect of the electric Citaro's series production suitability in Gustav Tuschen's eyes is the consistent optimization and application of selected key technologies that are perfectly tuned to one another: High-voltage battery system, electrically driven rear axle, standard plug-in charging system, and thermal management with highly efficient CO2 air conditioning and heat pump.

Answer to technical requirements of a transport operator and bridge to the eMobility Workshops

Tuschen explains that the eBus provides answers to the technical requirements of a transport operator to emphasize the fact that the electric Citaro is also ultimately fully operational for the customers. He adds that it is important for transport operators to have enough energy available to operate demanding regular-service routes. And that the bus must be able to carry a sufficient amount of this energy and use it efficiently. Operational strategy and energy supply must likewise go together.
After Gustav Tuschen's talk, journalists get the opportunity to learn more about the electric Citaro in three workshops.

Workshop one: Vehicle concept

The first workshop focuses on the general vehicle concept, presented by Wolfgang Prokopp, Head of Development City Buses, and Daniel Vorgerd, Head of Development for the electric Citaro. Right at the outset, Prokopp emphasizes that the electric Citaro is the culmination of development work to date toward locally emission-free driving: "After the Citaro NGT and the Citaro hybrid, the electric Citaro produces zero local emissions." The electric Citaro takes the well-honed and proven technology of the Citaro and expands upon it by adding the new innovations in electric driving. "This also allows our customers to choose from a wide range of Citaro equipment and us to benefit from economies of scale in the case of modular components," continues Prokopp.

The developers attached particular importance to easy accessibility during servicing to optimize maintenance of the complex charging and battery technology. Another priority is to ensure the safety of the service providers and all others who come into contact with the bus. "We have therefore tested the battery technology and the electromagnetic compatibility in accordance with the most stringent international standards," stresses Daniel Vorgerd.

The overall bus concept is nonetheless put through its paces using twelve prototypes in real-life situations so that, like all vehicles from Daimler Buses, the electric Citaro is a benchmark for quality and reliability by the time it reaches its customers. Be it in Finland at minus 15 degrees Celsius or in the Spanish heat – "while there are many reports of problems regarding the availability of electric buses, we are targeting availability on a par with our tried-and-trusted Citaro under all conditions," Prokopp tells the journalists.

eWorkshop two: Electric Drive Technologie

Andreas Mink, Head of Development Electronics/Electrics and Chassis Systems, and Roland Scharl, Head of Raised Floor Platform give talks on the topics of high-voltage technology and thermal management. "The ZF electric motors, each with an output of 125 kW and a torque of 485 Nm, are positioned directly on the axles and provide plenty of forward thrust even when there is a full complement of passengers on board," states Mink. A modular battery supplies the motors: Four battery modules now take up the space previously occupied by the combustion engine and the transmission. Another two to six modules can be mounted on the roof, depending on customer requirements. "This means our customers can choose precisely the battery they want - and save on both space and procurement costs," says Mink, highlighting the benefits of this solution. By way of example, a smaller battery can be flexibly combined with a system for top-up charging of the battery via current collector or charging rail, which will likewise be available for the electric Citaro.

With respect to the battery, both speakers emphasize that customers must be able to rely on the range. "We therefore distance ourselves from the fantasy ranges achieved under ideal conditions," adds Mink. With a full set of battery modules and a full complement of 80 passengers on board, the electric Citaro achieves a range of around 150 kilometers in summer in the demanding SORT2 test scenario, which is sufficient for 20-30% of the European city-bus routes. Since battery technology is continuing to develop at a rapid pace, Daimler Buses continually revises its battery solutions and also offers customers the option of updating their batteries.

One of the great technical innovations in the electric Citaro is its heating system. In the case of conventional drive systems, the waste heat from the internal combustion engine is used to heat the bus. An electric motor does not produce waste heat, however, so the interior must be heated using energy from the battery – accounting for half the entire battery capacity if conditions are unfavorable. "However, the engineers working on our electric Citaro have succeeded in cutting the amount of energy required for heating the interior by 40 percent!", claims Scharl proudly.

This is made possible among other things by the use of a heat pump operated using the particularly efficient refrigerant CO2. All heat-releasing components in the bus are networked and ensure an ideal temperature in the interior whatever the conditions. Axle load sensors even record the bus occupancy level and incorporate the thermal output of the passengers into the thermal-management calculations. Intelligent thermal control can also be used to preheat the interior of the bus during the charging period and, furthermore, always ensures that the batteries are at their ideal operating temperature.

Workshop three: eMobility consulting and servicing

"Rather than viewing the electric Citaro as a stand-alone product, we see it as one module in the overall electric mobility system," says Susanne Scheitenberger, Head of Future Mobility within the Innovation Lab Mobility Solution, by way of greeting the journalists. City bus operators face many challenges during the switch to electric mobility: How do I organize my timetables so that the buses have enough charge to complete their routes? How do I provide an adequate charging infrastructure? What about servicing of the new high-voltage system? To make the switch easier for transport operators, we will support our customers here and offer solutions.

As part of eMobility consulting, experienced staff will present the Citaro portfolio and analyze it line by line so that current operations can be covered by an electric drive system in the future, too. An in-house-developed simulation program helps calculate the vehicle range in this instance. The end result is therefore a customized feasibility analysis that shows the customer how to implement their own electric bus fleet, making it clear how many vehicles are needed, what type of charging infrastructure and charging strategy are required, what energy supply is necessary, which digital services are required, and how the workshop and the workforce need to be adapted. "We particularly focused on the issue of charging management," states Susanne Scheitenberger. How can we balance out peaks in the demand for charging energy, e.g. by means of coordinated charging times or by means of stationary battery storage devices? We prepare our customers for this challenge in our consultations, too.

"We are faced with new challenges as far as servicing is concerned. And this starts with the workshop equipment already. Many components and therefore also many work operations have been moved to the roof, which means we need a special roof working platform to perform the work safely," says Hans-Jürgen Bühler, responsible for service contracts at EvoBus. Another reason why the topic of safety is so relevant is the fact that the electric bus operates using high-voltage technology (750 volts). Service personnel require special training for this. The training program ranges from raising awareness of high-voltage systems to performing work on live systems. To deal with the first vehicles, the first EvoBus service outlets already have the required equipment, and the mechanics have received appropriate training.

There are several ways to maintain the vehicles: the bus operator assumes responsibility for servicing, an authorized EvoBus service outlet performs the work, or trained Daimler Buses personnel visit the customer to service the vehicles at the customer's own workshop.

Daimler Buses has therefore set up its own service unit for electric mobility, offering three service options: Classic - the bus operator assumes responsibility for service. Basic Plus - the OMNIplus competence centers perform the service work for the bus operators. Premium - trained Daimler Buses personnel visit the customer to perform the service work locally. "We therefore offer our customers full flexibility and the best possible availability," emphasizes Hans-Jürgen Bühler. To ensure transparency and cost predictability, there are configurable service contracts available for the electric Citaro models, too.

Workshop four: test drive with the all-electric Citaro

Testing of the electric Citaro is another highlight on the agenda. Here Andreas Türk, responsible for technical support during press activities, and Jonas Steinki, head of the test-competence team, offer a close-up insight into the technology of the electric bus in the eBus itself.

Prior to the test drives, the passengers get the opportunity to appraise the electric Citaro from outside. It demonstrates its strengths during the drive - on a realistic test route. The electric Citaro completes the course quietly and dynamically. The moving-off and acceleration on an uphill gradient as well as the bus stop are supposed to simulate realistic loads.

To sum up the day: A highly successful event at which the journalists got in-depth insights into the concept and the technology behind the electric Citaro.

Further information on the electric Citaro you can find on the Daimler Website.

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