The countdown is on: The end of 2018 will see the start of series production of the all-electric Mercedes-Benz Citaro E-CELL. Head of Development, Gustav Tuschen, gave us a sneak preview and took us through the possibilities of the upcoming E-platform. It's all about cost, capacity and range.
Electric drive is no longer a niche, it's a major player.
The time for trials and testing is over. "We are not interested in prototypes, we're all about series", said Gustav Tuschen. The Head of Development at Daimler Buses and member of the board at EvoBus is driving the development of all-electric buses. His mantra: Citaro E-CELL. "Electric drive is no longer a niche, it's a major player", Tuschen assured us. "By 2030, seventy percent of all newly-registered urban buses will have emission-free drive systems."
2030 sounds like a long way off, but in terms of the potential service life of a bus, it's just around the corner. Especially when you consider that electrically powered buses are a non-starter without the relevant infrastructure because an e-bus will only be able to seamlessly replace a diesel bus in rare cases. Getting the right blend of costs, capacity and range is a great planning feat. And it's about more than just a new bus -- policy decisions are needed on charging technology, recharge intervals and charge intensity. And about passenger flows, distances between bus stops, timetables, topography and climate conditions.
A proper vehicle for each line
This must be analyzed in great detail together with the operator: A high range requires large battery capacity, which results in a lot of weight and a higher price but a reduced transport capacity. In other words, Those who need to carry many passengers will see lower battery capacity and a more limited driving range, which means that more work has to go into the charging infrastructure. "People have to look at the specifics of their routes", explained Tuschen. Mercedes-Benz has already developed software to guide operators through the process. With this program on their tablet or laptop, in the future, field service representatives will be able to help their customers to make the right vehicle choice. The demonstration version has already shown some fascinating possibilities, The right configuration of Citaro E-CELLs and supporting infrastructure can be found for every route. For the purpose of comparison, a virtual diesel bus is also included. Tuschen explained "A bus is no longer considered on its own as an isolated product".
System design and consultancy are becoming a core expertise.
From 2018, with the Citaro E-CELL, it will be about more than just buses, it will be about mobility solutions. "System design and consultancy are becoming a core expertise", emphasized Gustav Tuschen. This new approach also brings new perspectives on customer groups. Different areas of commonality are gaining prominence over regional clustering. Viewed in this way, metropolitan areas like Hamburg and Singapore, which have set goals for zero-emission driving, suddenly seem much closer to each other.
A modern city bus - custom-made
Today's electric buses can't meet either the demands of the transport companies or those of Mercedes-Benz. "The first phase of electromobility has not yet begun", noted Tuschen. The Citaro E-CELL will change all that. "It will set new benchmarks in all the important areas", he told us. The engineers have derived a modular system from the often conflicting requirements – the Citaro E-mobility Platform. A single Citaro E-CELL design can't meet everyone's needs. However, thanks to the customization options, the model series covers every conceivable angle. The Citaro E-CELL will be a customized urban bus built on the basis of largely standardized components.
The Citaro E-CELL will come in a solo and articulated version. These will feature electrically driven axles with engines that are positioned close to the wheel hubs. These axles have proven themselves in the field and give more freedom for different passenger compartment layouts that accelerate passenger flow. Power is supplied by lithium-ion batteries. Mercedes-Benz will still offer different sizes of battery packages, giving scope for alternative configurations. In terms of the charging technology, the trend is moving towards trolley arms or pantographs on the bus's roof. Although this technology does increase weight, it simplifies the infrastructure and allows more flexible use of the buses. With the addition of plug-in solutions, the Citaro E-CELL can head into traffic with a full charge on board.
A challenge: saving energy
Gustav Tuschen identifies heat management as the critical factor. In the shoulder seasons, heating and air conditioning can double the use of electrical energy – and even triple it on cold winter days. Or to put it another way, Only a third of the battery capacity is available for powering the bus. "This means that we have to use intelligent energy management", explained Tuschen. By way of example, he highlighted the heating and air conditioning control system, which reacts to traffic conditions and the number of passengers, as well as the optimization of passenger flows to reduce the amount of time spent at stops with the doors open.
Energy consumption must be minimized and every discussion about electrically powered vehicles always comes back to one thing – the batteries. They dictate price, range and passenger capacity. But, there are advances on the horizon. Big-name manufacturers are promising batteries with twice the capacity at half the price in just a few years. And what's to say that any given battery has to spend its whole working life in a bus? "We want to implement technological advancements quickly", indicated Tuschen.
Additional possibilities present themselves when a holistic view is taken, as evidenced by a new project aimed at giving a second life to old batteries. Working together with partners, Daimler has developed a large-scale, stationary energy storage system, which incorporates used batteries from electric vehicles alongside other components. Its purpose is to act as a buffer for storing energy from fluctuating power sources, such as wind energy. The people behind the idea claim that they can get an extra ten years' use out of the used batteries. At the end of this period, valuable raw materials can be recovered from the batteries for reuse. It is ideas like this from the Daimler Group that are helping the Citaro E-CELL to open up the route to electromobility for urban buses.
Another focus of the development effort is to offer a fuel cell variant as part of the Citaro E-mobility Platform. The Citaro F-CELL is an E-CELL with additional technology. It is sophisticated and very efficient – An articulated bus is already able to travel 100 kilometers on just 8 kilograms of hydrogen. There is no need for discussions about range and charging stations when dealing with the Citaro F-CELL. Nonetheless, according to Tuschen, suitable infrastructure must be provided and "the cost of fuel cell stacks really needs to come down". This is something that will only happen through the widespread use in passenger cars.
Internal combustion engines for the future
We want to make the traditional bus even more efficient.
The Citaro E-CELL and F-CELL don't mean the end of the internal combustion engine in a Citaro yet though, not by a long way. A further double-digit percentage reduction to the already low fuel consumption will be seen in the coming years. With the future Citaro Compact Hybrid module, Mercedes-Benz is pursuing a strategy for a simple, cost-optimized hybrid concept. In this case, zero emissions are not the goal, but rather a significant reduction in CO2 emissions, accompanied by better fuel consumption and lower additional costs. Partial autonomous operation of urban buses is another concept being explored. This not only promises safer driving, but also improved fuel economy.
With the Citaro, internal combustion does not automatically mean diesel either. A practical addition is the gas-powered engine, currently to be found in the Citaro NGT in both solo and articulated configurations. With its new M 936 G gaseous fuel engine, it is already quieter than the equivalent diesel and has lower emissions. If fueled with biogas, gas engines are close to carbon neutral.
The future of the city bus is yet to come
The way of the future is to get new things done without abandoning what we already have. Emission-free driving, partially autonomous vehicles, more attractive E-ticketing options, new layouts and faster passenger flows – the future of the urban bus is just arriving. One thing is for sure: The Citaro E-CELL is fully charged and the lights are all set to green.