What can we do with used batteries from electric buses? Recycle them in an environmentally responsible way or rather repurpose them? Daimler Buses offers several solutions to safeguard a sustainable, economic cycle.
Omnibus Magazine
Second life for electric bus batteries.
Interview with Julia Stolz, Head of Product Management and Services, and her team.
Second life for electric bus batteries.
Interview with Julia Stolz, Head of Product Management and Services, and her team.
Throughout its entire service life, the ecobalance of an eCitaro is currently already better than that of a conventionally driven bus. However, there is still some work to do in optimising the CO2 footprint. For example, by reusuing used batteries in a sensible way. The Mercedes-Benz Omnibus Magazine asked three Daimler Buses sustainability experts how to do this.
Battery technology plays a key role in determining the life cycle of an electric bus. How is Daimler Buses dealing with this topic in terms of sustainability?
Julia Stolz: The switch from diesel to electric buses is more than just replacing the drive technology, it represents a transition to a completely new system. Even though the eCitaro is the centrepiece in this overall electromobility system, we at Daimler Buses rely on a comprehensive solution. In terms of the batteries, this means that after their use, or their first life, in other words, they find a second use.
Are we talking about recycling the batteries here?
Sarina Bögel: partly, but not primarily. We have analysed and assessed various recycling processes and have certified partners with whom we can already guarantee the recycling of used vehicle batteries today. In doing so, we set high standards and have defined internal standards at Daimler Buses that go beyond compliance with legal requirements. Although recycling batteries is currently feasible from a technological point of view, it is not always the best solution considering the entire life cycle. We are therefore primarily striving for a second-life application for our high-voltage batteries.
So batteries are practically-speaking given a second life?
Paula Rocha Schubert: Precisely! With a second-life application, the raw materials and materials bound in the battery can be used for longer. After the intended service life in the electric bus, the remaining capacity is around 80 percent. This is not enough for continued vehicle operation, as the necessary range can no longer be guaranteed, but the capacity is more than sufficient for use as a stationary storage solution. In particular NMC technology, applied to the batteries used in the eCitaro, is ideally suited for such a second-life application.
Is there any practical experience with using the battery as a stationary storage system?
Paula Rocha Schubert: The stationary storage system enables the compensation of peak loads as well as continued operation in the event of power cuts and the supply of the public charging infrastructure. The pilot project's energy storage unit has a capacity of approximately 500 kWh and is made up of around 20 battery packs that were previously used to cover thousands of miles in the eCitaro for test drives. The stationary storage system enables the recovery of energy from light rail operation. Electric buses can then be charged again with the electricity stored in this way.
Julia Stolz: With this second-life application, we are already very close to the goal of creating a circular economy: the first step is to use the electric buses in clean, scheduled-service operation, then to continue using the buses' used batteries for the charging infrastructure and finally to charge electric buses with the electricity stored in these batteries. This way of using the battery throughout its entire life cycle makes sense from both an ecological and economic point of view.
“Thanks to the second-life application, we are already very close to the goal of a circular economy.”
Which other potential second-life application uses are there for the batteries from an eCitaro?
Paula Rocha Schubert: For example, used eCitaro batteries can be used as interim storage systems for wind farms or solar-power farms, something we want to implement as part of a further cooperation. A new form of stationary storage will be used as part of this project. The aim is to absorb so-called "peak shaving" in power consumption or also in power generation.
“We are pioneers in this field.”
So many uses are conceivable here in the future?
Paula Rocha Schubert: The technical development here is moving at a rapid pace and I am sure that we will see many more potential uses for second-life applications. We are pioneers in this field, which of course makes it very exciting. In addition, we are witnessing a rapidly changing environment in electromobility.
Sarina Bögel: That’s why, at Daimler Buses, we don't want to focus on just one option for further use or reuse. Our aim is to be able to react quickly to changes in the market and the availability of different technologies. It goes without saying that every new technology must also focus on customer benefits.
“With every new technology, the focus must, of course, always be on customer benefits.”
What is Daimler Buses planning further down the line?
Julia Stolz: When it comes to electrification, we take into account the electric bus and all its components as well as the entire life cycle. This ranges from the improved usability of renewable energy sources, the operation of electric buses, the use of photovoltaic systems at the depot, intelligent charging management and the second-life solution down to battery recycling. This cycle makes the electric bus a real champion in terms of ecology and economy.
