Electricity Instead of Diesel: How Hamburg Is Reinventing Its Bus System

One of Europe’s most ambitious fleet transitions is taking place at the depots of Hamburger Hochbahn AG. At the heart of it is a partnership with ABB E-mobility that has grown over more than a decade—and a man who has driven the electrification effort from the very beginning.

Hamburg is showing its best side today. Bright sunshine shines over Hummelsbüttel, the light refracts off the steel beams of the carport structures and casts sharp shadows on the asphalt of the Hamburger Hochbahn AG depot. The weather matches the sense of optimism in the air here. Hendryk Münster, Head of E-Mobility and Surface Systems at Hochbahn, stands in the sun and looks up—to where charging stations don’t usually hang. That’s exactly the point.

Münster is accompanying us on an inspection that goes far beyond a routine site visit. It is a tour of a partnership between Hochbahn and ABB E-mobility that began more than a decade ago, when electric mobility in public transit was still a bold experiment for many. Today, it is an integral part of regular operations in Hamburg.

Vertical Charging Infrastructure

In Hummelsbüttel, it quickly becomes clear why standard solutions wouldn’t have worked here. Space at the depot is limited; every square meter is needed for the logistics of the large vehicles. The solution was as radical as it was efficient: the entire charging infrastructure was moved vertically. The ABB Terra HVC 150C chargers are mounted on crossbeams above the buses, installed on the roofs of the carports. Following a Europe-wide tender, it was the first installation of its kind in a German bus depot—and in 2019, it marked a milestone for the entire industry.

Forty-four of these DC chargers—each with a charging capacity of 150 kilowatts—power the fleet overnight at the depot. The design principle behind it is well thought out: The system is divided into three functional units—the charging box with the cable connection to the bus, the electrical supply unit, and the power electronics for power conversion. This modular separation significantly facilitates maintenance and future expansions. In terms of communication, the devices are CCS- and OCPP-compliant, meaning they can be seamlessly integrated into Hochbahn’s charging management system.

This engineering presented both partners with tangible physical challenges. The power electronics add significant weight, which pushed the structural integrity of the carports to their limits. Added to this is the issue of thermal management: considerable heat is generated in the compact enclosures under full load. Together, ventilation concepts were developed that ensure the technology does not throttle even at peak summer temperatures while remaining protected against wind and weather. It is precisely this detailed expertise that transforms a supplier relationship into a true development partnership.

Meiendorf: Hamburg’s First All-Electric Bus Depot

The journey continues to the northeast of the city, to Meiendorf. While Hummelsbüttel demonstrates the art of retrofitting existing infrastructure, Meiendorf represents a vision for a greenfield site. Spanning approximately 28,000 square meters on Meiendorfer Weg, Hochbahn’s first all-electric bus depot is taking shape. The opening is scheduled for later this year; as things stand, 130 electric solo and articulated buses will operate from here, primarily serving Hamburg’s northeast. The total investment amounts to 42.3 million euros.

In Meiendorf, ABB E-mobility is acting as a comprehensive system partner—and on a scale that goes far beyond mere charging infrastructure. ABB is supplying the complete energy chain here: starting with the medium-voltage switchgear that brings power from the public grid onto the site, through power transformers that step down the voltage to the facility’s internal level, all the way to the entire low-voltage distribution system on the premises. The charging points under the carports are then connected to this infrastructure, supplying the buses with certified green electricity overnight.

As we walk through the facility, which is still under construction, Münster explains the principle of sector integration, which is being consistently implemented here. The waste heat from the charging technology is not released unused into the environment, but is fed into the buildings’ heating system via heat exchangers. The carport roofs are greened and fully equipped with photovoltaic panels. The rainwater collected on the roofs is temporarily stored in cisterns, used for the bus wash facilities, and then recycled. Additionally, the facades and soundproof walls are greened. What is emerging is not merely a parking lot with outlets, but a well-thought-out ecological cycle within the urban fabric.

Intelligence as a Key Factor: Load Management and Storage

The success of such large-scale projects does not depend solely on the hardware. The real challenge lies in system integration. When hundreds of buses connect to charging cables almost simultaneously in the evening, enormous power demands are placed on an electrical grid that is not infinitely resilient. This is precisely where the load management system comes into play: it coordinates when and at what power level each individual bus is charged, and continuously aligns this with the grid’s capacity. Communication between Hochbahn’s proprietary charging management software and ABB’s control technology takes place via standardized OCPP protocols—which was by no means a given when the system was first implemented on this scale years ago.

Another technical component is the stationary battery storage system at the depot, which emerged from the KoLa research project (Coordination Function and Load Management) and has since become an integral part of daily operations. The storage system buffers load peaks that occur when many buses are charging simultaneously at maximum power. It thereby decouples immediate demand from the grid connection and additionally enables Hochbahn to optimize its electricity procurement—for example, by specifically utilizing off-peak electricity rates. Münster is convinced: Anyone electrifying a depot today cannot do without such a storage system.

This confidence in the technology has grown over the years. In the early stages, there were no blueprints for depots of this scale. It was necessary to analyze mistakes and develop solutions that would still be viable ten years down the line. By the end of 2026, Hochbahn’s charging infrastructure is set to provide charging points for more than 750 parking spaces. By then, roughly half of the approximately 1,200 Hochbahn buses will be electric.

Transformation as an Ongoing Project

As we say our goodbyes in Meiendorf, with the sun now low over the carport roofs, one thing becomes clear: what Hochbahn is accomplishing here is more than just swapping diesel for electricity. It is an industrial transformation that requires planning certainty, the courage to innovate, and resilient partnerships over long periods of time. Hamburg has long been regarded as a benchmark project in the industry—nowhere else in Germany are more electric buses in service.

Given the expiration of federal subsidies and a more complex financing situation, the original goal of fully electrifying the fleet by 2030 has realistically been pushed back to the early 2030s. More recent developments, such as changes in legal requirements for the protection of critical infrastructure, are also influencing procurement policy. But the direction is irreversible, and the Hochbahn remains firmly on the path to electrification. In Meiendorf, charging stations for electric vehicles are ready to keep the city moving quietly and cleanly. ABB E-mobility is proud to be part of this journey—from the first sketch to the state’s most modern bus depot.