World’s first hydrogen tug in Germany with ESS from EST-Floattech
A zero-emission, hybrid hydrogen and battery tug that is capable of pushing a 1,400 metric ton loaded barge from Berlin to Hamburg has just been developed. It seemed impossible at first, but a German consortium led by Gerd Holbach, a professor at Technischen Universität Berlin (TU Berlin), has shown with a new vessel that fuel cells as a propulsion option will soon no longer be only a theoretical concept. EST-Floattech is one of the partners in this prestigious research project.
Since 2016 a German consortium has been pioneering the development of Elektra, the first hydrogen- fueled tug in the world. Construction of the 130 metric ton displacement tug was on schedule to begin at the Hermann Barthel yard in Elbe-Parey in Q4 2019. Elektra will not only enable an investigation of hydrogen’s feasibility as an energy store, but will also enable new charging infrastructure as well as the use of onshore electricity to be explored, as well as the creation of hydrogen for fuel cells.
“Due to its very specific properties, concerns have been raised in the marine field about the feasibility of hydrogen as an energy store, says says Kilian Hoffman, account manager for EST-Floattech. However, combined with our established marine battery technology, we have the ability to enhance energy density in zero-emission marine operations, while also improving vessel durability.”
Years of in-depth research has paid off. The final design of Elektra is nothing short of impressive. The 20m-long pusher with a beam of 8.2m and a draft of 1.25m will deliver an electric power capacity of 21,200kWh for a round trip from Berlin to Hamburg. It is also emissions free. Elektra is designed to push the cargo barge Ursus, developed by the Design and Operation of Maritime Systems department at TU Berlin, and numerous other cargo boats. Elektra is to be used primarily for transportation of goods on the Berlin to Hamburg and inner-city routes in Berlin. Its most important transportation task will be carrying Siemens turbines, which need to be shipped from the production site in the center of Berlin to the Western Harbor or to Hamburg.
Elektra’s shape was a central focus during the development process, as Holbach notes: “A conventional tug can be designed as a ‘box’ shape because energy saving is less of a consideration due to the fact that fuel is more affordable than hydrogen and there are no restrictions on the size of the power system. However, as the new hydrogen vessel cannot be refilled quickly and easily at a bunker station, the conservation of energy was the most important element.”
To devise the shape of the fuel tanks, the team conducted extensive CFD simulation, which resulted in a long, shallow entry at the bow that shaved just a little off the hydrostatic parameters but resulted in a greatly improved hydrodynamic efficiency. The two thrusters (200kW, fully rotating Schottel propellers)
are not in separate ducts, but instead are in a single channel that spans nearly the entire rear of the vessel.
Independent energy systems
The basis of the newly developed hybrid system is the battery package, consisting of 242 DNV-GL approved GO1050 modules with a total capacity of 2.5MWh, delivered by EST-Floattech, as well as three maritime fuel cell systems (NT-PEMFC, 100kW peak power each). Although the power of the battery and the fuel cells will be used together to power the electric motors, for complete redundancy the two powertrains are entirely independent.The energy storage system (ESS) delivered by EST-Floattech has a raft of integrated safety features. Its unique active balancing and passive safety system is applied at the module and string level. Heat is dissipated by a simple off-the-shelf aircon unit. The battery racks are a favorable option as they can easily be installed in a modular fashion. At a weight of 22 metric tons, taking up 15% of the vessel’s total weight, the batteries will be positioned below deck, with the lower center of gravity helping to mitigate the fluctuating fuel levels of the hydrogen tanks. The ESS must have a high energy density but also be as light as possible, and it must have a very precisely calculated life. Although the power from the batteries can be drawn more deeply, the moderately intensive use profile should enable around 5,000 cycles and ensure 10 years of use before the battery’s capacity drops below 80%. “We have arranged for onboard and remote monitoring of the installation so that everyone can check the performance,” adds Hoffmann.
In battery-electric mode, the tug will cover 65km (40 miles) over an eight-hour period before recharging is required. On hydrogen, Elektra will be able to travel a minimum of 100km (62 miles) over a 16-hour day or longer. This has been made possible thanks to a novel hydrogen storage module, designed and engineered by one of the project partners, Anleg. The modules can be delivered by truck or train to pickup points, where empties can be swapped using the vessel’s onboard crane. These modules consist of bundles of 125kg- capacity (275 lb) type IV composite tanks. On Elektra’s rear deck there are six bundles of tanks holding 750kg (1,650 lb) of fuel in the containment area. The full hydrogen storage system weighs about 20 metric tons. “Anleg has managed to reduce the weight of the individual tanks by 30% – this operation wouldn’t be possible had they not achieved this,” comments Hoffmann. “The dynamic interaction between the batteries and hydrogen fuel cells will be further explored and optimized under field conditions in Q3 of 2020,” he continues.