With Flagship Project status and funding from the EU under its Horizon 2020 initiative, the E-Ferry project consists of nine partners, coordinated and led by the Danish municipality of Ærø. The latter will provide onshore facilities – the ferry will be run by its ferry company, Ærøfærgerne, and will sail from the port of Søby, in Ærø.
Designed by Danish naval architect Jens Kristensen in close collaboration with Søby Shipyard, the ferry’s lithium-ion battery, power system and electric drive train are the responsibility of Leclanché and Danfoss Editron. Tuco Marine Group investigated the use
of composite materials, while the Danish Maritime Authority and Danish Institute of Fire and Technology guided the partners from design to certification, acquisition and building
of the ferry, which has been christened Ellen. Finally, the Centre for Research and Technology Hellas (CERTH) in Thessaloniki, Greece, has been responsible for the dissemination of the project’s results and impact, as well as for market investigation and business plan formulation.
With a budget in excess of €20m (US$23m), the project builds on the Green Ferry Vision, addressing the need to reduce European CO2 emissions and air pollution produced by waterborne transportation. It aims to demonstrate the feasibility of a 100% electrically powered, emission-free, medium-sized ferry relevant to island communities, coastal zones and inland waterways.
Estimated annual environmental benefits of the electric ferry over a conventional vessel should see CO2 emissions reduced by about 2,000 metric tons, NOX and SOX slashed by 41,500kg and 1,350kg respectively, particulates cut by 2,500kg, and reduced noise and wave heights, both of which will benefit communities and wildlife.
Challenges and delays
“The whole setup has been a challenge, as it is very ambitious,” CERTH civil engineer and research associate Annie Kortsari tells E&H Marine. “Though there are some electric ferries in operation, the technology is still very new and in the E-Ferry project we are trying to break through further barriers. We’d like to be fully electric, operating without a backup emergency diesel generator, and are looking at distance, to see how far we can sail before recharging.
“Partners supplying the components have more or less had to develop them from scratch. For example, even though Leclanché has been producing batteries for over a century, it had no real experience with batteries for maritime use before the project started. Similarly Danfoss Editron had experience with electrification and a long tradition in compact electric motor engines, but again this had to be translated into more complex maritime systems.
“Additionally the ferry has been designed specifically for 100% electric operation, so various things had to be implemented to ensure a high degree of energy efficiency, weight distribution and so on. Essentially almost every little part of the ferry has been developed from scratch.
“A further challenge,” Kortsari continues, “has been that there are no regulations – such as SOLAS and IMO – for electrification, while class rules and regulations were more or less developed during the project. Leclanché got its maritime battery system type-approved, which was a big step forward, but the ferry’s entire energy storage system [ESS] was considered an alternative design, so going through a design and approval process was challenging: it had to be done according to IMO MSC.1/Circ. 1455.”
As Kortsari points out, rather than a conventional new-build project, this was a partnership in which each organization involved, partially funded by the EU, was tasked with specific roles. The partners have to develop, design, redevelop and redesign throughout the ferry’s construction.
“When you change or add components and systems for one part of a ship, you sometimes have a situation where you have to change other parts to accommodate the changes – redoing work that was already done,” Kortsari clarifies. “That is, of course, the nature of innovation; the process is iterative and thus more time-consuming,” she concludes.
E-Ferry project coordinator Dr Trine Heinemann tells E&H Marine: “The E-Ferry prototype, Ellen, will eventually operate between Søby-Fynshav and Søby-Fåborg in southern Denmark, with crossings expected to start on May 1, 2019. Ellen is a traditional name for ferries using the port of Søby, but the name is also a pun of sorts in relation to an electric ferry, as in Danish it can also mean something like ‘electricity one’ – the first electric ferry.
“For the foreseeable future, the existing conventional ferry, Skjoldnæs, will operate on one leg, Søby-Fåborg, while Ellen will sail the Søby-Fynshav leg. The ambition is that Ærøfærgerne will eventually replace its other ferries with electric vessels. That depends, however, not just on Ellen’s success, but also on economics – when the conventional ferries need replacing due to age – plus the transport needs of the municipality.”
Charging of the Ellen will be done only in Søby and is estimated to take no more than 20 minutes. That means Ellen will sail 22 nautical miles between charges. The onboard redundancy has been duplicated ashore for both the charging system and the electrical infrastructure: Ellen has its own supply network, independent from the town and port supply, with a dedicated cable supplying four transformers with 4MW/10kV. Charging is via a hydraulic arm – developed by Mobimar and placed on the ferry’s ramp – with two separate connectors, one for each ESS.
As Heinemann stresses, Ellen is a prototype and the E-Ferry project is designed to inspire ferry companies throughout Europe.
Tests, safety and reliability
The E-Ferry partners’ principal aim was to design a ferry that is at least the equivalent of a conventional vessel in terms of safety and reliability. Component testing was in three phases: first, by the partner responsible for it; second, by two or more parties, to ensure interoperability; and finally as part of the survey and approval process for and with classification society DNV GL and the flag state, Denmark. The E-Ferry team is currently concluding that testing, survey and approval process, which is scheduled to complete by the end of May.
How it works
The energy storage system (ESS) consists entirely of lithium-ion/NMC batteries and is Ellen’s only source of power – there is no emergency diesel generator. The ESS has a total capacity of 4.3MWh, and is stored in two separate but identical battery rooms below deck, forward and aft, giving the ferry redundancy that extends to two separate systems for charging and energy distribution. Each battery room is equipped with 10 battery strings and each battery module has a nominal energy of 5.12kWh.
Battery modules consist of 32 cells enclosed in an IP65 box, the bottom of which is equipped with water cooling. They are configured in four series of eight parallel connections and each module has an embedded battery monitoring unit that measures temperature and voltage per eight cells and transmits those measurements to a battery control unit for each string. The supporting safety systems for the ESS have type approval from DNV GL. The energy is distributed to separate DC bus energy systems that each have A750VDC switchboard for overall power distribution to battery strings, propulsion and hotel/other consumers, and 10 DC/DC converters that control the load to each battery string when charging and the voltage for the DC bus system when charged power is used in the system.
Each system also has three DC/AC drives that control the propulsion and thruster motors and convert the DC energy to AC for the motors, a hotel drive (DC/AC converter) that transforms the 750V DC to 500V AC plus a hotel transformer (310kVA) that transforms the 500V AC to 400V AC, a 400V AC switchboard, and two AC distribution boards.
The power management system (PMS) controls and monitors the overall energy distribution, including battery capacity, charging/discharging and energy consumption, and also monitors and controls the propulsion drives and motors. Again redundancy is built in – there are two PMS units per ESS, so that each controls only a quarter of the ferry’s total capacity.