A battery-powered vehicle ferry in Finland’s Turku archipelago is pioneering electrical technology and cutting emissions, reports Paul Gunton
It is an unusual experience to stand in a ferry’s engineroom without needing earplugs and to be able to have a conversation without shouting. But this is Elektra, the latest vehicle ferry operated by FinFerries serving Finland’s extensive coastal road network, and its diesel engines are cold and quiet: an electric motor in an adjacent forward space, together with another one aft, is driving the vessel forward at about 10kts, their energy drawn from banks of batteries.
It is a small ferry on a short route but it will have a big impact for a long time: it entered service in June 2017 and is Finland’s first electric ferry, marking a significant advance for battery-powered propulsion. Its concept and design reflect many of the ideas pioneered in Norway, in particular on the vehicle ferry Ampere, which has served a short route across a fjord in western Norway since May 2015 for the operator Norled.
That makes Elektra the second battery-powered ferry, but it is the first to recharge its batteries at each end of its run directly from the domestic power grid; Ampere draws its power from banks of batteries at each terminal which are themselves refreshed from the local grid while the ferry is in transit.
Its Finnish successor operates in south west Finland, between Parainen and Nauvo in the Turku archipelago, making four 10-minute crossings each hour, with five minutes at each end to load and unload its vehicle traffic and top up its batteries. This was made possible by development work on the local power grid. “We were lucky,” FinFerries chief executive Mats Rosin commented to Marine Propulsion during a visit to see the ferry in action in November.
That visit had been arranged by Siemens, which supplied much of the electrical equipment for Elektra, as it had also done for Ampere before it. Odd Moen is head of sales, marine and shipbuilding, at Siemens and he believes “the future is electric”.
Although they were not running during PST’s visit, the three diesel generators onboard – divided between two enginerooms, with space for a fourth unit – can each deliver 420 kWe when needed. These are called into action if the shore power should fail – as it did for a short period in October, Mr Moen told PST – or during operations in ice, when extra power is needed or the ship’s speed might be affected, reducing the time available to recharge.
In these situations the generators would normally be used to charge the batteries and Kaj Jansson, FinFerries’ project manager for Elektra, told Marine Propulsion that the generators automatically start if there is insufficient battery power. They would normally charge the batteries but can be switched to deliver power direct to the propulsion circuits. This gives three power modes: pure battery; diesel-battery hybrid and diesel-electric. All three modes can function at the same time, Mr Rosin said, which he said gave Siemens a challenge, but “it was a demand we had” to optimise CO2 emissions, he said.
Propulsion is delivered by a pair of Siemens electric motors, each driving a Rolls-Royce azimuthing thrusters rated at 900 kW, positioned fore and aft on the double-ended ferry, and the total battery capacity is 1 MWh, which would be sufficient for about six crossings of the one-mile route.
Mr Jansson explained that the batteries were sized so that they would not be overloaded either while being charged or when in use. “The heavier the load the shorter the [batteries’] lifetime,” he said. “So we were keen to keep the charging and discharging at a reasonable level.”
Each trip uses about 15% of the batteries’ capacity, which must be replaced during each brief port call. This requires a quick connection to the shore power to be made, which is achieved by lowering a plug into a socket that opens out of the superstructure (see box). Elektra’s batteries were made by PBES, whose product development work is done in Vancouver, Canada, with production in Trondheim, Norway.
There are two battery banks, one in the forward and one in the aft machinery space, and the captain can see the level of charge in each of them on the bridge. An alarm will sound if there is not enough to complete the trip when the ship sets off and the diesel generators will start automatically. Both banks are charged simultaneously but each is dedicated to one of the thrusters. The hotel load is taken from just one battery bank and is switched from one to the other for each trip: it is always taken from whichever is the forward bank, the captain said.
Further electrical power comes from banks of solar panels, supplied by Activesol of Poland, which provide enough power during summer months to run the air conditioning and other hotel loads, Mr Rosin said. At other times – such as the November day when Marine Propulsion was on board – an oil-fired boiler is used to heat the crew spaces and provide hot water; there is no waste heat available from the engines for these services, Mr Jansson pointed out.
Compared with the existing conventional ship on the route, Sterna, Elektra carries 40% more vehicles but with 60% less emissions and the electricity cost is trivial: just €5 (US$6) of electricity per crossing, Mr Rosin estimated. Vehicle emissions are also reduced, since queuing at peak times has been reduced from three hours to 20 minutes.
Much of the emission saving comes from taking account of the source of the electric power: mostly generated by nuclear and hydro-electric stations, Mr Rosin said.
Design work on the ferries was done by Deltamarin of the Netherlands and StoGda Ship Design & Engineering, which is based in Poland where the ship was built at Crist Shipyard.
Deltmarin’s brief was to prepare an outline design for the ship and an outline definition of its energy storage and shore supply requirements.
Head of sales and marketing at Deltamarin, Kristian Knaapi, told Marine Propulsion that this included a wide range of topics, including studying the project’s feasibility and defining all the ship’s main values ready for the next stage of development. “If the concept phase is not performed properly, the vessel will not be feasible,” he said.
StoGda was then responsible for delivering the vessel’s complete design, its website records, and for arranging model tank tests – which included manoeuvring tests and ice tank tests. Workshop documentation and as-built drawings were also prepared by StoGba.
Deltamarin was also involved in designing the linkspans used for the ship’s terminals. Because it is wider than the existing vessel on the route, called Sterna, new berthing arrangements were needed and Mr Knaapi said that its design was critical because of the short turnround time available. It had to be strong and practical to construct.
“One very notable point,” he said, was that the linkspan can be made to match the vessel’s draught if necessary. It can be ballasted and de-ballasted to give it a draught range of 0.95 m, he said. It also incorporates a de-icing method to make it usable in the winter, he said.
FinFerries operates 44 ferry routes around Finland, but the Parainen and Nauvo link is the busiest. So does the operator have plans for any more battery-powered ferries? Mr Rosin did not rule it out, but he wants to see how Elektra and its shore power system stand up to a Finnish winter and complete a year’s operation first.
But there is a complication: FinFerries operate services under tenders from the state and the Turku archipelago tender – covering four routes – is due for renewal in 2023. So no sister for Elektra will be considered until that renewal has been confirmed, he told Marine Propulsion.
Because there are so many routes, competing for tenders is a regular task and he is considering smaller vessels for use elsewhere, but he is careful “not to promise too much” to yards and suppliers by being specific about his plans. Rather, he needs to know that a tender is secure and that it can be confident there is a need for a ship. “Then we’ll go out with high integrity,” he said.
On one thing, though, he is definite: “I believe strongly in this technology otherwise I would not have started this project,” he said.
• Watch a video, made by Siemens during Marine Propulsion's visit, that shows Elektra’s shore connection and other features of its electrical engineering at http://bit.ly/PST-Elektra