‘Elektra’: Commercial battery ferries become a reality

Elektra’s 15.20m beam has 450m of lanes - five across - which gives it capacity for over 90 cars and 375 passengers
'Elektra’s' 15.20m beam has 450m of lanes - five across - which gives it capacity for over 90 cars and 375 passengers
The Cavotec plug descends from its tower and connects automatically
The Cavotec plug descends from its tower and connects automatically
Elektra has 360-degree views from the bridge
'Elektra' has 360-degree views from the bridge

The most important thing about ‘Elektra’, Finland’s new, double-ended ferry is that it paves the way for a new breed of vessel: battery-driven ro-ros. This is despite doubts that such a design was possible, let alone profitable.

It’s only the second electric ferry on a commercial route anywhere in the world: the first being Norway’s Ampere. The novelty comes with its headaches, first of all, for the naval architects: as Kristian Knaapi of Deltamarin explained: “There were no references, no other battery vessels that could be used a pattern.”

Secondly, as Mats Rosin, FinFerries’ CEO admitted, it’s meant a leap of faith in the technology: “We’ve had everyone’s eyes on us... some people were looking, saying ‘oh, this is so new, surely it can’t really work’.” Of course it meant close collaboration across the project, including the Polish Crist yard and Siemens who provided a complete electrical power and automation package, right down to the touch screens on the bridge and control suite below.

Despite its novelty, the 97.92m Elektra needs to be a 24/7 workhorse as it’s expected to run four times an hour during peak hours and once an hour overnight – the operator’s contract is explicit about the level of service. Rosin told MJ that the 1.6km ‘gateway’ between Parainen and Nauvo has between 600,000 and 800,000 vehicles crossing a year including heavy goods trucks but a sharp summer spike means over 100,000 vehicles in July alone. “We’ve sometimes had traffic queuing for three hours,” he explained, but added - with some relief -this has come down to “just 20 minutes or so” since Elektra started work in June.

The fast-turnaround pattern has its downside: it only leaves a minimal, five minutes at the quay for recharging so as time is of the essence there’s an automated recharge point at each end of the route. The plug itself, which descends vertically from its shelter in the Cavotec tower above, weighs several hundred kilos so even if it were safe, there’s no chance of guiding it by hand.

Therefore the ferry docks with a Cavotec vacuum auto-mooring system which holds the vessel in the right position. At the top of the tower (also by Cavotec) is travel-track governed by a sensor and linear motor that positions the plug explained Kaj Jansson, FinFerries project manager. A Wlan signal also triggers the hatch cover to pivot open; for redundancy’s sake these have been installed on both sides of the superstructure, allowing Elektra to turn and charge facing the other way.

Finally, the plug slides neatly down a flared receptor amidships: connection having been achieved by weight the charging begins automatically. It may seem like a lot of technology for a relatively simple operation, but this system achieves mating in seconds, not minutes, maximising plug-in time and keeping the 1MW, PBES battery bank within a 60% to 80% state of charge, necessary to guarantee the energy storage’s health and full, 10 year lifetime.

The turnaround’s not all been achieved by high tech solutions: there are also some basic elements that help the flow. Knaapi explained that by contrast with the other vessel on the route, Elektra has a straightforward loading pattern:  “If you have to use elevating ramps like Sterna’s it takes much more time in harbour, this is simply drive on.” Elektra’s 15.20m beam has 450m of lanes - five across - which gives it capacity for over 90 cars and 375 passengers. Knaapi pointed out: “This kind of vessel is way simpler, easier to maintain and faster to build”.

The new ro-ro also is fairly comfortable to operate, just as well since the shifts are 12 hours long, with just a captain, engineer and deckhand onboard. It’s quiet: even in the so-called ‘engine room’, there’s normally no need to raise your voice, the only residual vibration comes from the 900kW Rolls-Royce Z-drive thrusters although there are three auxiliary gensets for redundant power for charging failures or ice conditions. On the superstructure, just below the bridge, rows of photovoltaic cells from Activesol in Poland contribute just enough to support lighting, aircon and the machine responsible for infernally strong, Finnish-style coffee.

The bridge above is expansive, and not only is there the usual Faruno nav kit, but also a complete, 360° view from full-height windows. When it comes to turnaround, the captain’s Alutech chair just pushes backs on its track and spins, facing the opposite direction but leaving controls at his fingertips: “Elektra is truly double-ended,” added Mr Rosin. Below this there’s a coffee room, rest rooms and, quirkily, a small sauna with an ESO electric stove: “Finnish regulations,” explained the chief engineer.

While Elektra’s focused on reliability rather than speed, the propulsion still has to push some pretty meaty stuff. The ro-ro has Hydromega hydraulic ramps at either end and the hull itself is strengthened to meet 1A Ice Class: after one particularly bad year back in 2010 – which saw temperatures plummet all the way across Finland and 74cm of snow in Helsinki – the other vessel on the route had to be remodelled to meet ice of up to 3m thick. So, while the Turku Archipelago normally suffers less extreme weather than much of Finland’s mainland, Elektra still has double-spaced scantlings and thicker bottom plates.

Despite the investment, pegged at around 20mEuro for the total project including infrastructure “which is higher than usual because it’s still basically a prototype”, said Rosin, Elektra’s very cheap to run – based on Ampere’s figures it probably costs no more than a handful of Euros for each recharge.

By Stevie Knight

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