Echandia Marine has developed an electric-powered passenger ferry that now operates in Stockholm. The boat ‘super’ charges its batteries while docked.
The fog has lifted over Riddarfjärden, and the sun is shining down on the E/S Movitz’ 23 meter- long green and white hull, resting quietly in her mooring. On the dock next to the ship is a large reel mounted with a rolled-up heavy-duty charging cable. Like a discrete maritime signal, the cable reel flags an unusual set-up.
A pioneer of noise and emission-free traffic
Riddarholmen is the starting point and charging station for Green City Ferries, which in August 2014 re-launched the E/S Movitz as an electric boat. The former diesel vessel was retrofitted with an electric drive. The innovative battery and charging technology, developed in collaboration with Echandia Marine, makes it one of the world’s first electrically powered, fast-charging ferries. The project is partly financed by the Swedish Energy Agency.
Low-hanging fruit – public transport by water is environmentally friendly and improves air quality while reducing greenhouse emissions. Under typical conditions and with clean electric propulsion one ferry can save 300 tons of carbon dioxide emissions per year, compared to diesel propulsion. “Look at Amsterdam which is introducing a zero discharge policy for canal traffic. It’s not just about carbon emissions. Particle and nitrogen oxide concentrations are also the issue. Amsterdam will have a technology-neutral policy. And only electric power and fuel cells fulfill this, “says Joachim Skoogberg, CEO of Echandia Marine.
Cost-efficient battery technology
Echandia’s systems use batteries manufactured in Gävle by the Swedish-American company Nilar, which has a patented method for building bipolar cells with low production costs. While various forms of lithium-ion batteries have become increasingly common, in electric cars for example, Echandia has chosen to base their system on a different chemistry.
“The technical conditions for super charging lies in battery technology. There is nothing new with electric motors – the batteries have come a long way. We use bipolar nickel metal hydride batteries. Anodes, separators and cathodes are stacked on each other – as in lasagna. It is the battery itself that is compact, has low internal resistance and is robust and durable enough for high-speed recharge. Nickel metal is also cheaper than lithium-ion batteries,“ explains Skoogberg, arguing for the commercial viability of the technology. These conditions make it possible to recoup this kind of investment today – even without the reduced energy tax that slightly larger vessels may get while powering up on shore.“
‘Super’charging is an enabler
Ten minutes charging on shore equals an hour and ten minutes of operation, sufficient for the Riddarholmen to Solna Strand route with two morning and two afternoon tours. In the future, traffic will increase with more stops.
The ferry’s battery packs have an output of 180 kWh and are distributed throughout the hull. Joachim Skoogberg maneuvers through the tight battery stacks explaining how they are connected. “We need 75 kW to keep our cruising speed of 8.3 knots. By spreading out the cells, we maximize the limited space. The batteries power two electric motors placed in outlying azipods. Two diesel generators on board can also charge the batteries.“
The charging station at Riddarholmen and SolnaStrand deliver high power and fast charges. “We super charge with 300 kW. Soon, we will upgrade to 600 kW, says Skoogberg. “Super charging is key for this concept to work. The range depends on the battery size. It is easy to think that electrification is difficult – that sailing with such large battery packs is a burden and too unwieldy. But super charging, as we define it, is not primarily a question of power, but about the time it takes.”
“We sail an hour on a ten minute charge and take advantage of the time for boarding and disembarkation. From a propulsion standpoint, this is downtime. It is the frequent charging intervalsthat make electrification possible. It is a super charging mindset,“ concludes Skoogberg.
This article was published in April 2015