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With no bridge between the Danish island of Aeroe and the mainland, ferries play an essential role in keeping the island’s 6 000 inhabitants connected. Unfortunately, these diesel ferries are also major polluters and thus a major obstacle to the island’s goal of becoming carbon-neutral by 2025.
As a sustainable alternative, the EU-funded E-ferry project has developed Ellen – a state-of-the-art, 100 % electric car ferry. “Running completely on electricity generated from renewable energy sources, with no backup generator on board, Ellen achieves true emission-free ferry operations,” says Halfdan Abrahamsen, media and information manager at Ærø EnergyLab, the project’s lead partner. “In other words, by replacing an old diesel ferry with a fully electric one that sails on renewable energy, we’ve shown how we can drastically reduce the island’s carbon footprint.”
Carefully designing every component
Needless to say, developing such a revolutionary ferry was no simple task. “Every component, from the hull to the batteries to the charger itself was designed with extreme efficiency in mind,” explains Abrahamsen.
For example, the ship’s hull was engineered to ensure minimal resistance, which allows it to efficiently glide through the water with low energy use. Furthermore, to accommodate the ferry’s 840 batteries, the project had to design an extremely compact, cutting-edge electrical system – not to mention the custom software needed to ensure a balanced and fast charging of such an unprecedented number of batteries.
According to Abrahamsen, one of the most important design aspects was the charger. “If the charger doesn’t connect very quickly and solidly when the ship arrives in port, the operator won’t be able to get enough power to maintain service,” he notes. “Any disconnection or poor charging will result in delayed or cancelled service.”
Ellen addresses this risk by placing the charger on top of the ship’s ramp and uses a robotic arm to automatically connect the four charging lines. “When the ferry arrives in port, the ramp is lowered onto the car deck, meaning the charger follows the ferry as it moves in the water,” adds Abrahamsen.
Exceeding expectations
To replicate the service level of a diesel ferry, Ellen would need to be able to make five round trips daily. “I’m happy to say that not only was Ellen able to meet this standard, it exceeded all expectations,” remarks Abrahamsen.
The project demonstrated Ellen’s capability to make up to seven round trips daily – and to do so 10 minutes faster than the diesel ferry. Ellen even outperforms other e-ferries, sailing seven times longer between charges.
“We sail 22 nautical miles between charges, which is approximately 40 kilometres,” says Abrahamsen. “This range is more than enough to serve the needs of Aeroe and is enough to meet the needs of between 65 and 80 % of all Nordic ferry routes and at least 900 European routes.”
In terms of efficiency, project researchers estimate that Ellen saves 2 520 tonnes of CO2 annually and removes over half a tonne of dangerous particles from the air. “The e-ferry’s energy efficiency is 85 %, which is more than twice that of a traditional diesel engine,” notes Abrahamsen. “In other words, when we use energy, almost all of it goes into actually moving the ferry forward, with very little being wasted.”
Sailing electric also saves cash. “While the initial investment is slightly higher, operators will see savings as soon as after 4 to 8 years,” explains Abrahamsen. “It’s remarkably cheaper to charge batteries than it is to fill a tank with diesel.”
Abrahamsen adds that customers and crews also enjoy sailing with Ellen, particularly its quiet, smooth, smog-free operations. “Ellen is proof that we can move away from our dependence on fossil fuels,” concludes Abrahamsen. “By demonstrating how e-ferries can serve a variety of routes, we hope to see an uptick in the use of emission-free maritime solutions.”
This story has been recently updated