Wärtsilä and Wasaline’s close cooperation continues with world’s largest marine battery hybrid system project

Technology group Wärtsilä has been selected as the electrical integrator for a major battery extension project for the Wasaline ROPAX ferry ‘Aurora Botnia’. The project will increase the ship’s battery capacity by 10.4 MWh, from 2.2 MWh to 12.6 MWh, making it the world’s largest marine battery hybrid system in operation. The order with Wärtsilä was booked in Q3 2025.

In the transition to more sustainable ferry transportation, hybrid propulsion systems have emerged as a compelling solution, offering a multitude of pathways to reduce greenhouse gas (GHG) emissions. These systems, which combine energy storage capabilities with conventional engines, can significantly cut fuel consumption and, consequently, emissions.

The Aurora Botnia ferry, which is operated by Wasaline, is equipped with dual-fuel engines and batteries and is using biogas and batteries for the propulsion. Expanding its battery capacity is a major step in making the ship even more sustainable. Wärtsilä will lead the integration project and as a result, the battery capacity of the ferry will be extended by 10.4MWh. Wärtsilä will also deliver the Energy Management System, as well as upgrade the power drives and the control system integration. The system is scheduled to be commissioned in early 2026.

“Wasaline’s commitment to decarbonised shipping operations is central to everything we do,” says Peter Ståhlberg, Managing Director – Wasaline. “In this, our close cooperation with Wärtsilä is an essential element that benefits not only both our companies, and we can see that our cooperation sets standards for the whole marine sector. Through our continued collaboration, the ‘Aurora Botnia’ has become a working example of what is possible when it comes to delivering environmentally friendly transportation within shipping.”

This latest project will strengthen the existing collaboration agreement between Wärtsilä and Wasaline, with the Aurora Botnia acting as a floating testlab linked to Wärtsilä’s Sustainable Technology Hub. It allows further development of hybrid technologies to optimise fuel efficiency and minimise exhaust emissions. As a result, the vessel is one of the most environmentally sustainable ferries in the world, operating carbon neutrally already today.

“Wasaline once again demonstrates its strong commitment to decarbonisation by extending the electrification capacity of this ferry. Our latest contribution will optimise the ship's operations even further, creating fuel savings and a significant reduction in emissions,” comments Roger Holm, President of Wärtsilä Marine & Executive Vice President at Wärtsilä Corporation.

The Aurora Botnia, which entered into service in 2021, operates with a range of integrated Wärtsilä solutions, including four highly efficient Wärtsilä 31DF engines. The ultra-low emissions version of the engine has helped the ferry to significantly reduce methane emissions. The ferry operates between Vaasa in Finland and Umeå, Sweden.