Designing the World’s Largest Marine Battery Retrofit for Aurora Botnia

Foreship devised a unique set of specifications to support Wasaline with the installation of the largest battery energy storage system ever retrofitted on a ship.

Challenge

Wasaline’s 24,000 GT passenger ferry Aurora Botnia is already recognized as one of the most environmentally advanced vessels operating in the Baltic Sea. Equipped with dual-fuel LNG engines, shore-power capability, and 2.2 MWh of battery energy storage, the ship has delivered reliable, low-emission service on the Kvarken Link route since 2021.

In 2024, Wasaline set itself a new and ambitious target to accelerate the vessel’s decarbonization pathway by installing the largest battery-retrofit system ever deployed on a ship. The owner selected Foreship to design the upgrade and support through the technical and regulatory complexities of the project.

In doing so, Wasaline returned to a relationship with the naval architecture and marine engineering specialist which was also central to the concept design, supervision, and technical support during the newbuilding project for Aurora Botnia.

Applied expertise

Wasaline initially asked us to assess the feasibility of converting one or two engines to operate on e-methanol. However, when regional production plans were postponed, we broadened the study to evaluate alternative pathways to accelerated decarbonization. In doing so, we identified a substantial expansion of the vessel’s battery energy storage system (BESS) as the most effective near-term solution.

The resulting installation adds more than 10 MWh to the BESS capacity on board, transforming Aurora Botnia into a high-efficiency hybrid vessel capable of meeting current and future emissions requirements with increased utilization of bio-LNG.

Doing so involved an innovative integration of two different battery chemistries, to bring together Nickel Manganese Cobalt (NMC) and Lithium Ferro Phosphate (LFP) solutions. The vessel’s original NMC batteries deliver high power density and are well-suited to peak load shaving and maneuvering. The new LFP battery system, meanwhile, offers significantly greater energy capacity and a lower lifecycle cost profile.

We evaluated over ten battery configurations before selecting the mixed-chemistry architecture that could be safely accommodated in a single compartment, in accordance with stringent battery notation from Class and supported by a comprehensive safety philosophy.

Integrating the LFP bank required a full review of Aurora Botnia’s existing electrical, structural, and machinery systems, as well as stability calculations.

Impact

With the expanded BESS, the vessel can run on a single generator for the vast majority of voyages, with batteries supplying the remaining propulsion and hotel load requirements. This will reduce fuel use as well as emissions. Our modelling showed that the hybrid system also has the potential to generate surplus emission allowances within the FuelEU Maritime framework, further improving the already attractive business case for the larger capacity BESS.

In addition, our analysis demonstrated how greater use of the abundant low-cost renewable shore power in the region can offset LNG consumption and sharply reduce operating emissions.

In fact, it is fair to acknowledge the key role we played as an extension of Wasaline’s technical organization in this multi-million euro retrofit. Beyond feasibility work and classification design, we supported procurement, electrical integration planning, onboard supervision, and coordination with system integrator Wärtsilä and battery supplier AYK Energy.

Aurora Botnia is a leading example of how a carefully engineered hybrid architecture can deliver significant emissions reductions on one of Northern Europe’s most demanding short-sea routes.

Contact:  Joonatan Haukilehto – Head of New Technologies (joonatan.haukilehto@foreship.com)