Decarbonising in the maritime industry through hybridisation

Jasleen Mann explores how a hybrid propulsion system can help make vessels flexible and able to adapt to future technology developments.

Technology group Wärtsilä is supplying its hybrid propulsion system for three new roll-on passenger (RoPax) vessels.  

The order was placed in May and will allow the ships to operate using liquified natural gas (LNG) fuel or batteries. Ferry companies Stena RoRo and Brittany Ferries designed and developed the ships that will be chartered long-term to Brittany Ferries. 

The ships are currently being built at the China Merchants Jinling (Weihai) Shipyard and it is expected that they will be delivered in 2024 and 2025.  

The ships will operate between Portsmouth in the UK and the French ports of St Malo and Caen.

Record-breaking hybrid power

With a battery capacity of 11.5MWh, two of the ferries will be the marine industry’s largest hybrid vessels. The battery capacity is considered to be double the battery power that is common in current hybrid propulsion.  

Torsten Bussow, managing director at Wärtsilä, says: “At the moment the future fuel is unclear but with a hybrid system there is flexibility as this allows you to add future power source like solar or fuel cells to support the change to future fuels.” 

In addition, the use of hybrid systems will ensure that the vessels are able to adapt to green fuels and larger batteries. 

The large battery size will ensure that the ships are operating at full power. This will be done through the use of propellers and thrusters to travel between ports. There is also a built-in shore power solution which can charge the batteries while the ship is moored. 

The total hybrid propulsion system is supported by Wärtsilä’s Energy Management System. Wärtsilä places emphasis on making vessels more energy efficient in order to meet the 2030 for compliance with IMO’s Energy Efficiency Existing Ship Index and Carbon Intensity Index regulations. 

“If you read about a hybrid today it is typically a combustion engine and battery, The main benefits are lower fuel consumption, cleaner energy if sourced from the grid, load balancing and peak shaving on the main engines,” says Bussow.

Flexible fuel, flexible power

Wärtsilä was contracted to supply solutions relating to the main engine and auxiliary engines, gearboxes, controllable pitch propellers, thrusters, fuel gas supply system, Nacos navigation, and automation. In addition, Wärtsilä was responsible for the integrated control alarm and monitoring system. 

The Leclanché energy storage system, the Navius MRS-3, will be used for the ships. This system is considered large in terms of size and weight. Swiss energy storage solution company Leclanché launched the Navius MRS-3 at the 2022 Electric Hybrid Marine World Expo in Amsterdam. 

This system demonstrates increased battery energy density, modularity and safety. It also has a liquid-cooled design which ensures that the system is long-lasting. The carbon footprint is reduced due to the cells, modules, battery management system, and racks. 

The use of hybrid technology for its vessels is a part of Brittany Ferries’ fleet renewal programme. For Brittany Ferries, this development follows two LNG fuelled ships. Due to shore-side power capability, there is potential for investment by ports because of plug-in infrastructure.  

Bussow concludes: “A flexible fuel strategy is important to clients as they prepare for a zero-carbon future. Electrification of the vessel will be key in achieving this.”