NAUTILUS - Reduction of ship emissions

On the Way to Ship Emission Reduction With an Innovative Energy System

  • The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is collaborating with partners from 9 European countries to develop an innovative climate-friendly on-board energy supply system for long-haul passenger ships to reduce both carbon and non-carbon emissions. NAUTILUS is a short name for the Nautical Integrated Hybrid Energy System for Long-haul Cruise Ships.

  • The novel energy system is based on Solid Oxide Fuel Cells (SOFCs) coupled with batteries that can provide 5 to 60 MW of full ship power, depending on the various types of vessels considered in the project (ranging from 1000 to 5000+ passenger). For this, a full-scale digital demonstrator validated by a smaller operational field-demonstrator is in progress in the project.

  • The main feature of NAUTLUS genset is its high efficiency of almost 85% net, when utilizing combined heat and power, as well as its fuel flexibility as it will allow the energy system operations on LNG and with a range of sustainable future fuels.

  • The key benefits of the NAUTILUS energy system are the reduction in emissions, at least 50% reductions in carbon dioxide and more than 80% in the non-CO2 emissions and ensuring compliance with IMO emission targets for 2030 resulting in favourable impact on human health and environment.

Innovative Approach for the Emission-Free Maritime Transport

In the context of strategies aimed at reducing emissions in maritime transport, the shipping sector is currently undergoing a significant technological transformation. Traditional diesel generators, which run on heavy fuel oil, are continuously replaced by hybrid system applications. These cutting-edge technologies are increasingly being incorporated into the propulsion systems of vessels not only to minimize emissions but also to enhance the economic efficiency of ship operations.

The innovative technological solution proposed and developed in the NAUTILUS project is based on the combination of Solid Oxide Fuel Cells (SOFCs) and a battery storage system consisting of a conventional lithium-ion battery pack. This integrated system, referred as the Genset, is designed and tested to fulfil entirely the ship’s energy requirements during operation, manoeuvring, and accommodating hotel loads that represents approximately 15-20 percent of the cruise ship energy demand. Neither the SOFC nor the battery storage system can solely fulfil the total power demand of a cruise ship, which is the reason of coupling both in the propulsion system. The total power demand of a cruise ship will be split between the available power sources. The distribution of electrical power to the Genset requires intelligent control and management. The Energy Management Unit that can be embedded into the ship's grid is also developed by the NAUTILUS project consortium.

The NAUTILUS project develops process design and a digital demonstrator of the on-board energy system, a physical Proof of Concept (PoC: 30 kWe SOFC + battery) and a modularized functional demonstrator (60 kWe SOFC + battery). The digital design as well as the physical demonstrator are evaluated against the marine safety regulations. Emissions from the genset demonstrator will be characterised in order to demonstrate the feasibility of the overall ambition to meet the emissions targets of 2030 of the IMO directive.

To achieve International Maritime Organisation (IMO) emissions targets beyond 2030, the system is designed to be adaptable to various fuel options. Initially, the project will involve reformation of the LNG fuel for use by SOFC fuel cell. “The shift from diesel engines to gas engines is already happening,” explains Syed Asif Ansar of the DLR Institute of Engineering Thermodynamics, the coordinator of the NAUTILUS consortium. “Our immediate focus in NAUTILUS is to go beyond the IMO 2030 emission targets through an increase in the energy efficiency on board ships thanks to fuel cell and battery based power system. From there on, we intend to leverage synergy with the synthetic sustainable fuels, to complete the transition to net-zero.”

Adopted Project Arrangements as Response on Changing Conditions

To respond effectively to the rapidly changing business strategies and market demands, the consortium has recently implemented a setup for the demonstrator supporting this opportunity. In this arrangement, the fuel cell system is provided by SolydEra as a packaged solution, incorporating integrated auxiliary systems (Balance of Plant, BoP) as well as the system's control and piping. MAN Energy Solutions serves as the battery integrator, responsible for delivering a battery container equipped with a real-time PC, an electrical controller, and a safety protection system. Under the revised project infrastructure, DLR oversees the overall system integration of the battery container and SOFC system. The physical testing of the demonstrator at DLR’s Stuttgart premises is scheduled for the summer of 2024.

The adoption of this new setup offers numerous advantages. Firstly, it simplifies the implementation process and reduces complexity by consolidating multiple suppliers and ultimately saving time. Seamless coordination among all components of the fuel cell system is guaranteed by integrated Balance of Plant (BoP), controller, and piping systems that are provided by SolydEra. The coherent operation of all components assures greater interoperability of the whole propulsion system. Additionally, the delivery of the comprehensive battery container by MAN Energy Solutions, completed with real-time PC, electrical controller, and safety protection system, ensures efficient battery integration. This shift in approach demonstrates the project team's adaptability to the new technology solutions, ensuring the successful completion of the NAUTILUS project.

Highlights of the NAUTILUS project

For the Virtual Process Design Concept of the On-Board Energy System

  • System simulation indicated excellent electrical efficiencies of >60% based on operating conditions.
  • Completion of genset models, development of transient Large Stack Module (LSM) and Battery models, testing against experimental data obtained during the Proof of Concept, with good agreement and use for prediction of the Proof-of-Concept experiments.
  • Identified applicable codes and regulations, IMO safety codes, and integration requirements for different cruise ship designs.
  • The first scalable multi-MW SOFC concept design released, optimizing for high power density compared to current commercial systems.
  • Successfully tested the first version of genset models for technical feasibility with stakeholders.

For the Physical Proof of Concept and Genset Demonstrator:

  • Assembly, delivery and experimental characterization of a Large Stack Module (LSM) of 30 kWe SOFC validating a transient model, Delivery and testing of a Li-ion Battery to validate the model used in the energy management system.
  • Conducted LSM/Battery coupling experiments in the Proof of Concept with the control strategies provided through the energy management unit.
  • Conducted preliminary emissions analysis, emissions characterization initialised and evaluated preliminary results in preparation for emissions measurements at the demonstrator.
  • Realized a unitized control algorithm for the controls of the hybrid test bench in the form of an energy management unit embedded in a specific hardware environment.
  • Definition and execution of SOFC module testing on an inclination pod reflecting static and dynamic inclinations, providing important insights and recommendations into the effect of inclination on the operation of SOFCs.
  • Manufacture, qualification, and installation of SOFC component stacks into the system for the demonstrator. Provision of a list of specifications, technical drawings, and layout for the SOFC cabinet for integration into the demonstrator was completed. Specification and procurement of a battery container from a subcontractor for the demonstrator are in progress.


This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 861647. The project began in 2020, with an amount of 7.9 million euros over 54 months as a part of the Horizon 2020 programme. DLR coordinates the project joined by 15 leading shipping companies, cruise lines, shipyards, shipping authorities and research institutes:

Deutsches Zentrum für Luft- und RaumfahrtChantiers de l'AtlantiqueCarnival Maritime GmbHEcole Polytechnique Fédérale de Lausanne GRANT GarantLloyd's RegisterMAN Energy SolutionsMeyer Werft PapenburgRijksuniversiteit GroningenRheinisch-Westfälische Technische Hochschule AachenSolydEra S.p.A. ItalyDelft University of TechnologyLund UniversityVTT Technical Research Centre of FinlandSolydEra SA Switzerland.

Picture above: Test facility GALACTICA at DLR Stuttgart for system relevant testing of SOFC module, battery and energy management unit. Source: DLR.

This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 861647.

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NAUTILUS is a short for Nautical Integrated Hybrid Energy System for Long-haul Cruise Ships.

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This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 861647.