Minimizing energy demand for a 15,000 TEU ammonia-fueled container vessel concept

Impact of energy efficiency technologies

Ammonia holds promise as a scalable low-emissions maritime fuel.1 However, the implementation of ammonia fuel poses several challenges for the maritime industry, including in ship design. To help address some of these challenges, the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping (MMMCZCS) and our strategic partner Seaspan have collaborated on a multi-phase project to develop a design for a 15,000 twenty-foot equivalent (TEU) ammonia-fueled container vessel. In September 2023, we published the main output of the project’s first phase: a report that introduced the vessel’s concept design and outlined design opportunities and challenges, with a focus on safety and technical feasibility.2 The initial design from this project was granted approval in principle by the American Bureau of Shipping.3

As part of the first project phase, we identified optimization of the vessel’s energy efficiency as a key area for further development.2 Improved energy efficiency can be seen as a ‘win-win’ that both reduces the vessel’s operational costs and improves sustainability, helping companies meet environmental, social, and governance targets. In simple terms, energy efficiency results in reduced energy demand and thereby reduced fuel consumption. In the context of an ammonia-fueled vessel, these reductions bring several benefits:

Lower operational costs

Reducing fuel consumption through increased energy efficiency translates to lower overall operational costs. This benefit is highly relevant for vessels operating on low-emissions ammonia, which is currently notably more expensive than conventional fossil-based maritime fuels.

Reducing greenhouse gas (GHG) emissions

Although the ammonia molecule (NH3) itself contains no carbon, even low-emissions e-ammonia is associated with some well-to-wake GHG emissions. For example, production and transportation of ammonia fuel generates some upstream GHG emissions.4

Ammonia combustion can also produce the GHG nitrous oxide (N2O) – though available technologies can significantly reduce these emissions.5, 6, 7 Further, ammonia-fueled engines currently require some pilot fuel use for efficient ammonia combustion, creating a source of carbon dioxide (CO2) emissions.8, 9 In summary, reducing fuel demand through energy efficiency complements the use of low-emissions fuels by lowering the vessel’s GHG emissions even further.

Managing the overall demand for limited resources

Production of low-emissions ammonia will need to be scaled up considerably in the coming decades to meet the energy demand from international shipping10 – and other industries also generate demand for ammonia. Reducing individual vessels’ consumption of ammonia means more to go around, especially while production is still scaling up. Furthermore, energy losses during e-fuel production mean that decreasing onboard energy demand can ultimately decrease the upstream demand for renewable electricity by a factor of four.11

Energy efficiency can be improved through both technical and operational means. For this project phase, we chose to primarily focus on onboard energy efficiency technologies (EETs) as a subset of technical energy efficiency measures. Such measures are highly relevant when designing a newbuild vessel. We analyzed the impact of a range of EETs on our design for a 15,000 TEU ammonia-fueled container vessel, with the aim of understanding how to optimize the design’s energy efficiency.

In this report, we share our estimates of expected energy savings from each EET individually, as well as the expected combined energy savings per year based on a defined operational profile. As systems on the vessel are partly interdependent, the combined energy savings are not simply the sum of energy savings from each EET. We also share the results of a high-level cost estimate focusing on hull and propulsion upgrades, as we found that this category of EET offered the greatest potential annual energy savings. Finally, we share some general takeaway messages with relevance for projects seeking to optimize the energy efficiency of a newbuild alternatively fueled vessel design.

Scope and target audience for this report

Our project focused specifically on technology-driven energy efficiency improvements. Operational energy efficiency measures were outside of the project scope.
Our analysis centers on a newbuild ammonia-fueled vessel. Trends from our analyses may have some relevance for retrofit projects, but specific calculations would be required for any given project.
This report will not cover specific equipment suppliers. Our analysis focuses on general trends with respect to EETs.
Considering the variability in costs for both technologies and fuels, we only consider cost trends in this report.
The main target audience for this report is vessel owners and managers in the container segment. However, some of the findings may be adapted to other vessel segments.