Decarbonising maritime transport through route optimisation
Ship weather routing, which involves suggesting low-emission routes, has the potential to help decarbonise maritime transport. However, the quantitative impacts of this approach are still being fully explored. New developments in the graph-search VISIR-2 (discoVerIng Safe and effIcient Routes) model led by the CMCC’s Gianandrea Mannarini provide a step in the right direction.
The international shipping industry is estimated to account for approximately 2% of energy related CO2 emissions which makes decarbonization of this sector a key challenge in global efforts to slow down climate change. However, understanding how this can be done is not always straightforward as decision makers often lack the tools needed to analyse the true impacts of individual policies and decisions.
The open-source VISIR-2 (discoVerIng Safe and effIcient Routes) model, developed by a team of international researchers led by the CMCC’s Gianandrea Mannarini, assesses if and how voyage optimization can contribute to this ambitious goal.
“VISIR-2 can be applied to green corridors to save costly low-carbon fuels, generate reliable training datasets for future AI models, and serve educational purposes for ship officials, mariners, and beginner sailors,” explains Mannarini.
Thousands of optimal routes for varying departure dates were computed, returning potential CO2 savings for a ferry and route duration reductions for sailboats by considering factors such as waves and sea currents.
Optimal ferry routes from Porto Torres (Italy) to Toulon (France) considering both waves and currents. All northbound CO2-optimal routes in 2022 (for various engine load values) are presented, with the route colour indicating the departure month. Source: Mannarini et al 2024
“The VISIR-2 model is versatile regarding vessel type, and once its performance curve is established, it can also be applied to larger vessels such as container ships and bulk carriers,” explains Mannarini who also emphasised how the Python-coded VISIR-2 model has come with numerous technical innovations.
The CMCC designed and developed the VISIR-2 model from scratch, integrating naval architecture contributions from the University of Genoa (for sailboats) and the University of Zadar in Croatia (for a ferry). The work was funded by several European projects, including the CMCC-led Italy-Croatia Interreg GUTTA.
“Five years ago, when the work on VISIR-2 started, there were no open-source, Python-coded ship routing models available,” explains Mannarini. “We aimed to close this gap by providing an objective means of evaluating how much ship routes could be optimised and how the outcomes depended on the underlying hypotheses of the numerical model and the input data used. In doing so, we leveraged our previous experience with the MATLAB-coded VISIR-1 model.”
“Eventually, the Clydebank Declaration in 2021, the inclusion of shipping in the EU-ETS, and the revised IMO greenhouse strategy – both in 2023 – are testaments to the ongoing efforts of regulatory bodies and the industry to accelerate the decarbonization of shipping, and these milestones encouraged our developments. I believe that a full-featured and validated numerical model, shared in a simple and robust way such as VISIR-2 is, can be a valuable contribution from the R&D community to address the challenge of decarbonisation of shipping.”
For more information:
Mannarini, G., Salinas, M. L., Carelli, L., Petacco, N., and Orović, J.: VISIR-2: ship weather routing in Python, Geosci. Model Dev., 17, 4355–4382, https://doi.org/10.5194/gmd-17-4355-2024, 2024