Comparative Analysis of Emissions and Fuel Costs in Methanol Retrofitted Crew Transfer Vessels

The maritime sector is a significant contributor to global greenhouse gas (GHG) emissions, accounting for approximately 3% of total emissions. Retrofitting vessel propulsion systems for alternative, lower carbon fuels such as Methanol is thought to be a promising approach to assist in decarbonisation of this sector. However, retrofitting requires potentially complex propulsion system modifications along with shore-side and supply chain infrastructure upgrades. As such, the viability of a proposed approach requires careful analysis of costs and benefits (in terms of CAPEX/OPEX) around technology deployment and fuel costs/requirements. Additionally, assessment of the regulatory implications of retrofitting along with estimates of emissions reduction potential are required, to evidence viability and encourage stakeholder buy-in. To ease this analysis, data-driven analytical tools are gaining traction to support technical performance simulations and emissions estimation. This paper investigates data-driven emissions modelling and fuel cost quantification for Methanol Retrofitted Crew Transfer Vessels (CTVs). A calibrated model of a novel electrified propulsion system driven by a Methanol turbogenerator is first obtained for a typical CTV, and Boeing fuel flow two and P3T3 methods are then deployed to assess nitrogen oxide (NO), carbon monoxide (CO), and hydrocarbon (HC) emissions for typical vessel use cases. Data from the existing CTV Diesel propulsion system is used for comparative baseline. Results indicate a significant reduction in CO and HC emissions, with unchanged NO, but with an approximate doubling of fuel volume requirements. The latter may be compensated by weight reductions for removing mechanical linkages and prop shafts during retrofitting. Fuel cost increases are small, and in fact provide for overall reductions when Carbon tax is accounted for. It is concluded that the methods described provide promising insights and applicability for decarbonisation in real-world maritime operations.