The The Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping (MMMCZCS) presents key considerations for retrofitting ships for operation on methanol.
According to MMMCZCS’ “Vessel design considerations for methanol retrofits” report, methanol offers a technically feasible, cost-effective, and manageable transition fuel with fewer technical barriers towards installation and safety challenges compared to other alternative shipping fuels, such as methane or ammonia. While retrofitting to methanol is technically feasible for most vessel types, there are a number of considerations and constraints that need to be accounted for.
Design and space constraints
The design and space constraints related to retrofitting ships for methanol fuel need to comply with IMO IGF Code and MSC 1621 regulations. However, the IBC Code requirements for tank arrangements could be used to justify deviations, supporting alternative design approaches.
Methanol tank options
The methanol tank type and material should reflect the vessel’s specific operational needs and budget constraints. Independent tanks offer simple retrofits, while integral tanks maximize fuel endurance with minimal structural changes, and portable tanks allow for flexible and rapid bunkering. Stainless steel provides longevity with higher upfront costs, while zinc-silicate-coated steel offers a budget-friendly alternative with more intensive preparation requirements.
Tank location considerations
The choice of methanol tank location must balance installation ease, stability, capacity, and cost. Open deck tanks offer simplicity and quick retrofitting, while cargo hold tanks improve stability but reduce cargo space, and double-bottom/side/topside tanks maximize capacity while maintaining cargo volume but involve complex preparation.
Bunker station and gas freeing requirements
The bunker station design should permit methanol bunkering safely and efficiently with a vapor return fitted so venting is not required and should support safe gas freeing for dry docking. Designing the tank size and position is critical and requires a balance between endurance, bunkering frequency, and cargo capacity. A comprehensive review is required to select the tank size that considers the vessel’s expected operational profile and endurance.
Optimizing cargo and tank capacity
Options to optimize cargo and tank capacity exist, such as lengthening the vessel, using ballast tanks as cofferdam or fuel tanks, and potentially the removal of the cofferdam space altogether. However, these solutions require rigorous design and planning.
Challenges in methanol fuel conversions
Methanol fuel conversions are complex, requiring strong management, proficient engineering, and careful pre-planning to keep the agreed budget, quality, and schedule. Shipyards must be capable of handling specialized equipment procurement, electrical work, and strict coating procedures. Safety standards for methanol handling and collaboration with engine manufacturers are crucial for successful integration and commissioning, while prefabrication can significantly reduce downtime if thoroughly planned.
