In 2016, the International Maritime Organization (IMO) decided on global regulations to reduce sulphur emissions to air from maritime shipping starting 2020. The regulation implies that ships can continue to use residual fuels with a high sulphur content, such as heavy fuel oil (HFO), if they employ scrubbers to desulphurise the exhaust gases. Alternatively, they can use fuels with less than 0.5% sulphur, such as desulphurised HFO, distillates (diesel) or liquefied natural gas (LNG). The options of lighter fuels and desulphurisation entail costs, including higher energy consumption at refineries, and the present study identifies and compares compliance options as a function of ship type and operational patterns.The results indicate distillates as an attractive option for smaller vessels, while scrubbers will be an attractive option for larger vessels. For all vessels, apart from the largest fuel consumers, residual fuels desulphurised to less than 0.5 % sulphur are also a competing abatement option. Moreover, we analyse the interaction between global SOX reductions and CO2 (and fuel consumption), and the results indicate that the higher fuel cost for distillates will motivate shippers to lower speeds, which will offset the increased CO2 emissions at the refineries. Scrubbers, in contrast, will raise speeds and CO2 emissions.

In 2016, the International Maritime Organization (IMO) decided on global regulations to reduce sulphur emissions to air from maritime shipping starting 2020. The regulation implies that ships can continue to use residual fuels with a high sulphur content, such as heavy fuel oil (HFO), if they employ scrubbers to desulphurise the exhaust gases. Alternatively, they can use fuels with less than 0.5% sulphur, such as desulphurised HFO, distillates (diesel) or liquefied natural gas (LNG). The options of lighter fuels and desulphurisation entail costs, including higher energy consumption at refineries, and the present study identifies and compares compliance options as a function of ship type and operational patterns.The results indicate distillates as an attractive option for smaller vessels, while scrubbers will be an attractive option for larger vessels. For all vessels, apart from the largest fuel consumers, residual fuels desulphurised to less than 0.5 % sulphur are also a competing abatement option. Moreover, we analyse the interaction between global SOX reductions and CO2 (and fuel consumption), and the results indicate that the higher fuel cost for distillates will motivate shippers to lower speeds, which will offset the increased CO2 emissions at the refineries. Scrubbers, in contrast, will raise speeds and CO2 emissions.

This paper outlines a generic method for quantifying changeability level, to support better decision making in the early stages of design of engineering systems. Changeability represents the ability of a system to change form, function, or operation, and is a collective term for characteristics such as flexibility, adaptability, and agility. Quantification of changeability level must not be confused with valuation of changeability. The level of changeability in a design is essentially under the control of the designer. Two aspects of changeability are discussed, the first being how to structure changeable design alternatives using the Design for Changeability (DFC) variable. The DFC variable represents combinations of path enablers built into a design. Path enablers are characteristics of systems enabling them to change more easily. The second aspect is to quantify the level of changeability for a given design alternative, based on change cost and time. For the latter, we propose two measures for quantification: (1) bottom-up, measuring the reduction of cost and time enabled for each relevant change, and (2) top-down, measuring the span of change opportunities at given cost and time thresholds. A case study of a ship is presented to demonstrate the proposed generic method. K E Y W O R D S changeability, flexibility, systems design, uncertainty 80

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This paper investigates technical performance, acquisition cost and flexibility level for reconfigurable offshore ships. An offshore ship can be configured with various types of equipment; thus, its base structure constitutes a platform from which several end ship design configurations can be derived. A ship with equipment retrofit flexibility will typically have excess stability, deadweight and deck area to ensure physical compatibility. However, there are complex system interactions that need consideration, such as the effects of flexibility on cost and performance. The level of flexibility is quantified using filtered outdegree based on a tradespace network representation of the system. Technical performance is measured in terms of capability, capacity and operability, where a multi-attribute utility function is used to aggregate the total performance for comparison. Findings indicate that increased platform flexibility does increase capacity, but comes at a complex compromise with operability as resistance is increased, and roll periods become unfavorable due to high accelerations.