This calculator is a useful tool to visualise the difference in ship performance using alternative fuels compared to conventional HFO fuel. Ship performance is measured in terms of cargo attainment rate (CAR), specific energy (Es), specific cost (Cs), and carbon intensity indicator (CII); which are the ship performance indicators defined per unit of ship deadweight and ship voyage distance.
A total of 10 inputs need to be defined under “MY SHIP” user-defined parameters:
Three types of ships are included which are tanker, cargo ship and container. The figure below shows the ship length (meters) of various types of ships and their categories. Generally, tanker and cargo ship are categorised based on ship deadweight, whereas container is defined based on the ship cargo capacity in twenty-foot equivalent units (TEU).
From the statistics of ship capacity, the largest ship sizes in operation today are 550,000 DWT. Hence, users can drag the slider for deadweight to define the size of their ships.
From the statistics of ship speed, the voyage speed of fleet has been reduced to minimise carbon emissions. In this study, the user can adjust the voyage speed between 5 – 25 knots. This input is important to determine the voyage duration and is required for fuel tank sizing based on the fuel consumption rate. Please note that the voyage speed does not affect the power rating of the ship which is another user-defined parameter.
As derived from the AIS data, majority of ships travel between 4,000 to 11,000 nautical miles (n.m.). The voyage length input is adjustable between 2,000 to 20,000 nautical miles. This input is required for the calculation of voyage duration based on the input of speed. A longer voyage distance consumes more energy and requires more marine fuel to be stored onboard.
This input is required for calculation of total fuel consumption per annum. The default setting for this input is 280 days, considering the days where the ship is being bunkered.
As more alternative fuels are being considered for replacement of the conventional Heavy Fuel Oil (HFO), a detailed assessment was published to compare the various alternative fuel pathways for instance installation of carbon capture technology (HFO(CCS)), liquefied natural gas (LNG), liquefied natural gas with CCS installation (LNG(CCS)), hydrogen, ammonia, and methanol produced from fossil fuel primary energy (BLUE H2, BLUE NH3, BLUE MEOH), electricity produced from natural gas with carbon capture during fuel production (NG-E), biodiesel (BIO-DIESEL), and bio-methanol (BIO-MEOH). As hydrogen and ammonia can be powered by both dual fuel engine (ICE) and fuel cell (FC), users need to select the fuel type and their choice of energy converter.
After defining the fuel type (Parameter 6), users need to select an energy converter for their ship. Please note that the value of rated power which is in unit kilowatt (kw) is the maximum power rating for the energy converter. There are three type of energy converters which are internal combustion engine (ICE), electrical motor (EM), and Proton-exchange Membrane fuel cell in combination with electrical motor (PEMFC & EM). The energy conversion efficiency for ICE, EM, PEMFC & EM are assumed equal to 45%, 92.5%, and 55.5% respectively. This assumption is made based on the data available in the literature and the efficiency of energy conversion could be increased with more research & development. Refer to the paper “A Comparison of Alternative Fuels for Shipping in Terms of Lifecycle Energy and Cost” for more details.
Ships are generally not operated with 100% load; hence users can adjust the engine loading between 0-100%.
Users can check or un-check this parameter. This calculator assumes that an Amine-based post-combustion CCS with a 90% carbon capture efficiency is installed onboard when this parameter is checked. As onboard carbon capture (CCS) is a potential carbon reduction measure for ships powered by fossil fuels such as HFO, LNG, and MEOH, this input is included to study the effect of CCS installation on ship performance.
The quantity of cargoes that can be carried by a ship varies with the type of cargoes as they have varying densities and stowage factors. The figure below shows the general types of cargoes and their stowage factor in unit cubic meter per tons (m3/tons).
The result of assessment is presented under “MY SHIP Performance”. The performance of user-defined ship, “MY SHIP” is compared to the “REFERENCE SHIP”, whereby the “REFERENCE SHIP” is a ship with the same design parameters as “MY SHIP” except for the type of fuel (fixed at HFO) and the energy converter (fixed at ICE).
Using this calculator, the ship performance of “MY SHIP” is compared with “REFERENCE SHIP” in terms of cargo attainment rate (CAR), specific energy (Es), specific cost (Cs), and carbon intensity indicator (CII).
Cargo Attainment Rate (CAR) is a ship performance indicator which is defined as the percentage of cargo attainable by an alternative ship as compared to the cargo attainable by the reference ship, which has 100% CAR by default. CAR can be the ratio of deadweight or volume of “MY SHIP” to “REFERENCE SHIP”, depending on whether the reference ship is a weight-critical or volume-critical ship.
Explanation of the results obtained:
Specific Energy (Es) is a ship performance indicator which is measured in unit kJ/t.nm. Es is defined as the total tank-to-wake (TTW) energy (kJ) consumed by a ship per unit of ship capacity (tons or dwt, t) and voyage distance (nautical mile, nm).
Explanation of the results obtained:
Specific Cost (Cs) is a ship performance indicator which is measured in unit $/t.nm. Cs is defined as the total tank-to-wake (TTW) cost ($) incurred per unit of ship capacity (tons or dwt, t) and voyage distance (nautical mile, nm). The total TTW cost has included both CAPEX and OPEX cost for utilities, energy converter, storage tank, and cost of carbon capture.
Explanation of the results obtained:
Carbon Intensity Index (CII) is a ship performance indicator which is measured in unit gCO2/t.nm. CII is used globally as a carbon rating system for shipping; defined as the total tank-to-wake (TTW) CO2 emission (gCO2) released by a ship per unit of ship capacity (tons or dwt, t) and voyage distance (nautical mile, nm).
Explanation of the results obtained:
Apart from CAR, Es, Cs, and CII, this calculator can also be used to assess ship sizing based on the user inputs for instance ship type and deadweight. The ship dimensions, weight and volume distribution onboard can be estimated.
For different types of ships with the same deadweight, ship dimensions will differ due to the variation of deadweight coefficient values. The typical values are obtained from “Ship Design and Performance for Masters and Mates” which were written by experienced marine engineering consultants. A variation in deadweight coefficient values will result in varied ship displacement, which is a function of ship length (L), breadth (B), draught (T), and ship block coefficient (Cb). Hence, ship dimensions will change with displacement and are estimated based on deadweight and ship type inputs.
This calculator defines the weight distribution onboard of a ship as the sum of lightship mass, cargo deadweight, and non-cargo deadweight. The weight of fuel, energy converter and the additional weight due to CCS installation (including the additional weight allowance for storage of captured carbon dioxide) are included as part of non-cargo deadweight. Based on this definition, the weight distribution of “MY SHIP” is included as part of non-cargo deadweight.
This calculator defines the volume distribution onboard of a ship as the sum of superstructure volume, cargo volume, and non-cargo volume. The volume of fuel, energy converter and the additional volume due to CCS installation (including the space required for storage of captured carbon dioxide) are included as part of non-cargo volume.
