and by comparing them, identify the most optimised
designs, the ones candidate for implementation.
For this problem, a number of KPIs may be
selected to describe both the economic and
environmental dimensions. In this example, we
further assume that a decision maker selects as the
most appropriate for the ship economy three KPIs,
namely the CAPEX, OPEX to represent costs and
AAB for the revenues. CAPEX measures, in thousand
$, the funds that a ship owner uses to purchase a
vessel from a shipyard, OPEX accounts in thousand $
per year, the ongoing costs that a ship owner pays to
run the ship over a specific period, e.g. typical year of
operation, while AAB represents the revenues and is
the average annual benefits form the ship, measured
in thousand $ per year. The details (formulas, data
parameters) for the estimation of these KPIs are not
mentioned here due to the limited size of the paper.
Accordingly, the environmental savings are described
by EEDI (Energy Efficiency Design Index) and the
NOx and Sox emissions calculated from the technical
specifications of each alternative design.
The values of the above mentioned KPIs appear
in Table 1. In this table, the first design, indicated as
REF, corresponds to the basic ship reference that
participates in the assessment equally with the rest of
the alternative designs.
Table 1: The basic data set.
Desgin CAPEX OPEX AAB EEDI NOx SOx
REF 6582 1.454 5.836 6.8 13.81 3.45
d1 5377.1 1.447 3.494 7.7 12.3 2.26
d2 5751.8 1.507 3.613 3.6 11.46 1.25
d3 5924.2 1.362 5.284 4.5 11.99 2.92
d4 6914.8 1.61 3.856 4.2 11.14 1.96
d5 5432.2 1.328 5.397 4 12.09 3.74
d6 5754.8 1.567 4.728 3.9 14.37 1.98
d7 5650.4 1.6 6.023 3.1 11.01 1.5
d8 5524.8 1.362 3.863 2.9 12.9 2.21
d9 6718.6 1.61 3.8 4 12.09 3.74
d10 7180.9 1.328 3.893 4.4 11.39 1.81
d11 5944.9 1.424 3.875 5.6 14.44 3.75
d12 7056.5 1.575 4.388 4 12.09 3.74
d13 5360.7 1.338 5.879 3.2 11.35 4.98
d14 5412.5 1.297 4.691 6.8 13.99 2.48
d15 6247.4 1.547 3.474 7.7 11.66 3.76
d16 6526.3 1.61 5.157 4 12.09 3.74
d17 5337.8 1.328 4.058 3.4 12.51 2.6
d18 6260.3 1.435 5.165 7.9 11.03 4.43
From inspecting the data in Table 1, we may
notice that a number of alternatives (e.g. d2) have
adequate performance on economy and poor in the
environmental KPIs while for others (e.g. d14) is
vice-versa.
In order to estimate the values of the composite
indicators ECO, ENV, models (1), (2) are applied to
the data set. Before that, a normalization process (see
Section 3.3) eliminates the differences in the scales of
measurement and reverses to positive the values for
the indicators with negative utility such as CAPEX,
OPEX, NOx, SOx. In such an arrangement the two
composite indicators ECO, ENV appear both with
positive utility (the higher the values, the better is the
design). Moreover, for the estimation of the economy
indicator ECO, we considered as most important the
AAB sub-indicator, giving emphasis to the revenues.
Accordingly, for the ENV indicator, the most
important sub-indicator is considered EEDI. This
initial information is implemented to the modelling as
ordinal weight restrictions of type “share” (see
Section 3.2). The values resulted from the model
application for the composite indicators ECO and
ENV, appear in the last four columns of Table 1.
The values of composite indicators ECO, ENV
derived from models (1)-(2) appear in Table 2.
Table 2: The values of the two composite indicators ECO,
ENV obtained by Models (1), (2).
Model (1) Model (2)
Design ECO ENV ECO ENV
REF 0.949 0.708 0.935 0.644
d1 0.796 0.766 0.806 0.797
d2 0.784 0.935 0.788 0.802
d3 0.934 0.858 0.941 0.747
d4 0.747 0.923 0.757 0.894
d5 0.969 0.875 0.970 0.695
d6 0.863 0.788 0.844 0.763
d7 1.000 1.000 0.923 1.000
d8 0.840 1.000 0.855 0.780
d9 0.749 0.875 0.756 0.695
d10 0.791 0.898 0.842 0.908
d11 0.813 0.708 0.827 0.609
d12 0.790 0.875 0.799 0.695
d13 1.000 0.970 1.000 0.687
d14 0.928 0.700 0.936 0.710
d15 0.747 0.802 0.758 0.713
d16 0.863 0.875 0.848 0.695
d17 0.873 0.902 0.885 0.752
d18 0.898 0.839 0.902 0.719
Based on the results presented in Table 2, a
number of remarks are possible. First, focusing on the
results of model (1), several designs appear as
superior (score equal to 1) in one of the two
dimensions. This is the case for designs d7 and d13
on economy (ECO indicator) and d7 and d8 on the
environment (ENV indicator). Only design d7 is the
best in both economics and environment and
presumably this design is suggested as the optimum
that achieves reduction of costs and the best
environmental protection. Scores obtained from
model (2) with common weights are lower that those
from model (1). Consequently, alternative d8 loses its