For simplification reasons, costs that appear during any year are said to be paid by the end of that year. Therefore, the costs of planning and design will need to be discounted too, although they are the first costs to appear.
11. SUMMATION OF COSTS AND BREAK- EVEN ANALYSIS
The accumulated costs over the entire life of the ferry are presented in the following chart. The break-even points between steel and composite (4 years) and between aluminium and composite (12 years) are marked in figure 7.
The break-even between steel and aluminium is reached right after the beginning of the operation, as the costs for planning, design and production of the steel vessel are only slightly smaller than those of the aluminium vessel.
12. CONCLUSION
The planning and design costs show quite an even picture for the three versions with a slight advantage for the composite craft. The expectation of the conceptual formulation, that steel is the most economical material from a pure manufacturing point of view, is confirmed within this study. However, the inclusion
of the
machinery nearly balances the production costs of the investigated steel and aluminium ship. Due to the high material prices the composite ship is the most expensive alternative in the production phase, which contains
100 150 200 250 300 350 400
50 0 0 5 10 Steel 15 Years Aluminium Composite Figure 7. Accumulation of costs 20 25 30
engineering, material
and manufacturing costs. The
major part of the entire life cycle costs stem from the operation and maintenance. The steel version needs owing to its heavier weight additional machinery, what raises both fuel consumption and the maintenance costs. The major advantage of the composite version is the lower maintenance costs for the hull structure. Revenues and costs of the scrap do not significantly affect the life cycle costs of a ship.
The calculation indicates that the composite version is definitely the most economical option. The accumulated costs of the steel version exceed those of the composite version after only 4 years (2 years of operation). In the same perspective, the aluminium version tops to composite version after 12 years (10 years of operation).
The distribution of energy consumption onto the three ferries shows the highest energy consumption for the steel version, as expected. More than 99.5 % of the consumed energy over the entire life span of all versions comes from the operational
fuel consumption, as
illustrated in figure 8. The investigated aluminium version possesses slightly smaller energy consumption compared to the composite version. This difference stems from the energy consumption of material production, where carbon fibre has the highest energy rate per unit.
The well-optimised aluminium version possesses slightly smaller energy consumption than the composite ship. This is due to the carbon fibre production, which is high energy consuming. A structural composite version can change this order.
optimisation of the
Aluminium - composite
Steel - composite
B-8
©2008: Royal Institution of Naval Architects
M€
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