7. OPERATION AND MAINTENANCE COSTS
The operation costs consist of the fuel costs only, when other running costs are expected to be identical for the three concepts. The specific fuel consumption is given in table 6.
Table 6 Specific fuel consumption of gas turbine [12] and diesel engine
Power of GT
[kW]
100 % 22000 95 % 20900 20 % 4400
Fuel
consump. GT
[g/kWh]
232 6500 234 5850 394 1300
Power of diesel [kW]
Fuel
consump. diesel
[g/kWh]
210 215 340
The above figures combined with the operation profile presented earlier result in the annual fuel consumption presented in table 7.
Table 7 Annual fuel consumption per gas turbine and diesel enging Operation profile
Gas turbine Time
Annual running hours
% of max. power
(kW)
Annual (tons/ year)
19641 (kW) 3 % 133 100 % 22000 680 6500
Maintenance costs for the outfitting are irrelevant for this comparative investigation,
since they differ
within
marginal borders only. Since the maintenance costs are spread over the operating lifetime, they need to be discounted back to the base period. This is fully described in [1]. Herein, the annual costs are listed and summations thereof are based on current prices.
Based on experience at Aker Finnyards the maintenance costs of the machinery are estimated to be 100 US$ per running hour for each gas turbine and diesel engine.
An estimation of annual maintenance costs of the hull structure is
of various national a more difficult issue. The presented
mathematical formulation is of course a crucial simplification, but it might be the only way to compare the three versions in this perspective. All estimations are based on the experience
and
international ferry operators. For confidentiality reasons the companies as well as the names of their ferries are not disclosed in this paper.
Diesel engine
Annual (tons/ year)
82 % 3641 95 % 20900 17806 5850 4580 15 % 666 20 % 4400 1155 1300 Total 4440
182 294
5056
The used fuel is Marine Gas Oil (MGO), ISO 8217-F- DMA. The fuel price is very variable, depending on the actual market situation, political issues, port of refuelling and other circumstances. The cost assumed for this study is 233 US$/ton, or 207 €/ton [13].
Table 8 Total annual operation costs Cost element
Steel (M€)
Operation of two gas turbines
Operation of two diesel engines
Annual operation, total
Operation, 25 years of operation, at current prices total
8.
9.14 2.35
11.49 287.19 MAINTENANCE
In the course of this study only maintenance costs of the machinery and the
hull structure are considered.
Aluminium Composite (M€)
(M€) 9.14 9.14 9.14 9.14 228.40 228.40
For the steel hull, the annual maintenance costs are 0.6 M€ in the first years of operation. The aluminium hull with costs of 0.7 M€ per year is said to be slightly more expensive. The composite hull
is less expensive; its
maintenance costs are approximately 15 %, i.e. 0.10 M€ of that of the steel hull. Additionally, maintenance costs of a metallic structure will increase with the years of operation. The estimated simplification for this purpose is a constant cost for the first 15 years of operation, and a linear increase of the cost for the following 10 years. At year 25 the costs will be doubled the amount of the initial costs. This increase does affect both the steel and aluminium hull, but not the composite hull.
Table 9 Total maintenance costs Cost element
Steel (M€)
Machinery, total (4440 running hours/year) 47.89
Hull structure, total
Maintenance, total
17.70
Aluminium Composite (M€)
(M€)
23.95 20.65
65.59 44.60
23.95 2.40
26.35
The estimation of the annual maintenance costs is a crucial issue, as mentioned earlier. It affects the total LCC of the versions in a critical way, which is why extra attention must be paid on its uncertainty. This is fully discussed in [1].
9. DISPOSAL COSTS
The disposal of large structures are a very complex process. Its main steps are dismantling, cutting and crushing. Figure 4 illustrates the steps in the preparation semicircle for plastic materials but is valid for metals too
©2008: Royal Institution of Naval Architects
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