3. Theoretical Background
3.8. Calculating economic feasibility
Arctic navigation is very dangerous and needs money, human forces and strong machinery to deal with cold, wind and ice water. Approximately 20 years ago the concept of Double Acting Ship (DAS) was developed and the first such ship was built. DAS is a type of icebreaking merchant ship designed to run ahead in open water and astern in ice. Such ships can operate independently in severe ice conditions without icebreaker assistance but retain better open water performance than traditional icebreaking vessels (Juurmaa et al., 2001).
Many of double acting ships are using ABB patented Azipod propulsion system. Azipod is a podded electric propulsion unit where the variable speed electric motor driving the fixed pitch propeller is in a submerged pod outside the ship hull, and the pod can be rotated around its vertical axis to give the propulsion thrust freely to any direction. Thus the ship does not need rudders, stern transversal thrusters or long shaft lines inside the ship hull.
Many ice tests not only model but also full scale show superior ice breaking capacity of DAS because of its lower ice resistance supported by pod-propulsion system (Sasaki et al., 2001). The It can be said that DAS has a possibility of saving an operation cost such as fuel oil consumption, ice breaker escort fee etc.
The saving in costs can make the use of such ships feasible for transit international shipping at the NSR, despite higher build price of DAS. During finding out the answer it is needed to calculate environmental impacts and operational costs for DAS and for usual containership, which sails through Suez Canal, and then the results should be compared.
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Figure 3.4: Evaluation of economy and environmental impact (Sasaki et al., 2001)
Total required time to sail in a route depends strongly on the climatic conditions.
Therefore, the total required time to sail is not the same for one season to another season. For example, total required time in the winter season is longer compared with in the summer season due to ice.
Total required time to sail in a route is assumed summing up of required time in water condition, required time in ice condition and required time in harbor, which can be expressed as
(Sasaki et al., 2001)
Where, TOW is required time in water condition, TIC is required time in ice condition, and TH is required time in harbor.
The length of the route between two points can be calculated as a length of a straight line between them, but as the total route is not a straight line, it should be divided into smaller parts, that will be assumed as straight lines, where the speed of the ship is constant. Thus the total time of the route can be calculated as following:
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Where RAB is a function, which returns the length for each i straight line with constant speed, and VAB is returning the speed at i part of the route. This formula means, that it is needed to take the length of each straight line AB and divide it on the speed at that line, thus there is a sum of times needed for completing each straight line.
The time, needed for the whole route, if the route is partly covered with ice, can be calculated as following:
where T is time, Sice is the length of ice-fields, Sopen is the length of the area with open water, Vice is the speed of the vessel in ice water and Vopen is the speed за the vessel in open water.
According to Sasaki (2001), the calculation of required power is necessary for estimation of operational variable costs, which includes the costs of fuel and lubricating oil consumed, and for estimation of environmental impact. Required power depends on the ship bow shape a lot, because it determines the resistance of the ship, and can be calculated, using the following formula:
Where EHP is effective horse power and RT is resistance of ship, and η is the coefficient of efficiency. All the values can be obtained from a model test in open sea condition.
As previous researches have shown, the wave resistance of DAS is approximately 10%
higher than of an ordinary ship, but the propulsion efficiency of ABB Azipod aggregates is a little bit lower, than the efficiency of standard propulsion system. In spite of that fact, Increment ratio of cargo volume by re-arrangement of engine room will be 10-30% according to ABB Azipod references.
Talking about financial side, it is necessary to mention that a company, which will decide to buy ships for transportation through NSR, will not probably have enough money to pay the while price of the ships immediately, thus it will have to take a loan. When a loan is taken, the company
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will pay certain sum annually to cover it and the interest rate. It is needed to calculate the amount of annual payments and total sum that will be paid to the bank.
The most typical loan payment type is the fully amortizing payment in which each annual rate has the same value overtime.
The fixed monthly payment P for a loan of L for n years and an annual interest rate c is (Guttentag, 2009):
3.9. Summary
To summarize, it was emphasized that freight transport is a key of the value chain in manufacturing and the significance of this key can be measured. The main indicators of such measurement are transport demand and elasticity. Both of them are influenced on the calculating of the economic feasibility of the given transport route with the given type of transport. It was discussed the special features of using the double-acting ships as the primary type of vessel. This characteristic put the specific seal on the research, as the theoretical frame had shown.
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