The Determination of Optimum Ship's Design and Power Prediction Using Spreadsheet Model
The objective of this paper is to describe and evaluate a scheme of engineering-economic analysis for determining optimum ship's main dimensions and power requirement at basic design stage. An optimization designs the problem and is arranged into five main parts, namely, Input, Equation, Constraint, Output and Objective Function. The constraints, which are the considerations to be fulfilled, become the director of this process and a minimum and a maximum value are set on each constraint so as
... constraint so as to give the working area of the optimization. The outputs (decision variables) are optimized in favor of minimizing the objective function. Microsoft Excel-Premium Solver Platform (PSP), a spreadsheet modeling tool is utilized to model the optimization problem. This paper is commenced by the description of the general optimization problems, and is followed by the model construction of the optimization. A case study on the determination of ship's main dimensions and its power requirement is performed with the main objective to minimize the Economic Cost of Transport (ECT). After simulating the model and verifying the results, it is observed that the spreadsheet model yields considerably comparable results with the main dimensions and power requirement data of the real operated ships (tanker). It is also experienced that this kind of optimization process needs no exhaustive efforts in producing programming codes, if the problem and the optimization model have been well defined. The problems in designing ship and marine machinery appear due to numerous considerations that must be taken into account. These problems become even more difficult with the development of the machinery systems on board, in terms of complexity and number of components. These conditions increase the capital cost and the complexity of the design option. Therefore, ship's design and its selected machinery must guarantee that the ship and its machinery will operate with low level of failure, safely and efficiently, with high level of availability and will deliver an optimum rate of return on the capital being employed. In other words, precise ship's main dimension and reliable machinery would therefore be one of the most critical points in achieving reliable ship operation [1, 2] . Thorp and Armstrong  utilized a comprehensive method to select the machinery arrangement for a Panamax-size bulk carrier of 70.000 DWT. Their economic assessment was only focused on two alternatives of slow speed diesel installation and medium speed diesel installation. Some parameters that were included in their study are also taken in our study. One of the major differences with their study is that our study takes the problem since the basic design process which allows the optimization process determines the ship's main dimension and its machinery characteristics within the given constraints. Suich and Patterson  delivered an interesting report concerning the method for minimizing the cost by choosing optimal subsystem of a machinery system. The expected value concept was adopted to select the most profitable system. A probability approach, however, has a weakness in how much the approach can guarantee that the selected assumptions exactly consistent with the real condition. For that reason, our optimization scheme is developed to be able to accommodate input from real data and empirical formulas. This paper proposes an alternative method for optimizing marine designs, particularly in determining ship's main dimension and its power requirement at basic design stage. Spreadsheet modeling is utilized and non-linear programming (hereafter NLP) can express our problem. The Generalizedreduced gradient (hereafter GRG) method can work in conjunction with the NLP problems. Basic diagrammatic concepts of the optimization process and a case study are also given comprehensively. PSP and the basic optimization model In major engineering problems and decision making process, there are only few problems fit with a mono-criterion paradigm. The determination of ship's main dimensions and its machinery power requirement also encounters many constraints and considerations in its synthesized process  . A number of methods are available to solve the multi constraints and multi variables optimization problem such as those are summarized by Rao . Furthermore, The optimization of ship's design can be defined as an attempt to resolve the conflicts of a design situation, in such a way that the variables under the control of the decision-maker take their best possible value. The optimum value is achieved when the working area of the optimization problem is satisfied. Generally, a classic multiple constrained optimization problems can be represented as follows.