Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the floating structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective floating structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the 'typical' size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2-3 m/s. The general arrangement is also conceptualized in this paper.

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The world is being hit by a health crisis by the COVID-19 pandemic which has infected peoples across the globe. The cases of COVID-19 in Indonesia itself continue to increase every day. The transportation sector is one of the sectors that have experienced numbers of direct impacts as a result of large-scale social restriction in form of preventive regulation. Furthermore, this phenomenon causes health agencies to experience difficulties in distributing logistics for handling COVID-19, especially in water areas. In the era of the Industrial Revolution 4.0, various society aspects and industrial processes are digitally connected to increase productivity, especially for COVID-19 treatment and logistic handling. This research was conducted to analyze several proposed monohull-unmanned ship prototypes which are expected to be a proposed solution to assist COVID-19 countermeasure. A series of stability and motion analyses is conducted, then the results are assessed to conclude the best design among the proposed design options. Results of the study indicated that compared to three variations of hull types, design of the Model III has excellent characterisics of ship stability, hull resistance and seakeeping. These analysis parameters are considered as main criteria in the ship’s requirements since patient and logistic have to be transported safely to the designated location according to the given mission in assisting COVID-19 handling and treatment.

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This paper presents a design procedure based on optimization to contrive a floating structure for a commercial scale of OTEC power plant. In the aim to get a safe yet economical floating structure, a commercial oil tanker ship was converted as the plantship. The process was started by defining independent variables, constraints and fix parameters. The independent variables included the velocity of seawater transport and type of oil tanker ship. The next step was breaking down the fix parameters which were kept constant during the iteration process. These parameters were about the general requirements and the necessary equipment to produce 100 MW-net power output. Some constraints were also introduced as permissible borders to determine whether the particular case was acceptable or not. The constraints included the constraint due to provided space, allowed weight, net power output and fluid phenomena on the riser. During the iteration process, a spiral model was developed as analysis guideline. Based on the result of the optimization, it could be concluded that the typical Suez-max oil tanker ship was the best option and the most optimum seawater transport velocity was 3 m/s. Finally, the general arrangements and the base layout design were also conceptualized in this paper.

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The Bánki turbine is a cross-flow turbine with a simple structure that is easy to modify. Changing the turbine's runner geometry is one of the modifications that have an effect on its performance. The goal of this study is to quantify the effect of increasing number of blades and the angle of the blades on the performance of the Bánki turbine. This study was carried out using threedimensional modeling with the ANSYS CFX device and the computational fluid dynamics (CFD) method. The five angles of the blade, namely 10˚, 15˚, 20˚, 25˚, and 30˚, are used to create variations. In addition to the angle factor of the blade, research has been conducted on the number of blades, which are 12 blades, 16 blades, 20 blades, 24 blades, 32 blades, 36 blades, 40 blades, 48 blades, and 52 blades. In a steady-state modeling condition, the applied boundary condition is a water flow velocity of 3 m/s. The results of the CFD modeling are analyzed using a factorial design analysis (FDA). The results indicate that runners with a 15˚ Blade's angle and 40-blade perform best. Results of the factorial design analysis show that the blade angle factor and the number of blades interact.

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