Abstract
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.
Highlights
Ocean thermal energy conversion (OTEC) is a technology which utilizes the temperature difference between warm surface water and cold deep water
Monte Carlo simulation is used to vary the possible size of the oil tanker ship and for each size of the proposed plantship, the constraint satisfaction method is employed to optimize the OTEC system
Suezmax type is acceptable for case two, but compared with the first case, the required breadth of the plantship is larger. This is because in case two, the heat exchanger is arranged parallel to the seawater tanks which makes the required breadth of the plantship larger
Summary
Ocean thermal energy conversion (OTEC) is a technology which utilizes the temperature difference between warm surface water and cold deep water. With the surface temperature of about 25 °C and deep cold water of 5 °C, reduced by the efficiency of OTEC equipment, the efficiency of the Rankine cycle of this system was only about 3–5% [2]. Ammonia was selected as the working fluid due to its low boiling point which allows it to transform into gas and liquid phases with a small temperature difference [3, 4]. With the state-of-the-art OTEC system technology, the Rankine cycle efficiency of the OTEC system is predicted to be still around 6–7% [5]. The necessity of very high capital investment is a reason why this technology gets stuck on the pilot project [6]
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