Design Optimization of Floating Structure for a 100 MW-Net Ocean Thermal Energy Conversion (OTEC) Power Plant

Abstract

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.

Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia

“…The estimation yields a result that by setting up the lifetime of the cold water pipe of 25 years, the critical velocity of seawater transport is 3.7 m/s. This result is also stated in the previous study [25].…”

“…In the previous study done by the authors, several types of oil tanker ship have been examined to get the best size for the conversion. The size of the plantship was set to be constant based on several types [25]. However, in the real condition, it is merely hard to find the exact size of the plantship.…”

“…The thickness was estimated using the approximation formula for riser of oil and gas exploration [38]. The features of the cold water pipe were adopted here as reported in [13] which are also used in [25]. The cold water pipe (CWP) is made of a fiberglass-reinforced plastic sandwich construction with a laminate density of 4125 kg/m 3 ; the density of syntactic foam of 1015 kg/m 3 ; modulus of elasticity of 13,776 MPa; and flexural rigidity of 2.89 × 10 11 N m 2 .…”

“…The authors and other researchers made an introductory assessment about the most suitable type of oil tanker to be converted as the plantship [25]. Due to lack of the on-site data, the results were roughly focused on the required space and buoyancy without considering the installation of major OTEC system equipment.…”

System Parameters Sensitivity Analysis of Ocean Thermal Energy Conversion

“…Regarding the OTEC research in Indonesia, the baseline design and requirements for the OTEC floating platform were proposed by [6] in 2018. The baseline design was then applied to ship conversion from an oil tanker [7] as the plant ship for 100 MW-net OTEC to minimize capital expenditure by Monte Carlo simulation to yield the optimum size of the plant ship.…”