Oceanographic Survey for Installation of OTEC Plant in Okinotorishima (Assessment of seawater temperature, salinity, and dissolved oxygen from 2006‒2023)

Abstract

In order to implement Ocean Thermal Energy Conversion (OTEC), it is necessary to secure the stable temperature dierence between surface seawater and deep ocean water, and many oceanographic surveys have been conducted to select ocean areas suitable for OTEC introduction, not only in the seas around Japan, but also in other countries around the world. However, long-term oceanographic survey data for the Okinotorishima area, a strong candidate for OTEC, are not yet available. In this study, a long-term oceanographic survey was conducted to lay the groundwork for evaluation whether the Okinotorishima area is suitable or not for the installation of an OTEC plant. The survey items were the vertical proles of seawater temperature, salinity, and dissolved oxygen at each station, as well as their changes over time. The results indicated that the temperature dierence between surface seawater and deep ocean water, which is the most important item for OTEC, almost exceeded 20℃ that would allow an OTEC to realize except January and February. It became the groundwork to organize salinity graph etc. which are sources of calculating the heat transfer coecient and pump powers.