Effects of ocean thermal energy conversion systems on near and far field seawater properties—A case study for Hawaii

Abstract

In light of renewed interest and efforts in the development of ocean thermal energy conversion (OTEC) systems with a vision to provide mankind with a long-lasting energy resource, the potential environmental impacts of this technology should be considered from the perspective of sustainability. As an important step toward such a goal, we examine effects of OTEC effluent discharge on the physical aspects of the ocean environment near a Hawaiian Island in the North Pacific Ocean. We use modeling tools comprised of a mixing model that predicts the near field dilution of effluent plumes and a high-resolution ocean circulation model that simulates the dispersion of effluent in the far field. Numerical experiments are conducted to explore factors that influence effluent dispersal. We find that OTEC thermal resource is favorable and stable at the chosen location for the time period experimented. For a given OTEC design, the effluent discharge settles at a depth sufficiently far from the depths of discharge or intakes, and becomes dispersed quickly away from the site by highly variable ocean currents. Changes in ocean stratification and flow field are negligible for one OTEC device but are notable when multiple OTEC devices are present. These changes do not persist beyond 2 weeks after switching off OTEC activity.