Numerical simulations for behavior of discharged water from Ocean Thermal Energy Conversion plant

Abstract

The present study focuses on the influence of the discharge water from Ocean Thermal Energy Conversion (OTEC) plant of demonstration scales by numerical simulations. MEC-NEST is employed for calculating hydrodynamic processes, and a nested grid system is used to calculate the phenomena near the OTEC plant with finer grid. A lower trophic ecosystem model is embedded on MEC-NEST to analyze behaviors of nutrients and planktons. The simulations were carried out for 100MW offshore plant and 1MW onshore plant. For the offshore floating-type plant case, the discharged water from the plant descends as being mixed with surrounding seawater and horizontally spread at the depth where the density of mixed water becomes equal to that of surrounding seawater. Changes of water temperature and water qualities such as nutrients and planktons concentrations due to the discharged water aren't significant because it is diffused rapidly in the ocean current. For the onshore plant case, the impacted area is rather limited in the vicinity of discharged point because of the smaller discharge rate from the plant. It is also predicted the changes of water qualities becomes smaller when the discharge point is set at deeper location.