The off-design performance analysis of the 1MW OTEC turbine for the demonstration and Kiribati

Abstract

Recently, researches on the ocean thermal energy conversion (OTEC), which is one of power plants using marine energy, are actively conducted in Korea, USA, Japan, France and so on. In Korea, KRISO(Korea Research Institute of Ships and Ocean Engineering) will demonstrate a world·s highest capacity 1 MW OTEC plant this September in the East sea. Since the turbine of this plant is designed based on Kiribati condition, the East sea test condition corresponds to the off-design condition. Therefore, the prediction of the off-design turbine performance is required prior to the demonstration. To predict and analyze the performance of the turbine, the CFD analysis is carried out using the temperature data of Guryongpo buoy in August 2018. Numerical analysis is performed using single phase R32 refrigerant after the grid dependency test. An analysis with four different meshes is performed and the smallest number of grids (1,131,196 total nodes) which is independent on the number of grids is chosen. Also, following conditions are chosen for the simulation : SST turbulence model, periodic condition for the single nozzle and rotor simulation, mixing-plane interface and inhomogeneous mixture model. In the closed cycle-OTEC system, two-phase flow should be adopted in CFD analysis because the refrigerant pressure at the turbine exit can be lower than its saturated pressure. The simulated result shows that decreasing trend o