About the Influence of Density-Induced Flow on Tidal Stream Power Generation in the Sunda Strait, Indonesia

In recent years, assessments to evaluate the potentials of tidal current energy have been performed for many regions of the world. However, often for the sake of simplicity and because only tidal currents were of interest, density gradients due to salinity or temperature variations were neglected in simulations. This approach might be highly misleading in domains where flow conditions are strongly affected by the regional excess of freshwater supplied by ocean currents, such as Indonesian Throughflow. In this paper, the results of the investigation of the impacts of density-induced flow on tidal stream power generation in the Sunda Strait in Indonesia are summarized. Current speeds in the strait reach about 2-3m/s and total extractable power from tidal currents is exceeding around 300MW. A high-resolution, three-dimensional flow model providing sufficient spatiotemporal coverage has been developed for simulations. The model has been forced by the tide only and by the tide combined with the density gradients to capture the impacts of density-induced flow via comparison. Fixed layers in the depthwise direction were preferred in the model for the accuracy of the vertical distribution of salinity and temperature. Tidal forcing was extracted from TPXO Indian Ocean Atlas (1/12° regional model). To determine salinity and temperature at the open sea boundaries, models were nested into HAMSOM, the Hamburg Shelf Ocean Model developed in the Institute of Oceanography at the University of Hamburg. Results revealed the impacts of density-induced flow on tidal stream power generation during both northwest and southeast monsoon seasons of the region. Up to 100% increase in current speeds has been observed in the strait due to the density gradients, which leads to a more than three-fold increase of the kinetic power. It was also found that the energy hotspot becomes significantly larger, and the core of the current gets displaced due to the variations in density. The findings may help us to understand the importance of a holistic modelling approach in future resource assessments. Especially today, in the commercialization stage of tidal current energy, resolving flow fields with better precision is of utmost importance for the optimization of tidal farm configurations and efficient use of the resources of marine renewable energy.