Numerical modeling of Maranhão Gulf tidal circulation and power density distribution

Abstract

Marine resources are outstanding among renewable energy for their wide occurrence and diverse possibilities of exploitation. The tidal resource can be harnessed by the use of both potential (sea level) and kinetic energy (tidal currents). Maranhao coast presents one of the largest tidal ranges and strongest currents on Brazilian coastline, providing a good source of renewable energy. A 3D hydrodynamic model is implemented to numerically simulate the tidal circulation in the Maranhao Gulf so as to examine the tidal behavior and associated energy distribution. Amplitudes and current speeds are substantially increased by the estuary’s geomorphology and the shallow bathymetry. M2 tidal component presents the highest amplitudes among the tidal constituents, being the most energetic. Spring-neap cycle constitute an important factor in energy assessment due to their significant difference in power density and exchanged water volume between estuary and continental shelf. Maximum current velocities of 3 m s−1 are found around Medo Island, where tidal range can reach nearly 5.5 m. Three potential regions are located within the Sao Marcos Estuarine Complex, presenting surface velocities ranging from 1 to 2.15 m s−1 and power density as high as 5 kW m−2. The estuary is long and presents significant variations of tidal phase that allows a geographical disposition of turbines in order to lower the downtime.