Tidal and wave driven hydrokinetic power in atolls of an amphidromic region in the Pacific Ocean

French Polynesia is located in an amphidromic area of the Pacific Ocean, a region of low tidal ranges. Atolls, ring-shaped islands with internal lagoons that are common to this region, often show strong currents in channels that connect their lagoon to the ocean. This study shows long-term in-situ flow measurements using acoustic-Doppler current profilers that were deployed in the main channels of Manihi and Takaroa, two atolls of French Polynesia, to explore their kinetic energy potential. Despite the low tidal effects on sea levels, flow measurements show strong currents with a semidiurnal behaviour dominated by the lunar constituent. An asymmetry in the ebb and flood currents is observed, and correlation with wave climate indicate that the atolls operate as large wave overtopping devices, increasing the kinetic energy flux through the channel, and extending the ebb flow period. An energetic assessment shows a potential for tidal stream turbines to produce a substantial proportion of the energy demands of Manihi and Takaroa. This energy production would likely have a limited environmental and visual impact, and would allow for a reduction in carbon emissions and reliance on fossil fuels.