Reducing risks and costs of in-stream tidal energy using multi-scale computational fluid dynamic simulation

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Ocean renewable energy in the form of tides, waves and offshore wind is one of the most abundant, but relatively untapped, renewable energy sources available. Specifically for tidal energy, recent interest has focused on the development of in-stream tidal energy converters that transform kinetic energy from fast flowing tidal steams to electricity. In Canada, 190 potential sites have been identified with sufficient power to meet the annual electricity needs of 30.6 million Canadian households. Specifically, Minas Passage, located in the Bay of Fundy, is considered one of the world's best tidal energy sites and it has been estimated that this single site could provide sufficient electricity to power 1.4 million Canadian households. With such potential, it is surprising there are only a limited number of tidal turbines operating worldwide and only one turbine currently deployed in Minas Passage. The industry has admittedly progressed slower than anticipated, but now hovers at the edge of commercialization. Global installed ocean renewable energy doubled in 2017 and installed in-stream tidal energy increased to 17 MW. Slow industry progress has been largely due to high project costs and risks because turbines must operate in harsh energetic environments with site-specific turbulence. This creates fluctuating forces on tidal turbine blades and support structures, degrading turbine performance and shortens their lifespan. The US Department of Energy has stated that developing a thorough understanding of turbulence is a critical step to designing durable devices and accelerating the pace of technology development, leading to a significantly lowered cost of energy, similar to what was achieved in the wind industry. An additional challenge has been assessing the impact of these devices on the local environment, in particular, the effects on fish and marine mammal populations and sediment transport. This has resulted in slow social acceptance of the tidal energy industry in Canada. The objective of this research is to develop a multi-scale high-fidelity computational fluid dynamic tool that simulates in-stream tidal turbines in a realistic ocean environment. This software will then be used to quantify the impact of environmental turbulence on the turbine and the impact of the turbine on the turbulent environment. Emphasis will be place on identifying how environmental turbulence affects turbine performance and durability, while also quantifying how the presence of the turbine alters the turbulent flow characteristics, ambient noise levels, and local sediment transport. This will facilitate the in-stream tidal energy industry in Canada by providing developers with the knowledge required to reduce project risks and costs, while simultaneously determining the appropriate scale of tidal energy in the Bay of Fundy that is socially acceptable and environmentally compatible.