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

海洋可再生能源以潮汐、波浪和海上风能的形式存在，是最丰富但相对未开发的可再生能源之一。特别是潮汐能，最近的兴趣集中在开发流内潮汐能转换器，将动能从快速流动的潮汐蒸汽转化为电能。在加拿大，已确定的190个潜在地点有足够的电力满足3060万加拿大家庭的年电力需求。具体来说，位于芬迪湾的米纳斯通道被认为是世界上最好的潮汐能站点之一，据估计，这个站点可以为140万加拿大家庭提供足够的电力。有了这样的潜力，令人惊讶的是，全世界只有有限数量的潮汐涡轮机在运行，目前只有一个涡轮机部署在米纳斯海峡。诚然，该行业的发展速度比预期的要慢，但现在正徘徊在商业化的边缘。2017年，全球海洋可再生能源装机容量翻了一番，潮汐能装机容量增加到17兆瓦。行业进展缓慢主要是由于项目成本和风险高，因为涡轮机必须在恶劣的能量环境中运行，并伴有特定地点的湍流。这会在潮汐涡轮机叶片和支撑结构上产生波动力，降低涡轮机性能并缩短其使用寿命。美国能源部表示，深入了解湍流是设计耐用设备和加快技术发展步伐的关键一步，从而显著降低能源成本，类似于风能行业所取得的成就。另一项挑战是评估这些装置对当地环境的影响，特别是对鱼类和海洋哺乳动物种群以及沉积物运输的影响。这导致加拿大社会对潮汐能产业的接受缓慢。本研究的目的是开发一个多尺度高保真计算流体动力学工具，以模拟现实海洋环境中的流内潮汐涡轮机。然后，该软件将用于量化环境湍流对涡轮机的影响以及涡轮机对湍流环境的影响。重点将放在确定环境湍流如何影响涡轮机的性能和耐久性，同时也量化涡轮机的存在如何改变湍流特性、环境噪声水平和当地沉积物运输。这将为开发商提供降低项目风险和成本所需的知识，从而促进加拿大的潮汐能产业，同时确定芬迪湾潮汐能的适当规模，这是社会可接受的，也是环境相容的。

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.