Efficient simulation for analysis and optimization of a wave energy converter in non-linear random sea states

从随机源获得能量是可再生能源领域的基本问题。除了获得太阳能或风能的可能性外，还有从海浪中获得能量的可能性。因此，机械系统定位在海面上，并且发电机将系统的运动转换成电能。由于波浪能与风能和太阳能相比具有显着高的功率密度，因此它是一种有前途的可再生能源资源。然而，为了从波浪能转换器（WEC）中收获尽可能多的能量，机械系统必须以实现大的动态运动的方式设计。在真实的海洋上，海浪是随机发生的。此外，测量表明，线性波理论不适合于完全表示真实的海洋的行为。因此，WEC必须以这样一种方式设计，即在非线性随机海况下实现大系统动力学。然而，当前用于计算流体-结构相互作用的工具箱需要大量的计算工作来模拟浮体与流体之间的相互作用，并且因此模拟浮体在非线性随机波浪中的运动。该项目的目的是创建和验证一个有效的仿真模型，不仅考虑了WEC的机械部分，而且还考虑了浮体和水之间的非线性随机流体-结构相互作用。所创建的仿真模型用于分析WEC的动力学和WEC在非线性随机海况下获得的能量的量。将所得结果与线性随机海况下的相应结果进行了比较。这些比较的目的是证明使用非线性随机海况的必要性。所使用的WEC是一个机械系统，由一个浮动的圆柱体和一个发电机，已在线性海况的初步研究中进行了检查。发电机从气缸的运动中获取能量。在仿真中分析了系统的行为，并在实验中进行了验证。为了进行实验研究，该研究所拥有一个波浪水槽，可以在其中产生随机和非线性波浪。为了实现大范围水波作用下圆柱体的高速运动，利用仿真模型对WEC的几个系统参数（如圆柱体的半径和质量）进行了优化。此外，控制策略用于增加收集的能量的量。以这种方式，WEC的动力学被优化以从随机和非线性波（当它们出现在真实的海况中时）提取大量能量。

Obtaining energy from a random source is a fundamental problem in the field of renewable energy. In addition to the possibility of obtaining solar or wind energy, there is also the possibility of obtaining energy from ocean waves. Thereby, mechanical systems are positioned on the sea surface and electrical generators convert the motions of the systems into electrical energy. Since wave energy has a notably high power density compared to wind and solar energy, it is a promising resource for renewable energy. However, in order to harvest as much energy as possible from wave energy converters (WECs), the mechanical system has to be designed in such a way that a large dynamic motion is achieved. On real oceans, sea waves occur randomly. Furthermore, measurements have shown that a linear wave theory is not suitable to fully represent the behavior of a real sea. Therefore, the WEC must be designed in such a way that large system dynamics are to achieved in nonlinear random sea states. However, the current toolboxes for calculating fluid-structure interaction require a large computational effort to simulate interaction between floating bodies and fluids, and thus the motion of the floating bodies in nonlinear random waves. The aim of the proposed project is to create and validate an efficient simulation model that not only accounts for the mechanical part of the WEC, but also for the nonlinear random fluid-structure interaction between the floating body and the water. The created simulation model is used to analyze the dynamics of the WEC and the amount of energy gained by a WEC in nonlinear random sea states. The results are compared to the corresponding results in a linear random sea state. These comparisons are intended to demonstrate the necessity of using nonlinear random sea states. The used WEC is a mechanical system consisting of a floating cylindrical body and a generator, which has been examined in preliminary studies in linear sea state. The generator harvests energy from the motion of the cylinder. The behavior of the system is analyzed in simulations and validated in experiments. For experimental studies, the institute possesses a wave flume, in which random and nonlinear waves can be generated. In order to achieve high motion of the cylinder for a wide range of water waves, the simulation model is used to optimize several system parameters of the WEC (such as the radius and mass of the cylinder). In addition, control strategies are used to increase the amount of harvested energy. In this way, the dynamics of the WEC is optimized to extract a large amount of energy from random and nonlinear waves (as they occur in real sea states).