Modeling and Control of Novel Variable-Shape Converters for Natural Harvesting of Ocean Wave Energy

这项研究将为可再生海洋波浪能收集提供新的知识，促进科学进步和国家繁荣。海洋波浪能转换器捕获波浪能并将其转换为电力。据估计，总的理论波浪能潜力超过美国目前的电力年需求。通常需要复杂的波浪能转换器来有效地捕获波浪能，因此与其他可再生能源相比，从波浪转换的电力的成本很高。该奖项支持基础研究，以提供开发波浪能转换器所需的知识，以较低的成本产生电力。几乎所有现有的波能转换器都使用固定形状的刚性体（例如，浮标）。该项目将开发一种新型的可变形状浮标波浪能转换器，其中浮标的形状不断变化，就像水母一样，以有利的方式改变浮标周围的波浪场，以增加单元的捕获功率。因此，这项研究的成果将有利于美国的经济和社会。本项目将教育与研究相结合，通过普及教育，提高高中生对海浪能转换概念的认识，对社会产生积极影响。传统的刚性浮标波浪能转换器除了通常从动力输出装置获得的阻尼控制力外，还需要在浮标上施加类似弹簧的控制力。这种类似弹簧的控制力意味着该单元应该提供无功功率;也就是说，它应该能够不时地将功率投入海洋，以改变浮标的位置和速度，使得在其他时间可以收获更多的功率。启用无功功率所需的设备增加了单元的复杂性。可变形状的浮标将能够消除无功功率;类似弹簧的力将从波浪本身获得。随着形状的变化，作用在浮标上的水动力也会发生变化，从而影响浮标的位置、速度和周围的波场，并激发出一种非线性现象，否则这种现象就被忽略了。这种非线性力也将被用来增加所收集的能量。初步分析表明，在某些情况下，该装置的效率是相同尺寸的固定形状装置的效率的1.5倍。一些科学问题还有待回答，以实现可变形状浮标波能转换器的全部应用潜力。该研究将填补该装置在建模、控制和优化方面的知识空白。利用非线性水动力，该研究将开发最优控制问题公式，同时优化浮标形状和控制的框架，强化学习控制算法，以及设备的高保真数值模拟。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This research will contribute new knowledge related to renewable ocean wave energy harvesting, promoting both the progress of science and advancing national prosperity. Ocean wave energy converters capture wave power and convert it to electric power. The total theoretical wave energy potential is estimated to be more than the current US electric power annual needs. Complex wave energy converters are usually needed for efficient capture of wave power, and hence the cost of electric power transformed from waves is high compared to other sources of renewable energy. This award supports fundamental research to provide the knowledge needed for developing wave energy converters that produce power at a lower cost. Almost all existing wave energy converters use rigid bodies of fixed shapes (e.g., buoys). This award will develop a new variable-shape buoy wave energy converter, in which the buoy's shape changes continuously, like a jellyfish, to change the wave field around the buoy, in a favorable way, in order to increase the captured power by the unit. Therefore, results from this research will benefit the U.S. economy and society. This project links education and research, and positively impacts society via an outreach program that aims to raise the knowledge level among high school students regarding the concepts of ocean wave energy conversion.Classical rigid-buoy wave energy converters require a spring-like control force to be applied on the buoy, in addition to the damping control force that is usually obtained from the power take-off unit. This spring-like control force implies that the unit should provide reactive power; that is, it should be able to put power into the ocean at times, in order to change the buoy's position and velocity, such that more power can be harvested at other times. The equipment required to enable reactive power increases the complexity of the unit. The variable-shape buoy will enable the elimination of reactive power; the spring-like force will be obtained from the waves themselves. As the shape changes, the hydrodynamic forces on the buoy change, affecting its position, velocity, the wave field around it, and exciting a nonlinear phenomenon that is, otherwise, neglected. This nonlinear force will also be leveraged to increase the harvested energy. Preliminary analysis shows that in some cases the efficiency of the device is 1.5 times the efficiency of a fixed shape device of the same size. Some scientific questions are yet to be answered to realize the full application potential of variable-shape buoy wave energy converters. This research will fill the knowledge gap on the modeling, control and optimization of the device. Leveraging nonlinear hydrodynamic forces, this research will develop the optimal control problem formulation, a framework for simultaneous optimization of the buoy's shape and control, a reinforcement learning control algorithm, and high-fidelity numerical simulations for the device.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.