Generator Design and Operation: Bio-Inspired Structures for Tidal Energy Harvesting

Project Lead: Oscar Curet, Ph.D.
Affiliated Home Campus: Boca Raton & Seatech
Affiliated Department: Ocean and Mechanical Engineering
REU Scholar: Kevin Tumolva
REU Scholar Home Institution: Lipscomb University

A system modeled after the oscillation of mangrove roots in the water has the potential to generate power from tidal currents. The motivation for this project is to collect data from the existing system so that in the future, it can automatically change its features according to the tidal current’s flow speed to be more efficient. The design consists of a cylinder that is connected to a metal plate. Part of the cylinder is submerged underwater to capture the energy from the water flow, while the metal plate acts like a spring to provide a restoring force. In this configuration, the cylinder will start to oscillate due to vortex shedding when exposed to the flow. The resulting movement can be used with magnets and coils to generate electricity.

The project focused on observing the effects on the oscillation caused by changing the length of the metal plate, which effectively changes the stiffness of the system. The system was tested with 4 different plate lengths in varying flow velocity (14 cm/s to 37 cm/s). The system’s movement in the water was recorded and then analyzed in MATLAB to get the amplitude and frequency of the oscillations. The results show a linear relationship between the frequency of the oscillations and the velocity of the water in the range that it was tested. The graph for the amplitude of the oscillations shows a sharp increase at the beginning of its movement, then it flattens out as the flow speed is further increased, and eventually starts decreasing at the higher speeds. The results also show that the more flexible configuration of the system makes it reach its peak mechanical power earlier, but also reaches that decline early. These conditions are delayed as the stiffness of the system goes up. These data can be used to help make the system automatically match the flow speed with a corresponding stiffness to generate the most power.

Figure. Left: Mangrove trees are characterized by a complex root system. Center: flow visualization behind a patch of cylinder. Right: proof-of-concept device inspired in mangrove roots for energy harvesting of tidal flow.