Ocean currents carry vast amounts of energy, but turning that motion into electricity has always been a technical challenge.
Most existing designs rely on underwater turbines that resemble wind turbines, complete with spinning blades and complex machinery.
While effective in theory, these systems are expensive, difficult to maintain, and vulnerable to corrosion and marine growth.
Now, a researcher in Spain has proposed a much simpler alternative: a pendulum-like device that gently swings in the water and turns vibrations into usable energy.
The new system was developed by Francisco Huera, a researcher in the Department of Mechanical Engineering at Universitat Rovira i Virgili.
His work focuses on capturing energy from water currents by taking advantage of a natural phenomenon that engineers usually try to avoid—vibrations caused by flowing water. The study has been published in the Journal of Fluids and Structures.
When water flows past a cylindrical object, it creates swirling vortices behind it.
These vortices cause the object to vibrate, a process known as flow-induced vibration. In Huera’s design, a hollow cylindrical tube is submerged in moving water and suspended from an axis.
As the current flows around it, the tube begins to oscillate like a pendulum. This motion can then be converted into mechanical power.
One of the most appealing aspects of the system is its simplicity. Only the cylinder itself needs to be underwater.
All the sensitive and expensive components—such as the shaft, transmission system, and eventually the electricity generator—can be placed above the water on a floating platform. This could greatly reduce maintenance costs and avoid many of the problems that plague underwater turbines.
To test the idea, Huera built a scaled-down version of the system and placed it in a controlled water channel at the university’s laboratory. Sensors measured how the cylinder moved, while an electromagnetic brake was used to study how much mechanical power could be extracted from the oscillations. The results showed an energy conversion efficiency of around 15%.
This efficiency is lower than that of well-designed tidal turbines, which can theoretically capture up to 35% of the available energy. However, Huera points out that the trade-off may be worthwhile. The vibrating-cylinder system is far simpler, takes up less space, and avoids the need for complex underwater machinery. In essence, it is just a tube hanging from an axle, doing useful work as it swings.
The system is mainly intended for tidal currents, where water flows steadily back and forth. However, the same principle could also be applied to rivers with strong currents, without the need to build dams. With further development, similar designs might even be adapted for use in wind.
This research also represents a shift in thinking. Flow-induced vibrations have long been seen as a danger to offshore structures, such as pipelines, because they can cause material fatigue. Huera himself previously worked on ways to suppress these vibrations. Now, he is turning the same effect into a potential source of clean energy.
The current study focuses on theory and laboratory testing. Large-scale prototypes and economic analyses have yet to be carried out. The next steps will involve improving how energy is extracted, expanding the range of usable flow speeds, and exploring how multiple devices could work together to generate more power.
Source: KSR.
