Surfs up: tidal-steam turbines operate in waves

Tidal-stream turbines are underwater machines that transform the kinetic energy of streams into renewable electricity. However, the technology is still in its infancy and faces many challenges in terms of biofouling, environmental impacts, cost, unpredictability, and efficiency.

Implementation of tidal-stream turbines will depend on accurate models to predict energy generation. To this end, Zang et al. developed a model that examines how their power output changes in a current with waves and turbulence. The group hopes this work will help to improve the design, deployment, and operation of tidal-stream turbine technology.

“Much work on turbines has been done in steady and turbulent currents; however, little is known about how power and flow change in the presence of waves,” said author Yuquan Zhang. “Waves may change the flow behind the turbine, and this will have an impact on the deployment of multi-turbines. In addition, it will likely affect the lifespan and years of return on investment.”

The team created a miniature turbine in a channel, where a wavy current was created with a pump system and wave paddles. The waves induced periodic fluctuations in power compared to the current alone, but the performance was similar when averaged over time. Waves also affected the distribution of turbulence, which has implications for downstream turbines.

“Our experimental results can provide a reference for offshore tidal stream turbines and facilitate their design and optimization,” said Zhang.

In the future, the researchers aim to study a floating tidal-stream turbine, which will be necessary for water depths over 40 meters.

Source: “On the impact of waves and turbulence on the power fluctuations and wake structure of a tidal-stream turbine,” by Wei Zang, Yuquan Zhang, Yuan Zheng, Jisheng Zhang, Dawei Guan, and E. Fernandez-Rodriguez, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0142872 .

This paper is part of the Recent Advances in Marine Hydrodynamics Collection, learn more here .