Swinging Pendulum in Water Current to Generate Electricity - Okayama University

Copyright Okayama University

Okayama University announced on December 20, 2012, that it is jointly developing a new tidal current and river stream power generation method with a private business. The new method generates electricity by swinging a cylinder pendulum in the fast tidal current of, for example, the Seto Inland Sea or a river flow, and collects fluid energy.

A hollow cylinder lighter than water is submerged in the water and its bottom end is fixed on a rotating shaft, which keeps the cylinder upright due to its buoyancy. When exposed to water current, eddies that occur periodically around the cylinder induce vibrations in the cylinder at a right angle to the water current. This pendulum motion rotates the shaft, which transmits rotational power to an electric generator.

Because of its simple structure, this new mechanism is low cost, durable and unlike propeller generators, will not damage marine organisms with propellers. According to the latest experiment, the method increased energy conversion efficiency by 75 percent, which exceeds the theoretical limit for a rotating propeller-type generator, the so-called Betz limit. The research team plans further experiments to verify whether this power generation method using a swinging cylinder pendulum will have higher performance than existing windmill generators.

Related JFS article:
Test for Tidal Power Generation Underway in Kanmon Straits, Southern Japan