Japanese-developed pendulum tidal system claims improved efficiency and design over turbines
A Japanese engineer has developed a pendulum design for a tidal electricity generator that he says is more efficient and effective than the propeller-type designs being developed in Europe.
Shinji Hiejima, associate professor at the School of Environmental and Life Sciences at the Okayama Univeristy, has patented the design, developed prototypes and is now looking for an industrial partner to commercialise his tidal generator.
The Hydro-Venus (Hydrokinetic Vortex Energy Utilisation System) develops the idea of using cylinders placed horizontally underwater, which was pioneered at the University of Michigan in the US. Its Vivace (Vortex Induced Vibrations for Aquatic Clean Energy) system is being commercialised by the company Vortex Hydro Energy.
Electricity is generated from the movement of the cylinders in the tidal flow. The movement of the cylinders is caused by vortex induced vibrations, an effect that occurs whenever an object is placed in the path of an external fluid flow. The phenomenon is a consideration across many fields of engineering, from aerospace and automotive to the structure of bridges and buildings.
The major difference between Vivace and Hydro-Venus is that the Japanese design places the cylinders underwater vertically and produces rotational movement instead of linear translational movement of the cylinders from vortices in the tidal flow.
Hiejima said: “The translational motion of cylinders, such as used in Vivace, limits the efficiency of tidal flow induced vibrations of cylinders. My concept for the Hydro-Venus does not vibrate transnationally but rotationally, and initial tests yielded a power efficiency of 76%.”
According to Hiejima, European propeller-type turbine systems have three major drawbacks: the use of expensive materials for the rotor blades, the risk of waste in the water clogging up and damaging the blades, and their potential to harm marine life. All of these limitations are resolved by the use of cylinder systems, he said.
So far tests at Okayama University have been conducted using cylinders 1.5m in diameter and the next stage of development is to make 20m cylinders from a range of materials to determine the most efficient structure. “I have demonstrated the potential for my version of the pendulum-dynamo and am looking for industrial partners,” said Hiejima.
Read more related articles