Tidal energy could soon hit record conversion efficiency thanks to a new development from scientists at Australia’s RMIT. The engineers have developed a novel design for a convertor that they claim operates with far greater efficiency than current systems. They hope the breakthrough could pave the way for large-scale adoption of tidal energy technologies and thus smoothen out our transition towards renewables.

One common way to harness wave energy today involves a point absorber buoy, which consists of a floating device on the surface that’s tethered to the seabed. As the buoy moves up and down with the passing waves, it drives an energy converter mechanism, such as a geared drivetrain, built on the tether below the surface. That mechanism uses linear motion to spin a flywheel and generate electricity.

A downside of using a point absorber buoy to harvest wave energy is that these systems typically require sensors and other electronics to precisely synchronize themselves with the incoming waves, which leaves them open to maintenance and reliability issues.

Seeking to overcome this problem, the RMIT Scientists developed a novel generator that features a point absorber buoy but uses no sensors or electronics. Instead, the team went with a passive approach that has the device float up and down naturally with the swell. The novel system also features two turbine wheels stacked close together down below, which rotate in opposite directions and combine to amplify the power passed on to the generator.

The generator, in its turn, is housed inside the buoy to protect it from corrosion and is connected to the spinning turbines through shafts and belt-pulley drive transmission. Tests of the prototype showed that it was able to generate twice as much power from ocean waves than other point absorber designs, with a relatively simple and cost-effective solution.

“By always staying in sync with the movement of the waves, we can maximize the energy that’s harvested,” said lead researcher Professor Xu Wang. “Combined with our unique counter-rotating dual turbine wheels, this prototype can double the output power harvested from ocean waves, compared with other experimental point absorber technologies.”

The scientists now plan to test the technology outside the laboratory and are confident about its potential to bring tidal energy to scale and support our transition towards cleaner energy.

Study source: Applied Energy — Study of a novel rotational speed amplified dual turbine wheel wave energy converter