A low-cost, durable device to harness wave energy

Ocean waves hold a tremendous amount of untapped energy that is more than capable of meeting the world’s electricity needs. However, electricity generation from waves has a number of drawbacks that make it economically unviable. Current marine constructions are costly, and it’s difficult to build a device robust enough to survive the harsh ocean environment.

A new wave energy technology developed with EU funding for the POLYWEC and WETFEET projects promises to overcome these obstacles. A European team of engineers working on these projects have created a durable device that could help generate low-cost electricity for thousands of homes in the coming years. Their research has been published in the journal ‘Proceedings of the Royal Society A’.

In their study, the engineers introduce a wave energy conversion system that’s equipped with an innovative electrostatic power take-off device known as a dielectric elastomer generator (DEG). The DEG is less costly than conventional designs and has no sliding or rolling moving parts. It’s also made of inexpensive soft hard-wearing materials that can withstand the harsh marine environment, unlike today’s steel electromagnetic generators.

How the generator works

The DEG uses flexible rubber membranes and fits on top of a vertical cylinder, in which the water level rises and falls with the motion of the waves. The water entering the cylinder pushes trapped air up, in this way expanding the membrane. At wave troughs, the water level drops, causing the membrane to compress. Because there’s dielectric material in the rubber membrane, a voltage is generated both when it expands and compresses. This process produces electricity. For commercial exploitation, this electricity would be carried to shore via underwater cables.

The DEG is designed to be incorporated into existing ocean energy systems. According to University of Edinburgh’s Professor David Ingram the air turbines and oscillating water columns of current systems could be replaced with the dielectric rubber membrane. “[Y]ou’re doing away with a fairly complex piece of electro-mechanical equipment and replacing it with a sheet of rubber and a fairly sophisticated set of power electronics so it should be easy to maintain” he stated in a news item posted on the Institution of Mechanical Engineers website.

A scaled-down version of the system was tested at the FloWave Ocean Energy Research Facility of the University of Edinburgh, a partner in both projects. The experiments showed that one full-size device could generate the equivalent of 500 kWh, enough electricity to power about 100 homes. The engineers believe that fleets of low-cost, easy-to-maintain devices could be installed in Scottish waters within decades. “Wave energy is a potentially valuable resource around Scotland’s coastline, and developing systems that harness this could play a valuable role in producing clean energy for future generations,” said Prof. Ingram.

POLYWEC (New mechanisms and concepts for exploiting electroactive Polymers for Wave Energy Conversion) and WETFEET (Wave Energy Transition to Future by Evolution of Engineering and Technology) have now ended. POLYWEC’s objective was the development of novel wave energy models and methodologies. WETFEET sought to identify and develop components, systems and processes to improve the wave energy sector as a whole.

For more information, please see:
POLYWEC project website
WETFEET project website