Source: SBM France

Wave energy harvesting with artificial muscles

Tuesday 26 Sep 17
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by Lonnie Moldt Jørgensen

Contact

Anne Ladegaard Skov
Associate Professor
DTU Chemical Engineering
+45 45 25 28 25

Facts about the WEC project

Dielectric elastomers possess great potential as energy generators due to their amazing qualities. They are lightweight and flexible, and energy is directly converted from mechanical into electrical energy. The problem is that elastomers possess low energy density, which mean that they are not able to generate enough electricity. The aim of the Dielectric elastomers for Wave Energy Converters (WEC) project is to develop better elastomers with improved energy densities for use in wave energy converters.

The project is funded by SBM France and completed in Spring 2017.

Elastomers

Elastomers are a type of plastic characterized by being elastic. By the slightest force, they will deform. Elastomers can stretch up to hundreds of percent and regain their original shape without permanent distortion.
Dielectric elastomers do not conduct electricity, instead they isolate. Other types of dielectric materials are glass and rubber.

Dielectric elastomers, also known as artificial muscles, have emerged in recent years and hold great promise as energy generators. Researchers from DTU Chemical Engineering have developed elastomers with high energy density, which means they can utilize the waves' movements and create electric energy. This is good news for the development of new sustainable energy solutions.

The demand for sustainable and renewable energy sources is increasing. It is especially the forces of nature researchers and industry are aiming to become humankind’s future energy supplier. However, nature has a habit of being its own boss, and it brings sunshine, storm and wind whenever it fits - not when humankind demands it. Dielectric elastomers, also known as artificial muscles, are a relatively new technology that has proven to possess enormous potential when it comes to the utilisation of one of nature's own forces - waves.

High dielectric density

Associate Professor Anne Ladegaard Skov at the Danish Polymer Center (DCP), DTU Chemical Engineering, has throughout her career researched intensively in dielectric elastomers and their qualities as soft energy generators. Dielectric elastomers consist of an electrically insulating silicone film on which electrodes are placed on the surfaces. In the just completed “Dielectric elastomers for Wave Energy Converters (WEC)” project, Anne, in collaboration with SBM France, have optimized this rubbery material for it to exploit the waves' movements and create electrical energy.

"We are dealing with very large wave powers that expand whatever material we use, and this requires a material that is both lightweight and flexible – elastomers are ideal for this purpose. The problem is that silicone elastomers possess an inherent low value of permittivity, which means low density. This is a huge problem. In order to generate high amounts of electricity, high density is essential. In our laboratory, we have therefore worked on modifying the material in order to remove this shortcoming by making the silicone film even thinner as thinner films allow for a higher density”, Anne Ladegaard Skov explains.

Wave harvesting - from electric energy to mechanical energy

According to Anne, dielectric elastomers are the most obvious material to use when it comes to fulfil the need for efficient and sustainable energy due to the unique properties of the material. If dielectric elastomers are exposed to an electric field, they expand and convert energy from one form to another: Either as actuator, from electric energy to mechanical energy or as a generator, from mechanical energy to electric energy, as the case with wave harvesting.

Potentially, SBM France will place a 500-meter long elastomer tube of the coast of France - five meters below the bottom of the ocean. What will happened is that the elastomer generator will deform by the huge wave powers, and the mechanical deformations will in return turn into electric energy.

"We utilize the elastomer’s useful quality as a generator. At the same time, we avoid all the drawbacks of mechanical generators, as elastomers make no noise and are lightweight - unlike mechanical generators such as engines that are both noisy and extremely heavy. Unlike other sustainable energy solutions, dielectric elastomers are not dependent on weather conditions or if it is night or day as they are placed below the bottom of the sea and therefore not affected by, for example, major storms. And finally, there are also no environmental impact or corrosion of the material", Anne explains.

Thus, there are both technical and environmental advantages of using these artificial muscles to harvest wave energy. However, handling the material is still not without its challenges, she continues.

"The amazing quality of flexibility makes the silicone film extremely elastic but very difficult to handle because even the lightest force will deform the silicone, and therefore processing is a rather difficult task. In an earlier project with Danfoss PolyPower we have worked directly on processing thin films with high reliability, and the gathered knowledge is now also used in the project with SBM”.

Anne Ladegaard Skov has completed her task in the WEC project, and next step for SBM France is to test the 500-meter long elastomer tube in the ocean. The aim is to place the elastomers in conjunction with large wind turbine farms and use the existing energy.

Read more about the WEC project here.

 

 

 

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