Auxetic concrete draws energy from the sea

Auxetic concrete: energy from the waves

When waves batter the coast, energy is generated. Researchers Branko Šavija and Yading Xu from TU Delft want to capture that by using a special type of concrete to create an alternative energy source. For several years, Šavija has been working at the Department of Materials Science and Engineering at TU Delft on materials that behave ‘unexpectedly’, like auxetic concrete, a flexible concrete with special propertie. When loaded, it contracts, but if the load disappears, it expands like a sponge. Normal concrete also moves but not as much. This new concrete contains holes, as a result of which it is less strong but more flexible.

One possible application that the researchers see is using concrete in coastal protection. Breakwaters consist of large pieces of concrete. The vibrations that arise in the concrete when the waves hit it can be converted into electricity. And there are techniques available to convert such a movement into energy. As the Netherlands has 450 km of coastline, the researchers see a lot of potential in this plan. Šavija and his fellow researcher Yading Xu submitted a proposal to the NWO funding instrument Open Mind last year. In November 2020, during the online edition of innovation festival TEKNOWLOGY, they received a grant of 50,000 euros. With that, they have a year to test their plan. According to the jury, it was a ‘completely original idea to explore an interesting new source of energy’. In their lab, Šavija and Xu are currently working on linking piezoelectric polymer films to the concrete. This soft and

flexible film is capable of converting the movement from the concrete into electronic resistance.

Meanwhile, the ideas have also aroused attention outside the TU. They have now submitted a proposal for a European grant that has already yielded a number of contacts for the future, even if the proposal is rejected. For instance, contact has been made with an Italian university that is working on energy generation through human movements, for example through sensors in shoes. The researchers expect that if they are able to show a proof of concept at the end of the current project, it will then be easier to approach commercial parties who might be interested in supporting this type of research too.

Text is based on the article ‘Obtaining energy from concrete’ CiTG TU Delft.

Demonstration of power generation with auxetic concrete (Photo: TU Delft)

Video: TUD/YouTube Open Mind 2020 contestants - Auxetic concrete energy harvester Auxetics

Auxetic materials (auxetics) are structures or materials that have a negative so-called Poisson’s ratio1. When stretched, they become thicker perpendicular to the applied force. This occurs due to their particular internal structure and the way this deforms when the sample is uniaxially loaded. Such materials and structures are expected to have mechanical properties such as high energy absorption and fracture resistance.

1Poisson’s ratio is a measure of the Poisson effect, the deformation (expansion or contraction) of a

material in directions perpendicular to the specific direction of loading.

More about Auxetics>

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