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But most of the production of those energies depends on the weather, the time of day, the time of year, and does not always correspond to the time of consumption. Therefore, energy storage is becoming a major issue, in order to store the excess energy and redistribute it when needed. There is a growing urgency to develop new systems to supplement the current offer.

My PhD subject, which I have been working on for over two years, is part of a project to develop one of these energy storage devices.

The idea is to make it easy to use, simple to install and only operating with air, moisture and natural heat. That seems a bit unrealistic, but the use of hygroscopic salts might make it possible.

Indeed, these salts have an interesting property: by dehydrating and hydrating them, they can absorb and release a significant amount of energy. For example, they can be dehydrated in summer, in order to store energy, and rehydrated in winter, with humid ambient air, in order to release energy and heat living places. And, as this reaction is reversible, the cycle can be repeated over and over again.

But to make it possible, salts must be integrated into a host material with multi scale porosity to maximise thermal performances over time. A big part of my job is to develop these host materials. For that, I’m working with geopolymers, which contrary to what their name suggests, are part of the ceramic family. They are produced from the alkaline activation of an aluminosilicate source at room temperature, so no sintering step is required.

To maximise the porosity of these geopolymers and make it multi scale, we are trying to combine two techniques: direct foaming and direct ink writing (3D printing). Direct foaming consists in chemically incorporating a gas into our geopolymer paste. That way, I’m playing not only on the porosity between the filaments (by 3D printing) but also on the porosity within the filaments themselves (by direct foaming).

Obviously, the characterization of this porosity is an important step (SEM, X-rays tomography, mercury porosimetry), but I also study the rheology of inks for printing and the mechanical properties of the final samples. The samples are then impregnated with salts and their thermal properties are tested over several hydration/dehydration cycles. These lasts studies are currently in progress and I hope to be able to present some results soon.

If you have any questions/suggestions/comments, please do not hesitate to contact me. I hope to meet you in Lyon for the next ECerS Conference!

Camille Zoude

MatéIS laboratory – INSA Lyon

Villeurbanne

France

E-mail: camille.zoude@insa-lyon.fr