Sustainable, Binder Jetted Porous Metakaolin-Based Geopolymers for Thermochemical Energy Storage Applications in Buildings

For the past century, using resources to generate energy has undeniably caused major environmental damage such as global warming and pollution from burning and releasing fossil fuels. Recent research aims to utilize renewable energy sources to decrease CO2 emissions and to better match energy production with energy needs. Thermal energy storage (TES) appears to be a crucial technology for renewable energy systems and within TES, thermochemical storage (TCES) is quite promising. It uses reversible reactions to store heat and can store significant energy, like heat from summer, and release it later when needed, with very little energy loss. Moreover, it’s excellent for storing energy long-term because there's very little heat loss. This makes it ideal, especially when space is tight, like in buildings. Among the various materials being explored for thermochemical energy storage (TCES), salt hydrates have become a key area of interest, particularly for applications within the built environment due to their capacity to function effectively at lower temperatures via reversible hydration and dehydration reactions. Nevertheless, a significant challenge associated with salt hydrates is their insufficient mechanical strength when used. To address this inherent drawback, the use of porous host materials is crucial. These matrices are designed for several vital roles: By confining the salt within their structure, they effectively reduce the problems associated with mechanical instability. they promote effective water vapor diffusion, essential for the reversibility of the reactions; and they ensure the long-term structural reliability of the storage system during repeated charge and discharge cycles. Geopolymers are emerging as a really attractive option for these host materials. They’re sustainable, made from readily available materials, and naturally porous. Moreover, they are relatively inexpensive compared to things like zeolites or MOFs. Additive manufacturing, and specifically binder jetting technology, presents a significant advantage in this context. It is particularly valuable for producing geopolymer hosts because binder jetting enables the fabrication of complex shapes and, crucially, provides the ability to precisely control the porosity. This level of control is fundamental for ensuring optimal salt absorption and maximizing the overall performance of the TCES system. This combination of geopolymers and binder jetting looks like a fantastic way forward for creating advanced, sustainable TCES systems for buildings. The real challenge lies in achieving effective seasonal energy management, and the research activities are actively focused on developing solutions that are both cost-effective and deliver superior performance. This study explores a novel approach to energy storage materials using 3D printing. During this research binder jetting technology is used for the production of metakaolin-based geopolymers which are impregnated and infiltrated by two different thermochemical salts solutions: CaCl2.6H2O and SrCl2.6H2O for thermochemical energy storage. This research aims to develop a more effective metakaolin-based geopolymer for sustainable energy storage. Specifically, it investigates how adding vermiculite, prover, and perlite aggregates affects the mechanical strength and porosity of the geopolymer, with the goal of enhancing its salt solution absorption. In addition, the thermal properties of samples are determined by thermogravimetry analysis (TGA), the differential scanning calorimetry (DSC) and thermal conductivity. The novelty of this work lies in the integration of geopolymer materials, binder jetting technology, and thermochemical energy storage principles by using thermochemical salt solutions to address the growing need for sustainable and efficient energy solutions in the energy storage of buildings.