Development of a cementitious material for thermal energy storage at low temperature

Khadim Ndiaye (1, 2) , Martin Cyr (2) , Stéphane Ginestet (2)

1 L2MGC - Laboratoire de mécanique et matériaux du génie civil
2 LMDC - Laboratoire Matériaux et Durabilité des constructions

Energy storage systems are increasingly being used to improve energy performance in industry, transport and building. The storage of energy in the form of heat is widely used in the building sector in order to increase the use of solar energy, which is necessary to streamline energy management. The storage of excess summer solar energy appears to be a solution to compensate for the thermal energy deficit in winter and to reduce the environmental and socio-economic impacts of buildings. Currently, there are several adsorbent materials capable of storing thermal energy but they use high temperature storage (around 200 °C). Ettringite is a common hydrate found in cement-based materials and has the advantage of storing energy at high density but at low temperature, around 60 °C. Portland cements used in most construction materials produce small percentages of ettringite but calcium sulfoaluminate cements (CSA) can produce much larger amounts of this compound, with fairly rapid kinetics. In this paper, the hydration of CSA-based ettringitic systems is investigated with a view to synthesizing a new heat storage material. The hydration of CSA paste samples, with and without the addition of gypsum and portlandite, constituents allowing the exclusive production of ettringite, was followed by XRD and TGA. The ettringitic system (ES1) containing CSA, gypsum and portlandite produced only 48% of ettringite with an unstable structure (swelling), so ES1 was not selected. However, the ettringitic system (ES2) containing only hydrated CSA could reach between 65% and 70% of ettringite with a very stable solid structure. In order to use the ES2 as heat storage material, it was necessary to improve its permeability, thus enhancing its storage capacity. Improving the material by foaming provided an aerated ettringitic system (AES2) with high permeability, appropriate for heat storage. This allowed the development of an ettringite-based material with high heat storage density in low temperature conditions. The heat storage prototype allowed reaching a storage density of 117 kWh/m3 with a heat storage yield of 71%.

Mots clés: Ettringite; Calcium sulfoaluminate cement; Hydration; Thermodynamic modelling; Heat storage

Domaines: Construction durable; Eco-conception

Khadim Ndiaye, Martin Cyr, Stéphane Ginestet. Development of a cementitious material for thermal energy storage at low temperature. Construction and Building Materials, 2020, 242, pp.118130. ⟨10.1016/j.conbuildmat.2020.118130⟩. ⟨hal-02501170⟩