Thermal energy storage (TES) capacity of a lab scale magnesium hydro carbonates / silica gel system

In this paper the focus is on the reactive material, reactor design, and heat capacity properties of a TES process. A standardized method for producing the reactive material is being developed, for use in a TES reactor vessel. The magnesium hydro carbonate (Nesquehonite, MgCO3· 3H2O) used can be produced by a carbon capture and storage by mineralization process. A composite material for the TES using chemisorption of water is a mixture of MgCO3· 3H2O and silica gel. Several heat effects are tested simultaneously with a recently constructed set up for 40-70 g composite material using temperature and relative humidity sensors to monitor the reaction and its conditions. The cyclability of the reversible reaction and the performance of the reactive material are analysed. A thermal storage capacity of 0.41 MJ/kg using 70 g composite material could be measured, while using 3 g sample hydration/chemisorption effect of 0.71 MJ/kg was obtained. Earlier studies addressed application concepts of combining the TES reactor with heat pumps, to be used as an extra heat source during colder periods to improve the efficiency and COP. For the current paper, operating temperatures and humidity were measured in the reactor, as to match the parameters in of technical concepts, while also the maximum reaction heat effect using the composite material was measured.