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

Abstract

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 was developed, for use in a TES reactor vessel. The magnesium hydro carbonate used (Nesquehonite, MgCO3·3H2O) can be produced by a carbon capture and storage by mineralisation process. A composite material for the TES using chemisorption of water is a mixture of MgCO3·3H2O and silica gel. Several heat effects were tested simultaneously with a set up for 40–70 g composite material using temperature and relative humidity sensors to monitor the hydration reaction and its conditions. Operating temperatures and humidity were measured inside the reactor, in a set up design that matches the parameters of a novel technical concept, while also the maximum reaction heat effect using the composite material was measured. A thermal storage capacity of 0.41 MJ/kg using 70 g composite material could be measured, while using 3 g sample a hydration/chemisorption effect of 0.71 MJ/kg was obtained. Heating system containing a heat pump would use the TES as an extra heat source during colder periods which implies improved efficiency and COP.