Numerical Assessement of Energy Storage Performances of Magnetite and Quartzite for CSP Storage Applications

Abstract

this paper pinpoints the thermal energy storage performances of two TESM, quartzite as classic thermal energy storage material commonly used in CSP and magnetite as emerged thermal energy storage filler material. The TES performances included charge, discharge and cycle efficiencies (utilization rate). In the first place, the developed numerical code for thermocline energy storage is presented and validated. Subsequently, and for both filler materials, the thermocline behavior and TES performances during charging and discharging process are examined. These performances are investigated for two potential scenarios: the first one considers the same storage tank size and the same discharge period. While, the second one, concerned sized storage tank for each combination HTF/TESM. Different heat transfer fluids are utilized involving natural oils, synthetic oils and molten salt. The obtained results showed that no significant difference of the zone thickness between the two materials. Moreover, we noted that quartzite presents slightly higher charge discharge and storage efficiencies. However, magnetite, for the same storage tank size and the same discharge time, magnetite is able to restore a great amount of energy. Furthermore, magnetite requires less storage tank volume. More important, we deduced that the TES performances are not impacted only by the TESM properties but they are also driven by the HTF nature and that molten salts are largely more efficient. Keywords—thermocline energy storage; TESM; HTF; magnetite; quartzite; thermocline behavior; charge efficiency; discharge efficiency; storage efficiency.