A new type of single-tank thermal energy storage (TES) with an actuated, loose-fitting insulated divider plate positioned between the hot and cold fluids is described, based on the CSPonD volumetric molten salt thermal receiver with integrated TES concept. A 240 L lab-scale assisted thermocline tank was fabricated and tested using water as the working fluid, connected to a 5 kW heat addition and extraction loop. The axial position of the divider plate was controlled to follow the thermocline interface as energy was added or removed under various charge-store-discharge profiles. For 6 hour storage cycles, the divider plate tank exhibited a round-trip storage efficiency of 0.53, compared to 0.46 for the baseline tank, a 14% improvement. Output temperatures remained within 90% of initial values for 89% of the divider plate tank volume, as compared to only 58% for the baseline case, representing a 53% improvement in usable storage capacity. Internal conduction losses were found to be less for the divider plate tank and correlated well with models (measured 83–93% values vs 86% internal loss prediction).

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