Although model predictions of thermal energy storage (TES) performance have been explored in several previous investigations, information that allows experimental validation of performance models has been very limited. This is particularly true for high-performance TES designs that facilitate fast input and extraction of energy. In this paper, we present a summary of performance tests of a high-performance TES unit using lithium nitrate trihydrate phase change material (PCM) as a storage medium. Our experimental program also included thorough property determinations and cyclic testing of the PCM. Performance data is presented for complete dual-mode cycles consisting of extraction (melting) followed by charging (freezing). These tests simulate the daylong cyclic operation of a TES unit for asynchronous cooling in a power plant. The model analysis is found to agree very well, within 10%, with the experimental data except for conditions very near the initiation of freezing. Slight deviation from the predicted performance at that time is a consequence of sub-cooling that is required to initiate solidification. The comparisons presented here demonstrate the viability of thermal energy storage for augmentation of power plant air-cooled condensers as well as other potential applications.