The objectives of this project were based on (or consist of) evaluating the technology at a scale at which the results are sufficiently representative of the real circumstances facing a commercial plant that utilizes this storage technology. To this end, the TES plant was operating continuously and satisfactorily for more than 32,000 h. This allowed securing of representative results for the analysed technology. Key points such a material corrosion, analysis of possible leakage points, calculation of performance or true efficiency of the storage (including a thorough assessment of thermal losses) and analysis of plant operation were the lines that were analysed at this plant.