In the context of concentrating solar power (CSP) systems, the thermocline thermal storage system is a potentially cost-effective alternative to the more common storage system based on two tanks, one hot and one cold. As part of the European ORC-Plus project, ENEA (Italian institute for new technologies, energy and sustainable development) has proposed an innovative molten salt storage system based on thermocline technology, of which a 1:100 scale prototype has been built at the Solar Collector Test Facility (PCS) at Casaccia. The aim of this thesis is to numerically evaluate the potential to insert phase change material (PCM) into the tank in terms of thermal performance.