Thermal energy storage technology can balance volatile energy production as well as power consumption by increasing thermal power plant flexibilities. Therefore, an experimental investigation with latent heat thermal energy storage, utilizing sodium nitrate (NaNO₃) with a melting point of 306 °C as phase change material, was carried out in the present study. The heat source and sink for the experimental setup is a thermal oil plant using Therminol VP1® as heat transfer fluid. To increase the heat flux into the storage material, a bimetal tube consisting of a circular steel tube and an aluminum tube with fins was used. The storage operates around the melting point to use the enthalpy of fusion as primary storage mechanism. The temperature distribution in the storage is measured, as well as the heat transfer fluid temperatures and mass flow. For the experiment a novel fin-geometry, based on the combination of transversal and longitudinal fins, was introduced. A more than 40 % lower melting time compared to former fin geometries (equal bimetal tube with only longitudinal fins) was observed. The heat transmission coefficient from the heat transfer fluid into the storage material was determined. Storage parameters like power, capacity and heat losses to the surrounding were logged. Different mass flows of the heat transfer fluid and different temperature spreads were tested in order to determine the storage behavior. Reliable storage parameters for the latent thermal energy storage were gained.