This research studies a binary mixture composed of sodium nitrate and urea for use as a phase change material in latent thermal energy storage systems between 75 and 90 degrees C. This temperature is suitable for heating and domestic hot water applications, such as solar thermal systems and cogeneration devices. This work is divided into two parts. In Part I, the phase diagram of the system was experimentally determined via DSC, the synthetic visual method and X-ray diffraction. A eutectic composition was found at 71.25% (w/w) urea and 21.75% (w/w) sodium nitrate. The main thermal properties and density of this composition were studied in detail to evaluate its potential as a PCM. The results showed a melting temperature of 85 degrees C and a melting enthalpy of 172 J/g. These properties are suitable for the intended purpose. Currently, the mixture presents an approximated market price below 1(sic)/kg, which is highly competitive. In this Part II, the water uptake of the material was evaluated to gain knowledge of its hygroscopic behavior. XRD measurements were also performed to study the formation of new phases or compounds caused by, the presence of water. In addition, because urea undergoes thermal degradation upon heating, a preliminary accelerated thermal cycling study was performed to determine the thermal reliability of the mixture. After 210 accelerated thermal cycles, the latent melting enthalpy of the sample was reduced by 1.2%. These results were complemented by chromatographic analysis used to detect any presence of degradation byproducts. According to the results, the mixture formed by sodium nitrate and urea shows potential for use as a PCM in the applicable temperature range. Further research focused on thermal degradation over longer periods of use is encouraged to establish whether the material has a proper lifespan for actual thermal energy storage applications. (C) 2016 Elsevier B.V. All rights, reserved.