Theoretical modeling and experimental validation of a thermoelectric generator (TEG) integrated with a phase change material (PCM) are reported in this paper. The proposed device converts the daily ambient temperature variations into a temperature difference on the TEG using a PCM, thus temperature variations can produce electrical energy. Thermal modeling is developed and compared with the experimental result. The developed system is evaluated by using a temperature-controlled oven as well as an actual ambient environment. The maximum output power can reach 0.6 mW which corresponds to a power density of 37.5μW/cm under the ambient temperature variants from 5 °C to 35 °C (using the temperature-controlled oven) while it is approximately 11.9 μW/cm in the real ambient environment (outdoor evaluation with ambient temperature variation in range of 12 °C to 24 °C). The effects on the output power of the TEG in both cases with and without PCM have been evaluated and the effect of the PCM is confirmed. Also, we are not only concentrating on the phase change states of PCM to generate the electrical energy but also focusing on the non-phase change state which could open the possibility for low-power applications. The proposed system could be considered as an electrical power source for miniature systems such as wireless Internet of Things (IoT) sensing systems. 2 2