Design and Validation of a PCM-TEG Energy Harvesting System for Powering Distributed Sensors

Energy harvesting technologies offer a promising approach for powering low energy devices by utilizing ambient energy sources such as temperature gradients. These technologies are particularly relevant for distributed sensing and monitoring systems in modern energy and critical infrastructure, where long-term autonomous operation of sensors is essential. In this study, an energy harvesting system integrating a thermoelectric generator (TEG) with a phase change material (PCM) is designed and experimentally evaluated to convert low-grade heat accumulated on exterior building surfaces into electrical energy. The system exploits the temperature difference across the TEG module, while the PCM acts as a thermal buffer to maintain and enhance the temperature gradient. Two PCM materials, polyethylene glycol 600 and 1000 (PEG600 and PEG1000), were investigated under real-world conditions, as well as controlled temperature variations, considering multiple heater-to-system distances and two boundary configurations (free convection and external insulation). Experiments were conducted starting from an initial temperature of approximately 16◦C, with the hot-side temperature gradually increased over three hours. The results show that the high est electrical power output of approximately 315 µW was obtained using PEG 600 without insulation with an approximately 11◦C temperature increase, while the lowest output (about 90 µW) occurred with PEG 1000 under insulated conditions. The optimal configuration produced approximately 2184 mJ of energy during the heating period. In addition, a theoretical model was developed, calibrated, and validated against experimental data with global root mean squared error and mean absolute error values of below 0.25◦C and 0.18◦C, respectively, for PCM temperature predictions, and about 0.1◦C error for the TEG temperature sides. The findings indicate that the proposed PCM-TEG system can provide a viable supplementary energy source for low-power distributed sensors in smart buildings and infrastructure monitoring applications.