Small amounts of waste heat from factories and industrial equipment are often difficult to recover. We have developed “metamaterial thermoelectric conversion,” which harvests such unused heat as thermal radiation using metamaterial absorbers and converts it into electricity. The technology can generate power even in an environment with uniform thermal radiation without an externally imposed temperature difference, offering a potential self-sustaining power source for sensors and IoT devices. We further propose a hybrid system combining this technology with optical wireless power transmission, providing continuous power from ambient waste heat and additional optical power when needed, such as during wireless data transmission. This presentation introduces a new energy-harvesting approach for utilizing waste heat and reducing battery replacement.