Waste heat is a highly promising source of renewable energy; however, the efficiency of using heat to generate energy has historically been much lower than hydroelectric, wind or solar power. While there are a number of materials that can be used for the generation of energy from waste heat, they all suffer from various issues ranging from low stability to low efficiency. Nevertheless, the fact that a large number of industries generate copious amounts of waste heat have driven research into this field.
source https://phys.org/news/2020-12-layered-cobalt-oxide-record-setting-thermoelectric.html
