A substance created by West Virginia University researchers has the potential to significantly reduce the amount of heat that power plants send into the atmosphere.
A team led by Xueyan Song, professor, and George B. Berry Chair of Engineering at the Benjamin M. Statler College of Engineering and Mineral Resources, has created an oxide ceramic material that solves a longstanding efficiency problem plaguing thermoelectric generators. These appliances have the ability to produce energy from heat, including global warming-related heat emissions from power plants.
The breakthrough oxide ceramic Song’s team produced “achieved a record-high performance that had been deemed impossible,” she said. “We demonstrated the best thermoelectric oxide ceramics reported in the field worldwide over the past 20 years, and the results open up new research directions that could further increase performance.”
Cesar Octavio Romo de la Cruz, Yun Chen, Liang Liang, and Sergio A. Paredes Navia contributed to the study, supported by $639,784 in National Science Foundation funding. The findings appear in Renewable and Sustainable Energy Reviews.
Oxide ceramics, which contain a variety of metallic elements, belong to the same family of materials as ceramics including pottery, porcelain, clay bricks, cement, and silicon. They are strong, abrasion and heat-resistant, and suitable for high-temperature applications in the air. They can be used as a building material for parts of thermoelectric generators.
Oxide ceramics, on the other hand, contain “polycrystalline” structures made up of several linked crystals. As the “grain boundaries,” or the locations where those crystals meet, hinder the current and electron flow that power thermoelectric generators, engineers have difficulty using those materials for large-scale thermoelectric applications.
This work is at the cusp for large-scale, high-temperature waste heat recovery. It leads toward a new era for oxide ceramics and aligns with the U.S. Department of Energy’s Industrial Heat Shot initiative to develop cost-competitive industrial heat decarbonization technologies with at least 85% lower greenhouse gas emissions by 2035. Our findings could facilitate and accelerate materials design that is magnitudes higher than the current state of the art.Professor Xueyan Song
Song’s team converted that stumbling block into a stepping stone.
“We intentionally added ‘dopants,’ or metal ions, into the polycrystal ceramics, driving special kinds of dopants to segregate to the grain boundaries,” said postdoctoral researcher Romo de la Cruz. “That’s how we turned the unavoidable and detrimental grain boundaries into electricity-conducting pathways, significantly improving thermoelectric performance.”
The study addresses the growing issue of waste heat, a byproduct of most processes that turn fuel into electricity and a factor in climate change. Lightbulbs emit waste heat when they become warm to the touch. Waste heat is additional energy that is inefficiently used for something other than creating light.
It is estimated that the global market for systems to collect waste heat would surpass $70 billion by 2026. Waste heat is emitted into the atmosphere by a variety of systems, including power plants, residential heating systems, and automobiles.
“Heat is used to make almost everything from food to metals and electricity,” Romo de la Cruz explained. “But during those processes, around 60% of the energy produced is unproductively released to the environment in the form of heat. Waste heat recovery will play an increasingly key role in balancing growing demand for electricity against the carbon footprint of industrial processes. Thermoelectric oxide ceramics like ours come into play by substantially improving the ability of thermoelectric generators to convert waste heat into electricity.”
Because they are easy to use and maintain, thermoelectric generators are a potential technology for waste heat recovery. The waste heat from a power plant could be captured in large quantities by a strong thermoelectric generator.
But “for the majority of applications, thermoelectric technology is too inefficient to be economical,” Song said. “Thermoelectric’s lack of effectiveness in converting energy severely hampers the development of thermoelectric devices, even though they are desperately needed.”
Her team developed a dense, textured polycrystalline material that outperforms the currently used single-crystal materials by modifying the ceramic’s atomic-scale crystal structure in a way that can only be observed with an electron microscope.
Although decades of intense theoretical and experimental work have been devoted to optimizing the performance of various materials for thermoelectrics, Song believes that her lab is the first to demonstrate for bulk oxide ceramics a notable improvement in the efficiency of energy generation from heat through the nano and atomic-scale engineering of grain boundaries between crystals.
“This work is at the cusp for large-scale, high-temperature waste heat recovery,” she said. “It leads toward a new era for oxide ceramics and aligns with the U.S. Department of Energy’s Industrial Heat Shot initiative to develop cost-competitive industrial heat decarbonization technologies with at least 85% lower greenhouse gas emissions by 2035. Our findings could facilitate and accelerate materials design that is magnitudes higher than the current state of the art.”