Nanomanufacturing of Nanophononic Devices: Ultra-High ZT Thermoelectrics for Efficient Conversion of Waste Heat
Waste heat is widely considered an untapped resource for improving energy efficiency. According to the Lawrence Livermore National Laboratory/DOE 2017 Energy Flow Chart, approximately two-thirds of all energy consumed in the U.S. was wasted, much of it as heat. Waste heat capture technology, which turns excess thermal energy into electricity, has the potential to provide consumers with billions of dollars in energy savings each year. Thermoelectric materials can harness waste heat by converting it to electricity. The key requirement for maximum thermoelectric efficiency (ZT) material is to concurrently have low thermal conductivity and high electrical conductivity. The challenge is that these two properties cannot be tuned independently in existing materials, particularly in inexpensive industrial materials like silicon. Over the last two decades, ZT has typically been increased by embedding small imperfections (such as topological holes, ions, particles and/or interfaces) within the material to scatter the heat-carrying phonons and reduce thermal conductivity. While modestly successful, this strategy has not been transformational and can impede the flow of electrons, reducing the electrical conductivity.
Project Innovation + Advantages:
The University of Colorado Boulder aims to revolutionize thermoelectrics, the semiconductor devices that convert heat flow into electricity without moving parts or emitting pollutants, by creating a “nanophononic” thermoelectric device. This concept relies on a newly discovered phenomenon where closely packed tiny structures added perpendicular to a thin solid membrane impede the flow of heat down the membrane through atomic vibrations (phonons). The device is predicted to convert waste heat to electricity at twice the efficiency of today’s best thermoelectric devices.
The project team aims to build and test a record-efficiency prototype thermoelectric device based upon theoretical advances in nanophononic metamaterial design, generating significant improvement over the current state-of-the-art.
Turning waste heat into usable electric power adds an alternate energy stream.
Efficient waste-heat recovery will significantly lower global emissions.
The technology’s disruptive impact on waste-heat recovery will reap large economic rewards for the U.S. Applying the technology to automotice exhaust could produce a 5% increase in efficiency that yields $20 billion annual savings in fuel expenditure.