Engineering 101

Turning Heat into Electricity—Cool

A new nanophotonic material just broke records for high-temperature stability. Implications are that the material may enable more efficient electricity production and new possibilities in controlling and converting thermal radiation. The material controls the flow of infrared radiation and is stable at temperatures of 2,000 degrees Fahrenheit in air, a twofold improvement over current approaches.

University of Michigan researchers say that the material uses a phenomenon called destructive interference to reflect infrared energy while letting shorter wavelengths pass through. Potentially this will reduce heat waste in thermophotovoltaic cells, which convert heat into electricity by reflecting infrared waves back into the system. The material could also be useful in optical photovoltaics, thermal imaging, environmental barrier coatings, sensing, camouflage from infrared surveillance devices, and other applications. Researchers published their findings in Nature Photonics.

The approach is a significant departure from the current state of engineered thermal emitters that use foams and ceramics to limit infrared emissions. These materials are stable at high temperatures but offer minimal control over which wavelengths they let through. Nanophotonics offers more tunable control, but past efforts haven’t been stable at high temperatures, often melting or oxidizing.

The new material works toward solving that problem, beating heat resistance records among air-stable photonic crystals by more than 900 degrees Fahrenheit in open air.

While commercial implementation of the material tested in the study is likely years away, the core discovery opens up a new line of research into a variety of other nanophotonic materials that could help future researchers develop a range of new materials for a variety of applications.

For more information, see Nanophotonic control of thermal emission under extreme conditions.

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