Nanophotonic Structures Convert Thermal Energy

Conversion of thermal energy into electrical energy is an important area of research and development. There are many distributed heat sources from which thermal energy is simply wasted. A technology that could effectively harness this thermal energy could increase the overall efficiency of engines, turbines, etc.

Most research to date has focused on thermoelectrics and thermophotovoltaics as a means to convert thermal energy.

However, exciting new work by SPIE member Brhayllan Mora-Ventura and colleagues in Mexico and Spain has highlighted an alternate approach to leveraging the thermoelectric (Seebeck) effect by combining high Seebeck coefficient bi-metals with nanoantennas.

In “Responsivity and resonant properties of dipole, bowtie, and spiral Seebeck nanoantennas,” published in the Journal of Photonics for Energy in May, the team performed detailed finite-element modeling in the range of 10 to 150 THz of such nanoantennas. They first showed that the resonance frequency of the nanoantennas is shifted from what would be expected by classical antenna theory, an important design insight.

The team then studied the responsivity of various metals within a fixed nanoantenna geometry (3 micron dipole) and showed the expected current levels for each metal.

Three different antenna geometries were compared (dipole, bowtie, and square-spiral), and it was shown that the bowtie nanoantenna is the most desired geometry due to the highest thermal gradients induced in the structure.

Finally, the paper showed that combining the dipole nanoantenna with nickel and titanium, the highest voltage responsivity may be obtained. The researchers further suggest that Ni-Ti bowtie nanoantennas are a leading path for further research and design.

Coauthors of the open-access article are Ramón Díaz de León and Jorge Flores, SPIE Fellow Javier Alda, and SPIE members Guillermo García-Torales and Francisco J. González.

Source: dx.doi.org/10.1117/1.JPE. 6.024501

–Loucas Tsakalakos is manager of the photonics lab at GE Global Research and an associate editor of the Journal of Photonics for Energy.

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