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  • Open Access

Fundamental Limitations of Thermoradiative Energy Conversion

Maxime Giteau*

Michela F. Picardi and Georgia T. Papadakis†

  • *Contact author: maxime.giteau@cnrs.fr
  • †Contact author: georgia.papadakis@icfo.eu
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PRX Energy 4, 043001 – Published 14 October, 2025

DOI: https://doi.org/10.1103/8yz7-djk1

Abstract

Understanding the fundamental limits of various energy conversion approaches is essential for assessing their efficiency and power output. In this work, we derive general performance bounds for thermoradiative heat engines that exchange heat radiatively with a cold sink, establishing power-versus-efficiency thermodynamic bounds for several configurations. We find that the performance of these engines is always bounded by that of radiative engines, which harness the thermal radiation emitted by a hot source, making thermoradiative engines inherently less favorable for energy conversion. By unifying the results of radiative and thermoradiative engines within a common thermodynamic framework, which also encompasses dual-engine configurations that combine both features, this work provides a comprehensive understanding of the thermodynamic limits of radiative energy conversion. Our framework offers general metrics for evaluating specific devices and raises critical questions regarding the relevance of thermoradiative cells for energy production.

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Popular Summary

Efficiently harnessing heat to generate electricity is a key opportunity for energy conversion technologies. This work investigates the fundamental limits of thermoradiative devices – engines that produce power by radiating heat away to a cold environment, such as outer space. The authors establish general performance bounds and reveal that thermoradiative devices are inherently less efficient and generate less power than conventional radiative engines, like solar cells, that absorb heat from a hot source. The developed unified thermodynamic framework shows that, for a given efficiency, radiative engines operating with a cold-side converter outperform their thermoradiative counterpart. While combining engines on both hot and cold sides could enhance performance, this requires breaking fundamental symmetry conditions (nonreciprocity), which is experimentally challenging. These results clarify the practical limits of thermoradiative energy conversion and guide future research and device design by highlighting where improvements are possible and where fundamental constraints exist.

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PRX Energy 4, 043001– Published 14 October, 2025
  • Received 22 July 2025
  • Accepted 22 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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