Theoretical model provides fresh route to more efficient cooling using light and heat - phys.org

Self-sustaining thermodynamic system boosts radiative cooling power by coupling a heat engine with a thermoradiative diode to enable autonomous generation of positive photon chemical potential and enhanced cooling power. Credit: Journal of Photonics for Energy (2025). DOI: 10.1117/1.JPE.15.022507

As climate change and growing energy demands strain global systems, scientists are increasingly turning to passive cooling technologies—ways to cool objects or spaces without using electricity. One promising method is radiative cooling, which works by reflecting sunlight and releasing heat in the form of infrared radiation into space. But despite its potential, this method is limited by natural laws that cap how much heat can be emitted. Now, a proposed theoretical model has the potential to boost the power of radiative cooling, potentially changing the way we manage heat in a warming world.

As reported in the Journal of Photonics for Energy, researchers recently developed a theoretical system that links a thermoradiative diode (TRD) with a heat engine, forming a self-sustaining setup that can release more heat than previously thought possible. This approach could allow for more effective cooling without relying on constant electricity from external sources.

The key lies in a concept called photon chemical potential, which influences how much energy can be carried away as infrared light. Normally, achieving a positive photon chemical potential—which increases heat emission—requires energy input. But by pairing a TRD with a heat engine, the system can generate this effect internally, making the setup more efficient and potentially passive.

Using theoretical calculations, the researchers showed that their combined system could reach a cooling power of up to 485 watts per square meter. This figure has the potential to surpass the typical radiation power from a blackbody at room temperature (around 459 W/m²), which has been a limiting factor for passive radiative cooling systems until now.

The team also examined how different setups—such as pairing the TRD with a thermoelectric generator instead of a Carnot engine—might affect performance. They found that certain configurations and design choices, like the size ratio between components, significantly influence efficiency. Importantly, their analysis confirms that integrating a TRD and a thermoelectric generator to turn waste heat into radiation can be effective even without active power sources, as long as the system is properly designed.

While this work is currently theoretical, it offers a new direction for sustainable cooling technologies that could one day reduce the need for energy-hungry air conditioning systems. The researchers hope their findings will guide future experiments and designs for managing heat more efficiently in buildings, electronics, and beyond.

by SPIE

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