Reviewed by Lexie CornerMay 19 2025
According to a study published in the Journal of Photonics for Energy, researchers have developed a theoretical system that couples a thermoradiative diode (TRD) with a heat engine. The configuration forms a self-sustaining cycle capable of dissipating more heat than previously considered possible.
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. Image Credit: Zhang and Li, doi 10.1117/1.JPE.15.022507
As climate change and increasing energy demands strain global infrastructure, researchers are exploring passive cooling technologies—methods that dissipate heat without external power input. One such method, radiative cooling, works by reflecting sunlight and emitting thermal energy as infrared radiation into space.
Although promising, radiative cooling is limited by thermodynamic constraints that cap the amount of heat that can be emitted. A new theoretical model proposes a way to enhance its efficiency, potentially advancing the design of next-generation cooling systems.
The approach centers on the concept of photon chemical potential, which governs the energy that can be removed via infrared radiation. Typically, achieving a positive photon chemical potential requires external energy.
However, by coupling a thermoradiative diode (TRD) with a heat engine, the system can internally sustain this condition, eliminating the need for external power and potentially enabling passive operation.
Theoretical calculations show that such a system could deliver up to 485 watts per square meter of cooling power. This figure exceeds the standard blackbody radiation limit at room temperature (about 459 W/m²), which has traditionally constrained passive cooling performance.
The study also examined alternative configurations, including pairing the TRD with a thermoelectric generator instead of a Carnot engine. The results suggest that system performance is sensitive to component design choices, such as size ratios and material properties.
The analysis indicates that waste heat can be converted into outgoing radiation even without an active power supply, provided the system is appropriately built.
While still theoretical, the work outlines a promising direction for developing low-energy cooling technologies. The authors suggest their findings could inform future experimental designs aimed at improving thermal management in buildings, electronics, and other applications.
Journal Reference:
Zhang, X., and Li, W. (2025). Photon chemical potential-driven power enhancement in passive radiative cooling: a theoretical model. Journal of Photonics for Energy (JPE). doi.org/10.1117/1.JPE.15.022507