Endoreversible description of photothermal Vuilleumier refrigeration machines

Abstract Sustainable cooling is critical for climate change mitigation and energy resilience, potentially reducing global greenhouse gas emissions while addressing rising demand for cooling. Solar refrigeration technologies offer alternatives to electricity-intensive refrigeration systems but remain underutilised in industrial applications where thermal energy is required for many manufacturing processes. Specifically, Vuilleumier refrigerators – heat-driven devices with mechanical simplicity – show unexplored potential when powered by concentrated solar energy, as no existing models integrate a solar concentrator with the refrigeration cycle irreversibilities. Here, we develop an endoreversible thermodynamic model of a solar-driven Vuilleumier refrigerator, coupling optical concentration, absorber design, and regeneration effect. Numerical analysis reveals that the coefficient of performance ( β ) exhibits concentration-dependent thresholds ( ξ > 0.18 at 273 K; ξ > 0.11 at 253 K), with asymptotic plateaus at β ≈ 9 and β ≈ 4 respectively. Normalised sensitivity analysis identifies regenerator effectiveness ( ɛ ) as the dominant parameter (12–16 times more influential), compared with the solar-specific parameters. These results resolve a critical gap in solar-thermal refrigeration by demonstrating that regenerator design – not concentrator scaling – limits maximum coefficient of performance. This work provides a thermodynamic blueprint delineating the fundamental performance boundaries of solar-Vuilleumier technology, governed by irreversibility constraints and asymptotic efficiency limits.