Integrating latent heat storage and sorptive cooling for photovoltaic panels: Experimental, exergy, and environmental insights

Photovoltaic (PV) modules operating in hot and arid climates suffer from elevated temperatures that degrade electrical efficiency and accelerate aging. While recent review studies have identified phase change materials (PCMs) and sorptive materials as promising passive cooling solutions, their conclusions are largely based on simulations or laboratory-scale investigations, with limited experimental validation under real outdoor conditions. This study presents a direct, experimental comparison of two fundamentally different passive cooling mechanisms: latent heat storage using calcium nitrate tetrahydrate (CNT-PCM) and adsorption-driven evaporative cooling using a green-synthesized MOF-801. Side-by-side outdoor experiments were conducted during spring, summer, and autumn under identical climatic conditions, and the systems were evaluated using a unified thermal, electrical, exergy, economic, and environmental (4E) framework. The CNT-PCM system achieved a maximum surface temperature reduction of 18.2 °C, improved electrical efficiency by 10.9%, and reached an exergy efficiency of 30.7%, while maintaining stable performance over repeated cycles. In contrast, MOF-801 provided a moderate temperature reduction of 4.4 °C and an efficiency improvement of 2.8%, with partial performance degradation observed after cyclic operation. Over a projected 20-year lifetime, the CNT-PCM system could reduce CO2 emissions by 9.6% compared with an uncooled module. Unlike previous review-based conclusions that broadly emphasize the potential of sorptive materials, the present experimental results demonstrate that inorganic PCMs offer more robust and reliable long-term thermal regulation for PV modules under real outdoor conditions. This work provides the first side-by-side field comparison of PCM- and MOF-based PV cooling strategies and offers experimentally grounded guidance for sustainable PV thermal management.