Zero-Energy Cooling for Agricultural Applications Using PVDF-NP-Based Radiative Coatings

Passive Daytime Radiative Cooling (PDRC) represents a promising zero-energy strategy for thermal regulation by reflecting solar radiation while emitting heat through the atmospheric window (8–13 µm). In this study, PVDF-based PDRC coatings embedded with MgO and ZrO₂ nanoparticles were developed, characterized, and applied for sustainable cooling in agro-based systems. Nanocomposite coatings were prepared using polyvinylidene fluoride (PVDF) as the polymer matrix, incorporating MgO and ZrO₂ nanoparticles individually. Optical characterization showed that ZrO₂-PVDF achieved the highest solar reflectance of 0.96 with only 0.02 absorbance and 0.02 transmittance, while MgO-PVDF exhibited 0.94 reflectance, 0.02 absorbance, and 0.04 transmittance, indicating a high solar rejection and radiative cooling capability.

To evaluate practical cooling performance, coatings were applied on 5×5 cm metal and PET strips and exposed to ambient conditions. The MgO-PVDF-coated strip achieved surface temperatures as low as 28.7°C at 16:00 hours, compared to at 38.2°C ambient temperature and up to 52.9°C for black-coated controls. ZrO₂-PVDF also showed significant sub-ambient performance. For application-level validation, a transparent PET box was coated externally with the PDRC films. Under peak sunlight (10:00–16:00 hours), the coated PET box consistently maintained internal temperatures 8-11°C lower than the uncoated box, demonstrating the material’s effectiveness in real agro-climatic environments. This study establishes PVDF-based MgO/ZrO₂ nanocomposite coatings as scalable, passive, and power-free cooling solutions, suitable for post-harvest storage, packaging, and field-level applications in agriculture to reduce thermal stress and spoilage.