Scalable, waste-derived radiative cooling coating for photovoltaic efficiency enhancement: Field validation and techno-economic assessment

Overheating significantly degrades the performance and longevity of photovoltaic (PV) modules and power grid infrastructures. While radiative cooling offers a zero-energy thermal management solution, widespread adoption is hindered by the high cost and complex fabrication of existing functional materials. Herein, we propose an ultra-low-cost and sustainable radiative cooling coating developed by upcycling coal fly ash, into a ∼100 μm-thick single-layer composite coating dispersed within an acrylic resin matrix. Unlike conventional coatings relying on expensive purified ceramics, this waste-derived solution utilizes the intrinsic phonon-polariton resonance of fly ash to achieve a high mid-infrared emissivity of 89%. Field experiments demonstrate substantial net cooling capabilities under real-world conditions. Specifically, the coating reduced the surface temperature of metallic substrates by an average of 5 °C (up to 12 °C). More importantly, when applied onto the backsheet of operational PV modules, the coating yielded a 5.24–6.67% increase in daily power generation. This performance enhancement is predominantly governed by passive mid-infrared radiative heat dissipation, complemented by localized natural convection along the inclined surface. Techno-economic analysis reveals a material cost of only $0.39/m2, which is significantly lower than existing commercial and literature-reported solutions. With huge global fly ash reserves, this work presents a scalable, commercially viable, and eco-friendly strategy for enhancing renewable energy efficiency.