Improving Combined Solar PV and Thermal Applications with The Use of Nanofluids

Abstract

Photovoltaic (PV) modules convert only a portion of incident solar radiation into electricity, while the remaining spectrum contributes to heating, which reduces efficiency. Managing this unwanted spectral energy is essential for improving PV system performance. Nanofluids— suspensions of nanoparticles in a base fluid—offer a potential solution by enabling both optical filtering and heat removal through spectral splitting techniques. This study investigates the optical and thermal characteristics of nanofluids containing Al2O3, CuO, and ZnO nanoparticles in deionised (DI) water, with a focus on their applicability in hybrid optical–thermal management for PV systems. A solar simulator was employed to evaluate spectral attenuation under both static and dynamic flow conditions. Prior to optical testing, nanofluid stability was characterised using zeta potential, dynamic light scattering (DLS), sedimentation studies, and electron microscopy. Beneficial zeta potential values were observed for Al2O3–DI water nanofluids, which maintained stable dispersion for up to two months. Optical experiments revealed that Al2O3–DI water nanofluids exhibited high extinction coefficients in the spectral regions corresponding to unwanted solar wavelengths. Attenuation was influenced by nanoparticle size and shape, with 50 nm spherical particles achieving greater suppression in these bands than 20 nm or 50 nm flaky particles. Flow-based experiments were conducted at velocities of 0.056, 0.083, and 0.111 m/s, corresponding to Reynolds numbers of 1044, 1566, and 2089, representing conditions relevant to practical cooling systems. Spectral behaviour aligned closely with predictions from the Beer–Lambert law, and thermal testing up to 65 °C revealed no significant variation in transmittance. These findings suggest that Al2O3–DI water nanofluids can serve as dual-function media for optical filtering and heat regulation, offering a pathway to enhanced PV performance through integrated photonic and thermal control.