Optical properties and transmittances of ZnO-containing nanofluids in spectral splitting photovoltaic/thermal systems

Spectral transmittance comparison of among water-ZnO nanofluid, water-Cu9S5 nanofluid, and water- polypyrrole nanofluid. [Display omitted] •Scheme of solving optical properties and radiative transfer of nanofluids is built.•The usability of ZnO nanoparticles in spectral splitting PV/T systems is studied.•Optical properties and transmittances are studied using different nanofluids.•Overall effective spectral transmittance coefficient δE for PV cells is put forward.•Water–ZnO has higher overall transmittance than water–polypyrrole and water–Cu9S5. As ZnO nanoparticles had the advantages of high thermal conductivity and low cost, the possibility of using ZnO nanoparticles in spectral splitting photovoltaic/thermal (PV/T) systems was initially studied from the perspective of optical properties. Water–ZnO and glycol–ZnO nanofluids were prepared via a two-step method and used for model validation and stability testing. The scheme employed to investigate the optical properties and radiative transfer of the nanofluids was developed using Mie scattering theory combined with the Monte Carlo ray tracing (MCRT) method. The overall effective spectral transmittance coefficients of PV cells were utilized for comprehensive evaluation of the spectral transmittances of the nanofluids in spectral splitting PV/T systems. The overall effective spectral transmittance of a PV cell water-ZnO nanofluids was 21.54% higher than that those of cells containing water–polypyrrole and water–Cu9S5 nanofluids, respectively. The effects of the nanoparticle diameter, mass concentration and the optical length of the nanofluid on the spectral transmittance of glycol–ZnO nanofluid were also investigated.