Dr. Fuqiang Wang
Professor, School of New Energy, Harbin Institute of Technology at Weihai, China

Speech Title: Experimental investigation of cost-effective spectral splitting CPV/T system

Abstract: Utilization of concentrator photovoltaics (CPV) can reduce market investment cost and shorten payback time because that CPV have high photoelectric conversion efficiency and the expensive solar cells are replaced by cheap solar concentrators. As the result of the solar cells’ fixed band-gap, solar cells can only convert photon energy close to the semiconductor band-gap to electricity. Photon energy both higher and lower than the semiconductor band-gap is converted to heat and lead to severe heat load, which greatly reduces photoelectric conversion efficiency and solar cells life. The spectral splitting technology directs the photon energy close to the semiconductor band-gap to solar cells and directs photon energy both higher and lower than the semiconductor band-gap to thermal absorbers, which offers a possibility for reducing solar cells temperature, increasing photoelectric conversion efficiency and solar cells life. Herein, starting from the wavelength band and energy grade of solar energy, taking the principle of customer demands for electricity and heat cogeneration, the spectral splitting technology based on interference thin film and that based on nanofluid were theoretically and experimentally analysed, respectively. The main contributions of our work were: (1) SiO₂/TiO₂ interference thin film based spectral splitting PV/T system was designed and fabricated, the interference thin film designed by the authors achieved a high average reflectance (R≥96.8%) for PV bands, outdoor testing indicated that PV cells of such system decreased by 3.0 K, the overall energy and exergy efficiency of such system reached 22.72% and 18.81%, i.e., 4.94% and 1.03% higher than those without a SiO₂/TiO₂ interference thin film, respectively; (2) as ZnO nanoparticles had the advantages of high thermal conductivity and low cost, optical properties and transmittances of glycol-ZnO nanofluid were studied by Mie scattering theory combined with the Monte Carlo ray tracing (MCRT) method, overall effective spectral transmittance coefficient was utilized for evaluating the spectral transmittances of nanofluid, the overall effective spectral transmittance coefficient of glycol-ZnO nanofluid was 21.54% and 8.74% higher than that those of water–polypyrrole and oleylamine–Cu₉S₅ nanofluid, respectively; (3) the possibility of using glycol-ZnO nanofluid in spectral splitting CPV/T systems was verified experimentally, outdoor testing indicated that photoelectric conversion efficiency of such system was 2.6%, 1.3% and 8.64% higher than those of other systems using water-polypyrrole, oleylamine-Cu₉S₅ and water-Ag-SiO₂ nanofluid as spectral splitting filter, the overall exergy efficiency of such system was 2.32% and 2.86% higher than those of other systems using water-polypyrrole and water-Ag-SiO₂ nanofluid as spectral splitting filter. Based on the analyses, it can be concluded that spectral splitting CPV/T system would be promising and market competitiveness.

Acknowledgements: This work was supported by the Natural Science Foundation of China (Grant No. 51676061) and the Taishan Scholars of Shandong Proviance (tsqn201812105).