Design and experimental validation of a beam-splitting and light-guiding solar concentrator for photovoltaic-thermal applications

This work presents the design, modelling and experimental validation of a high-concentrating beam-splitting and light-guiding solar concentrator developed within the SolDAC project framework. The architecture combines a linear Fresnel reflector (18.6 × ) with optimised free-form secondary optical elements (SOEs) (31.8 × ), reaching a global geometric concentration of 591 × . The SOEs integrate a circulating deionised water-filled cavity that performs spectral splitting and heat extraction while transforming the line focus into a light guiding-compatible point focus. Ray-tracing simulations show a global optical efficiency of ∼ 55%, accounting for reflection losses, transmission through the SOEs and absorption in the liquid cavity. The integrated system exhibits a tracking acceptance angle of ± 0.4°, consistent with high-concentration optics. Irradiance non-uniformity at the SOE exit is mitigated through a kaleidoscopic homogeniser to ensure stable photovoltaic operation. Experimental measurements on a full-scale prototype confirm the main optical trends provided by the design model, including the irradiance distribution at the Fresnel focus, the spectral transmission of the secondary receiver and the system-level optical performance. The proposed architecture demonstrates the feasibility of integrating high-concentration optics, liquid spectral splitting and light guiding into a single configuration intended for future CPVT (concentrating photovoltaic–thermal) systems for solar-driven CO 2 capture and conversion.