Design and performance analysis of a fluid spectral-splitting PV/T receiver with prism for flattened linear Fresnel micro-concentrator

The customized flattened Linear Fresnel reflector (LFR) features a compact profile and low wind load, making it ideally suited for solar energy harvesting on building facades. The integration of LFR with spectral-splitting techniques enables efficient harvesting of solar energy to meet both thermal and electrical energy demands in buildings. Due to the limited internal space of the flattened LFR, a compact spectral-splitting receiver is required. The filter inside the receiver must steer the beam accurately while maintaining high efficiency, an enhanced concentration ratio, and uniform solar irradiance. This paper presents a transmission-type spectral filter based on prism-based total internal reflection (TIR), designed for a compact spectral-splitting receiver. The filter consists of a concentrating prism and an arc-shaped photothermal conversion tube. The filter achieves secondary concentration and uniform sunlight distribution through refraction and TIR. The filter's geometric design enables effective etendue matching with the primary mirror field of the flattened concentrator. This allows it to efficiently capture and steer marginal beams reflected from the concentrator's outer mirrors. Experimental results validate the filter's capability to steer large-angle incident beams effectively. Simulations and etendue matching analyses indicate that the proposed filter significantly improves optical efficiency, concentration ratio, and light spot uniformity in flattened LFR systems, outperforming existing receiver designs. The filter's structure and design methodology provide valuable insights for advancing solar spectral-splitting technologies in building-integrated applications. Additionally, they facilitate the integration of liquid spectral-splitting research with established concentrator technologies like compound parabolic concentrators (CPC).