Photothermal conversion potential of full-band solar spectrum based on beam splitting technology in concentrated solar thermal utilization

It is still a great challenge for the concentrated solar thermal (CST) technology to promote the utmost out of solar energy further because the CST's receiver generally discards the longer wavelength spectra to prevent radiative heat loss due to high temperatures. Spectrum splitting is a well-known technology generally used in multi-energy cogeneration devices, such as Photovoltaic/thermal (PV/T) systems, aiming to improve photoelectrical efficiency. In this study, the solar spectrum splitting technology is employed in the CST system to take full advantage of solar radiation through enhanced absorptions and conversions of piecewise solar radiation. The exergy efficiency of a beam-splitting photothermal (BSPT) system is used to evaluate its effectiveness. Here, the mechanisms of beam splitting under different splitting wavelengths (λ_sp) and concentration ratios (C_r) are investigated. Furthermore, the influence of the split number is evaluated, and the performance of the dual-segment BSPT system is compared with traditional photothermal systems with real and assumed coatings. It shows that beam splitting can play an excellent role in improving exergy performance. The exergy efficiency improvement ratio of the BSPT stabilizes at around 9% when λ_sp is 1300 nm, and the proposed dual-segment BSPT system can maintain an excellent performance even under off-design working conditions.