Investigation of two-stage concentrating splitting photovoltaic/thermal system with a flexible heat-electricity ratio based on nanofluid

As an emerging technology, the photovoltaic/thermal system adopting spectral beam splitting has been a promising field of solar energy research. This study proposes a two-stage concentrating splitting photovoltaic/ thermal system based on nanofluid, which realizes the thinner splitting layer and the effective thermal management of the optical nanofluid. At first, the optical characteristics of the proposed system are simulated by the Monte Carlo ray-tracing method. Otherwise, the thermal and electrical performance differences of four photovoltaic/thermal systems are analyzed comparatively by the energy balance method. The results show that when the mounting height and the relative focus length of the secondary reflector increases, the illumination distribution on the photovoltaic module presents a M-?-M variation, while it presents a widening M distribution on the secondary reflector. On the other hand, the two-stage concentrating splitting photovoltaic/thermal system without a cooling channel outperforms the traditional splitting photovoltaic/thermal system by a maximum of 1.4% and 2.9% in terms of thermal and electrical efficiency, respectively. Furthermore, it realizes the hightemperature protection of the nanofluid. Ultimately, a hybrid photovoltaic/thermal system with a flexible heat-electricity ratio is proposed under two basic operating strategies: maximum electrical output and maximum thermal output. The electrical output of the flexible hybrid system is 14.3% and 10.0% higher than that of traditional photovoltaic/thermal and two-stage concentrating splitting photovoltaic/thermal systems without the cooling channel, respectively. The proposed two-stage concentrating splitting photovoltaic/thermal system also has potential for further development at high concentrations.

Automated summary

This study proposes a two-stage concentrating splitting photovoltaic/thermal system based on nanofluid, which achieves better thermal and electrical performance through a thinner splitting layer and effective thermal management. The system has advantages in illumination distribution and thermal-electric efficiency.