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In the traditional PV/T system, there is a certain contradiction in the collection process of heat and electric energy. This paper describes a spectral splitting PV/T system, which effectively alleviates the negative effects of high temperature on monocrystalline silicon cells, and separates the soalr radiation so as to improve the utilization efficiency of full spectrum energy. Then, through the all-day experimental study, the results show that the maximum temperature of the spectral splitting medium can reach 38.21 °C, the maximum thermal and electrical efficiency were 38.7 % and 11.77 %, respectively. The output power of the PV cell is more affected by solar radiation, and the filling factor is more affected by the temperature of the battery. In addition, the mathematical model is established and verified. The results show that the optimal nanofluid concentration of the system is 1*107 μg/m3 and 5*106 μg/m3 in Xining and Hefei, respectively. When applied in Beijing area, the optimal nanofluid concentration is 1*106 μg/m3 in summer and 1*107 μg/m3 in winter. Finally, we calculated the annual electric energy and heat output in the three regions using the best nanofluids, namely 126.6 MJ/m2 and 1186.68 MJ/m2 in Xining, 154.44 MJ/m2 and 948.96 MJ/m2 in Hefei, 164.46 MJ/m2 and 1062.43 MJ/m2 in Beijing. • Experimental and numerical investigation on spectral splitting PV/T system under natural conditions. • Excellent thermal and electrical performance, loss coefficient of heat energy. • The applicability of spectrally selective nanofluids in the system were evaluated. • Optimal nanofluid concentration for different regions based on annual performance analysis. [ABSTRACT FROM AUTHOR]

Firstly, this paper introduces a novel multi-functional BIPV/T wall system in order to satisfy building's seasonal energy demand in China. This system can generate electricity during the whole year. In heating season, hot air is created to decrease heating load for the building. In non-heating season, hot water is generated to supply the household demand. Meanwhile temperature of PV panel is decreased by water cycle, therefore higher electrical performance is able to be achieved. Secondly, mathematical model is established and verified by the experimental results. Thirdly, annual performance of the system in three different typical cities are evaluated. The annual electrical generation in Beijing, Hefei and Xining are 247.7 kWh, 152.6 kWh and 268.4 kWh respectively. The solar fraction in Beijing, Hefei and Xining are 49.9%, 38.7% and 41.3% respectively. The system is able to satisfy 79.1%, 66.8% and 60.4% hot water energy demand in these cities respectively. The overall annual energy saving in Beijing, Hefei and Xining are 2661.8 kWh, 1908.4 kWh and 2412.3 kWh respectively. Fourthly, the impact of external/internal PV structures, Si/CdTe solar cells and aspect ratio of the system are investigated respectively. • This paper introduces a novel multi-functional BIPV/T wall system for building in cold winter and hot summer area. • Mathematical models are established and verified by experimental results. • Annual performance of the system in three different typical cities are evaluated. • System's performance under different parameters are conducted. [ABSTRACT FROM AUTHOR]