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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]

The concept of solar-air dual source heat pump has been proposed to overcome the limitations of single source heat pump system. In this paper, a comparative investigation is presented among three types of solar-air dual source heat pump with different heat source configurations: solar-air series source heat pump (SA-SHP), solar-air parallel source heat pump (SA-PHP) and air-solar series source heat pump (AS-SHP). The impact of environmental parameters has been discussed, and the optimal working condition for each system has been identified. The results indicate that SA-SHP is suitable for working under the environment with low solar irradiation, AS-SHP shows the best performance under the condition with low ambient temperature and high solar irradiation, and SA-PHP can achieve the optimal state at high ambient temperature or high solar irradiation. The dynamic performance of SA-SHP, SA-PHP and AS-SHP in the daytime has been compared. The dynamic behavior of each system is significantly different. The COP of SA-PHP is the highest ranging from 4.50 to 4.58, followed by AS-SHP ranging from 4.39 to 4.50, and the COP of SA-SHP is the lowest ranging from 4.33 to 4.41. Moreover, the annual performance and economic feasibility for each system in different climatic regions are evaluated. • Dual source heat pump with different heat source configurations is compared. • Optimal working condition for each system is identified. • The role of air source evaporator and solar evaporator in each system is discussed. • The annual and economic performance is evaluated in different climatic regions. • The annual average COPs of each system in Hefei, Beijing and Xining are above 3.0 [ABSTRACT FROM AUTHOR]