Experimental study on a direct-expansion micro-channel PV/T evaporator using water-ZnO nanofluid as the spectral beam splitter

Mengqi Peng, Tao Zhang, Haifei Chen, Zhengrong Shi, Qifen Li and Jingyong Cai

Energy, 2024, vol. 309, issue C

Abstract: Introducing nanofluid (NF) as the spectral beam splitter (SBS) in photovoltaic/thermal (PV/T) evaporators can significantly enhance their performance and energy flexibility. In this study, a novel direct-expansion micro-channel evaporator using water-ZnO nanofluid as SBS (i.e., NF-MC-PV/T evaporator) was manufactured. Particularly, the stability of low-viscosity water-ZnO nanofluid was first optimized and natural convection within the NF-MC-PV/T evaporator was directly formed. Further, a direct-expansion heat pump system based on the NF-MC-PV/T evaporator was developed and tested. According to the findings, adding sodium hexametaphosphate as a dispersant with the dispersion ratio of 1:5 and ultrasonic treatment for 1.5 h can achieve the optimal stability of water-ZnO nanofluid. The nanofluid's natural convection can reduce the evaporator's operating temperature and improve the PV module's temperature distribution uniformity. Specifically, the NF-MC-PV/T evaporator's operating temperature was lower than the environment temperature and a pure PV module. Besides, the PV module's temperature distribution was uniform in the direction perpendicular to the refrigerant flow with a max temperature gradient of only 4.59 °C. The typical photothermal efficiency of the NF-MC-PV/T evaporator reached 102.55 % while the heat loss coefficient was only 4.37. Moreover, the average photothermal efficiency, photovoltaic efficiency, and COP of the system were 103.58 %, 12.03 %, and 5.09, respectively.

Keywords: Spectral beam splitter; Direct-expansion; Stability optimization; Experimental study; Heat pump; Natural convection (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:309:y:2024:i:c:s0360544224028974

DOI: 10.1016/j.energy.2024.133122

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