Experimental study on the switching logic of a photovoltaic solar-assisted loop thermosiphon /heat pump hybrid system in enthalpy difference laboratory

Tao Zhang, Shijing Feng, Jinming Zhai, Zhengrong Shi and Jie Ji

Renewable Energy, 2025, vol. 239, issue C

Abstract: Combining active or passive two-phase heat transfer methods such as heat pump (HP) and loop thermosyphon (LT) into a photovoltaic/thermal (PV/T) system could overcome freezing and corrosion issues commonly found in water-cooled PV/T collectors. However, HPs waste solar energy resources under sunny meteorological conditions, while LTs cannot satisfy temperature demands under cloudy or rainy meteorological conditions. Hence, combining the above two methods can provide more efficient operation. In this study, a prototype of the hybrid system named photovoltaic solar-assisted loop thermosiphon/heat pump (PV-SALT/HP) was proposed and constructed for the first time. The PV-SALT/HP system could independently operate in LT-PV/T or PV-SAHP modes and could realize the switching operation. The performance and switching logic of PV-SALT/HP system in various operation modes under four typical meteorological conditions were revealed through massive experiments. Particularly, an enthalpy difference laboratory with a solar simulator was applied to manage meteorological conditions. Furthermore, the switching logic decided by water temperatures of PV-SALT/HP system was evaluated based on its fitted performance. Results revealed that to satisfy users' water temperature demands, LT-PV/T mode realized it only under meteorological condition of 600 W/m2 & 30 °C; as for PV-SAHP mode, it only consumed 172.5–330 min, which was much shorter than the average daily radiation time. Under meteorological condition of 400 W/m2 & 30 °C, PV-SALT/HP system demonstrated an optimal switching water temperature of 36.0 °C. Moreover, under meteorological conditions of 400 W/m2 & 20 °C and 600 W/m2 & 20 °C, the optimal switching water temperatures, which were determined based on fitting formulas, were 29.0 °C and 44.0 °C, respectively. The above switching temperatures simultaneously balance temperature demands, full utilization of solar radiation, and energy-saving under different meteorological conditions.

Keywords: Photovoltaic/thermal; Loop thermosiphon; Heat pump; Enthalpy difference laboratory; Switching logic (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:239:y:2025:i:c:s0960148124022444

DOI: 10.1016/j.renene.2024.122176

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