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Experimental investigation on thermal characteristics of a flexible separated heat pipe developed for tracking photovoltaic/thermal systems

Author

Listed:
  • Lu, Zaikang
  • Cao, Jingyu
  • Zheng, Ling
  • Zhao, Misheng
  • Chen, Jun
  • Peng, Jinqing
  • Hu, Mingke
  • Wang, Qiliang
  • Liu, lifang
  • Tian, Zhen
  • Li, Hongqiang

Abstract

This study aims to address the efficiency limitations in conventional photovoltaic/thermal (PV/T) systems caused by support structure shading and hot spot formation, which reduce effective light collection and lead to uneven heat dissipation. To mitigate these challenges, a novel flexible separated heat pipe system is proposed for application in solar tracking-enabled photovoltaic thermal systems. The conventional coil-type water tank is replaced with shell and tube heat exchangers, and metal bellows are integrated to enable a flexible connection between the evaporator and condenser. By integrating dual-axis solar tracking with a gravity-driven separated heat pipe cycle, efficient phase-change-based heat transfer is achieved. Experimental evaluations were conducted under various conditions, including different levels of solar irradiance, combinations of inclination and altitude angles, and varying cooling water flow rates. The results demonstrate that the system achieves a thermal efficiency of 63.5 % at an inclination angle of 15° and an altitude angle of 30°. The maximum thermal efficiency reaches 65.5 %, representing an improvement of up to 56.3 % compared to conventional fixed PV/T systems. However, when the inclination angle decreases to −30° or −45°, the elevation difference between the evaporator and condenser reverses, disrupting the thermosiphon effect and resulting in efficiency reductions of 22.1 %–45.0 %. This study validates the technical feasibility of the proposed integrated system under variable inclination conditions, identifies its optimal angular operating range, and provides both a novel methodological approach and a theoretical foundation for the application of flexible heat pipes in high-efficiency solar energy conversion systems.

Suggested Citation

  • Lu, Zaikang & Cao, Jingyu & Zheng, Ling & Zhao, Misheng & Chen, Jun & Peng, Jinqing & Hu, Mingke & Wang, Qiliang & Liu, lifang & Tian, Zhen & Li, Hongqiang, 2026. "Experimental investigation on thermal characteristics of a flexible separated heat pipe developed for tracking photovoltaic/thermal systems," Energy, Elsevier, vol. 342(C).
    • Handle: RePEc:eee:energy:v:342:y:2026:i:c:s0360544225053551
    DOI: 10.1016/j.energy.2025.139712
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    References listed on IDEAS

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