**5. Conclusions**

The potential of PVs in hot and arid climates, although promising, may be adversely a ffected by the high intensity of solar radiation and high temperatures. This study carried out an investigation using a heat pipe heat exchanger (HPHE) system as a retrofit mechanism for passively cooling PV panels. Computational fluid dynamics (CFD) was used to determine the optimum spanwise arrangemen<sup>t</sup> of heat pipes integrated with PV panels.

The work undertaken analyzed the temperature formations on the PV panels using a range of heat pipe spacing combinations. The work has identified that the HPHE has the capacity to provide the required cooling of the photovoltaic panels installed in the HCT Ecohouse in Oman, which are usually exposed to a maximum temperature of 64.5 ◦C (337.65). The major finding from this study indicates that the 50 mm HPHE spacing (2.5D or 2.5 times the diameter of the pipe) has the greatest potential to decrease panel temperature, with a maximum reduction down to 55.32 ◦C (328.47 K) or approximately 9 ◦C. The recommended HPHE design installation is expected to be made of a double-sided condenser, having a middle section installation with a 90◦ spanwise orientation towards the PV panel. Current experimental testing has indicated a temperature drop between 2 to 5 ◦C, which is lower than the numerically predicted results.

This paper provided a proof-of-concept towards integrating heat pipes within PV panels to increase e fficiency by 2.19% in order to restore the design power capacity specified in the previous design of the HCT Ecohouse, especially for PV panels operating in hot arid climates such as Oman. Furthermore, having heat pipes operating with water as the working fluid, as opposed to artificial refrigerants, underlines the suitability of this technology towards the development of sustainable solar energy in hot countries.

**Author Contributions:** Conceptualization, S.A.A.-M. and H.N.C.; methodology, S.A.A.-M., H.N.C. and M.S.G.; software, S.A.A.-M.; validation, S.A.A.-M.; formal analysis, S.A.A.-M.; investigation, H.N.C. and M.S.G.; resources, S.A.A.-M.; data curation, S.A.A.-M.; writing—original draft preparation, S.A.A.-M.; writing—review and editing, H.N.C. and M.S.G.; visualization, S.A.A.-M., H.N.C. and M.S.G.; supervision, H.N.C. and M.S.G.; project administration, H.N.C.; funding acquisition, S.A.A.-M.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would like to thank Heriot-Watt University and Higher Colleges of Technology, Oman for providing computational and experimental resources to carry out this research.

**Conflicts of Interest:** The authors declare no conflict of interest.
