energies Article Investigation of an Inclined Heat Pipe Heat Exchanger as a Passive Cooling Mechanism on a Photovoltaic Panel Samiya Aamir Al-Mabsali 1 , Jay Pillo Candido 2 , Hassam Nasarullah Chaudhry 3, * and Mehreen Saleem Gul 1   Citation: Aamir Al-Mabsali, S.; Candido, J.P.; Chaudhry, H.N.; Gul, M.S. Investigation of an Inclined Heat Pipe Heat Exchanger as a Passive Cooling Mechanism on a Photovoltaic Panel. Energies 2021, 14, 7828. https://doi.org/10.3390/en14237828 Academic Editor: Dmitry Eskin Received: 19 October 2021 Accepted: 18 November 2021 Published: 23 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh EH14 4AS, UK; saa83@hw.ac.uk (S.A.A.-M.); M.Gul@hw.ac.uk (M.S.G.) 2 Department of Engineering, University of Technology and Applied Sciences, Muscat P.O. Box 74, Oman; jay.candido@hct.edu.om 3 School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University Dubai Campus, Heriot-Watt University, Dubai Knowledge Park, Dubai P.O. Box 38103, United Arab Emirates * Correspondence: h.n.chaudhry@hw.ac.uk Abstract: An investigation on the heat transfer coefficient (HTC) of a heat pipe heat exchanger (HPHE) was carried out while being installed as a cooling mechanism on photovoltaic panels. The Ecohouse at the University of Technology and Applied Sciences in Muscat, Oman, was used as the case study. The experiment monitored the effect of temperature variations on PV-HPHE-induced power generation. The heat pipes were arranged in a double-sided condenser in a spanwise manner with spacing 50 mm in the center with an inclination angle of 3 ◦ . J-type thermocouples (exposed wire, polytetrafluoroethylene (PTFE) insulated) with a tip diameter of 1.5 mm were used. The results indicated mean values of HTC that were measured at 2.346 W/m 2 K. The findings showed that the HTC values possessed a minimal standard error from the effect of variations of the ambient temperature. The mean HTC value of 2.346 W/m 2 K can be used in the succeeding experiments using the same novel PV-HPHE setup. Additional results showed the recorded variations from the mean value of the HTC effect on the HPHE heat flow generation, which resulted in a 29% increase in power performance efficiency using PV-HPHE. Keywords: heat transfer coefficient; heat pipe; photovoltaic 1. Introduction The Sultanate of Oman has a strong commitment to the promotion of an eco-friendly lifestyle with the creation of a greener future for generations to come. The government of Oman created an initiative to generate energy from renewable resources with a long-term program that started in 2008. Furthermore, the country aims to reduce the reliance on local fossil fuel energy resources, as well as produce a surplus of power that can be shared for the benefit of its citizens [1]. The current study was conducted in the Ecohouse research facility in Oman and aimed to provide a solution to the low power capacity due to the exposure of photovoltaic (PV) panels to the very high ambient temperatures that are experienced in the region. This study is a continuation of Al Mabsali et al.’s [2] experimental investigation, which specified the optimal heat pipe heat exchanger (HPHE) arrangement and installation that can restore the loss in PV performance efficiency and increase power production, as shown in Figure 1. Table 2019 reached 33.8 TWh, 0.7% higher than in 2018, which was 32.5 TWh and the 2018 supply was 3.7% higher than in 2017 based on the APSR in 2018 [3] and 2019 [4]. In addition to energy management strategies, renewable-energy-driven technologies are the most viable alternatives as solutions to meet the increasing energy demand of the Sultanate. Among these technologies, solar photovoltaics (PVs) are the most promising technology due to the strong support from the Omani government. The APSR, [1] developed a Energies 2021, 14, 7828. https://doi.org/10.3390/en14237828 https://www.mdpi.com/journal/energies