Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener An innovative method to control surface temperature of a rooftop photovoltaic system Ali Rahmatmand ⁎ , Stephen J. Harrison, Patrick H. Oosthuizen Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON K7L 3N6, Canada ARTICLE INFO Keywords: Photovoltaic solar panels Snow removal Panel insulation Temperature distribution Eﬃciency ABSTRACT Photovoltaic solar systems in cold regions deal with energy loss due to snow accumulation on the system during the winter and panel temperature increase during the summer. In this paper, a method is proposed to control the surface temperature of a rooftop PV panel during all seasons via having a particular insulation mounted on the back of the PV panel. The main reason for such insulation is the need for snow removal from the panel during the winter. Using a heating snow removal system with the insulation can improve the panel performance sig- niﬁcantly; however, during the summer, it can increase the panel temperature, reducing the energy production of the panel. Therefore, a modiﬁed insulation system has been proposed to reduce the adverse eﬀect of having insulation during the summer. The insulation on the back of the panel produced an air channel of approximately 3 cm depth equipped with several vents. The insulation was also painted black on the side facing the panel to increase radiative heat transfer from the panel. In the summer, natural convection through the vents and ra- diation heat transfer between the panel and the insulation help to control the panel temperature. On the other hand, during the winter, closing the vents maximizes the eﬀect of a snow removal system. Several experiments were conducted under natural conditions for a rooftop system equipped with the new insulation. The eﬀect of solar radiation and vent conﬁgurations on the panel output were studied to ﬁnd the optimum conﬁguration for the vents. A numerical simulation was also conducted to investigate the eﬀect of other parameters: wind speed, panel tilt angle and surface emissivity of the insulation. The proposed venting system can provide approximately 50% less energy loss as compared to the case that the insulation did not have any open vent, while still mini- mizing the energy required for snow removal in the winter period. 1. Introduction Photovoltaic systems in cold regions deal with energy loss due to snow accumulation on the system in the winter as well as panel tem- perature increase during the summer (Corbin and Zhai, 2010; Koyunbaba et al., 2013). Previous studies have indicated that annual losses related to ice-buildup on a PV system can be as high as 0.3% to 26% depending on the orientation, tilt angle of the PV modules and meteorological factors (Andrews et al., 2013a, 2013b; Becker et al., 2008; Marion et al., 2005; Townsend and Powers, 2011). Considering the signiﬁcant eﬀect of snowfall on PV systems and the owner/manufacturer concerns about not damaging the panels (by me- chanical snow removal), various active and passive heating snow re- moval systems have been proposed in the literature (Rahmatmand et al., 2019, 2018; Ross, 1995; Van Straten, 2017; Weiss and Weiss, 2016). Previous studies have shown that using a heating snow removal system with a proper insulation can save up to 50 to 90% of the output energy loss caused by snow accumulation on the PV panels (Rahmatmand et al., 2019, 2018). Regardless of the method used for heating the panel, using proper insulation is crucial for having an eﬃcient heating process. However, while there is a positive eﬀect of mounting insulation on the back of a PV system for more eﬃcient snow removal, the insulation can increase the panel temperature during the summer as well. Since higher panel temperature reduces PV eﬃciency, there is a trade-oﬀ between the adverse eﬀect of insulation during the summer and its positive eﬀect for removing snow from the panel during the winter. For designing a proper heating snow removal system with the in- sulation, the eﬀect of insulation on the panel temperature and conse- quently on the panel performance during seasons without snowfall should also be determined. The main inﬂuence of having insulation on a PV system will be reﬂected on the panel temperature. The eﬀect of the operating tem- perature on a photovoltaic module is well documented (Andrews, 2015; https://doi.org/10.1016/j.solener.2019.11.043 Received 25 April 2019; Received in revised form 16 July 2019; Accepted 12 November 2019 ⁎ Corresponding author. E-mail address: a.rahmatmand@queensu.ca (A. Rahmatmand). Solar Energy 195 (2020) 581–591 Available online 05 December 2019 0038-092X/ © 2019 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. T