Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener An experimental investigation of snow removal from photovoltaic solar panels by electrical heating 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 method Heater Reverse current Frame effect ABSTRACT A key challenge to the wide-scale implementation of photovoltaic solar panels (PV) in cold and remote areas is dealing with the effects of snow and ice buildup on the panel surfaces. In this study, a thermal method for snow removal from PV solar panels was experimentally tested. Nine PV panels were mounted at tilt angles of 30, 45 and 55° (three panels at each angle). One of the panels at each angle was insulated on the back with a heater embedded between the panel surface and a back layer of insulation. The other two panels remained unheated as reference cases. Outdoor tests were conducted under natural conditions including different snowfall conditions. Solar radiation, ambient temperature, relative humidity and wind speed were also measured during each test. Results showed that the frame at the bottom edge of the panels prevented the snow-cover from sliding off the panels. In addition, it was observed that the entire panel surface requires heat to remove snow, as the panel thermal conduction was not sufficient to conduct heat to unheated areas. To investigate these issues, the lower edge of the frame for one of the reference panels at tilt angle of 45° was removed, and the panel was heated using reversing electrical current flow through it. For most of the experiments with this panel, the snow-cover slid off the panel in less than 30 min. 1. Introduction Increased concern related to climate change is driving the devel- opment and implementation of alternative energy sources as a means to reduce emissions related to the use of carbon-based fossil fuels. The use of photovoltaics (PV) to generate electricity from solar energy is being promoted as a promising technology for supplying significant “green” energy to the electrical grid. The continuous decline of the cost of solar systems has driven research into photovoltaic-thermal (PV/T) systems all around the world. This includes regions with cold climates that can lead to snow and ice accumulation on collector surfaces (Breyer et al., 2009; Burrett et al., 2009; Swanson, 2009). A key challenge to the wide-scale implementation of solar photo- voltaics in cold climates like Canada is dealing with the effects of snow and ice buildup on the panel surfaces. PV panel output depends on ensuring that solar panel surfaces are not shaded by obstructions such as snow and ice. The problem is severe as even partial snow-cover on PV modules may significantly reduce the output of a complete string of PV panels. As well, there currently is no practical mechanism to remove snow-cover from PV surfaces and long shut-down periods occur while plant operators wait for mild weather. Mechanical removal of snow from PV arrays has also been rejected by plant operators due to the fragile nature of the glass panels used to support PV cells. Consequently, a thermal snow removal method to melt snow or induce the snow sliding off from PV panels would be beneficial in re- gions with significant snow fall. 1.1. The effect of snow accumulation on PV output Several experimental and numerical studies have been performed to study the effect of snow on annual and monthly PV systems perfor- mance. Experiments on PV systems undertaken by Nakagawa et al. (2003) revealed that in a solar array which is connected in series, if only some cells are covered by snow, the module output will drop. Previous studies have indicated that annual snow losses on a PV system can be as high as 17% for a low profile system in Truckee California (south-facing panel tilt angle of 24°) and as low as 0.3–2.7% for a highly exposed roof mount system located in the New Munich Trade Fair Centre in Germany (south-facing panel tilt angle of 28°) depending on the orientation, tilt angle of the PV modules and meteorological factors (Becker et al., 2008; Brench, 1979; Marion et al., 2013; Ross, 1995; Townsend and Powers, 2011; Yoshioka et al., 2003). Townsend and Powers (2011) mounted three pairs of photovoltaic modules at fixed south-facing tilt angles of 0°, 24° and 39° over a winter https://doi.org/10.1016/j.solener.2018.07.015 Received 10 April 2018; Received in revised form 29 May 2018; Accepted 6 July 2018 ⁎ Corresponding author. E-mail address: a.rahmatmand@queensu.ca (A. Rahmatmand). Solar Energy 171 (2018) 811–826 0038-092X/ © 2018 Published by Elsevier Ltd. T