sustainability Article Defects Impact on PV System GHG Mitigation Potential and Climate Change Waqas Ahmed 1 , Jamil Ahmed Sheikh 2 , Shahjadi Hisan Farjana 3 and M. A. Parvez Mahmud 4, *   Citation: Ahmed, W.; Sheikh, J.A.; Farjana, S.H.; Mahmud, M.A.P. Defects Impact on PV System GHG Mitigation Potential and Climate Change. Sustainability 2021, 13, 7793. https://doi.org/10.3390/su13147793 Academic Editor: Idiano D’Adamo Received: 30 May 2021 Accepted: 7 July 2021 Published: 13 July 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 Secret Minds, Entrepreneurial Organization, Islamabad 44000, Pakistan; engnr.waqasahmed@gmail.com 2 Department of Sociology, University of Wah, Wah Cantt 47040, Pakistan; jamil.sheikh@uow.edu.pk 3 Department of Mechanical Engineering, University of Melbourne, Melbourne, VIC 3053, Australia; sfarjana@unimelb.edu.au 4 School of Engineering, Deakin University, Geelong, VIC 3216, Australia * Correspondence: m.a.mahmud@deakin.edu.au Abstract: Solar photovoltaic (PV) systems are widely used to mitigate greenhouse gases (GHG), due to their green renewable nature. However, environmental factors such as bird drops, shade, pollution, etc., accommodation on PV panels surface reduce photons transmission to PV cells, which results in lower energy yield and GHG mitigation potential of PV system. In this study, the PV system’s energy and GHG mitigation potential loss is investigated under environmental stresses. Defects/hotspots caused by the environment on PV panel surface have unknown occurrence frequency, time duration, and intensity and are highly variable from location to location. Therefore, different concentrations of defects are induced in a healthy 12 kWp PV system. Healthy PV system has the potential to avoid the burning of 3427.65 L of gasoline by 16,157.9 kWh green energy production per annum. However, in 1% and 20% defective systems, green energy potential reduces to 15,974.3 and 12,485.6 kWh per annum, respectively. It is equivalent to lesser evasion burning of 3388.70, and 2648.64 L of gasoline, respectively. A timely solution to defective panels can prevent losses in the PV system to ensure optimal performance. Keywords: PV system; defects; GHG; hotspots 1. Introduction Solar photovoltaic (PV) energy systems are widely used as green renewable energy sources across the globe. PV systems have a combustion-free nature, i.e., no burning of fossil fuels such as oil, gas, coal, etc., in the running phase. Hence, there are no production and emissions of greenhouse gases (GHG) such as CO 2 , NO X , water vapors, etc. GHGs are the leading cause of global climate change [1–3]. Moreover, fossil fuels are limited energy resources and are depleting fast [3]. However, across the globe, a major portion of energy production is based on conventional thermal power plants. For example, Pakistan’s energy production is heavily based on fossil fuel technology [4]. In contrast, the PV system offers a green solution because of its 1500–50,000 EJ per year, which is direct free solar energy potential across the globe [1]. PV systems have the advantage that small-scale PV systems can be installed on load sites, i.e., on rooftops of end-energy users. It reduces transmission and distribution losses; hence, GHG emissions reduction [2]. As a result, PV system energy production capacity was increased to 117 GW in 2019 [3]. Despite the tremendous potential, PV system efficiency varies depending upon ge- ographical location and natural parameters. These factors in turn affect PV system out- put [2,5]. PV systems like other power system components such as insulators are exposed to environmental stresses. Environmental stresses include ultraviolet radiations, inert and active pollution, rain, snow, etc. [6]. These factors reduce the PV system’s performance [7]. Moreover, hotspots/defects that arise in the PV system due to the environment such as bird drops [3], shading effect [8], dust [9], etc., are responsible for energy losses and affect Sustainability 2021, 13, 7793. https://doi.org/10.3390/su13147793 https://www.mdpi.com/journal/sustainability