sustainability Review Identification and Analysis of Impact Factors on the Economic Feasibility of Photovoltaic Energy Investments Rômulo de Oliveira Azevêdo 1 , Paulo Rotela Junior 1,* , Luiz Célio Souza Rocha 2 , Gianfranco Chicco 3 , Giancarlo Aquila 4 and Rogério Santana Peruchi 1 1 Department of Production Engineering, Federal University of Paraíba, João Pessoa, 58051-900 PB, Brazil; [email protected] (R.d.O.A.); [email protected] (R.S.P.) 2 Department of Management, Federal Institute of Education, Science and Technology, North of Minas Gerais, Almenara, 39900-000 MG, Brazil; [email protected] 3 Dipartimento Energia “Galileo Ferraris”, Politecnico di Torino, 10129 Torino, Italy; [email protected] 4 Institute of Production Engineering and Management, Federal University of Itajubá, Itajubá, 35903-087 MG, Brazil; [email protected] * Correspondence: [email protected] Received: 9 August 2020; Accepted: 30 August 2020; Published: 2 September 2020 Abstract: The introduction of environmental impact targets around the world has highlighted the need to adopt alternative sources of energy, which can supply the demand and mitigate the damage caused to the environment. Solar energy is one of the main sources of alternative energy, and is considered an abundant source of clean energy. However, to facilitate and encourage investors interested in the installation of photovoltaic energy systems for electricity production, it is essential to evaluate the factors that impact the economic viability of the projects. Therefore, the objective of this research is to present a systematic analytical framework, in order to identify and analyze the main factors that impact the financial feasibility of projects for the installation of photovoltaic energy plants. For this purpose, a systematic literature review was carried out, analyzing the main studies related to the topic and identifying the main factors that may financially affect investments in photovoltaic energy systems. From this review, 29 influencing factors were identified and separated into five categories, namely, location, economic, political, climatic and environmental, and technical factors. The main factors highlighted are the investment cost, power generation, operation and maintenance costs, solar radiation, lifetime, energy tariff, efficiency, electricity consumption, and interest and taxes. The results may assist policy makers, investors, researchers, and other stakeholders to identify the key factors that are being examined in the literature, and to evaluate which ones should be considered in their study to ensure the sustainable development of power generation through the solar source. Keywords: solar energy; photovoltaic; economic viability; economic feasibility; risk factors 1. Introduction The generation of electrical energy is essential for the quality of life and human development. However, the way in which this energy is generated can cause damage to the environment and harm human life. Non-renewable energy sources are used on a large scale in the world, and this causes various concerns. According to the International Energy Agency (IEA) [1], electricity in 2016 was still dominated by fossil fuel sources. Moreover, the world’s total primary energy supply (TPES) increased almost 2.5 times between 1971 and 2016, oil being the dominant fuel source (although it reduced from 44% to 32% of TPES). The IEA [1] also highlights the reduction in the use of fossil fuels and the trend of Sustainability 2020, 12, 7173; doi:10.3390/su12177173 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 7173 2 of 40 growing participation of renewable energy sources (RESs), reaching about 11% in the world energy matrix in 2016. Energy resources considered renewable include solar, geothermal, wind, biomass, oceanic, and various types of hydroelectric energy [2]. RESs are viable alternatives to fulfill energy demand, reduce energy costs, and mitigate environmental impacts. Within these sources, photovoltaic (PV) energy stands out, converting sunlight into electrical energy. The sun is the main source of energy on our planet, but today a minor portion of that energy is harnessed, and the potential for further developments is huge. Several factors can influence the economic feasibility of PV systems in the world. According to Karimi et al. [3], the implementation of PV systems on the roof, for example, can be economically viable, but these systems could not offer great economic benefits. As such, an incentive policy is recommended, in which the owners can sell the electricity generated by the PV systems and obtain benefits. Viana et al. [4] state that the investment cost in PV generation systems is high and this makes access in the short term difficult; thus, improved policies are needed to encourage this generation of energy. However, as indicated in Spertino et al. [5], the target for PV systems is to reach the grid parity, namely, the condition in which the generation cost using PV equals the price of the electricity taken from the grid. Specific technical aspects relevant to the investments refer to the PV plant structure. Fixed PV plants are generally cheaper than the corresponding PV plants that could be installed in the same site with sun-tracking configurations [6]; the latter would also need higher maintenance due to the mechanical stress of the moving parts. Furthermore, to avoid the shading effect, which decreases the performance efficiency of the PV arrays, the distance between the PV modules has to be sufficiently high [7], limiting the area available for PV array installation. Moreover, the cost of the PV plant is also affected by the presence of different types of PV system cooling technologies [8,9]. According to Tervo et al. [10], the addition of battery energy storage is a factor that optimizes the PV energy system and, for the locations studied, could represent a substantial gain in the electricity use of the system. For Cucchiella et al. [11], the profitability of PV plants highly depends on the self-consumption portion of energy. When the PV plant is installed on land with high levels of sunlight, with longer battery life and adequate capacity, the net present value (NPV) is increased, making the investment more economically viable. A broader view of the economic feasibility of PV energy investments needs to identify the risk factors that can make investments in PV energy financially unviable. Several factors have been pointed out around the world and vary among different studies. Thus, the aim of this paper is to investigate which are the main impact factors on the economic feasibility of PV energy investments. These impact factors are identified, discussing how they are treated in economic feasibility analyses, and finally are organized into five categories. For this purpose, a systematic literature review (SLR) was carried out, to group and examine the main publications related to the topic and indicate the parameters that affect financially and are evaluated in economic feasibility analysis studies. Such information is relevant, as the interest of the stakeholders has grown substantially, and much of the previous research in related fields lacks integrity and universality. In addition, no reviews were found that present an insightful discussion of such factors. Thus, the extensive systematic literature review about PV investment analysis aims at providing a summary and guidelines, for both researchers and investors, on the main variables that directly impact on the return on investments. 2. Materials and Method In this research, the SLR was used for searching and grouping articles and research reviews that deal with the economic viability of PV systems in the world. According to Webster and Watson [12], a relevant literature review is an essential feature of any academic project. 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