1. Introduction
Society’s dependence on non-renewable resources is reflected in oil price fluctuation with companies considering any increase to be a threat to profitability. However, the effects of global warming have made society rethink and become aware of the impacts of prioritizing economic development and lifestyle witnessed in recent decades.
Theoretical frameworks and expert positions provide insights that improve the understanding of the need for sustainable development in the face of the exhaustion of natural resources [
1].
Global energy availability will limit and shape the fate of future civilizations. Despite the serious environmental problems and the energy crisis faced, the world’s primary energy consumption of 5508.80 million tons of oil equivalent (Mtoe) in 1970 increased by 7676.68 Mtoe until 2018, when it reached 13,185.48 Mtoe, resulting mainly from fossil fuels and increased consumption [
2]. With the trend of continuous increase in energy consumption, the use of fossil fuels is widely regarded as unsustainable due to the prospect of resource depletion and the increase in the concentration of greenhouse gases in the atmosphere [
3].
The transition from the use of non-renewable resources to sustainable resources has technical constraints that prevent a gradual change [
1]. One of the obstacles is the considerable cost increase of the energy supply to meet all economic processes. However, technological progress makes it feasible to implement other forms of energy, such as the use of increasingly cheaper solar cells [
1]. The participation of renewable sources in energy matrices is favored by the increase in hydraulic, solar, and wind generation. In addition, due to an increase in the supply of black liquor and biodiesel, there will be a reduction in the supply of oil and derivatives and a reduction in the supply of natural gas, according to the Energy Research Company [
4].
Renewable energy sources play a dual role: to mitigate global warming and to ensure energy security over the years [
5]. Solar energy is widespread, is considered an important source of renewable energy, and, in the long term, will bring major contributions to society, such as security of energy supply and protection of the environment. Distributed generation of photovoltaic (PV) solar energy and solar water heating are benefits from the point of view of energy security [
5].
The technological potential of PV energy integrates the solution of energy problems with social interests, environmental interests, and economic principles. Brazil is considered an ideal country for solar energy production due to various factors, including a large number of sunny days, ideal intensities of solar irradiation, and a large geographic area with these conditions. In addition to these factors, the costs of installing the equipment have been decreasing rapidly, which encourages and provides better energy use [
6]. Brazilian solar electricity generation in 2018 was 3461 GWh, representing an increase of 316.1% compared to the previous year. The installed capacity in 2017 was 935 MW, while in 2018 there was an increase of 92.2%, reaching 1798 MW [
4].
Distributed generation is any small-scale electrical generation technology that generates electricity in a location that is closer to customers than the central station generation. In addition, it is usually interconnected to the distribution system or directly connected to the customer’s installations [
7]. Therefore, in this scenario of evolution, the National Electric Energy Agency created Normative Resolution 482/2012 [
8], which regulates the criteria for the application of distributed generation, through micro- and mini-generation, as a way to introduce renewable energy source mechanisms in the Brazilian energy matrix.
This Resolution operates in Brazil through the consumed energy compensation system, called net metering, which consists of measuring the energy flow of the small generation consumer unit through bi-directional meters. Besides being a safety requirement of the system, this standardization encourages the incorporation of renewable energy sources into the Brazilian energy matrix [
9].
Economically, PV technology has its insertion compromised due to the initial high investment. However, in the first decade of the 21st century the price dropped to between 3 and 5 USD/Wp for small buyers and between 2 and 4 USD/Wp for large buyers [
5]. The costs for financing and the tax burden on micro-generation investments are directly related to the specific economic conditions of consumers in each Federative Unit. Sensitive analyses indicate that financial risk is still impacted by the incorporation of taxes such as the ICMS (Tax on Circulation of Goods and Services) and the PIS/Cofins (Social Integration Program and the Contribution to Social Security), in the case of Brazil [
9].
In view of this, small-scale green electricity generation has become the focus of study of some researchers. The analysis of its economic feasibility supports the decision-making by investors, because the objective of any electric generation system is to achieve a positive cash flow [
10]. Developing simulations of performance rate of PV models and tools is critical to economic decision-making.
In the Brazilian scenario, feasibility studies have been proposed, evaluating different perspectives and aspects, such as regulatory, tax exemptions and incentives, social and political issues, and isolated communities, and more recently, the use of energy storage systems (ESS) has aroused interest. Distributed generation systems (DGs) were evaluated from an economic perspective considering tax exemptions [
10]. In addition, economic analysis of the impact of regulatory changes to DGs, recently proposed by ANEEL, were carried out [
9,
11,
12]. The viability of the PV generation considering social programs has also been evaluated [
13,
14] by programs such as “Light for everyone” (from Portuguese,
Luz para todos) and “My house, my life” (from Portuguese,
Minha casa,
minha vida).
There is no regulation for ESS in Brazil so far, but studies on the use of technology have already been presented. The economic viability of PV systems with fuel cells and battery energy storage systems (BESS) in an isolated community in the Amazon region has already been evaluated, using the HOMER software [
15,
16]. A model for dimensioning an isolated PV system with BESS in a small rural property has already been presented [
17]. Regarding the utility-scale, more recently, studies that evaluate the implementation of the use of storage in the Brazilian energy market have been carried out [
18,
19]. However, none of the studies presented above assess the economic feasibility of using BIPV technology.
Based on the studies presented, it is noted that the connection between performance and profitability of the PV system is influenced by the initial investment, maintenance processes, and several other factors [
20]. Its profitability is assessed based not only on costs and revenues, but also on climatic particularities [
21]. The analysis of the initial investment cost is the most recurrent factor in economic studies of photovoltaic energy, and is often considered the main parameter for determining financial viability [
22]. In the specific case of building-integrated photovoltaic (BIPV) technologies, the development of research has made the useful life of these systems longer, with shorter payback time. This makes investing in the sector more profitable, especially in tropical regions, such as Brazil [
23]. In addition, relevant research on the deployment of BIPV technologies in regions with high solar irradiance is scarce [
24].
Thus, the objective of this study was to analyze deterministic and stochastic models of investments in two types of photovoltaic systems, one incorporated into the enterprise’s architecture (BIPV), and the other, the conventional one, in different Brazilian locations, covering the predominant climate types in the country.
This study can be seen as a successful case of the application of these methodologies in the evaluation of investments in BIPV technologies, and will contribute to the literature with regard to the development of future studies on the feasibility of applying this technology. Finally, the comparison between conventional and BIPV technologies, helps to demonstrate the current level of maturity of BIPV technology when compared to conventional technology, which is already consolidated in the market. Finally, in our literature review, no studies were identified that stochastically, through Monte Carlo simulation, assessed the economic feasibility of implementing BIPV technologies in Brazil.
3. Results and Discussion
After performing the deterministic simulation for all selected locations, the NPV values were obtained for each of them. The results are presented in
Table 7.
Some initial physical aspects, according to
Table 5, differentiate the two models and influence the values obtained through the simulations. The first point is the factory default settings of the equipment, because the BIVP semi-transparent photovoltaic panels have smaller dimensions and lower efficiency compared to the conventional one. However, both reach similar power, allowing the BIVP to meet the requested demand even with a smaller area. The second point is the value of the investment per kWp, because the cost of a BIPV system is more than three times that of the conventional one.
As observed in
Table 7, all simulations returned an estimate of NPV > 0. Despite the variations among the locations and among the two proposed models, all applications are considered feasible, according to the economic criterion of the NPV. In any case, in a comparison between them, the conventional model proved to be more accessible from the point of view of investment values, and with better levels of return.
As illustrated in
Figure 3, an inverse quasi-proportionality was identified between the investment value and the NPV obtained. The largest investments occurred in the municipalities of Manaus-AM, Irati-PR, and Bagé-RS, and the smallest investments were found in Pau dos Ferros-RN, Ouricuri-PE, and Aracaju-SE. Regarding the values of NPV, the situation was reversed, with the highest values in Aracaju-SE, Pau dos Ferros-RN, and Ouricuri-PE, and the lowest returns in Irati-PR, Bagé-RS, and Manaus-AM, in this order. According to Rocha et al. [
36], the value of the investment directly impacts the NPV result.
This dissimilarity between the values of investment in different cities has a direct relationship with their climatic particularities. The load and production of photovoltaic energy are affected by the local climate, including differences in air temperature and seasons [
54]. The locations with the lowest investment values belong, respectively, to the climate types As, Am, and BSh, which are characterized by well-defined drought periods and relatively short rainy periods [
27].
On the other hand, the largest investments are found in the climate types Af, Cfb, and Cfa, characterized by high rainfall and cloudiness throughout the year, which directly interfere in the amount of daily hours of sunshine and irradiance levels to which the panels are subjected [
27]. This fact is confirmed when the Cwa and Cwb types are compared with Cfa and Cfb, respectively, because despite their general similarities, the former have a dry period that favors them with better PV generation data. It was also found that the ranking of investment values is equivalent to that of the means of daily insolation hours among the analyzed cities and the irradiance values, as observed in
Table 2 and
Table 3.
Ascencio-Vásquez et al. [
55] state that the highest electricity production occurs in places with high irradiation. They concluded that the unit capacity factor (UCF), which represents the percentage of annual time in which the photovoltaic system is operating, can reach more than 20% in locations with high irradiation and a large amount of sunshine hours. Tropical climates show UCFs between 16 and 18%, because, despite the high irradiation, they have rainy and cloudy periods throughout the year. In cloudy places, the values hardly exceed 14% [
55].
Pranadi et al. [
56] state that the level of receptivity to photovoltaic technology is mainly influenced by the initial value of the project. However, the project’s NPV is most significantly impacted by the cost of local electricity. Cui et al. [
21] also identified that the price of electricity had the greatest influence on the increase in NPV, and these variables were directly proportional. This relationship and the good levels of solar energy certainly contributed to Aracaju-SE being considered the location with the best NPV.
However, the best returns of NPV are achieved with the greatest amount of electricity produced [
21]. Climatic conditions can influence energy generation, to the point where places with higher tariffs generate lower returns, as occurred with the municipality of Pau dos Ferros-RN and the others. Rocha et al. [
10] identified a similar event, where Petrolina-PE obtained better returns than Belém-PA and Uberaba-MG, even with lower tariff, due to its greater solar potential.
Similar case studies, carried out in Brazil, presented results in line with those found in this study. Branco and Affonso [
57] concluded in their two cases, which differed from each other in terms of demand, that the NPV is always positive, confirming that both projects are economically robust and attractive. Sorgato et al. [
58] analyzed the technical potential of the integration of a thin-film cadmium telluride (CdTe) BIPV system in a commercial building, in six Brazilian locations, and also obtained positive NPV values in all types and scenarios. Gholami et al. [
59] proposed a method to establish and quantify, as much as possible, the social and environmental advantages of a BIPV system and import these values into economic analysis to measure their effects in a life-cycle cost analysis. In this scenario, the analysis performed found a positive NPV in the Brazilian cities analyzed.
The practical implications of these results reveal the different factors that impact the feasibility of implementing photovoltaic systems. Facility planning is case-specific and a holistic view of the situation must be taken. Although weather conditions directly affect electricity generation, the value of the local utility’s energy tariff has an important bearing on the return on investment. In addition, qualitative values must be considered, such as the visual impact and the feeling of well-being of the implanted models.
Regarding the application of stochastic simulations for the municipality of Pau dos Ferros-RN, 10,000 NPV values were returned for each of the PV installation models. As shown in
Table 8 and
Figure 4, in both cases the cumulative frequency and probability of positive NPV return are 100%, reaffirming the economic feasibility and solar potential of the site.
Based on the statistical treatment for comparing samples of simulated NPV values between the two suggested photovoltaic models, it was possible to affirm that the conventional is more profitable. A
p-value of 0.000 was obtained through the two-sample t-test, so the null hypothesis, which establishes equality between the samples, was rejected. The mean value of the NPV of the conventional model was significantly higher than that of the BIPV model, with a difference of around 66%.
Figure 5 shows the dispersion pattern of the samples.
The sample of values of the conventional model has great dispersion, ranging from R
$ 2,097,118.71 to R
$ 9,874,294.74, with an average value of R
$ 5,083,210.02. The BIPV sample has lower dispersion, with minimum of R
$ 948,587.38 and maximum of R
$ 6,596,273.94, with an average of R
$ 3,070,653.92. Both have outliers. In any case, the results of the present study do not indicate unfeasible implementation of BIPV systems because the savings with the construction materials that would be used if the conventional model were not considered and the benefits of BIPV systems go beyond economic barriers and reflect the concepts of design, thermal control, and real-estate appreciation [
60], which were not included in the objectives of this analysis.
4. Conclusions
Photovoltaic energy is seen internationally as a sustainable alternative to achieving energy security and mitigating climate change. Therefore, the number of solar installations has grown greatly in recent years. This prosperous scenario requires strategic planning to ensure that a favorable financial return is achieved for the investor, making the best use of locally available climate characteristics.
From the economic analyses performed in the present study, it was possible to verify that both proposed systems are feasible in all predominant climate types of Brazil. It was observed that there is a deep relationship between the peculiarities of each climate type and the results obtained. The municipalities with higher levels of irradiation and hours of daily insolation had higher values of electrical generation and, consequently, better returns of NPV with lower initial costs. These are found in locations corresponding to the climate types monsoon, tropical with dry season, and semi-arid, all in the Northeast region of Brazil.
However, with this research it was observed that it is not only climatic factors interfere in the return on investment. The values of local electricity tariffs play a key role in the value of the NPV. Locations with lower levels of solar irradiation still proved to be viable, despite the greater investment required, due to the compensation of the higher tariffs charged.
The municipalities of Pau dos Ferros-RN and Aracaju-SE have the lowest investment value and the highest simulated NPV, respectively. Manaus-AM and Irati-PR have the highest investment and lowest NPV, in this order. In any case, the conventional model was more attractive than the BIPV model, from the point of view of application and return values.
Regarding the stochastic simulations in the municipality of Pau dos Ferros-RN, the results remained equivalent to the previous ones. Both systems obtained 100% cumulative probability of NPV > 0. The conventional model continues to have more attractive values than the BIPV model, with a significantly higher mean of NPV. Although it does not have the best results, the BIPV model is still considered feasible for the studied locations, with positive values in all NPVs calculated. In addition, its benefits go beyond monetary barriers, acting in the areas of thermal control and design and even in real estate appreciation, due to its architectural differential.
Despite reaching economic viability, a statistically significant difference was identified between the NPV results of conventional and BIPV technologies. However, the advantages of BIPV technology must be recognized, in particular, the greater areas for installation and the reduction of construction material costs. It can be seen that the main barriers to BIPV technologies are technical and financial. In this way, public policies to encourage this technology necessarily involve a greater capacity for research resources, seeking its evolution with consequent cost reduction, in addition to better financing conditions and tax exemptions.
As a suggestion for future studies, researchers could consider savings with construction materials, lighting, and cooling and/or heating, in specific environments due to integration of photovoltaic systems to the respective facades and to other climatic particularities such as temperature and wind speed. In addition, consideration could also be given to different types of materials in the composition of the photovoltaic cells used, as well as the energy payback time (EPBT), the greenhouse gases payback time (GPBT), and the return at the end of the equipment’s useful life, through the sale of recyclable materials.