Economic viability: A bibliometric study in the Scopus database

The present work aimed to perform a detailed search on the methods applicable to the calculation of economic viability. The database used to develop this systematized literature review was Scopus Elsevier, accessed through the Capes Journal Portal. The study allowed to obtain a theoretical contribution to the accomplishment of the general objective of this dissertation. For each method, the resulting articles 3 were analysed and selected for presentation of a brief summary in order to exemplify the content available. It was possible to observe the state of the art of the theme, since the methodology allowed to identify the years with the highest frequency of periodical publication, and authors who published that subject, the countries with more engagement in this context, the types of mostly used publication and the areas of knowledge with the highest volume of published articles .It is also, possible to verify that the method tends to be increasingly applied, mainly within the area of Engineering, which was the area that stood out in this study ,due to its flexibility to apply it in different scenarios. It was also found that China is the country with the most indexed documents on this basis, according to this issue.


I. INTRODUCTION
According to Capaz and Nogueira (2016), although energy efficiency projects have great benefits in reducing energy, it losses and contributes to the environment, only these factors are not enough to attract investors. Energy efficiency projects also need to be economically viable, so that an external investment can be better justified by those who intend to execute it. Thus, before choosing to raise investment for a particular project, it is necessary to calculate its economic viability.
According to Neumann (2017), the economic viability of a project is calculated through methods that aim at analysing data in comparison to the target for this particular project. That is different, companies have different goals and therefore can make use of different methods. What all companies have in common, regardless of the method used, is the need to analyse the economic efficiency of a particular project, by grouping all costs, the value obtained must be less than the estimated value that it can generate as revenues or benefits.
Based on this scenario, this study intends to address eight financial methods that are considered more compatible and recommended for economic feasibility analysis for projects such as the application of photovoltaic panels in a company located Macaé city / RJ -Brazil. For this purpose,concepts and a bibliometric study will be carried out regarding the selected methods, with the objective of analyzing and identifying the authors, periodicals, countries, type of publication and areas of knowledge with the greatest publications on financial methods. The aim of this study was to present three practical application studies for each method selected.
author bases his assertion on the justification that the cash flow presents a great variety of information to be analysed, for example, payment deadlines in comparison with the payment deadlines, reduction in the volume of revenues, extrapolation of costs against the planned, among others. According to Sebrae (2018), cash flow is a "financial management instrument that projects for future periods all the inflows and outflows of the company 's financial resources, indicating how the cash balance will be for the projected period". cash flow becomes a tool that allows for more conscious decisions that affect the overall outcome of the company. In the same way, cash flow can be segmented according to the information to be analysed, making the results more precise. For example, the returns on investment and the costs of obtaining resources are the interest paid, the interest dividends and the interest (CRCRJ, 2018) Marques (2007, p.82) states that "NPV is the difference between inflows and outflows of money from an investment brought at prices of the same date by the opportunity cost ". In practice, a basis for comparison needs to be defined so that a more indepth analysis can be carried out and based on other available investment options. To carry out the calculation, attention must be paid to the use of a Minimum Attractiveness Rate -TMA or Capital Cost adequately. According to Camargo (2007, p.25), the minimum rate of attractiveness -TMA corresponds to the devaluation rate imposed on any future gain because it is not available at the time. Your choice requires great care, because the analysis of the same investment can show different results ". This statement reinforces the importance of using a set of indicators to carry out the analysis of the financial viability of any project in order to mitigate the risks of a partial and poorly-based analysis. Chenço (2009) points out that in the case of discounted cash flow, for external factors and that may directly interfere with their future results, such as the country's economic situation or even at the global level. This means that not always a project with good NPV -Net Present Value or Internal Rate of Return will be, in fact, good investment. In order for the investor to be able to protect himself from the risks that cause incorrect decision making, the author gives tips such as, for example, asking about the reasons that lead the project to present a positive NPV; if it is possible to produce an d distribute the product or service efficiently, and whether it will be possible to market the product or service at an attractive price to the final consumer. Regarding the discount rate, Jaffe et al. (2015, p. 139), states that "conceptually, the discount rate of a risky project is the return that can be expected to be earned on a financial asset of comparable risk." That is, discount rate is the rate used so that the following portions of the cash flow are deducted.
These three instruments are related to each other, as affirmed by Chenço (2009, p. 113), when stressing that "present value, discount rate and equivalence of cash flows are absolutely interconnected concepts." The Internal Rate of Return (IRR) central importance in the decision-making process. Jaffe et al. (2015, p.143) state that "as a general rule, IRR is the rate that makes the NPV of the project zero." This method has as main objective to gather the maximum information to facilitate the analysis of the investor, taking into account intern al aspects of the project in question and focusing its analysis on the issue that has the greatest impact on the overall economic viability: the expected cash flow. According to Gitman (2010) the Internal Rate of Return is composed by the discount rate at which the NPV -Net Present Value is equal to zero, since it reaches the same value of the initial investment as the investment opportunity in question. In practice, knowing the IRR of the project has as purpose to compare this percentage with the interest rates offered by the market, arriving at the conclusion that it is a profitable investment or not (Jaen, 2009) Jaffe et al. (2015) states that Payback is a way to focus attention only on the projects that interest the company, according to its estimated term of return. That is, if the company expects to work with a maximum return of three years, it can discard projects that have a return in term and analyse in greater detail only those that meet the established requirement. Chenço (2009) makes a comparison between the use of Payback and NPV for the analysis of investments, stating that the former is more suitable for projects with higher risk involved, since the latter does not take into account the time aspect of the investment. When you talk about Payback, your analysis can still be segmented according to the type of analysis you want to do, which in the case of this method can be classified as Simple Payback and Discounted Payback. According to Fapan (2018), Simple Payback is the attainment of the point at which the net related income is equal to the total amount of the investment previously made.
Jáno Payback Discounting the amounts received in the form of net income are then counted so that they can be compared to the initial investment volume, according to the analysis method used. "Another method used to evaluate projects is the so-called ILL. It is the quotient of the present value of the future cash flows expected after the initial investment divided by the amount of the initial investment. "(JAFFE ET AL, 2015, p.154) The profitability index is used to evaluate capital budget projects. This considers the value of money at current time, and can be used at the beginning for the selection of projects under capital rationing conditions (GITMAN, 2010).
The analysis of the result obtained in the operation performed to find out the IL of the determined project is If it is less than 1, it means that the investor will at least get his investment back, and will have a return proportional to how much greater than 1 is the result. If the IL is equal to 1, the investor should know that he will have his investment recovered, however, at the same rate as was initially required. However, if the IL is less than 1, it means that there will be no return of the invested amounts, meaning losses to the investor. According to Romeiro Filho (2011) Return on Investment -ROI "measures the return on investment made and accounted for in months in which it will be amortized and then start to generate profits." The author stresses that the calculation of ROI can be done in several ways, according to the need for analysis. For example, by dividing net income by total assets, the investor will know the percentage of return offered by the company. Already dividing liquid by the invested amount, it will be possible to know the percentage value of investments. By doing this last operation in reverse, the inves tor will find the time it takes to recover the invested capital.

III. METHODOLOGY
The methodology selected for the elaboration of this work was the bibliometric study, since this one has the intention to present the scientific contributions on a certain theme or phenomenon (JUNG, 2004). It performs the state of the art through investigation or screening of the scientific production (OKUBO, 1970). In this way, a research will be carried out using key words related to eight different financial methods of economic analysis, having as base the Base Scopus, being accessed through the CAPES Platform. Financial methods are used to aid in the control and achievement of a company. This study intends to address eight financial methods that are most commonly used to analyse economic viability in companies, and thus, analyse them from the point of view of the application of the photovoltaic panels in a company located in the municipality of Macaé / RJ. For this purpose, concepts and a bibliometric study will be carried out regarding the selected methods.
The model used is the one proposed by Costa (2010), which is divided into six steps. The definition of the sample of the research, the research in the sample, the identification of the periodicals and of the authors with the greatest number of publications on the subject, a survey of the production chronology, identifying cycles of higher production and the selection of articles for composition of the "starting nucleus" for the bibliographical research. In this scenario, the objective is to analyze and identify the authors, periodicals, countries, type of publication and areas of knowledge in a large number of publications about eight financial methods.
The aim was to present three practical applications of the studied theme for each selected method.

Regarding the purpose
Concerning technical procedures, this is a theoreticalconceptual article, exploratory in nature and approach to qualitative research, inspired by the method, suggested by Costa (2010), to carry out the systematized literature review.

As to the methods
The work will follow six proposed steps: definition of the sample of the research, use of the keywords in the research of the samples, identification of the journals with the largest number of articles published on the theme, to carry out the identification of the authors with the greatest number of publications, the chronology of production is lifted, so that the cycles of greater production are identified. Finally, the articles are selected for the composition of the "starting nucleus" for the bibliographic research to be carried out. The database used was Scopus Elsevier, accessed in January of 2018, through the Portal of Periodicals of Capes. Exclusion filters were not used so that the document range of the area found was larger. The search criterion were established for the purpose of broadening the publications on the eight financial methods chosen. Table 1 shows the results obtained in the research.

IV. RESULTS AND DISCUSSION
In this stage, the documents were analysed and a sample of articles was designed for each of the eight methods, and of these samples, three will be presented in brief summary formats. These were considered by the author as the most relevant on the topics, since they are the most cited according to the Scopus data base. Thus, using this nucleus, graphs are presented here containing these publications, insofar as it relates to the quantity of publications per year, which authors published on the topic, where are the origins of the articles, as well as their affiliations. The amounts of publications by country and by area are also shown, presenting those that are highlighted

Net Present Value -VPL
For this method, the words "Net" AND "Present" AND "Value" were used as search terms, returning a total of 17,187 results.

Year of publication
The data contained in figure 1, illustrated below, demonstrate through graphic the frequency between 2000-2018.

Authors who published on the subject
The data contained in Figure 2, illustrated below, demonstrate through the graphic the authors with the highest frequency of publications per year in the period 2000-2018ch. It can be verified with the image that among the authors who publish more on the subject, stand out Durlofsky L.J. and Jansen J.D., with 32 publications.

Source of publication
The data contained in Figure 3, illustrated below, demonstrate through the graphic.

Affiliation
The data contained in Figure 4, illustrated below, demonstrate the most frequently affiliated frequently published.

Number of publication by country
The data contained in Figure 5, illustrated below, demonstrate the most frequently published countries through the graphic. As shown in the image, the United States continues to lead among the countries that publish on the financial method in question, with 4,931 publications, far above the others, such as China (1,190), United Kingdom (1,132) and Germany (933).

Number of publication by areas
The data contained in Figure 6, illustrated below, demonstrate through the graphic the areas of knowledge with the highest frequency of publication. Among the areas that can be seen, we highlight Engineering, Agriculture and Biological Sciences and Environmental Sciences.

Analysis of articles
In Table 2 we present the articles selected as most relevant by the author, which were provided by the data base.  Stulz (1990) examined the financing policies of a holding company owned by atomistic shareholders that did not observe cash flows or management investment decisions. It was observed that the administration receives investment benefits and invests as much as possible. Once the cash flow is very low, the author guides the financing of all projects net present positive value, thus, their claim will not be credible when cash outflow is really low. Consequently, management will be forced to invest very little when cash flow is low and should choose to invest more when it is high. Funding policies, by influencing resources under management's control, can reduce the costs of overinvestment. Kaplan (1989) presented evidence of changes in operating results for a sample of 76 large management buyouts of public enterprises that were completed between 1980 and 1986. It was noted that in the three years following the purchase, these companies experienced increases in operating income (before depreciation) and a decrease in capital expenditures and increases in the cash flow. Thus, according to operational changes, the average increases in market value (adjusted for market returns) are 96% and 77% of the two months before the purchase announcement for the post-purchase sale. It has been noted that the evidence suggests that operational changes are due to improved incentives rather than layoffs or managerial exploitation of shareholders through inside information.
The authors evaluated the attractiveness of investing in renewable energy sources by continuing to use oil for electricity generation. The method used was the real options approach to analyze how the time of investment in renewable energy depends on the volatility of the price of diesel, the price of electricity and the externality for the use of oil. In their results, they presented a Net Present Value -NPV positive for investment in renewable energy. Under uncertainty in oil prices, dynamic optimization looks at how it expects or delays investment in renewable energy in losses. Reducing the local price of electricity and incorporating negative externalities favors investment in renewable energy over continued use of oil for electricity generation. They concluded that the real options approach emphasizes flexibility when making investment decisions. In the latest energy regime in the Philippines, replacing renewable energy is a better option than continuing to import oil for electricity generation. Politics should aim to support investment in maizesustainable energy sources, imposing externalities for the use of oil or reducing the price of electricity (AGATON et al, 2018)

Internal Return Rate -IRR
Using the keywords "Internal" AND "Rate" AND "of" AND "Return", search done for publications on the Internal Rate of Return (IRR) method returned 4,610 results, which were incorporated into the database for the analysis.

Year of publications
The data contained in Figure 7, illustrated below, demonstrate through the graphic the frequency of publications per year in the period 2000-2018. The same behaviour was observed previously, that is, the one with the greatest publication was 2017 and the year 2018 already presents 29 publications until the publication of this research.

Authors who published on the subject
The data contained in Figure 8, illustrated below, demonstrate through the graphic the authors with greater frequency of publication.

Source of publication
The data contained in Figure 9, illustrated below, demonstrate through THE GRAPHIC the periodicals with greater frequency of publication. In Figure 9, it is noticed that a Brazilian newspaper called Cost agrobusiness is among the list, however, it occupies the last position among the most published. The highlight is for the Engineering Economist, with 71 publications.

Affiliation
The data contained in Figure 10, illustrated below, demonstrate through the graphic the affiliations with the highest frequency of publication.

Number of publication by country
The data contained in Figure 11, illustrated below, show the most frequently published countries through the graphic. The United States remains the leading among the other countries, common publication number well above all others, with 1,358 publications, while the second place (United Kingdom) has only 265 publications.

IV.2.6 Publication Number by Areas
The data contained in Figure 12, illustrated below, show the areas of knowledge with the highest frequency of publication through the graphic. The publications were grouped in 10 knowledge areas, as shown in Figure 12. The Engineering stands out with 1,038 published articles, followed by Medicine, with 832 publications and Energy with 815.

4.2.7
Analysis of articles In Table 3 we present the articles selected as most relevant by the author provided by the database.  (2018) Schultz (2004) sought to evaluate how the Progress program, which offers low-income students in rural areas of Mexico, affected the number of enrolments made. Poor children residing in communities randomly selected to participate in the early phase of Progression compared to those residing in other (control) communities. The preprogram comparisons verify the design and the difference estimators of the double effect program effect on the treatment are calculated by grade and sex. Probity models are also estimated as to the probability of enrolment of a child, controlling the additional characteristics of the child, their parents, local schools and community, and the friction of the sample to assess the sensitivity of program estimates.
These estimates of the short-term effects of the program on enrolment are extrapolated to lifelong schooling and the gains of adults to approximate the internal rate of return on public school subsidies are likely to increase expected private salaries. A recent study found empirical evidence that the initial relative deprivation of families in their referenced village group plays a significant role in migration from Mexico to the US. Controlling the initial absolute income and expected income gains from migration, appropriation of households to participate of international migration was directly related to the relative deprivation of families. The rationale for the analysis is threefold. First, there is reason to expect that papal of relative deprivation is different between international migration and migration within a country, as explained below. Second, the sharp discontinuities in human capital returns between work of the country of origin and the host country may affect the ability of families that differ in their human capital endowments to achieve income earning gains through international migration. Third, a relative deprivation approach to migration has important implications for developmental politics. In section I of the paper, they described the model of relative deprivation of migration and presented an illustration of the divergent political implications of a model of relative deprivation versus an absolute income model. In section II, a migration decision model is estimated and used to explore open and relative income motives for internal and international migration in a sample of rural Mexican households, as well as to test to what extent the labour market discontinuity shapes the choice of migrant destination. In Section III the conclusions were presented (STARK et al., 1991). Peasnell (1982) presented a series of results concerning the relation between accounting and accounting values and income and economic values. Some of the results have appeared before in the literature and some are new. These were gathered together in a common analytical framework to demonstrate their formal and mathematical character. It is shown that the present value can be obtained by discounting almost all profit numbers; that the accounting rates of return define a discount function directly analogous to the structure of the term and the internal rate of return; and that the internal rate of return can be expressed as a linear sum weighted return rates.

Authors who published on the subject
The data contained in Figure 14, illustrated below, demonstrate through the graphic the authors with the highest frequency of publication. According to the data presented in Figure 14, the most influential periodic in this theme is the Indian Journal of Agronomy with 31 publications, followed by the Expert Systems with Application, with 27, and Journal of Dairy Science, with 24

Membership
The data contained in Figure 15, illustrated below, demonstrate through the graph the most frequently published affiliations.  Figure 15 is that the State University of São Paulo (UNESP) is the highlight among the institutions that study and publish on the Profitability Index (IL) method, after which two Indian institutions, the Indian Council of Agricultural Research an Indian Agricultural Research Institute.

Number of publication by country
The data contained in Figure 16, illustrated below, demonstrate through the graphic the countries with the highest frequency of publication. The data show that Brazil is once again among the leading countries provided by the database, fourth place after China (430), the United States (420), and China (430). India (196).

Publication Number by Areas
The data contained in Figure 17, illustrated below, demonstrate through the graphic the areas of knowledge with the highest frequency of publication

Analysis of articles
In Table 4 are presented the articles selected as most relevant by the author provided by the database in the Lucratively -IL method. In order to investigate whether there are conditions of exchange between customer satisfaction and productivity, a school of thought is analysed that argues that customer satisfaction and productivity are compatible, since improvements in customer satisfaction can reduce time and effort to commit returns, rework, guarantees, and complaint management, while reducing the cost of making future transactions. Importantly, increasing customer satisfaction can increase costs as it often requires efforts to improve product attributes or product design. A useful conceptual framework is developed to address these contradictory points of view. (Anderson, EW et al.) The model predicts that customer satisfaction and productivity are less likely to be compatible when: 1) customer satisfaction is relatively more dependent on personalization, the degree to which the company's supply is reliable, standardized and free from disabilities; and 2) when it is expensive to provide high levels of customization and standardization simultaneously. The central feature of this database is the set of customer satisfaction indexes provided by the Swedish Customer Satisfaction Barometer (SCSB). The SCSB provides a uniform set of comparable company performance measures based on the customer and provides a unique opportunity to test the hypotheses of the study. The findings indicate that the association between changes in customer satisfaction and changes in productivity is positive for goods but negative for services . In addition, while customer satisfaction and productivity are positively associated with ROI for goods and services, the interaction between the two is positive for goods but significantly less for services. Taken together, the results suggest support for the contention that compensation is most provable for services. Thus, concurrent attempts to increase customer satisfaction and productivity are likely to be more challenging in these industries. The findings should provide motivation for future research on the nature of customer satisfaction and productivity, as well as appropriate ethical strategies for each. (HANIFFA, R. M. ET AL.) It is worth noting that this is a problem that is not only important today but will certainly become even more important in the future. As service growth continues and global markets become increasingly competitive, the importance of customer satisfaction will also increase. In order to compete in such a world, companies must find the right balance between their efforts to compete efficiently and their efforts to compete competitively (Anderson et al., 1997) Since 1961, accounting researchers have investigated associations between corporate characteristics and disclosures in annual corporate reports. It was observed that the results consistently showed that company size and listing status were significantly associated with disclosure levels, while mixed results were found for leverage, profitability and size of the audit firm. The authors aimed to integrate previous disclosure studies and to identify the underlying factors that caused the apparent variation in results. (Anderson et al., 1997). The method used was the metaanalysis of 29 studies, so it was possible to confirm significant and positive relationships between levels of disclosure and corporate size, listing status and leverage. However, no significant associations were found between the corporate profitability or the size of the audit firm, with aggregate levels of disclosure. As a conclusion, this study also found that, in addition to the sampling error, the results are driven by differences in the construction of the dissemination index, differences in the definition of the explanatory variables, and differences in search configurations (AHMED ET AL, 1999). Raffournier (1995) aimed to relate the extent of disclosure in the annual reports of Swiss companies, in order to list the possible determinants that represent the political and agency costs. The object of the study was chosen because, prior to the implementation of the new company law on 1 July 1992, Switzerland's disclosure requirements were very low, so that most of the content of the annual report could be considered as voluntary disclosure. The sample included the 1991 annual report of 161 industrial and commercial companies. Where the extent of disclosure is measured by an index based on information the disclosure of which is required by the four and seventh directives of the European Union. Independent variables are measures of firm size, leverage, profitability, ownership structure, internationality, auditor size, percentage of fixed assets and type of industry. Relationships are evaluated using univariate analyses and multiple regressions. The main result is that size and internationality play an important role in the dissemination of companies, large and internationally diversified companies that tend to disclose more information than purely domestic companies. (RAFFOURNIER, 1995).

Simple Payback
For this method, periodic searches were performed using key words "Simple" AND "Payback", which ended up returning 769 results. With this information, different perspectives, such as the year of publications, most published authors, origin of publications, among others, will be analysed from this topic.

Year of publications
The data contained in Figure 18 It should be noted that there is a growing trend in publications. The largest anode publication was 2017, with 82 publications, and the year 2018 is already with 6 scientific works until the moment of the realization of this research

Authors who published on the subject
The data contained in Figure 19, illustrated below, demonstrate through the graphic the authors with the highest frequency of publication.

Figure 19: Graph of authors with higher frequency of publication Source: Adapted from Scopus (2018)
It is already a great highlight for the writer Stuart P., who has 10 articles published, still 40% ahead of the second, third and fourth post that have only 6 publications each.

Source of publication
The data contained in Figure 20, illustrated below, demonstrate through the graphic the periodicals with the highest frequency of publication.

Affiliation
The data contained in Figure 21, shown below, demonstrate through the graphic the affiliations with the highest frequency of publication.

Figure 21. Graph of affiliations with higher frequency of publication Source: Adapted from Scopus (2018)
The institution that most republished on this financial method was Lawrence Berkeley National Laboratory, with 15 scientific papers, followed by EcolePolytechnique de Montreal, with 13 and Texas A and M University with the same number.

Number of publication by country
The data contained in Figure 22, illustrated below, demonstrate through the graphic the countries with the highest frequency of publication. The United States appears as absolute leader in the publications, respons ible for 244 of them. In second place is Canada with 43 publications and third with 42.

Number of publications per area
The data contained in Figure 23, illustrated below, demonstrate through the graphic the areas of knowledge with the highest frequency of publication It can be noted, Figure 23, that the most published areas of knowledge were Engineering, with 384 publications and Energy with 371, well in front of the third place, Environmental Sciences, which had only 101 publications.

Analysis of articles
In Table 5 we present the articles selected as most relevant by the author provided by the database.  Chuang et al. (2014) observed that the processing of solutions is promising for the realization of low cost, large areas, flexible and light photovoltaic devices with short and high power return time specific. But in contrast, solar cells based on generally reported organic, inorganic and hybrid materials suffered from low air stability, requiring an inert atmosphere processing environment or high temperature processing, which increases the complexities and manufacturing costs. According to Rehman et al. (2007), the manufacturing conditions low temperature and good atmospheric stability remains a great technical challenge, which can be approached, as demonstrated by the authors, with the development of ZnO / PbS quantum solar cells processed in ambient temperature solution. It was observed that by including the alignment of the quantum dots layers through the use of different ligand treatments, a certified efficiency of 8.55% was obtained. In addition, the performance of encapsulated devices remains unchanged for over 150 days of airborne storage. This material system introduces a new approach to the goal of stable high performance solar cells, compatible with simple solution and deposition processes on flexible substrates. Wies et al. (2005) sought to discuss the economic analysis and the environmental impacts of the integration of a Photovoltaic Matrix (PV) in energy systems dieselelectric to remote villages. Thus, MATLAB Simulink was used to combine the load with the demand and to distribute the electrical production between the PV and the diesel-electric generator. Since the economical part of the model calculates the fuel consumed, the kilowatt hour obtained per gallon of fuel supplied and the total cost of the fuel. The simulations were based on a real system in the Alaskan remote community of Lime Village were performed for three cases: 1) diesel only; 2) diesel battery; and 3) PV with diesel battery using a period of one year.The simulation results were used to calculate the energy return, the simple return time for the PV module and the avoided CO2, NOx and PM costs.

Discounted Payback
For the performance of the searches related to the PaybackDescontado method, the keywords "Discounted" AND "Payback", return as data were used 304 results.

Year of publications
The data contained in Figure 24, illustrated below, demonstrate through the graphic the frequency of publications per year in the period 2000-2018.   Analyzing the main authors represented in Figure 25, it can be seen that Cucchiella, F. and D'Adamo, I. stand out among the others because they have more than two thirds of the list, Rosa, P., which presents only 5 published works on 12.

Source of publication
The data contained in Figure 26, illustrated below, demonstrate through the graphic the most frequently published periodicals.

Figure 26: Graph of journals with higher frequency of publication
The main journals presented as a result of the energyrelated research data are Energy, Energy and Buildings and Energy Conversation and Management.

Affiliation
The data contained in Figure 27, illustrated below, demonstrate through the graphic the affiliations with the highest frequency of publication

Number of publication by country
The data contained in Figure 28, shown below, demonstrate through the graphic to the countries with the highest frequency of publication.

Publication Number by Areas
The data contained in Figure 29, illustrated below, demonstrate through the graphic the areas of knowledge with the highest frequency of publication.

Analysis of the articles
In Table 6 are presented the articles selected as most relevant by the author supplied by the base. presented a methodology for the optimization of the project and the economic analysis of systems connected to the photovoltaic netwo rk (PVGCSs). The purpose of this study was to suggest, from a list of commercially available system devices, the number and type of optimized system devices and optimum details of PV module installation details, so that the total net economic benefit achieved during the period operating system is maximized. The decision variables included in the optimization process were the ideal number and type of photovoltaic modules and DC / AC converters, the optimum angle of inclination of the photovoltaic modules, the ideal arrangement of the photovoltaic modules within the available installation area and the ideal distribution of the PV Modules between DC / AC converters. The economic viability of the resulting PVGCS configuration was exploited by the net present value, the return period of counted, and the internal rate of return methods. The proposed method was applied to the ideal design of a PVGCS interconnected to the electrical grid of an island with significant potential of solar irradiation. (KORNELAKIS ET AL. (2009) There are many factors that contribute to the definition of the economic and environmental performance of investments in solar energy, such as annual irradiation, consumer consumption, tariff incentive system, energy portfolio, emissions produced by photovoltaic system, nominal power of the modules modules, available income of the investor, availability of surface for the installation of photovoltaic panels and mission, which characterize the project (environmental maximization, economic maximization or self-sufficiency of the system during the first year) (KORNELAKIS ET AL Cucchiella et al. (2015) developed a study in Italy, taking into consideration and estimating the economic profitability and the environmental impact of these systems, first at the provincial scale and then at the regional scale, to delineate the general characteristics that were not caused by a single c Indicators used include the following: net present value (NPV), internal rate of return(IRR), discounted payback period (DPbP), aggregate cost-benefit ratio

International Journal of Advanced Engineering Research and Science (IJAERS)
[ Vol-5, Issue-9, Sept-2018]  https://dx.doi.org/10.22161/ijaers.5.9.6  ISSN: 2349-6495(P) | 2456-1908(O) (BCr), and carbon dioxide emission reduction (ERcd). The final objective of the work was to define the number of photovoltaic (PV) systems needed to achieve the objective of producing renewable energy in the above configurations. Where an appropriate overall scenario was examined to achieve the objective, as well as the implementation of the total wealth generated by this framework and the reduction of CO2 emissions resulting from the implementation of this plan. The indicators u sed were the net present value per capita and the reduction of per capita carbon dioxide emissions. (CUCCHIELLA ET AL., 2015) Herrando et al. (2016) analyzed the potential and cost-effectiveness of a photovoltaic solar power plant to meet the demand for energy from clothing in Jaipur, India. In addition to estimating the energy demand of garment zoning for 2011 (2.21 MW), and the 2.5 MW solar photovoltaic power plant project was proposed, which requires about 13.14 aces of area of land. Noting the shortage and the cost of land near the city, a proposal for the plant outside Jaipur was also considered and compared to the option in place. For the internal rate of return of the photovoltaic solar on-site network (IRR) was 11.88%, the discount rate of NPV 10% was INR 119.52 million, single return operation was 7.73 years and the discounted payback period 10% was 15.53 years, while the IRR of the off-site energy system was 15.10%, the NPV was 249.78 million INR, the simple payback period was 6, And the discounted payback period was 10.14 years. The energy cost is Rs. 14.94 and Rs. 11.40 per kW / h for solar photovoltaic plants in the off-site locale, respectively, discount rate of 10%, which is quite attractive. (HERRANDO ET AL., 2016).

Minimum Attractiveness Rate
The keywords "minimum" AND "attractiveness" AND "rate" are used in the search for this method, returning 55 results.

Year of publications
The data contained in Figure 30, illustrated below, demonstrate through the graphic the frequency of publications per year in the period 2004-2018. As can be observed, the year of greatest publication, as expected, was 2017 with 10 articles, followed by 2015 with 7 publications.

Authors who published on the subject
The data contained in Figure 31, shown below, demonstrate through most frequently published authors. Pacheco, P., with 5 articles, followed by Vaz, F. N., with 4 publications, Pacoal, L. L. with 3 papers and Restle, J, also with 3 papers.

Source of publication
The data contained in Figure 32, illustrated below, demonstrate through the graphic the periodicals with the highest frequency of publication. Among the journals presented in Figure 32, two Brazilians stand out: Costs and Agribusiness, leading the list with 8 publications, and Annals of the Brazilian Academy with only 1.

Affiliation
The data contained in Figure 33, shown below, demonstrate through the graphic the affiliations most frequently published In terms of affiliation, Brazil again represents the majority of institutions that seek to study and publish on the topic, as can be seen in Figure 33.

Number of publication by country
The data contained in Figure 34, illustrated below, demonstrate through the countries with the highest frequency of publication. Analyzing Figure 34, it is possible to identify that the United States ranks second, with 15 publications, followed by Germany with only.

Number of publication by areas
The data contained in Figure 35, shown below, the areas of knowledge with the highest frequency of publication. It should be noted that the main knowledge area returned by the research data was Agriculture and Social Sciences, with 24 publications, followed by Engineering with 10 and Medicine with. 4.6.7 Analysis of the articles In Table 7 the selected articles are presented more pertinent to the theme of the Minimum Attractiveness Rate method, returning works from the authors provided by the base research.   Catapan et al. (2015) aimed to use the technical analysis of investments, to determine the break-even point, in number of animals, to allow the implantation of bio-digesters for the generation of electric energy with the use of swine projects. As methods, interviews were carried out with final owners, analysis of cost sheets and budget control with suppliers for the cash flow project. Then, the deviation indicators were calculated and the Monte Carlo simulation was done to measure the sensitivity of the input parameters. The results of the research pointed out that the balance point is 1009 pigs. Considering the premises of the Monte Carlo Simulation considering that p (Net Present Value <0) = p (Internal Rate of Return <Minimum Attractiveness Tax) should be a maximum of 0.20, it is suggested to implant biodigester in properties with in at least 1075 pigs. Hydrogenated Diesel (HRD), which is defined as paraffinic hydrocarbon vegetable oil and animal fat, has received worldwide consideration with alternative diesel fuel. In this work, the production of DRH from palm oil fatty acid distillate (PFAD) was elaborated and a technoeconomical evaluation of a heat integrated HRD production plantRD was attractive for investment with a VPN of 61.89 M $ (KANTAMA et al., 2015) . Silva et al. (2017) aimed at theoretically determining the electric power of LFG using the Maximum Net Benefit (MNB) methodology, taking into account the economic, demographic and regional aspects of the Inter-municipal Consortium of the Micro-region of Alto Sapucaí for Landfill (CIMASAS, as an acronym in Portuguese), located in the southern part of the state of Minas Gerais, Brazil. To this end, the prognosis for a 20-year period of household solid waste generation in this region has been estimated and quantified on the basis of population data in order to estimate LFG production and energy that can be generated. From this point, the ideal power for the power plant (TPP) by LFG was determined. The results indicated that the landfill in this region could produce 66,293,282 m3 of CH4 (with a maximum power of 997 kW in 2036) in twenty years and that there would be no economic viability to generate energy from the LFG, since the Net Present Value (NPV) it would not be positive. The population for this can achieve a minimum attractiveness rate (MAR) of 15% of 3,700,000 inhabitants under the conditions studied. Considering the Resolutions of the National Electric Energy Agency (ANEEL), it would be 339,000 inhabitants installed 440 kW capacity. In addition, the result of the CIMASAS case study demonstrated the applicability of the MNB methodology for determining the potency of TPP

Cash Flow
For the researches carried out on this method, the key words "Cash" AND "Flow" were used, which returned which formed the basis of data for the analyzes on this topic.

Year of the publications.
The data contained in Figure 36 Again, as can be seen in Figure 36, the year 2017 follows as the highest number of publications made, 907, followed by the year 211 with 838 publications. Although between the years 2001 and 2011 there has been an exponential decline of publications in this area, there was some stability from 2012, with reduced growth.

Authors who published on the subject
The data contained in Figure 37, illustrated below, demonstrate through the graphic the authors with the highest frequency of publication. In this methods the data returned a large number of works published the identification of the author, that is, anonymous publications. These represent a major part of the results, followed by Kahraman C. and McCue M.J., with 26 and 20 publications, respectively.

Source of Publication
The data contained in Figure 38, shown below, demonstrate through the graphic the most frequently published. Among the journals presented in Figure 38, the following stand out: Engineering Economist, Journal of Financial Ecnomics and Journal of Finance, with 159, 141 and 136 published works, respectively.

Affiliation
The data contained in Figure 39, illustrated below, demonstrate through the graphic the affiliations with greater frequency of publication New York University was the institution that most published about the method, resulting in 108 articles published.

Number of publication by country
The data contained in Figure 40, illustrated below, demonstrate through the graphic the countries with the highest frequency of publication.  The United States has more publication than the sum of the other Dalista countries, with 4,565. Brazil ranks tenth in the list of the most relevant countries, with 289 publications.

Publication Number by Areas
The data contained in Figure 41, shown below, demonstrate through the graphic the areas of knowledge with the highest frequency of publication. As can be seen in Figure 41, the most relevant publications related to the areas of Business, Management and Accounting, with 5,194 publications, and Economics Econometrics and Finance, with 5,092 published works.

Analysis of articles
The selected articles are presented in Table 8 as more relevant by the author provided by the bas is for the Cash Flow method. energy companies to identify potential photovoltaic markets and investigate the political landscape in Western EU countries. In the work of Pullikkas (2009), a study feasibility study was carried out to investigate whether the installation of parabolic solar thermal energy generation technology in the Mediterranean region is economically viable. The case study took into account the available solar potential for Cyprus, as well as all available data on the current Cyprus renewable energy policy, including the relevant feed-in tariff. In order to identify the least cost feasible option for the parabolic solar thermal plant, a parametric cost-benefit analysis was carried out through variable parameters, such as parabolic capacity through solar thermal energy, parabolic investment through solar thermal energy, hour operation, system price of carbon dioxide emissions trading, etc. For all of the above cases, the cost of the unit of electricity was estimated before taxes, as well as the cash flow, net present value, internal return rate and return period. The results indicated that, under certain conditions, these projects may be profitable The penetration level of a photovoltaic (PV) system is often limited due to the violation of the voltage variation introduced by the large generation of intermittent power. Lin et al. (2012) discussed the use of an active energy reduction strategy to reduce the injection of photovoltaic energy during peak solar irradiation to avoid strain violation so that the PV penetration level of a distribution feeder can be increased to use fully to solar energy. The generation of photovoltaic energy was simulated according to the hourly data of solar irradiation and temperature provided by the meteorological agency.
By using the voltage control scheme proposed to limit the injection of photovoltaic energy into the study distribution feeder during periods of high solar irradiation, the total energy generation and the total energy delivered by the photovoltaic system over a period of one year are determined according to the annual solar radiation. The annual cash flow from sales of photovoltaic energy, the O & Mao cost over the life cycle of the system and the capital investment in the photovoltaic system were used to calculate the PV project's amortization years and net present value (NPV). With the voltage control proposed to execute partial generation of photovoltaic systems, the ideal installation capacity of photovoltaic systems could be determined by maximizing the net present value of the system so that a better cost-effectiveness of the PV project and a better energy utilization could be obtained

Return on the Investment -ROI
A research on the periodicals related to the Return on Investment method -ROI, used the set of keywords or key terms "Return" AND "on" AND "Investment", reaching 35,152 results.

Year of publications
The data contained in Figure 42, illustrated below, demonstrate through the graphic the frequency of publications per year in the period 2000-2018.

Authors who published on the topic
The data contained in Figure 43, illustrated below, demonstrate through the graphic the authors with the highest frequency of publication. The identified author who most publishes is Psacharoulos G., with 29 publications, followed by Hall C. A. S.com 22.

Source of publication
The data contained in Figure 44, illustrated below, demonstrate through the graphic the periodicals with the highest frequency of publication The most relevant journals in the publication of this method in question, as can be seen in Figure 44, are the Journal of Banking and Finance and the Lecture Notes in Computer Science Including Subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics.

Affiliation
The data contained in Figure 45, illustrated below, demonstrate through the graphic the affiliations with the highest frequency of publication. Result, it can be seen in Figure 45 that the National Bureau of Economic Research has 188 publications, the University of Pennsylvania has 179 and UC Berkeley has 171 articles published.

Country publication number
The data contained in Figure 46, illustrated below, demonstrate through graphic the countries with the highest frequency of publication. As can be seen, the United States leads the list of countries with 12,155 published articles, followed by the United Kingdom (2,951), China (2,092), Australia (1,523) and Canada (1,345).

Number of publication by areas
The data contained in Figure 47, illustrated below, demonstrate through the graphic the areas of knowledge with the highest frequency of publication.
It is possible to analyze, through Figure 47, that the Economy, Econometrics and Finance area has the largest number of publications, with 9,468. In second place, we have Administration and Accounting, with 8,267 published in Engineering, with 7,645 publications.