# Renewable Energy and Sustainability from the Supply Side: A Critical Review and Analysis
## 3 Method and Data  
### Method  
A bibliometric analysis was performed, seeking a better understanding of the directions of scientific trends concerning the relationship between renewable energies and sustainability. Bibliometric analysis looks at publications and their properties [64] and adds knowledge domain visualization to gain a sense of the development and evolution of a knowledge field. The quality of a bibliometric analysis depends on the quality of the input data, and it is essential to approach the literature in an unbiased way. The Scopus database for the period 1997-2019 was used to collect data. This time range was chosen because 1997 was the period when the literature on renewable energies and sustainability began to grow (see Figure 1). Our period of analysis finishes in August 2019, the month in which the data were collected. Figure 1: Literature search. Bibliometric analysis relies on quantitative methods to investigate a body of publications. The bibliometric indicators used herein include the total of publications on the research topic during the period, the main journals in which the research is published, the scientific fields in which the topic has been covered, the number of citations by journals, the network analysis, and keywords occurrence. The visualization software VOSviewer (v1.6.10, Centre for Science and Technology Studies CWTS, Leiden, The Netherlands) was used, which is a science mapping method of bibliometric analysis [65]. The four-step methodology suggested by [PERSON] and [PERSON] [66] was followed in this study: (i) define the search keywords; (ii) clean and format the data; (iii) make an initial analysis; and (iv) perform the final data analysis. Regarding Step (i), using the approach suggested by [PERSON] et al. [67], the title, abstract, and keywords were searched in the Scopus database (Elsevier, Amsterdam, Netherland). The Scopus database (Elsevier) was selected because it is the largest database of abstracts and citations for scientific peer-review literature and includes more than 22,000 titles from international publishers. Keywords searched in title and abstract were renewable energy, its synonyms (renewable resources, bioenergy, and bio-energy) and the following renewable energy types: biomass, biofuel, biodiesel, ethanol, biofhanol, wind energy, wind power, solar energy, solar power, photovoltaic cells, geothermal energy, heat energy, ocean-power, hydropower, water-energy, water power, hydroelectric power, and landfill gas. All these keywords were included in a non-exclusive way (with the \"OR\" particle) to identify all the articles covering all types of renewable energies. Additionally, the keyword sustainability (social, environmental, economic sustainability) was also included to those keywords be presented in the search fields (title, abstract, keywords) in each publication. This procedure made possible to identify the publications that cover not only the topic of renewable energies but also some dimension of sustainability. In Step (ii), the search was limited to articles not only written in English, but also published in indexed journals that are subject to the peer review process. Books, book chapters, and conference proceedings were not considered since not all are subject to peer review practices. This stage identified 526 articles. To use VOSviewer, the data were standardized and formatted to a plain text making it possible to analyze their relevance (see Table 1). A total of 316 records adhered to these filtering criteria. A summary of the bibliographic search is presented in Figure 1.  
In the next steps, an analytical framework was developed to identify some patterns in the research field. The articles extracted in the second phase were used as the input data and processed using the _Excel_ (Version 2019 (16.0), Windows, Microsoft, Redmond, Washington, EUA) and _VosViewer_ softwares (v1.6.10, Centre for Science and Technology Studies CWTS, Leiden, The Netherlands).