Renewable Energy Research in Africa: A Bibliometric Review (1979-2022)

3.1 General information

Table 1 highlights the importance of bibliometric research on renewable energy research in Africa, portraying it as a vibrant and continually evolving field of study. The dataset included the publications, which were refined to 3109 publications by focusing on the period from 1979 to 2022. The significant number of sources (1134) and documents (3109) emphasizes its prominence in the field of research. Furthermore, the high annual growth rate of 13.39% suggests sustained interest in this subject.

Table 1. The main information on the survey

The substantial average citations per document (21.89) underscore the significant impact of research in this field on the scientific community. Additionally, the extensive number of keywords (11029) and authors (7095) associated with a field of research publications reflects the substantial interest and commitment of numerous researchers in this area.

The bibliometric analysis covered various aspects, enabling the measurement of researchers' productivity, identification of key research areas, mapping of collaboration networks and academic institutions, and evaluating the influence of publications within the scientific community.

3.2 Annual growth production

The number of publications per year is an important parameter that reflects the importance of the field and its dynamicity. Figure 2 presents a bibliometric analysis showing the publication trends in publication from 1979 to 2022. The graph demonstrates a steady increase in the number of papers published, rising from 2 in 1979 to 445 in 2022. This upward trend can be attributed to the industry's acknowledgment of the significance of renewable energy research and the growing demand for practical solutions in the field of energy in Africa which boasts immense potential in renewable energies.

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Figure 2. Growth of publications in renewable energy in Africa over the years (1979-2022)

3.3 Most relevant authors

In this section, Table 2 presents the top 10 most prolific authors in the field of this research, based on the number of peer-reviewed publications, utilizing data extracted from Scopus. Notably, authors such as Brent, Kusakana, and Kanzumba, specializing, emerge as highly productive in the area of research with a total production of orders of 37 and 28 respectively.

The table also includes the authors' H index, affiliations, country, and first year of publication. Furthermore, Table 2 indicates that South Africa boasts the highest number of affiliations in Africa concerning research on renewable energy, totaling six affiliations.

Co-citation analysis is a fundamental tool in bibliometrics used to explore the intellectual structure of a field by analysing the co-occurrence of different items. This analytical approach, introduced in 1973, examines how two items from previous academic works are cited together in subsequent publications. Co-citation analysis can be applied to various items such as authors, keywords, or sources.

In this section, author co-citation analysis (ACA) was employed as the basis, focusing on the frequency of co-occurrence among authors. The analysis utilized VOSviewer, setting a minimum threshold of 200 co-citations for an author. Out of 7095 authors, only 51 met this threshold, as depicted in Figure 3. The authors were categorized into four clusters based on their field of study. In the visual representation, the size of the circles indicates the number of co-citations for each author, and the connecting curves signify collaborations between authors. Authors within the same cluster demonstrate stronger collaboration, often sharing publications. The proximity of authors on the map reflects the degree of relatedness in co-citation. It is noteworthy that VOSviewer in co-citation analysis examines the frequency of cited works where an author appears as the first author in publications.

Table 2. List of the most prolific authors in research area extracted from VOSviewer (1979-2022)

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Figure 3. Co-citation map of authors in research area (1979-2022)

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Figure 4. Most productive institutions in the research area (1979- 2022)

3.4 Affiliations analysis

From Scopus records, the analysis focused on the top 10 most productive institutions out of 1134 different ones, based on the number of publications during the period from 1979 to 2022, which are presented in Figure 3. Notably, the leading 10 institutions have contributed significantly, each publishing over 43 articles within this specified timeframe, a noteworthy observation is that a majority of these prolific institutions are located in South Africa.

In this section, we present the most affiliations productive and cited. Figure 4 shows the affiliations with the highest number of published papers in the field of renewable energy in Africa over the period from 1979 to 2022. the figure shows that the top affiliation is the ''University of Cape Town'', South Africa with a total of 174 papers, closely followed by ''Stellenbosch University of Netherlands'' with 158 papers, the top 10 affiliations with 43 articles occupied by ''Tshwane University of Technology of South Africa''. Figure 5 presents the most cited affiliations, the figure shows that the ''faculty of Economics Administrative and Social Sciences Istanbul Gelisim University, Istanbul, Turkey'' with 1182 citations and an average citations /paper of order of 59 followed by 'Department of Economics, University of Pretoria, Pretoria, South Africa'' with a total and average citations of the order of 55 and 455 respectively.

Figure 5. Top 20 most cited institutions in the research area (1979- 2022)

3.5 Countries analysis

Figure 6 and Table 3 illustrate the distribution of articles in the renewable energy field in Africa published by country and number of citations. The mapping presented in Figure 7 shows that South Africa leads with the highest production of papers, boasting 962 articles and a total citation of 11111 followed by the United States and the United Kingdom with respectively a total of documents 361 and 347 and citations of order 7981 and 9456 respectively. This analysis provides insights into each country's research interests and supported areas, directly reflecting their available resources and deficits.

Table 3. Top 10 most cited countries, number of publications and citations (1979-2022)

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Figure 6. Countries with the highest productivity

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Figure 7. Mapping countries productivity

3.6 Most relevant sources

Figure 8 displays the leading journals in terms of published articles. At the forefront is the "Renewable and Sustainable Energy Reviews" with an impressive 125 articles, followed closely by the " Renewable Energy" with 117 articles and "Energy Policy" with 106 articles. Other noteworthy journals include the "Journal of Energy in Southern Africa," "Energies" "Environmental Science and Pollution Research," and "Sustainability (Switzerland)," which have played crucial roles in advancing research and making significant contributions to this field., publishing 88, 67, 65, and 58 articles respectively. This section also delves into high journal cited, furthermore, ranking papers based on their average citation in descending order was conducted in this section. Focusing on the frequency VOSviewer was utilized for the analysis, employing a minimum threshold of 200 co-citations for each journal, among 1134 sources, only 49 journals met this threshold. In Figure 9 we present the average citation of each journal as depicted in Figure 9 average citation varying between 10 to 60 citations, the journal most cited is " Renewable and Sustainable Energy Reviews'' followed by ''Renewable Energy'' and ''Energy Policy''.

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Figure 8. Highest productive journals

Figure 9. Highest cited journals

3.7 Most relevant documents

Table 4 reveals that the most cited papers in the field of research were published in esteemed journals like ‘’Reviews’’, highlighting the significance of these journals and their ability to attract top researchers and innovative work. However, it's crucial to acknowledge the presence of other high-quality journals in this field, as mentioned in Figure 8. Of special mention is the work by Wanner, Heinz, which has garnered a maximum citation of 1294 citations.

An intriguing observation is that the journal ‘’Science of the Total Environment’’ presents 3 papers of the top 10 most cited papers. Additionally, this section includes the citation graph of the most cited documents. Figure 10 was constructed using VOSviewer which is based on a minimum number of co-citations of authors of 200 citations only 46 authors met the threshold are shown in Figure 10.

3.8 Most relevant keywords

This analysis aids in pinpointing crucial areas of focus within a specific subject. Out of 3109 documents, 110029 keywords were identified. The most commonly occurring keyword was "Renewable Energy," mentioned 685 times, followed by "Renewable Energy Resources" (644), "South Africa" (561), and "Africa" (539). The remaining keywords are detailed in Figures 11 and 12.

Analyzing co-occurrence keywords can unveil the interrelation between research topics, providing insights into relevant and comprehensive research trends. This approach helps identify connections among specific terms, reveal lesser-explored terminology, and shed light on current and emerging themes in energy optimization research. In this study, a total of 11029 keywords, encompassing author keywords and those extracted from the titles and abstracts of 3109 documents, were analyzed.

Figure 10. Highest cited authors

Table 4. Most cited documents on the field (1979-2022)

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Figure 11. Most relevant keywords in research area

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Figure 12. Word cloud of the most frequent keywords

3.9 Co-occurrence and collaboration network analysis

Consequently, a curated list of keywords with higher research significance was generated, highlighting the top 77 keywords in the co-occurrence network related to renewable energy in Africa, fixed keywords to 88 only 77 keywords met the threshold illustrated in Figure 13 and Table 5.

Also, for a better understanding of the scholars' collaborations, the contributing authors were taken as a unit for analysis. Using VOSviewer, the collaborative network among countries in the research area was examined. The analysis of publications revealed authors and affiliated institutions from various nations. Consequently, the participating countries were identified and differentiated by different colors in Figure 14, illustrating the collaboration network.

This analysis aids in visualizing international collaborations, offering insights into the network's dynamics. It serves as a valuable tool for researchers, enabling them to identify new collaboration possibilities and research avenues.

This analysis helps to visualize the collaborations between countries in the field of corrosion inhibitors and to understand the dynamics of the collaboration network, which can help researchers identify new collaboration and research opportunities. It is important to mention that a single publication might be associated with multiple countries due to collaborations between different institutions, a factor that has been duly accounted for in this study.

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Figure 13. Co-occurrence of keywords

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Figure 14. Co-authorship map

Table 5. Most relevant keywords on the field (1979-2022)